Author Topic: Idle speed solenoid (Read 24091 times)

rwaw · « **on:** June 23, 2003, 13:41:49 »

Finally seem to be getting to the bottom of rough idle/misfiring/rich running.
All checked and adjusted/renewed: points/plugs/leads/timing/dwell angle/accelerator linkage etc.
Result: no more pinking whatsoever, massive improvement in performance/fuel consumption.
Only problem now: tendency to stall when idling in "D" eg at traffic lights, with revs at just over 500/min.
When idling in "P" revs fine at 700-800/min.
Problem seems to be non-working idle speed solenoid (part of accelerator linkage on right hand side of engine).

Does all this make sense to the experts and does a price of £ 240 sound right for this part ??

Thanks again !

Cees Klumper · « **Reply #1 on:** June 23, 2003, 13:51:35 »

Yes it does. And, yes, the cost of a new one is really steep. But, before you go that route: check whether your current one works (with the engine running, put the car in gear, obviously applying your foot to the brake). If it attempts to move the linkage, it is working but encountering too much resistance. In this case, try cleaning and lubricating all the linkages and check whether the solenoid is allowed to move properly against the little lever it pushes against, that it is not binding.
If the solenoid does not budge, hook up a test lamp, to see whether the wiring etc may be at fault.
These solenoids are difficult to service, since they cannot be taken apart easily. You have to basically drill it open and, after done servicing (I have a document which Bob from Brisbane sent me some time ago on this procedure), weld it closed again.
I replaced mine one off an old spare engine I bought. I have also seen them offered for something like $25 at classic car fairs. You can get one at a breaker's yard for something like that or less. Chances are it will work fine.
I am pretty sure on many (automatic or airconditioned) Pagoda's this solenoid does not work properly. When you put your car in gear and/or turn on the A/C, the idle should not budge. That's how it is now on mine and I can tell you that, after a few years of experiencing what you describe, it sure is nice!

rwaw · « **Reply #2 on:** June 23, 2003, 14:07:02 »

Cees,

Thanks a lot for the speedy reply which sounds encouraging (or:confirms my worst fear !);if I do decide to install a new solenoid is it then a straightforward DIY job ?
Thanks again.

pembash · « **Reply #3 on:** June 23, 2003, 14:50:50 »

Cees, Thanks for your input. My 280SL idles fine and steady at approx.900r.p.m. in Park mode but drops to 450-500rpm fluctuating when in D position but thank God it does not stall atleast as yet!
My car is parked in a garage presently but should I be looking for the idle solenoid in the meantime. I am also interested to acqire an owner's manual to help me service and maintain my car.
Your advice please!
Cheers
Bob

ja17 · « **Reply #4 on:** June 23, 2003, 20:46:48 »

Try adjusting the large slotted air screw with the car in drive and warmed up. Have someone hold the brake on while doing this.
A lot of these cars do just fine without the solenoid.

Joe Alexander
Blacklick, Ohio

hands_aus · « **Reply #5 on:** June 24, 2003, 04:22:48 »

Make sure there is absolutely no play in your linkage rod ends. Remove the rods, clean the ends and re-grease them. Adjust the rods (without increasing the rod length) until the play has gone.
Replace them if necessary.
If you plan to swap your solenoid they just unbolt, the cable is the same.
The solenoid works electrically through contacts of the idle switch on the inlet manifold. If it is not adjusted correctly the constant speed solenoid will not work.
Test your system first, it might just be the idle switch adjustment.
You could manually test the difference in revs by having the car run at idle and pushing the solenoid plunger. The revs should increase marginally.
If no increase is detected then you might need to adjust the length of the screw on the end of the plunger, or adjust the linkages.
If your auto transmission is changing smoothly both up and slowing down then there is a fair bet your idle switch is working properly.
If you experience hard clunking when slowing down then your idle switch most likely will not be working properly.

Bob(Brisbane,Australia)

rwaw · « **Reply #6 on:** June 24, 2003, 13:49:08 »

Bob,

Do I understand you correctly when you imply that it is possible to move the idle speed solenoid's plunger by hand ?
'Cause mine seems frozen solid.
Accelerator linkage etc seems absolutely fine as do up/downshifts on the auto' box.
also power seems to be going OK both on solenoid and on switch on left hand side gearbox.
Raoul.

Cees Klumper · « **Reply #7 on:** June 24, 2003, 14:36:31 »

If the solenoid is frozen, you might try to free it up with some penetrating fluid. It should be free and easily movable by hand.
The owner's manual is still available from the Classic Center. Also, there is a CD-rom available from the classic center that has the parts manual, the owner's manual AND the workshop manual ("BBB" or Big Blue Book) on it, in .pdf format, that you can print from. And there is always the Haynes manual and other workshop manuals that can be very useful to guide you through most of the maintenance and repairs jobs.

hands_aus · « **Reply #8 on:** June 25, 2003, 01:00:09 »

Hey Raoul,
Yep the plunger should move by hand. With the engine OFF, hold the linkage rod so as to have the venturi valve open. You should now be able to move the plunger fully.

Bob(Brisbane,Australia)

Naj ✝︎ · « **Reply #9 on:** June 25, 2003, 05:16:14 »

Raoul,
Whereabouts in the UK are you?
Were you at the MB club SL gathering at Beaulieu?
Sorry guys - off topic!
naj

naj
'Kloines Scheisserle'
65 230SL
68 280SL

n/a · « **Reply #10 on:** June 25, 2003, 05:51:40 »

Well....
It seems I have similar problem.
But it only starts when the car is warm and when I am in traffic...
for the first time last night, the car kept on stalling while I was parking in it in the garage. It also started stalling sometimes even if I was in N position.

Could it be that I have the same problem as our UK friend???
(does any one know the word for solenoid in French...??

merci!!

Fabrice

Silver 1971 280 SL
New York City

n/a · « **Reply #11 on:** June 25, 2003, 07:56:09 »

Le' Solenoid?

Rudy
Los Angeles
1971 280 SL

graphic66 · « **Reply #12 on:** June 25, 2003, 08:53:56 »

When checking my idle speed solenoid I found in my transmission manual that the solenoid is switched at the transmission by oil pressure on 2 switches that sense when the car is in forward or reverse. The solenoid has positive power supplied at all times by fuse #5 and the negative is the switched side. The negative is actuated at the transmission.

To quote the Automatic DB Transmission - Group 27 manual, When placing the selector lever in one of the driving positions, pressure oil is fed either to the brake band piston of brake band B1 or to brake band B3. This provides also oil pressure for the oil pressure switch forward [connected to brake band B1], or shifting end to the oil pressure switch reverse [ connected to brake band B3] to establish contact.In this manor the solenoid is energized and operates the regulating lever over the regulating linkage the throttle flap in the throttle duct is opened just that much that the idling speed remains constant.

This in plain English means to check your switches the car must be running and in gear, forward and reverse and a test light must be at the solenoid, on my 230 Sl the right terminal is positive and the left terminal is the switched negative from the transmission. You can check the solenoid by unhooking the feed wires and jumping power to it from a 12 volt source. However to check your wiring system, the car must be running and in gear and you must check both forward and reverse. Remember the line that is switched is the negative from pressure switches mounted on your automatic transmission.

Do not put the car in gear and get out to check as the car will leave without you. Chock your wheels put on the parking brake and get a volunteer to sit in the car so you dont get run over.

My question is how do you hook your air conditioner to this solenoid to switch the neutral. I believe you must use a relay to switch to ground when the AC is activated. Does any one know if this is so, or has some clever German engineer come up with something simpler? Thank you for all of your help, I read all posts and my car just keeps getting better and better.

n/a · « **Reply #13 on:** June 25, 2003, 09:11:12 »

Rudy, you crack me up!!!

and a car is le "car" in French???

Silver 1971 280 SL
New York City

rwaw · « **Reply #14 on:** June 25, 2003, 10:55:50 »

Naj,

Am on eastcoast, North Yorkshire; never been to Beaulieu.
Hoping to get a new solenoid tomorrow and fit it, will let you know.
Raoul.

Cees Klumper · « **Reply #15 on:** June 25, 2003, 16:03:50 »

Fabrice - "le solenoid" does not influence the idling when the car is in neutral in any way. The car should not be stalling like that, and certainly not if nothing has been done to the tuning of it recently. Maybe you have a fuel starvation problem e.g. through a clogged fuel line, filter, gas cap etc etc.

n/a · « **Reply #16 on:** June 25, 2003, 16:11:13 »

ok. I am not a great mechanic....yet!!
How come it has been happening when the car is warm?
In any case, it looks like I need to bring it to the doctor!!

thank you for your headsup, I will keep you posted, I will probably use it again tonight, weather is finnally so nice in New york, I would risk being sued by the club for not using it!!!!

Silver 1971 280 SL
New York City

Cees Klumper · « **Reply #17 on:** June 25, 2003, 16:19:16 »

Once the engine gets warm, a fuel enrichment system cuts out and the fuel mixture gets leaner. So maybe your engine does not receive sufficient fuel once this happens. Also - if the engine gets very warm in traffic, there could be a "vapor lock" (air in the fuel line system) that prevents fuel from getting to the engine, a problem you will never have with a cold engine. A knowledgeable mechanic ought to be able to diagnose all of this for you. There is a basic test of the fuel flow (quantity per minute) that can be performed for example, if that is indeed a likely cause. But I am a "shade tree mechanic" myself, so there's probably many other possibilities that could explain your issue. I just don't think it's the solenoid (looks like a French word actually)

Bon chance,

Benz Dr. · « **Reply #18 on:** June 25, 2003, 17:59:38 »

Well, here I am. I'm sure you all missed me. hehehehe

So, we have a bit of an idle speed problem , eh? Seen this before a few times. All the advice is good so far and the solenoid must be free to move easily. Put a test light on it and see if you have power coming above idle speed. No power = no movement.
Also to really test the whole fuel volume delivery, do it at the fuel tank. Undo the hose from the return line and clamp the hose shut first. Turn on the fuel pump for 15 seconds and you should have close to a liter if the system is working right.
The test in the engine bay won't tell you if there's a restriction in the return line - a more common problem than you'd ever think.
Dan c

Daniel G Caron

rwmastel · « **Reply #19 on:** June 25, 2003, 21:19:21 »

Welcome back, Dan! We did miss you.

Rodd
1966 230SL Euro
1994 E420

n/a · « **Reply #20 on:** June 26, 2003, 06:45:46 »

Download Attachment:

engine280closer.jpg
60.97 KB

Good morning!!!

I discovered I have an unconnected wire. It is tied up to the set of wires that are plugged to the engine bloc, on the right of the last spark plug (n. 6) see picture. 3 sets of wires go together...the one unplugged or unconnected has an round ending with a hole: it needs to be fixed by a nut....
WHERE DO I FIX IT BACK?

I am not a good mechanic and still learning, so pardon my ignorance...

Many thanks!
Fabrice

Silver 1971 280 SL
New York City

n/a · « **Reply #21 on:** June 26, 2003, 07:45:25 »

Fabrice, this is off topic but that is the cleanest engine compartment I have ever seen!

Rudy
Los Angeles
1971 280 SL

n/a · « **Reply #22 on:** June 26, 2003, 08:05:54 »

Rudy..

unfortunately it is not mine....but it is the only picture I found that could illustrate what I am talking about!!!!
This is from a concours level car sold recently for over 50k......

Silver 1971 280 SL
New York City

rwaw · « **Reply #23 on:** June 29, 2003, 13:14:14 »

Just an update;
Have fitted the "new" idle speed solenoid (it looks as old as the box in came in!)and certainly no more drop in revs when shifting from "P" to "D" etc.

Only remaining problem now is misfiring/hesitating when pulling away from idle up to +/- 1500 revs; happens only once engine has warmed up;any suggestions very welcome as usual

Cees Klumper · « **Reply #24 on:** June 29, 2003, 15:40:48 »

my 2 cents: (double) check the wires' ('leads'?) and wire ends' resistance first and then the rest of the circuit - ballast, resistor etc. I had this exact problem last year, misfiring once engine was warm, until revs got up high enough, then smooth running. It turned out to be a spark plug wire which had been replaced only 1-2 years prior.

Naj ✝︎ · « **Reply #25 on:** June 30, 2003, 02:24:02 »

Raoul,
Your cold start circuit may not be shutting off completely, thus allowing a bit of air thru and leaning out the mixture.
Its hard to tell if some air is still going thru the small air filter on the FI pump.
You can remove the filter and check if any air is still going thru with the engine warmed up. If so you'll need a new thermostat on the FI pump.

naj
'Kloines Scheisserle'
65 230SL
68 280SL

rwaw · « **Reply #26 on:** July 04, 2003, 14:07:20 »

Cees,

Showing my technical/electrical ignorance here but how do I check the HT-leads' resistance because that sounds the logical next step to me ?
Thanks,

Cees Klumper · « **Reply #27 on:** July 05, 2003, 11:39:34 »

Never did this myself, but I understand one uses an ohm-meter to check the resistance of the spark plug wires. Here's earlier posts on this topic by three experts:

Joe Alexander: The original spark plug wires are solid copper and very rarely go bad. However the screw-on spark plug ends have built in resistance and these do go bad. Chances are if you replace the whole set, you will never get another set that looks as good or lasts as long as the originals. I advise that you check each wire and replace the bad ends. Finding original ends may be a challenge, but I am sure some listers have spares. Make sure you still have the original solid copper wire and that it has not been replaced by those troublesome carbon resistance wires. If you do have some damaged plug wires, original solid copper plug wire is still available from some motorcycle and farm tractor sources. JC Whitney used to sell it by the roll. I usually check all my plug wires and ends with an ohmeter during a standard tune-up. Mercedes used several versions of wire ends during the 113 years. Same vintage Mercedes sedans used the same in many instances and are good parts donors! The coil wire was also solid copper originally, and had a screw-on resistance end.

Pete Lesler: the early, pre-transistorized ignition cars already had bakelite resistor terminals installed rated at 1K ohms, the steel resistor ends starting with the transistorized ignition was rated at 5K ohms. Don’t use resistance plugs or silicon resistance impregnated wire. Use of one or both will materially reduce the intensity of the spark. You may be forced to make up your own plug wires with solid copper core spark plug cable. I have used Packard 440 cable in the past. The terminations screw into the copper core and the ends that plug into your distributor are available as a kit as is the cable from almost any good auto parts supplier.

Dan Caron: be careful when buying ignition wires. The 230 SL uses wires with bakelite ends. K&K's wires are correct and is what I use and sell. Some are made by Beru but they are still correct. Stay away from any wires that have carbon core in them. All wires should have the 1K ohm spark plug ends and the best ones don't have any resistors at the distributor cap. I prefer the 230 SL wires over almost anything else. I also use the 26KV coil with a 1.8 ohm balast resistor. Very good set up. What you want is really low impedance wires so all the spark can get to the plugs. The standard black coil used on some early cars is only 13,000 volts , the blue ones are around 20,000 volts and the hottest standard coil is rated at 26,000 volts. This is the one I convert to. You need to use the 1.8 ohm balast or twice what the black coil uses which is .9. Total package with Bosch wires runs about $160 for all the parts you need.

p.s. - SL Tech sells correct wire sets.

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Author Topic: Idle speed solenoid (Read 24091 times)

rwaw

rwaw

pembash

rwaw

n/a

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graphic66

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rwaw

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rwaw

rwaw