M103 Engine Flooding Itself (1988 300E)
 

My car starts fine cold then once it gets up to operating temp at idle it will start to flood itself, choke and die. I know this because #1 I have looked down the intake afterwords and there is a pool of gas in the bottom (verified by Q-Tip on a stick) and #2 because I have watched the duty cycle while it dies and it shows it going richer and richer before it dies.

I would assume the EHA is what would be increasing the flow to flood it but I don't think the EHA itself would be bad so much as something that tells that EHA what to do would be bad. What do I need to check? Which sensors tell it what to do?

Also, would disconnecting the EHA just to be able to drive the car be safe for the car if I try to tune the lambda to 50% with it disconnected?

The only other thing I can think of is if something is triggering the cold start valve or the cold start valve is leaking or the CIS unit is leaking out the bottom. But being that it runs fine cold, I think it's a electronic issue.

Is there any known issue and cause of this problem?

I have tried adjusting the lambda leaner but seems to only be a temporary fix.

Your injector(s) could be failing. As they age the pressure they close at drops, which can cause flooding or dripping when the car is turned off, leading to flooding.

It's flooding itself out while the engine is running. It's a continuous injection system where they always spray when the engine is running. Something is causing them to spray too much in once the engine warms up.

something is telling it that it is running lean, and is trying to correct.

Does it go into closed loop? how long after that point does it go rich/stall?

I would be looking at the o2, temp switch. I cant really think of the rest.

I could be wrong, but if the eha is unplugged, it just reverts to open mode?

I chased a similiar problem where it was seeming to run rich when hot and 02 started to show rich, ended up being spark =kv was getting weaker as car got hotter at idle, eventally confirmed with black smoke coming out tailpipe,changed ignition coil and fixed my problem

Sorry, I should mention I just replaced the O2 sensor trying to fix this problem (OEM $80 Bosch) and no difference made.

I also just replaced the coil and spark plug wires about 4 months ago (both Bosch OEM).

It runs in closed loop for a good 7-15 minutes before it chokes and stalls out.

If I rev it up before it stalls out and hold the RPM's up to keep it from dieing it'll mis some and blow smoke.

Now it won't even start cold.

http://www.youtube.com/watch?v=A31U4JnF1NE

Now it won't even start when cold.

Mercedes-Benz 300E M103 W124 Won't Start - YouTube

I've decided to pull the cap and rotor to go over with a fine tooth comb.

Is there supposed to be readable resistance between the spark terminals? Some are in the M and some are actually in the K.

6-3 = 300k ohm

Basically getting 300-400 kohms between neighboring spark terminals.

1.1 kohm between rotor center and arc end.

Another thing to check is fuel pumps , if you have two pumps one pump may quit intermittantly, car will run but poorly and stall,to test put amp clamp on individual + wire and measure amp draw they should be equal.the symptom while running down the road is poor acceleration , and if idling stalling and poor starting

If you suspect the cold start valve why not unplug it when the car is near its operating temperature to see if the problem persists?

The car can still run with EHA uplugged provided the mixture has been adjusted rightly before that. Once the basics are messed up it's hard to get the car even started.

Don't throw money just yet. Try to have a fuel pressures test first. The car starts alright so the CIS unit shouldn't be leaking. You can still read the lambda meaning the O2 sensor still works.

If you have no spark, it could be a crank sensor. It fits with the whole stalling when it gets warm. I believe you can test resistance. I would do a search to be sure, but I think it was 1200 ohms.

800-1200 ohms

It won't even start cold now (see video in post #6).

It back fires and kicks back, to my knowledge a fuel problem can not cause kick back like that, which is why I am looking deep into the distro cap and rotor, that's the only thing that can make a spark in the wrong cyl at the wrong time because even if the coil is off beat, the rotor still has to be in position.

Is there supposed to be readable resistance between the spark terminals? Some are in the M and some are actually in the K.

6-3 = 300k ohm

Basically getting 300-400 kohms between neighboring spark terminals.

1.1 kohm between rotor center and arc end.

P.S I've tested the CPS many many times, both before it ran and after it dies, always been within specs.

I'd buy a car that works.

Have you checked to see if you are getting a good spark? I saw the video, and it sounds like it is firing randomly.

It's really hard to get these cars to actually not start. If you have no or weak spark, it can be cps,ezl, coil, wires, or plugs.

I cannot think of any scenario that would cause the spark to be out of time.. I don't think it is possible.

Fuel, spark, compression. The timing chain would be spot on, or busted..