Pagoda SL Group
W113 Pagoda SL Group => Drive train, fuel, suspension, steering & brakes => Topic started by: col320ce on March 03, 2021, 08:44:06
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Looking for advice on the warm start issue with the 250SE (same engine and set-up as the SL so I figured it was more useful here).
Basically it won't start at all when hot no matter how hard I try (yes, tried flooring or half accelerator pedal, 10 seconds fuel pump before starting etc). However it WILL start if I disconnect the relay to the injection pump fuel enrichment solenoid. Cold start is fine.
Tests I have done:
All relays cleaned and work fine on the bench. Has the 2 rectangular relays and the cylindrical "1 second" relay.
both relays #87 female to positive - activates both FIP solenoid and CSV solenoids individually (ie I can hear it click)
Test light on pin #86 to ground - FIP solenoid - light stays on continuously. CSV stays on 1sec (warm) or longer depending on if warm or not.
As the car starts reasonably well when warm if I disconnect the FIP solenoid relay, then I assume that there is too much petrol being released BUT is it possible that the FIP solenoid could be wired with the + and - reversed? The wire connection closest to the engine is negative/ground brown wire.
Thanks for any help or ideas on trouble shooting this
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Assuming the SE is setup the same as an SL:
The fuel enrichment solenoid always engages when you turn the key to start whether hot or cold. It pushes the rack on the FIP forward enriching the pump only when cranking.
In my experience 🤪 when the engine is cold the rack is already pushed forward due to the WRD not in warm running mode so the fuel enrichment solenoid (when activated) has no effect. I have tested this theory on several cars by inserting the 5mm bolt in the front FIP (rack access) and activated the fuel enrichment solenoid. I have never seen any movement of the rack bolt when engine is cold.
Like you stated it seems to be getting too much fuel when trying to start hot. Have you tried disconnecting the linkage and have someone slightly crack open the throttle body intake while starting the car?
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That's a great idea... No I haven't tried it but that would help prove that it was too rich... As it's a rhd car I think I can do it myself... I'll report back tomorrow.
I can probably use the same technique with the 5mm bolt but I'm not sure where it is. If it moves the bolt when warm it means that the solenoid is wired correctly?
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There are some pictures of the bolt in the access hole in some posts. I just couldn’t find them now. Do some searching.
I have attached a picture of a 280sl pump. The access hole for the rack is circled. It’s usually covered with a black plastic/rubber cap. Just insert a 40mm? X 5mm bolt. Once done you can push/pull and feel the rack move. I think early pumps have a metal cap that has to be removed 🤷♂️
When the car is warm the bolt should move forward when starting. I usually put a reference mark on the bolt so I can see movement better. Movement is very small. I also lightly place my finger on the bolt and activate the solenoid manually and you should feel the movement.
When the car is cold and I activate the solenoid I don’t see or feel any movement. You should feel the click of the solenoid activating though.
Regarding the solenoid itself, it is adjustable. I have examined 3 different pumps. 2 of them had the same solenoid pin lengths. The 3rd pump was different but was known to be messed with. I’m assuming someone already tried to fix hot/cold starts🤷♂️ You can come back to that when all else fails.
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Sounds like you could simply disconnect the enrichment solenoid to solve the problem. Although it would be better to check whether the car is running too rich all the time, and remediate that.
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I agree with Cees that your car could be running so rich that solenoid could be just putting it over the edge during starting. I just like to verify that everything is working properly and move on.
Here is a thread that has pictures. There was a reference that the bolt was 4mm but I think it was later determined it is supposed to be 5mm.
https://www.sl113.org/forums/index.php?topic=28596.0
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I've seen plenty of cars that are in permanent cold start so always running rich. Have you checked the Co when hot?
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Col,
If it makes you feel better, my 280SE does the same thing when hot. I too tried to adjust the length of the solenoid rod to limit how much it richened the mixture when hot. It is simple, with the starting solenoid disconnected, the engine starts perfectly when hot. Connected, it floods every time. I gave up and just left it disconnected. What I found though is that cold starting took longer with it disconnected. So I added the cabin CSV switch and I give it a shot before cranking. Now all starts are just about prefect every time.
I even tried the "hot start" fix from Mercedes and that only made it worse.
BTW, my WRD shuts off, CSV does not leak, spark plugs look just fine and the engine runs just fine. So I could never figure it out and chalked it up to 50+ years of wear.
Wallace
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Thanks everyone... I've got a number of things to test out today. It's been hard to tune because I couldn't restart it when hot so I'll check this.
Before doing this I'll add air as per mrfatboys suggestion at hot start to prove it's too rich.
I'll check the CO too.
BTW... Wrd is working fine. It wasn't when I got the car so it was tuned to run with the wrd still in cold start mode.
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Update...
I've leaned the fip right off (almost all the way) and I'm getting about 1000 rpm. Car is fully warm and no air sucking in on the fip wrd.
I've adjusted idle in gear to about 700.
So it's still a idling in neutral a little too high but I'll re tune it after a few more longer runs to see how it's settling.
So far it's now starting with the fip solenoid hooked up so I'm almost there.
There was also a problem with the linkages... I did the split linkage test and simply disconnecting the links was changing idle. Thought I had it perfect to start off with but it doesn't take much for these to be out.
Other weird thing is that the fip thumb adjustment is engaging in the slot but not clicking although it is moving (it does on my other car).
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As you move the thumb screw out, eventually it will move past the little springs that cause the "clicking". This is a good sign that you are almost too far. If all your speed ranges seem to be rich, you can also adjust the rack leaner or remove a thin shim under the baro compensator. Either one of these will lean the mixture at all speed ranges. You will probably have to go back and re-adjust the thumb screw inward then to hit the correct mixture on the idle. Your clicking should return once the screw is turned in a bit. Of coarse make sure that your tuning, engine linkages, fuel pressure, and your cold start valve is not leaking before tampering with the IP.
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Thanks Joe
Just as you said ... I screwed the idle adjustment in and the clicks started! I have the 2 thick washers and 2 thin... (One looks non original) under the BC making it 4.17 or 4.77mm with/without the non original one. Average pressure here is 1020mb (765mmHg). Without test equipment (that is rare as hens teeth) am I correct in saying that at this pressure the BC should depress the bit it acts on in the fip by 3mm (resting preload) and I should adjust the washer/shims under the BC to keep it at 3mm? (this would equal about 4.7mm of shims)
Then I want to adjust the rack if its still required ... does screwing all the FIP adjustment screws in make them richer and screwing out leaner (ie same direction as the thumbscrew?)
Thanks again
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If the BC goes bad a lean situation is usually the result. Since your car seems to be rich, you can probably rule out the BC. Try doing a split linkage test at higher rpms to see if your engine is rich at all speeds. Do it after full warm up.
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Thanks again Joe...
I'm starting from scratch and have replaced all the linkage connections. The return spring in the fip is a little sluggish and I think this may be where the richness is coming from. Looks like a PITA to replace!
How is the vertical rod adjusted? I think this is related to gear changing in the autos? I'm pretty sure it does not affect setting idle.
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Are you referring to the vertical linkage rod?
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Thanks again Joe...
I'm starting from scratch and have replaced all the linkage connections. The return spring in the fip is a little sluggish and I think this may be where the richness is coming from. Looks like a PITA to replace!
How is the vertical rod adjusted? I think this is related to gear changing in the autos? I'm pretty sure it does not affect setting idle.
This spring feels sluggish - that is the way it is. it is not a return spring for linkage, there are two other springs responsible for linkage return.
You may want not to touch this spring at FIP! Nor the shaft it is on. Just adjust the length of the rod.
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Yes Joe it's the vertical linkage rod that I haven't worked out how to adjust.
Thanks Pawel for this info... I assumed the fip spring was supposed to be strong enough to act as a return spring. I've put a stronger spring on the venturi and it now snaps back well. All the linkage ends are new now and greased. I'll order the correct spring as I don't want there to be too much tension there as I think things will wear out quicker with too much tension.
I'm hoping it will be a simple matter of tuning it now
Thanks again for helping me work through this
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Ok, the socket ends of the linkage rod screw on. One is a right hand thread and one is a left hand thread. There should be an 8MM nut which locks the socket end from moving on it's own. Loosen both ends and twist the rod to change the length.
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Is the correct length though in a neutral position? At the moment the vertical linkage is 15mm off neutral position.
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The FIP arm/lever has to rest against its stop. Then you take the 10mm tube through the hole in the linkage support and if you do not have this hole (you have 230SL), you measure the FIP rod to have 233mm from center of socket to center of socket. Clip this rod to FIP arm ball stud and linkage cross-shaft ball stud. This will now determine the length of the throttle rod - from the other end of linkage cross shaft to throttle ball stud on throttle arm while throttle arm is resting on its stop position.
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I understand the the way to set up the fip and venturi linkages. My 2 problems now are that even with the stronger spring the fip does not return fully all the time and I'm tempted to adjust its stop as it's only half a mm. I know it's factory set but I also don't know if it's been fiddled with. This part is causing the variation in idle as it sometimes goes all the way but mostly doesn't. I've tried lengthening the venturi linkage the "force" it home but it doesn't work.
The rod I don't know how to do is the one that runs vertically from the constant speed solenoid to the rhs of the engine. Should this be centered over the balls as well?
Thanks again... I'm definitely getting closer
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Have you checked the linkage where it attaches to the firewall? There is another spring there.
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Which of the following is happening:
1. The whole linkage is not going back to stop. When you force it to go back - it does, otherwise the springs are not able to move it back to stop - is that the case?
2. You disconnect the FIP-shaft rod from the shaft ball socket, pull the rod up and still the FIP arm does not come to stop position?
I think these are two very different conditions. I do not know if you can do anything about 2.
If it is 1 - there are number of things to check, starting from checking both return springs (one at the throttle, one at the firewall) and if it does not help - trying to determine what holds the linkage from coming back. There is a number of points to check, including the shaft that goes on the firewall from gas pedal to linkage arm on the passenger side. It could be constant speed solenoid, which for the duration of adjustments should be unbolted and moved aside. All other elements of the linkage such as dash pots, etc., also should be put aside if you have them. It is about determining what is blocking the linkage. Trying to alter anything in FIP shaft - I would not do it.
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Update...
The idle is OK at the moment but there are still a few problems.
BTW the fip linkage is now correctly stopping on the stopper.
When warm the idle is mostly at 800 in neutral and 800 in gear... I know this is a little high but the idle fluctuates when driving and sometimes goes as low as 500 and sometimes stalls. What are the common reasons for this?
BTW split linkage test is OK
Also when cold there is a low idle and it wants to stall (and it regularly does stall). I did the split linkage test at startup and it was lean so I added a coke can thickness oval shim under the wrd a now it's a little rich on split linkage test. What are the ways to increase idle when cold... The only fuel adjustment is the shims and there's minimal air adjustment with the round shims. Are there any other cold adjustments that make sense?
Thanks again...
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You are getting there👍 Have you measured the CO at warm idle? When dialing the mixture in it really helps to know the numbers.
Once you are happy with the warm idle you can adjust the WRD shims to enrich/lean the FIP during warm up like you have. Again, knowing CO numberS really helps. There is a graph of how the CO tracks over time in the tech manual for you to compare to.
The other adjustment is the round shims in the WRD that adjust at what temperature the WRD turns off. Maybe a PO messed with shims and they could be adjusted wrong.
With all that said, automatics have more complexity than manuals with the linkages that can affect idle. Somebody with more experience hopefully will chime in. 😃
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I'll measure the CO on the weekend.
When the car slows and drops a gear the revs drop to about 600 at the gear change... Is this normal or possibly the reason I am stalling occasionally?
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This is automatic, right? Do you have constant speed solenoid working properly?
But perhaps before addressing that, finish idle settings with CO checks. Then move to the issue of stalling with gear in (I understand this is what you describe perhaps).
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I'll measure the CO on the weekend.
When the car slows and drops a gear the revs drop to about 600 at the gear change... Is this normal or possibly the reason I am stalling occasionally?
Col, what do you use as a CO tester? I am in the market for a home use model.
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It is the automatic... And I think the constant speed solenoid is close to adjustment as I need to change it slightly each time otherwise the car does not drive. I think part of my problem are these linkages around the css.
I also think the power steering part of the css needs adjustment too but I think this will be the last of the warm idle things to set up.
I've got a small gunson meter and an 80s bosch unit that is massive. I haven't compared together but will do it on the weekend. I'll take some photos of the units for you.
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Tuned the car to 4%CO when warm which is richer than I had it.
I used the gunson as my bosch is a massive compactest MOT unit and the pagodas engine was in the way so the sensor couldn't reach the exhaust.
Set to just over 800rpm
In gear css set to 800 rpm as well (I realise it should be a tad lower)
Now for the warm up... It's still stalling so I was going to check the CO levels at start up... But couldn't find them... Anyone know what they are or do I just do the split linkage test to assess lean/rich.
I also couldn't find the CO levels at say 2000 and 3500 rpm... Does anyone know those?
Thanks again for everyone's help
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Have you looked in the tech manual?
https://www.sl113.org/wiki/Fuel/Injection
Play around with F.I.P.i. A lot of the info you are looking for is in there also.
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Thanks MrFB
That is excellent.
I ended up loosening the screws on the wrd where the oval shims are and as it is spring loaded backed out the screws until it idled OK. This was a long way and ended up making a 1mm shim.
My concern is that there are a few adjustments that are so out of 'normal' that something else is a wrong.
I still have the fip start solenoid disconnected otherwise it floods the engine.
I'll test it all again tomorrow when it's properly cooled down.
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Can anyone tell me if the ip lever is pushed but the thermostat (indirectly) as soon as it moves? Or is there a distance it travels before it changes to fuel setting?
I think my round washers are too thick and is the reason the oval washer I required needed to be so thick. Does anyone know the standard thickness used of the round washers? I think I'll start with this thickness (it's a PITA to change them so I want to get it right first time if possible).
Then I'll sort the oval washers...
Thanks again everyone
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When the thermostat pin moves it directly affects the rack. Take off the FIP air filter and use a mirror to look inside the hole. When at operating temperature you can see the air slide completely closed the airway. When cold the air slide is up and out of the way. Using the mirror you can watch the air slide piston move to its final position during warm up.
I can’t remember the round shim thickness. Info might be in tech manual.
Here are some more notes.
Upper Stage WRD
Removing round shims adds air and fuel only during cold start/warm up
Adding round shims removes air and fuel only during cold start/warm up
Adding round shims does push the piston and pin assembly down and reduces the time it is open and the fuel. But it also reduces the air as well. Look close at the WRD housing where the air comes in. You will find a stepped opening comprised of three rectangular shapes. As the piston moves from the top down, the size of the opening decreases and therefore less air. So as the piston is dropping, you have less fuel but also less air.
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Col,
I went through many gyrations of shimming the air valve with round shims and documented what I did. On my '68 280 engine, I found that the minimum shim thickness is around.030". That was when the air valve just barely closed when warm. Any less that, you would feel air sucking in when the engine was hot. I have .052" worth of round shims in there now and am happy with it. These are just approximations and will be slightly different on yours. But gives you a starting point. There is a specific engine temp when the air valve should shut off. If I remember correctly, it is something like 165 to 170*F.
The oval shim and the round shim do two totally different things and are not really related. The round shims as mrfatboy stated, change the temperature when the air valve shuts. The oval shims change the fuel mixture during the entire warm up process or when the WRD is active. The engine needs a certain amount of enrichment when it is cold and reduces as it warms. If you set the air valve to go off at the specified temperature it should also have the correct amount of enrichment during the warm up process.
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That was when the air valve just barely closed when warm. Any less that, you would feel air sucking in when the engine was hot.
Don't get too hung up on whether the air valve fully closes or not; it does exactly the same as the idle air screw so a little bleed can be compensated for at the idle air screw.
The main thing is that you should see/hear a large change in the volume of air as the coolant temp rises.
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I checked the round shims... There was 1.5mm there but they were all ones I made. I've now got 0.6mm in there and I've removed the 1mm oval shim I added the other day. It seems to start OK now but it's been raining so I haven't taken it out for a spin or got it fully warm.
My air was shutting off 100% before so I should be able to get this to shut off at the right temp.
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I get what Stick is saying and that is correct. Not a big deal. Being that the air is being drawn in through this tiny air filter though, I wanted to minimize the amount of air so not to prematurely clog the filter. Plus that would also indicate that the pump could be ever so slightly richer. Mine still does have the smallest amount of air being sucked in and probably due to wear between the air valve and the cylinder.
I think as long as the WRD is functioning as it should and you shim it so that it shuts off at the specified temperature, the rest follows suit. The main reason to check the air draw is to determine if your air valve is stuck in the open position.