Starts Great, Dies as soon as Warms up! - PeachParts Mercedes-Benz Forum

Chiappino · #1 02-24-2007, 04:00 PM

Still trying to figure this thing out!!! Just cleaned the Idle control valve, new warm up regulator. So when I start the car when it is completely cold, it fires right up, idles at 1000rpm. As it gets to around 60 Degrees Celsius, the idle drops and it dies. You can give it gas and it will run, but wants to die. Any ideas? Thank you again!!!!!

Chiappino
84 Euro 500Sl

MattBelliveau · #2 02-24-2007, 04:14 PM

Fuel pump relay (if equiped).

Chiappino · #3 02-24-2007, 05:52 PM

Yeah it has a fuel pump relay. Is there any way to test it?

just-n-time · #4 02-25-2007, 10:51 PM

Quote:

Originally Posted by Chiappino

Still trying to figure this thing out!!! Just cleaned the Idle control valve, new warm up regulator. So when I start the car when it is completely cold, it fires right up, idles at 1000rpm. As it gets to around 60 Degrees Celsius, the idle drops and it dies. You can give it gas and it will run, but wants to die. Any ideas? Thank you again!!!!!

Chiappino
84 Euro 500Sl

High Idle 1000 should only be for a few seconds then it should drop to say 800 and as it warms on down till it reaches the 700 mark,in gear 600 to 650you have a vacuum leek. smoke test the engine, you probably will find that the idle air lines are one of the leeks,Have fun let us know how you are getting along with it, others would like to know too.

Chiappino · #5 02-26-2007, 03:08 AM

Very interesting..... I'll do some more looking around. Not sure if I can do the smoke test myself. I'm almost to the point of dropping it off at my local shop and saying "fix it"!!! That may be out of my price range. I'll keep you all updated. Thank You

Chase
84 Euro 500SL

Chiappino · #6 02-27-2007, 02:58 AM

After reading some other posts.... and having issues with my ignition module blowing up. I decided to get a new coil.

SO.....

Started her up as usual, let her warm up, started running a little rough, idleing at around 700rpms.... still a little shakey. I try to give it a little gas, expecting it to die. Doesn't die, returns back to idle. Impressive.
Tried it again. Same reaction.

Time for a test drive.

Took her out on the road, 1 mile down the road. She dies as I'm slowing at a stop sign. I pull it into a parking lot. Try to start it, seems like I'm not getting spark (could have just blown another Ignition module) BUT NOPE!!! I let it sit for 10 minutes, and she started up while giving it a little gas and she fired up and idled around 600. I adjusted the air/fuel mixture more lean thinking I'm fouling the plugs. Seems to work.

I hop in the car, take her on and off the freeway for a couple laps, she dies twice as I'm slowing, but stayed at idle about 10 times. HUGE IMPROVEMENT!!!!

I was able to drive the car, even able to park it in it's usual spot. Which has been hard when it wouldn't run. So that's that for now, I'll keep ya updated.

Also found that one of the spark plug wires is arching after it gave me a jolt after touching the top of the distributor. Time for new wires. That should fix the rough idle.
Thanks all...

Chase
84 Euro 500 SL

Chiappino · #7 02-27-2007, 10:29 PM

Well, got new wires today.... took all the plugs out, they were extremely carboned up. I cleaned them up, cause they are extremely new, threw them back in and put on the new wires. Thought I would see a big diffrence!!! Sure did.....car wouldn't idle again!!!! Started up fine, but no go after moving it.

As I got back home, the exhaust sounded really funny..... looked underneath the car. The catalytic converter was glowing bright red!!! Which I'm guessing is because I have so much excess fuel. Guessing my fuel/air ratio is way off. I think I have to bring it into the shop to fix this one.

Chase
84 Euro 500Sl

ctaylor738 · #8 02-28-2007, 01:18 PM

It seems unlikely that the mixture setting could be that far off, so ...

There is an o-ring on the plunger in the FD that can wear out and cause extremely rich running. Definitely worth checking out.

Then I would look at system pressure. It should be around 5.2 bar. If if is high, you might have a fuel pump that's gone hyperactive on its way out or need a new pressure regulator.

Then check your control pressure when warm. It should be around 3.8 bar. If it is low, then you may have a blockage in the fuel return line, a malfunctioning warm-up compensator, or your FD may have gone south.

Chiappino · #9 02-28-2007, 08:03 PM

What is the possiblity the catalytic converter is bad too? or is bad now? Should I replace the cats before trying to fix the problem, or should the cats not be an issue once the fuel issue is fixed..... Thanks.

Chase
84 500SL

ctaylor738 · #10 03-01-2007, 09:40 AM

Personally, I would chase down the rich mixture, get the car running as best I could and then see how the cats do. If you have a good burn on the plugs and the cats are still lighting up, your next step would be to replace them, obviously.

david s poole · #11 03-01-2007, 10:07 AM

if i read correctly this is 84 euro 500sl.get under the glove box and take off the panel around the fuse box.there are some relays there and one of them is an ovp relay.the car is obviously running rich.a cold engine will tolerate this quite well but not a warm one.suggest that you start car cold and back off the fuel with 3mm at the fuel distributor as far as you can without dropping the cold idle too much below 1000rpm.see if this will allow it to idle when warm.you probably have issues with the warm up regulator[which controls the control pressure at top of piston in fuel distributor] that will require a phone conversation[i only type 10 words a min] so feel free to call me.

Chiappino · #12 03-05-2007, 04:03 AM

To all that helped.... THANK YOU VERY MUCH!!!!

Chuck, you ended up being 1000% right.

My brother finally came out to help with the car. (my mechanic)

We took the fuel distributor off, the o-ring was fine, even though we had a new one.

We tried to move the piston. Nothing...... wouldn't budge.

Tried spraying throttle body cleaner and tapping it. Nothing. Let it soak. Tapped some more. Nothing. After about 30 minutes of that. We finally got it to push in a little bit. (as it was already almost all the way in, pushing it in would be much easier than trying to pull it out) It pushed in about half a centimeter. Still sprayed cleaner and tried to break it free. After tapping the sides of the distributor the piston finally started to wiggle out.

The Piston finally freed itself!!!! We took it out and it was pretty bad. The car sat for years and it definately had some rust colored stains. We cleaned everything up. oiled the piston up a bit. put it back in. New o-ring. Slapped it back on. VOILA!!!! The car started right up, reved like a dream!!!

Couldn't be much happier. Although I'd love to find out why she's missing a little bit. Especially after new plugs, wires, coil, and ignition module.

No word on the catalytic converters yet. Haven't driven it enough to see if they are still getting red hot. I probably need to replace them anyways to get it to pass smog.

Thanks again everybody. Hopefully this post may help somebody in the future.

Chase
84 Euro 500SL

ctaylor738 · #13 03-05-2007, 08:10 AM

Now that you don't have to worry about the car dying or the cat blowing up, I'm sure you can track down the other problems, which are probably vacuum related: injector seals, vacuum connections, etc. Driving the car with some Techron in the gas may also help.

just-n-time · #14 03-06-2007, 09:48 PM

Great follow up wish more would do the same.JNT

250 Coupe · #15 03-06-2007, 11:46 PM

Cats will glow from a massively rich condition. I got the ones on my '87 5.0 Mustang to about 1100F one night by washing the engine and not drying the distributor cap out. I never had a problem passing emissions with that car but it had a newer generation cat VS the older ones in your car.

Double check the firing order and plug wires. You stated that it ran poorer then you expected after a wire change. It is also possible that you damaged the O2 sensor with the extreme heat. This assumes that you have the Lambda system added to your CIS. I'm not sure what year that happened and the Euro thing adds a twist. www.w116.org has the CDROM online so you can do some research about pressures and on/off ratios etc…

Also, see my post in the Vintage forum about checking fuel pressures.

Michael