stop lever stopping my car from starting? - PeachParts Mercedes-Benz Forum

WANT '71 280SEL · #1 02-20-2005, 12:30 AM

Last Sunday I completed my glow plugs and delivery seal job. I thought it went well, but the car now takes longer to start. The glow light comes on as it should, and I've pulled the purple striped wire out of the harness so I have the afterglow setup. 3 times since I've done the procedure, the car wouildn't start. Sometimes it would almost cath, or it would run for about 5 seconds at 300 rpms before it would stall. To fix this, I popped the hood and saw the stop lever was down to the point it was past the top of the delivery valves. So I pushed it back up to the normal position and it started right up! Well, I picked my g/f up (the car was then turned off), then we went to the movie, started fine leaving her house and the theater. Since the movie was sold out we went to a rental place and when we came out the car wouldn't start. Popped the hood, and the stop lever was down again, what gives? I have to take this car to Colombus the first weekend of March and I don't want to have to worry about potential problems.

Thanks
David

Johnhef · #2 02-20-2005, 12:56 AM

pop off as many throttle linkage ball sockets as you can get to and lube them up! check to make sure none of them are bent and hanging up on any of the brackets.

WANT '71 280SEL · #3 02-20-2005, 08:51 AM

I should have said something in the original post, but I am speaking about my 300SDL. The stop lever on it is directly connected to the shut-off valve so I fail to see how throttle linkage lubricity could affect it.

Thanks
David

FineOlBenz · #4 02-20-2005, 08:59 AM

I could see how the vacuum to the shut off valve may not be releasing when the key is turned on though

Jim H · #5 02-20-2005, 09:15 AM

If I remember, my Stop level drops when the engine is shut off and pumps right back up on its own when started. I played with it a few times, pressing down when it was running, but just to idle down lower. When I let go, the rpm pick up and the lever rises. At some point, the rpm continue drop even though I stop pressing, the engine stops and the lever drops all the way.

I'm going to guess that your Stop lever is not the cause, but an effect, like there is not enough pressure building up in the IP. Since you just did delivery seals, are you sure all are back in correctly, springs 'n things, and the seals are holding?

This is only a guess.

Someone else here should know more about what moves the Stop lever, and what the lever moves...

Best Regards,
Jim

WANT '71 280SEL · #6 02-20-2005, 08:38 PM

It was my understanding that if I didn't do the delivery valves correctly that it would run very poorly and knock like crazy. It sometimes has a slight knock, but it's always been like this. In the past, with the car off my stop lever would always be fully up. Like I said, when the car doesn't start, I just raise the lever and it starts right up. Also, in the mornings, the stop lever will be all the way up and it will take 2 cycles of cranking to get the car to finally start. It used to always start immediately bun run poorly when it only had 5 of 6 GP's working! Tomorrow I'm going to try and put a wire on the lever to hold it all the way up and see what happens. It's raining now so it will have to wait.

Thanks
David

Jim H · #7 02-20-2005, 08:57 PM

Well, it's a puzzle for sure.

I can't help thinking that the last thing you did was seals on the IP, and somehow that's important.

Um, you didn't disconnect the electric plug on the rear of the IP, the one that powers the idle speed positioner, did you? If that's disconnected, you're stuck with the low mechanical idle, 500rpm or lower, depending on where it is set. If so, it may not advance the fuel rack enough to start!

Good Luck
Jim

#8 02-20-2005, 09:48 PM

Just wondering, what brand of GP did you use?
My 300SD came with Autolites...brand new...not even 10 hours on the engine since they were changed and 4 of them were bad.

Just a thought/comment

WANT '71 280SEL · #9 02-20-2005, 10:49 PM

Brandon, I installed Bosch GP's from Autozone. I got them there since they were the cheapest I could find.

Jim H, No, I didn't unplug that on the back of the IP. Once the car is started it runs fine. If it's cold it smokes and skips a little bit naturally, but nothing too far out of the norm. It's just that, let's say it's 40F and I go out to start the car. I'll crank it for maybe 20 seconds, wait 30 then crank for about 15 before it will start. That is a cold start that it will do that. The stop lever usually does its drop after only setting anywhere from 10 minutes to 4 hours.

Thanks
David

TonyFromWestOz · #10 02-21-2005, 08:58 AM

I did a quick check on my 300D last night.
I used my Mityvac to check out my vacuum shutoff valve. I can pull a vacuum and the engine shuts down. It will hold the vacuum and not allow the STOP lever to return to the UP position until the vacum is released.

I then reconnected the vacuum line to the shutoff valve. Started the car and then turned it off. The STOP lever dropped and the engine shut down. then the lever rose up again.

On the W123 at least, the vacuum valve on the ignition switch had 2 ports, and one has a vent hole associated with it. If the vent hole becomes blocked, it is possible that the vacuum valve will be applying a vacuum to the shutoff valve, but not alowing it to leak off and allow the STOP lever to return to the Run position.

Using a Mityvac, on the vacuum line to the shutoff valve, turn the engine off (it won't shutdown because you have the vacuum line off) then manually shutdown the engine using the STOP lever. The vacuum should be at maximum (less the leak) and then leak down. If not, you may have a blocked vent in the ignition shutdown valve.

WANT '71 280SEL · #11 02-21-2005, 05:50 PM

Tony, I'm hoping it's some sort of vacuum problem but I'll have to wait till tomorrow till I have access to my mity-vac.

My indie mech mentioned something to my dad about maybe some vacuum lines being reversed? I looked and there's only one line that goes to the shut-off valve, and it's on there correctly.

Starting last night, the lever drops everytime the car is shut off now.

Thanks
David

WANT '71 280SEL · #12 02-21-2005, 06:04 PM

UPDATE:

I went out and did some testing...

I pulled the lever up so the car would start. I then started it, ket it run for about 35 seconds then shut it off. Stop lever snapped down and didn't return. I then restarted the car and pulled the vac. line off the shut-off valve. I wanted to see if the stop lever would go down instantly or what, so I turned the key off in the car but the car kept running, so I reconnected the line and it shut off while at the same time snapped the lever down. If you try to pull the lever up right after shutting down, it's more difficult than if the car had been sitting an hour. It seems like the lever is being held down by vacuum.

I've been having problems lately with the key switch, well since I've owned the car that is. When you start the car, you have to turn the key back to the run position or the blower won't work, etc. So the key isn't fully returning to its run position. Do you guys think that maybe the key switch being faulty would cause this?

Thanks
David

Fisherman · #13 02-21-2005, 06:15 PM

Tony is right in that the key switch has a vacuum switch attached to teh backend of it that has a port for vacuum (shutdown mode) and a port to bleed off vacuum (start mode). If the key is not returning to the correct spot it could be that the vacuum switch is not returning to the spot it needs to plug off the vacuum circuit and bleed whatever vacuum is there for startup.

I know nothing about the 87 but this is the way that my cars work.
I'd check that vacuum switch that it is moving to the correct position. You could do this with a mityvac by putting it on the feed line to the shutoff valve and then cycle the key after the car has built up vacuum.
When it is running the mityvac should read zero vacuum, when you turn it off the mityvac should read full vacuum (how ever much your car makes) and then when you turn the key back to the on position the vacuum in the line should disappear.

Now again I have to state that I do not know your car. Hiopefull someone who does will confirm that this method of testing will work...

WANT '71 280SEL · #14 02-21-2005, 06:21 PM

If, while the lever is down, I unplug the vac. line, then the lever shoots right back up to its normal spot. So I guess the port must not be letting the vac. out is it thus not letting the lever back up. How do I access the bleed-off port?

Thanks
David

Johnhef · #15 02-21-2005, 07:42 PM

On a S class its a little more involved, but I had to go into the igntion on my 124 diesel awhile ago when my steering lock broke apart. Your blower problem is due to the electrical portion of the ignition, on the back of the steering lock piece. The vacuum valve in the lock might be able to be removed and still leave the lock in- its held on by two small screws. Its possible if something is starting to come apart in your steering lock (like mine did) something might have wedged itself into part of the vacuum switch, or the switch could just have gone bad. It also matters which way it all goes back together if you pull everything out- I had mine 180 degrees off from what it should be and it wouldnt let me start the car, just cranked and cranked because it was letting vacuum go right to the shut off valve.

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