Author Topic: Warm engine starting (Read 19291 times)

chumps · « **on:** March 10, 2016, 15:26:55 »

I have owned my 1971 280SL for about twenty years. There as been an ongoing starting problem that has bothered me but not enough to really dig into the fix until now. The car stars instantly and runs perfectly when cold. It runs perfectly all the time (maybe a bit rich). If I shut it off and start it again within 15 or 20 minutes it starts up instantly. If it sits longer than that it has to crank 5 to 10 seconds before it will start and then runs roughly for a second or 2 before it starts to run smoothly. If it cools down substantially (1 1/2 to 2 hours) it will start instantly again. All of the starting aids that I have checked appear to be operating normally. I have a 123 ignition and fully operational emissions control system. Linkage and timing are spot on. I have read many threads, but none that said they were able to completely fix the problem. Any suggestions will be appreciated. Thank you, Terry

66andBlue · « **Reply #1 on:** March 10, 2016, 16:39:54 »

With a warm engine it is normal that it doesn't start up right away, you need to press the pedal about 1/3 down while starting.
It is described in your owner manual.

Tyler S · « **Reply #2 on:** March 10, 2016, 19:42:10 »

There once was a dealer installed time relay and sub-harness to correct this complaint. The parts are since NLA. The relay would energize the cold start valve for 1 second even with the engine warm, giving the engine a small burst of fuel. You can use the accelerator as Alfred suggested (which is what I do) or you can add a momentary push button switch and wire it to the cold start valve. Then give it a quick push before starting.
Tyler

mmizesko · « **Reply #3 on:** March 10, 2016, 21:37:51 »

I had the same exact symptoms. Joe Alexander and I worked on the injectors and replaced a couple that didn't chirp right, and that has helped. I still have a partial problem but not nearly to the extent that it was. Still more forensics to do. I'll see how it does in 90 degree weather.

Mike Mizesko
Columbus, OH

Baybear · « **Reply #4 on:** March 10, 2016, 23:18:39 »

I have this same problem as well. I believe Chuck Taylor has a fix for this which does what Tyler describes in his post. Hopefully he will see this and chime in and describe the "fix".
Will

wwheeler · « **Reply #5 on:** March 12, 2016, 02:44:10 »

I had (have) the same problem. I installed the factory fix and must have got the kit just before it went NLA. I installed it and while the later warm starting was a bit better, the hot start was much worse and seemed flooded. The other problem with the kit is that if the engine didn't start on the first crank, on the next crank another shot of fuel is given. So yes, every time the starter is engaged, the circuit is activated. Easy to flood your engine if you are not careful.

Tyler S · « **Reply #6 on:** March 12, 2016, 05:03:01 »

Wallace, Adding the push button gives you control of when fuel is added. If the car is being started hot then you dont have to push it.
The Dealer kit/mod is a "dumb" system meaning it has no imputs and no way of knowing engine temp.

wwheeler · « **Reply #7 on:** March 12, 2016, 15:16:26 »

I must be talking about a different factory mod. This one is 108 540 10 09 for the harness and 001 545 16 24 for the relay. It uses an a one second timer to activate the CSV. Everything is automatic on this one. It is here on the site http://www.sl113.org/wiki/Engine/TimeSwitch. I don't believe this has a manual push button.

Tyler S · « **Reply #8 on:** March 12, 2016, 15:26:46 »

Wallace, yes you are correct. That is the kit.
The push button I am talking about is a mod you would add yourself. Independent of the kit. I should have separated my paragraphs above.

66andBlue · « **Reply #9 on:** March 12, 2016, 17:49:59 »

Hmm ... I don't understand the need for the "dumb" kit and the push button modification.
They don't seem to be that much different from using sing the accelerator pedal during cranking, or?
Also I don't crank continuously but always in short 2-3 second attempts; if not on the first try it will always start on the third when warm or hot.

ctaylor738 · « **Reply #10 on:** March 12, 2016, 18:45:10 »

I use a timer relay from Allied Electronics to provide ground to the cold start valve relay for a variable amount of time while the engine is cranking. .5 to .7 seconds seems to work best. This has fixed stubborn hot start problems on 3 or 4 cars. It basically does the same thing as the factory fix.

I have a couple of kits made up that plug in between the cold start valve relay and the connector. You plug in, connect one wire to ground and optionally run the wires through the firewall. PM or email me for details.

Cheers,

Steven A · « **Reply #11 on:** March 13, 2016, 06:11:55 »

Warm start; in our hot summers here in West Australia I find it best to disconnect the CSV for summer as CSV + FIP start solenoid in summer makes it too rich (this is for a very early 230SL - version II) for warm/hot start...and then have to crank for ages to start. This is with all start/enrichment relays operating/switching in correctly. This is using 1/3 (or more) throttle. For cold start in summer (relatively cold that is!) just the FIP start solenoid is enough for a good cold start. As with Tyler, I do have a separate push button to CSV, should it be needed to get extra fuel in. In winter, CSV gets re-connected to the relay control.
Regards

dante53 · « **Reply #12 on:** March 13, 2016, 08:55:10 »

I had the same problem on my '65 230SL. I fixed it just disconnecting the time relay (I mean the round little one).

catjim813 · « **Reply #13 on:** March 13, 2016, 19:05:14 »

Chumps, please keep us posted on which direction you go with this problem. I have the exact same problem but all of it started after reseal of injection pump and rebuilt CSV by Hans. CSV appears to have been leaking fuel all the time there fore making very easy hot starts. Before CSV rebuild car would start with just a turn of the key and not having to depress the pedal. I will reach out to Chuck for the allied switch for more information.

chumps · « **Reply #14 on:** March 14, 2016, 13:34:40 »

Thank you for your input. It appears that there are a number of ideas to try and correct this problem. I don't really want to make any modifications that were not stock from the factory. I will try what Alfred said (throttle down 1/3) first for a while. Alfred, I also start my car as you described - crank for a second or 2, stop, crank again and it almost always starts the second crank. Although this always seems to work, it still bothers me a bit to have to do this. If I'm still unhappy after trying the throttle thing I will experiment with some of the other options that are mentioned above. Like I said in my previous post, I have lived with it for twenty years - it is just a minor nuisance. The car is such a work of art I hate to see anything not right on it. After I try all of the above I will repost results. Thank you all.

A-230 · « **Reply #15 on:** June 13, 2016, 15:35:34 »

Hi, I have had warm start problem on my -64 230SL since I bought it in 2008. The former owner had disconnected the CSV, and told me to start with the pedal to the floor. It worked most times, but not always. Then my local specialist reconnected the CSV and said that was the best. Well, it was not. After that I have had huge starting problems when warm and often had to rollstart the car.

Last week I asked for tips on a Facebook page for Pagodas. I got a simple tip, as also given above. Install a pushbutton between the battery and the CSV. My problem has disappeared. A quick push on the button is all needed. Every time it starts immediately after. I now have a new life with my Pagoda, can use it for as many small trips as I like, not only one long trip each time.

Good luck from A-230 in Norway.

wwheeler · « **Reply #16 on:** June 14, 2016, 19:57:54 »

After reading the many posts over the last several years about this topic, I have come to a conclusion about the fuel injection systems. The many parts involved have uniquely aged and worn over the years, and now no two are alike. And people are operating them in very different types of climate. So trying to reproduce the starting performance as it came from the factory may be next to impossible. That also means that one engine responds better to a modification more than another even though they both may be adjusted as close to factory as possible.

As an example on my '68 280SE, I ended up disconnecting the start solenoid. After many years of adjusting this and shimming that, I found that the hot starts are perfect with the solenoid disconnected and would stall with it connected. To compensate, using a slight manual burst of fuel from the CSV will make the cold and warm starts almost as good. The manual burst seems more effective with the engine not cranking. So I too will add a push button switch to fire CSV when I think it needs it. BTW, my CSV is still connected and works as normal when cold.

chumps · « **Reply #17 on:** June 14, 2016, 20:56:36 »

I agree with WWheeler. All of my start system are working as they should. I tinkered a little with the mixture (a couple of clicks), a little with the timing(1 0r 2 degrees). I tested all of my injectors, ended up putting all new ones in. Car runs super. Warm starting got a little better. I am still a bit confused - activating the CVS valve gives it more fuel which would indicate that the problem is too little fuel, but pushing the accelerator half way down (allowing in more air) would indicate to me that it is getting too much fuel. My thoughts - I am just a garage gearhead. Chumps

Benz Dr. · « **Reply #18 on:** June 14, 2016, 21:50:41 »

Our engines will continue to inject a bit of fuel after you shut the engine off until it stops. This extra fuel will provide a rich mixture until it evaporates inside the cylinder. Adding extra air on a hot engine shortly after shut down can help to even out that rich mixture as the injection pump takes over and the engine is running.

On a cold engine, you need extra fuel and air. On a warm engine you may need just a whiff of fuel to get the engine spinning fast enough for the IP to take over. This is why a cold engine won't start without a working CSV. You need about 800 RPM to get the IP to create enough pressure so that the injectors will start to spray. This is why you can get your engine to start only after a lot of cranking.

Tyler S · « **Reply #19 on:** June 14, 2016, 22:03:50 »

Wallace is right. Every one is different. There are different injection pumps as well. Some with enrichment solenoids (230 250) and some without(280). I have Modded my injection pump delivery valves to the newer style ball and seat valves This solved most of my starting issues. So much so that I too needed to disconnect the enrichment solenoid or it would flood out when warm or hot. Doesn't get very cold here so the CSV is enough to get it started when cold. Just a slightly longer cold crank.

wwheeler · « **Reply #20 on:** June 16, 2016, 05:19:45 »

Tyler,

I am so glad you said that about your enrichment solenoid!!! I thought I was crazy all these years for disconnecting mine. Actually what I did in the end was to adjust the rod back far enough so that it did not contact the rack when activated. The net effect is the same as disconnecting it. I just hated having a loose wire hanging around. I believe when I had my pump rebuilt a few years back, they installed the newer ball valves. And so maybe that is why when hot or warm, it starts better without it as yours does. The later pumps did not use the solenoid which tells me that given the right climate and conditions, it is not necessary.When it does get cold in Dallas and I start the engine (40*F or so), the engine starts and initially runs better cold than it does when starting at 80*F.

Pushing on the pedal when starting is not straight forward. The amount of air added is a given as it is a direct mechanical connection. The fuel side is more complicated. The governor in the pump controls how much fuel is added via the rack from the throttle input and is based on engine speed. So the faster the engine speed, the more the throttle pushes on the fuel rack. The speed of the engine during starting is very slow and so the throttle has a limited amount effect on the fuel rack. The enrichment solenoid acts directly on the rack bypassing the governor. My opinion is that the throttle has little effect on the fuel mixture when starting the engine.

ja17 · « **Reply #21 on:** June 16, 2016, 06:20:44 »

First the cold start valve on the intake, must function. Just checking the solenoid is not enough. The intake fitting at the valve has a fine screen built into it and it can be plugged with fuel varnish or dirt. Clean it. Also the "squirter" jet can also be plugged with fuel varnish or dirt. Make sure the solenoid works, the screen is not plugged and the pair of fuel jets spray nicely. Find the which version starting aids your engine has and check cold and hot activation of the intake valve and injection pump solenoid if applicable. Next, low fuel pressure in the system will hinder starting. Check your fuel pressure. Fuel which will not circulate back to the tank, will overheat in the fuel lines, and cause vapor to form causing starting problems. Make sure the fuel returns to the tank constantly to cool down. The higher the alcohol content of the fuel the lower the boiling point, so starting will also suffer. Allow the ignition switch to remain on for a second or two to clear fuel lines of vapors before starting. If you have a dirty injector or ball valve in the injection pump, fuel in the lines may leak down causing a temporary rough idle at start until the effected line is primed up again. If yours is the 230 with the round time relay, make sure it is working. They are adjustable also. Most of the time they are just not working. Cleaning the contacts in the round time relay will usually get them working again. Over rich starting also can cause hard starting. If all else fails trail dis-connecting one device at a time for diagnostic purposes. Lots of things to check have fun!

Tyler S · « **Reply #22 on:** June 16, 2016, 15:27:45 »

Quote

I just hated having a loose wire hanging around.

Wallace, I left everything intact and just unplug the connector on the relay. Can't really be seen and can be quickly reconnected if needed for some oddball reason.

A Dalton · « **Reply #23 on:** June 16, 2016, 18:27:43 »

Two points to ponder.

There is also another good reason for unhooking the power feed to the start sol. on the early pumps [Up to and including R18]
And it is a mechanical reason .

The lever that is actuated by the sol is mounted on a stub shaft [ meaning it has support only at it's base] , so as they age, they snap off from the constant/repeated snap of the electric sol. ...and when they do break, the loose parts can then destroy the bottom end of the pump, casing included.
I have repaired some of these that were caught before being ruined by adding a support hole in the case and making a longer shaft to reach the new support hole. The new shaft then has support on the other end [ now both ends are supported]
This eliminates the possiblity of shaft failure , but is a machinest job that requires the proper equipment. Not an easy job.

The point being, the easy remedy and preventive measure is to eliminate the sol function [ by wire disconnect] , and simply add the newer style Ball valves. You will notice that all pumps that came with the ball valves upgrade [ after R18] do not have a factory sol . B/C it is waqs longer needed.

While here , I will state that I also have had much better luck over the years of using the Cabin switch for the CSV. [ As many of you already know the advantage of taking control of whether the engine wants gas or doesn't]

So, it is the simply an electric primer, manually activated ...

But here is the trick to much better starts.
Do not wire the CSV cabin sw to the existing relay/circuit or starter circuit.
Simply wire it to key ON .
This allows CSV actiavtion BEFORE starter draw, engine crank.
The start process is
1- Key ON for a sec or 2, [ this pressures the system]
2-Cabin sw if needed [ that depends on situation..cold start , warm start, etc.]
3-Then Crank.
The plenum is now already primed before you even turn the engine over.
Much faster starts and a better CSV operation b/c there is no system voltage drop from starter.

Another trick I like about this wiring system is that if one suspects a CSV problem, you can hit the cabin sw when the car is warmed up and running and you will instantly know if it is working correctly b/c the engine will attemp to stall from the added CSV injection...just a diagnostic by- product with this type of wiring of the cabin sw/csv circuit.

A Dalton
BenzTechs

Tyler S · « **Reply #24 on:** June 16, 2016, 19:27:47 »

The legendary Mr Dalton surfaces

It was he that advised me about disconnecting the enrichment solenoid. Great post my friend.

wwheeler · « **Reply #25 on:** June 17, 2016, 04:06:38 »

This thread has been very enlightening to me. Interesting thought on two counts. I have noticed that when I do disconnect the start solenoid, the engine seems to crank faster. Am I crazy or is it the draw from the solenoid as mentioned. If so, it gets disconnected! I did not know about the shaft wear and yet another reason to disconnect if not needed.

I was going to hook the CSV manual switch up to a keyed power source (not start circuit) and can do so easily because my W111 has power windows. That source is very close to the CSV. With my first crude test, I did notice that firing the CSV before the engine cranks yields better results. I first turned on the fuel pump, ran over and jumped the solenoid, then ran back and stared the engine. The manual switch will be easier but I won't get as much exercise

I am adding this CSV switch tomorrow and will test this weekend. If that works then I will make the CSV a full time manual and even further improve the voltage during starting.

Very interesting to know that the newer ball valves have a direct correlation to the elimination of the Start solenoid. I knew there was an improvement, but didn't know what it was.

Great tips and thank you!

Tyler S · « **Reply #26 on:** June 17, 2016, 05:10:06 »

Wallace, your not crazy. I think it is a combination of the solenoid, relay, and the extra load the injection pump is put under when having to go rich- those 6 little plungers have to pressurize and move more fuel.

Benz Dr. · « **Reply #27 on:** June 17, 2016, 06:06:15 »

Also known as a Viagra switch.

ja17 · « **Reply #28 on:** June 17, 2016, 06:18:00 »

Hello Arthur,

Nice to see you here again. your wisdom is appreciated. I am not a big fan of the add-on switch, but I like the idea of the newer ball valves and the elimination of the solenoid.

Cees Klumper · « **Reply #29 on:** June 17, 2016, 14:53:45 »

Welcome back Arthur!

A Dalton · « **Reply #30 on:** June 17, 2016, 16:32:12 »

JA

I agree.
The ball valve and sol eliminate are the main upgrade for these early pumps and brings them up to date of the later style pumps design improvements.
I actually prefer upgrading the early pumps b/c they have their own oil reservoir.
Later crankcase oil fed pumps are using engine oil , which can be contaminated with gas/sulpher. etc........
It is easy to see why they made that lube change, but fellows who care and feed their pumps seem to agree on this point.

On the cabin sw mod, it should be noted that this mod in no way interfers with the Factory stock system design. It is simply a By-pass/Over-ride of that system. When not used , the system is stock and has not been rewired/re-designed in any way.
It simply give the operator the option of a manual squirt to aid in certain conditions. The perfect example would be the infamous Heat Soak condition the later systems had on hot starts. They did make the 1 sec relay kit to add to these systems as a remedy, but the man cabin takes having to add that facory mod off the table.
I personaly never liked that mod and think they were looking for a quick fix.
Much has been written on the matter.

So, a cabin sw addition hinders nothing and there are times when one will be happy to have it available.

May never even need to use it, but choice is nice.

I have always been amazed that these systems can and do work as well as they do w/o the aid of closed loop technology... and there is not a " one size fits all"
tune process...they all need individual tweaking and they do respond well to adjustments.

A mechanical marvel, to say the least..

These thought are only personal observations from my experiences with these systems and not meant to be the rule... simply passed on info.

Tyler S · « **Reply #31 on:** June 17, 2016, 18:10:07 »

The simplest way to wire the switch would be on the passenger side near the CSV. There is already a keyed B+ wire for the radio and a grommet to run through the firewall.

There are a lot of creative ways to hide a momentary switch. On a previous vehicle of mine, I used a relay that was energized by grounding its coil through the cigarette lighter element. To start the car you would have to light up a smoke!

wwheeler · « **Reply #32 on:** June 18, 2016, 00:44:36 »

I am not super excited about having to add this switch, but I have tried everything I know to get the factory systems to work as designed. Worse than the added switch is when you are at a car show and your car takes several short cranks to fire up.

The CSV switch fixes that I hope.

Arthur was a bit before my first post in 2007, but his reputation is legendary. In fact I used his rear axle alignment diagram to make my own tool. Worked perfectly!

Concerning the drain from solenoids during starting on automatics: wouldn't the 3 way transmission solenoid be a big drain? With the pedal not depressed and engine cranking, the solenoid is at the low pressure position and drawing power to do so. If you depress the pedal, say half way, the solenoid release to the neutral position and no power draw. I am pretty sure depressing the pedal 1/2 way at cranking speed has very little effect on the fuel mixtures because of the governor in the injection pump. What do you think?

Tyler S · « **Reply #33 on:** June 18, 2016, 01:05:39 »

Wallace. Keep in mind the "factory systems" didn't always work as designed. Hence the dealer mod of adding the one second relay. It may be from Mercedes but its still a "mod", Added after the cars were already on the road. So dont beat yourself up too much about adding another starting aid.
If you want to hide it a bit you could intercept the wire on the drivers side at the relay on the load side terminal. Would be really easy for a black wire to be visibly lost under everything in situ there.

On a second note, replacing my starter with the updated higher speed unit really helped the overall "startability" of the car. I also replaced the battery cables at the same time so cant say the starter was 100% the result. But close to it. The faster that IP spins, the quicker you get delivery.

wwheeler · « **Reply #34 on:** June 18, 2016, 05:08:53 »

Good point on the new starter and I already have that as my original went kaput a while back. I have a 123 distributor and so I have already bypassed the resistor. Good thoughts. What do you think about starting with the pedal half way to de-energize the trans solenoid? It is a big one compared to the CSV solenoid and would seem to have more of an effect on starting voltage.

I just hooked up a temporary CSV bypass switch and it works. Now for the test tomorrow. I did jump off the aux. radio terminal block and is powered at the #1 key position. If this works, I'll go back and pretty it up a bit.

I wired the CSV solenoid so that there is no input from the thermo time switch. So for now it is a totally manual system. Do you see any harm in leaving the power wire from the TTS relay on the solenoid and simply adding the new switch wire to that? That way you would have the TTS control the CSV in situations below 95*F or so and then manual when you want it.

BTW, it is hovering around 90 to 95*F as I type in Dallas, so the CSV would never operate automatically in this weather. This is where I think the manual override will come in handy.

Fintail · « **Reply #35 on:** June 18, 2016, 08:28:04 »

Hi Mr Dalton

Is there a part number for the new ball spring type upgrade? Thank you in advance. Are the non return valves for a 230 pump smaller, requiring a different part number.

regards John

mbzse · « **Reply #36 on:** June 18, 2016, 11:37:56 »

Quote from: Fintail

.../... the new ball spring type upgrade.../..

Some info in this thread
http://www.sl113.org/forums/index.php?topic=7684.0
/Hans S

Tyler S · « **Reply #37 on:** June 18, 2016, 16:16:51 »

Quote

Do you see any harm in leaving the power wire from the TTS relay on the solenoid and simply adding the new switch wire to that?

Wallace, You should leave everything connected as be and ADD your switched power directly to the wire for the CSV solenoid. Either at the solenoid itself or at the other end of the wire near the relay, on the "load side". This way you are not energizing the relay when you push the button. The relay is there to handle the current that the CSV solenoid draws. The TTS Is not rated to handle this larger current draw, so the relay was used.
This way it will still be functional automatically at cooler temps. You will have to learn when the car will require the extra shot. Will take a bit of trial and error. Take notes of your temp gauge when the bypass is required.

Jonny B · « **Reply #38 on:** June 19, 2016, 15:29:16 »

There is also a detailed description of the parts and such in Pagoda Notes Volume 8 No 1, article by Richard Simonds.

ja17 · « **Reply #39 on:** June 20, 2016, 04:41:08 »

Now consider that the starter upgrade has the extra terminal which energizes during starting. It can be used for a ballast resistor by-pass for starting. It can also be used to eliminate the relay and wiring for the injection pump starting magnet. With cars that have the starting solenoid energize during all starting, the starter solenoid can be used in place of the original relay and wiring!

wwheeler · « **Reply #40 on:** June 22, 2016, 02:35:16 »

Unbelievable, unbelievable. That is all I have to say regarding the manual CSV switch. With the start solenoid disconnected, the CSV solenoid disconnected, I used a manual switch used to activate the CSV. I hadn't started the engine in three weeks and normally would take 2 or 3 cranks to fire up. I activated the fuel pump, gave the CSV switch two quick hits and cranked the engine. Wow! 1/2 second crank and the engine fired up and ran great.

First time in years that has happened.

I was so excited by that, I hooked the CSV power wire back up and simply added the new switch so that when cold, the CSV would activate as normal but then I could add fuel as needed. So then I tried to start when the engine was around 110*F. I did only one short manual burst and same result - 1/2 second crank and the engine fired up. Amazing! Btw, the hot starts are still quite good and I do not add any fuel for that. It seems that as Arthur said, firing the CSV before the engine cranks is quite helpful.

Over time, I will know when and how much fuel to add and will make this switch a permanent feature. The power for the switch came from the radio power take-off. In my case, the manual switch resolved my fuel issues during starting.

Tyler S · « **Reply #41 on:** June 29, 2016, 01:45:17 »

Wallace,
I have come up with what I think could be a solution to a functioning enrichment solenoid for our modded pumps with the newer ball style delivery valves. As we know the engine is over-fueled and floods out with the solenoid connected and starting the engine warm or hot. My idea involves removing the enrichment solenoid relay ground wire (pin 85) from the fender well mounting point and tying it into pin 85 of the cold start valve (csv) relay. This would allow the enrichment relay to only be energized when the engine is cold. Would effectively only be energized when the CSV relay is also energized. Would still help out during cold starts but would be disabled for warm or hot. I will do some testing and report back. If it works out I will start a new thread in the Research & Development section.

wwheeler · « **Reply #42 on:** June 29, 2016, 04:09:22 »

That sounds like a brilliant idea! I was on the verge of permanently mounting the manual CSV switch, but I think I will hold off. Yours could be the best of both worlds. No odd additional switches on the dash and is automatic. I understand what you are proposing and makes sense to me.

My solution over the years was to back off the start solenoid engagement so that it wouldn't enrich the pump as much. Hot starts kept getting better as I reduced the rod's length. But then the cold starting also began to degrade. I was OK with that because I would rather have a cold engine needing longer cranking times rather than a hot flooded engine that won't start.

I did measurements last month to determine how far the solenoid rod has to protrude in order to contact the rack. From that, I adjusted the rod back so there was no rack change with the solenoid connected. That is where the solenoid is today. I have kept detailed records so I know exactly where I started.

So if your plan works, I will go back to factory specs on the solenoid and see what happens. Thanks!

ja17 · « **Reply #43 on:** June 29, 2016, 06:12:11 »

The latest version injection pumps had no enrichment solenoids at all. Also no deceleration solenoid. Don't forget that there are four or five different versions of starting aids on these cars. The different types of components, their function and their quantities will vary between the types.

Pagoda_84 · « **Reply #44 on:** June 29, 2016, 11:00:33 »

I literally have the exact opposite problem.

My 280sl is really hard to start when it's cold. It takes a lot of cranking, splutters a bit and then when it eventually comes alive it runs really nicely.

When it's warm, it starts instantly, almost on the first turn.

The engine runs smoothly all the time but I do notice some black smoke on heavy throttle, it's particularly noticeable at night in the car behinds headlights. It looks like fuel smoke to me....

Do you think my car is running in cold start mode all the time or something? It seems to use a lot of fuel also.

Benz Dr. · « **Reply #45 on:** June 29, 2016, 13:15:37 »

Take the small air filter off on the warm up regulator ( WRD ) and see if any vacuum is present after the engine is at full operating temp. This often involves driving your car to get it fully warmed. If you have a small amount of vacuum it's not shutting off completely. If you have a lot of vacuum the slide valve is probably stuck open. Either condition will result in a rich mixture.

Tyler S · « **Reply #46 on:** June 29, 2016, 14:39:25 »

Joe, I forgot to mention that Wallace and I both have pumps that were modded/upgraded with ball type delivery valves from the old needle and seat. So this will pertain only to those who have the same upgrade. Will edit my post above.

Pinder · « **Reply #47 on:** July 05, 2016, 00:18:25 »

I just spend the last few hours wondering why when my car is hot it takes longer to start. at cold its starts in 1 sec

Charles 230SL · « **Reply #48 on:** July 22, 2016, 01:50:23 »

Wallace, you noted earlier in this string that you backed off the start solenoid engagement to avoid enriching the pump as much (during hot start..). Can the solenoid rod be accessed and adjusted by removing the solenoid or do you have to remove the pump? My car stumbles from over-fueling following a hot start and I suspect the solenoid is enriching the pump too much. If possible i'd prefer to adjust the solenoid rod rather than disconnect the solenoid.
thanks for any advice, Charles

wwheeler · « **Reply #49 on:** July 22, 2016, 15:32:35 »

You can test this easily by removing the wire to the solenoid if you hadn't done that already. When I did this, I instantly noticed a profound change in the hot starts. No pedal needed or extra cranks. Fires right up. The down side is when cold, may take a bit more time to get fuel to start. But as I have stated, I would rather do that than over fuel which takes a significant effort to get the engine started.

Yes, you can remove the solenoid (will need a new gasket that is NLA) and adjust the rod back. You might get lucky and can reuse the old gasket. For a new gasket, you can get a 60/70 shore A nitrile or neoprene sheet rubber material that is 1/32" thick from Mcmaster Carr. I find that most fiber gaskets are too hard to seal well. The old original was some special "soft" fiber gasket and couldn't tell you where to get it. Pacific Fuel may be able to supply some.

You use (2) 8mm wrenches because there is a cone nut and a lock nut. Yes, it just that easy. But I would take very close measurements of the rod length so you find your way back if needed.

I found that in the end, I had backed the solenoid off so much, it wasn't making contact with the rack. You can measure that as well with a depth micrometer when the solenoid is off. So I just disconnected it and saved electrical draw as per Dalton. Use a rag under the solenoid when it comes out to catch oil (not much comes out though).

Charles 230SL · « **Reply #50 on:** July 22, 2016, 17:43:40 »

thanks much Wallace,
I'll remove the solenoid as soon as I source material for the gasket. I'll trial-and-error the rod adjustments to reduce the initial over-fueling. thanks again, Charles

wwheeler · « **Reply #51 on:** July 22, 2016, 18:15:09 »

So I guess you discovered that with the solenoid disconnected, your hot starts were better?

The best gasket material is called diaphragm material and has a very thin layer of fabric in the middle of the rubber outer layers. It will still be 1/32" thick. Hard to find but maybe McMaster has it. The fabric will not allow the rubber to "squeeze" out when compressed.

From the Pacific Fuel rebuild, my solenoid rod measured 1.890" from the metal base to the top of the rounded nut when the rod is bottomed out. I discovered that a 1.750 rod dimension will not engage the rack. so it seems it may only move the rack about 1/8"? Seems too little but that is what I got and maybe not totally accurate. Yes, the rod stroke is much longer, but it has to depress the spring loaded lever before contacting the rack. Let me know what initial measurement you came up with.

Charles 230SL · « **Reply #52 on:** July 22, 2016, 18:59:23 »

yes, hot starts were better with the solenoid disconnected but I can tell that a 'slightly' richer start (but NOT as rich as with the solenoid connected) would be better.

I'll let you know what the initial rod measurement is once I remove the solenoid, and what the final measurement is following adjustment.

Incidentally, I've got an early R11 pump and all else has been sorted out (CSV jets spray correctly, 1 sec time switch and TTS are good).

Charles 230SL · « **Reply #53 on:** July 23, 2016, 13:32:26 »

I removed the solenoid but unfortunately, the rod appeared to have been adjusted (actually maladjusted) some time in the past so I can't attest to what it was leaving the factory.

The rod measured 1^3/32 (1.09375) from the metal base to the top of the cone nut, which was over-fueling during hot start. I adjusted the rod back to 1^1/32
(a reduction of only 1/16 inch) which is where it is today. The hot start has improved - but it could still be better.

I'll leave it as is for a couple days before adjusting the rod back a little further - it doesn't take much!

wwheeler · « **Reply #54 on:** July 24, 2016, 19:13:34 »

My pump is a later versions and very well could be a different rod adjustment. The good news is that you see improvement. You are correct, doesn't take much to change quite a bit.

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