ChamaRiver

My 500 SEL ran perfectly, but then started to idle up and down whenever I would come to a stop, but ran perfectly if I gave it gas. This occurred for about two weeks, then one day I drove about a block down the road at my house (under 20mph), came to a stop, and the car stopped running. Would not start after that.

Found that coil was weak, and no spark to plugs, SO, replaced coil, rotor and cap. Now have good spark at plugs, but car still will not start or fire up even with squirt of starting fluid. Checked timing marks on left and right cam gears, and TDC timing mark on crank, all just as should be. Good compression. Checked fuel input, ok there also. Overload Protection Relay good. Checked Idle Air/Speed Control Valve, cam inside fuctions correctly, audible click, and visually moves inside. Replaced Idle Control Unit two years ago, should be no issue there. Ignition Control Unit/Module appears to work ok, if not I would think the spark at plugs would not be correct with timings.

Read in one thread that the Crankshaft Position Sensor, if goes bad, would keep engine from starting. The only issue I have with that view is that the sensor (three wire plug) is located in the Diagnostic connection plug for computer diagnostic testing at the shop, otherwise the three connection are not connected to anything, so do not see how this sensor could do anything to keep engine from starting.

I am disabled, I purchased this car for comfort and safety. Love this car, any suggestions would be greatly appreciated.

Dan

BENZITCH

Sounds like the fuel pump relay might have gone bad.

ChamaRiver

Benzitch, how can I test to see if bad, before replacing?

ChamaRiver

Dear Benzitch. Replaced the electronic fuel pump relay referenced in your reply. No change, still will not fire up.

BENZITCH

Had you recently purchased fuel that was not high test but one of the blended gases?

Is the tank low now, at present as it sits?

Are the fuel pumps powering up?

Had the car been sitting for a long period of time?

ChamaRiver

Always use highest grade gas, no blended fuel. Tank is at 3/4 full, fuel pump working. Car was being driven, just stopped a few weeks ago, and would not restart or even fire up using starting fluid.

ChamaRiver

Another post said that if fuel comes out of the fuel line that goes to theFuel Distributor inlet hose with the key on then the electronic fuel pump relay should be replaced, also. The fuel comes out when cranking the engine over with the old relay, but does not with the new relay. Also, the post said to wire-jump from fuse box/fuel pump relay pin-sockets #30 to #87. and if there was a humming sound in the distributor then that was good. The humming sound was present.

Update: replaced fuel pump relay, but when key in run position the fuel pump does not come on, when wire-jump pin-sockets #30 to #87 in fuse box, fuel pump relay socket, fuel pump comes on and that was what the humming was at distributor. Can get the car to start now but dies right after starting, so, had another person start car while I sprayed starting fluid in chamber and car would run until I stopped spraying fluid, then it would die again. Checked fuse box sockets #15 (Input) and #30 (hot for #87; to start fuel pump), both are hot with key in run position. *noticed, with key in run, that if I pulled the fuel relay out far enough not to have connection, then barely make connection and move back and forth, that once in a while the pump would come on for just a second, then stop. could feel and hear clicking inside the fuel relay. Also, I am not getting hot at the Idle Speed Adjuster Solenoid, which I understand should go hot when key is turned to run position. I connected direct hot positive wire from battery to solenoid and can hear (click) as it engages.

ChamaRiver

This is another update. I had a Mercedes serviceman out to diagnosis my MB but unfortunately he did not have the Service plug connection for the 85 500sel so he just started looking around. He found gas in the oil and said it was caused by the Fuel Pressure Damper leaking back into the engine.

I purchased a new one but that did not help, and checked the old one and found no leak. I figured that the gas in the oil came from the engine not starting and gas that was being injected into the cylinders was getting into the oil pan pass the rings.

I have flushed and replace oil and filter 3-times to get all gas out, so now fresh again. Tried to start but still will not run. Is there anything in reference to the ignition that could be causing the problem?

gretchen

cold start valve.sounds like a preliminary starting enrichment problem. Probably starting fluid in the oil.Good man for changing the oil right away.Check all fuses and relays also.May also be fuel pressure damper leaking off line pressure.

ChamaRiver

I will check the cold start valve. after I research how to test. Don't think any starting fluid was in the oil, but did have the gas. Changed the oil and filter a couple times over, the idea of seizing the engine doesn't thrill me. I have check all related fuses and relays I found accessible. I replaced the fuel pressure damper, still had the same outcome, no start, only fires a couple times. No leaking from lines/fittings or vac hose at rear.

gretchen

Possibly the crankshaft sensor.Trace the grey wire from the 11 pin connector[round and black] down and across the distributor area in front of the engine to the harmonic balancer.You will see a little sensor that is on the right upper side of the balancer.Sometimes some road grime, grease,or a bad sensor will render the car inoperable.Not saying this is the problem,but it is something to check out. You will not be able to start the car,but the car will try to turn over.This is a symptom of the magnet not being able to count the revolutions,or even sensing the balancer is there.
Hope this helps.
I only mentioned starting fluid in the oil as you tried to enrich through the metering orifice.This will leak down the intake plenum.And since the car won't run,possibly entering the combustion chamber,past the rings and into the sump.

ChamaRiver

The crank shaft sensor does not affect this yr/model, it is only used for computer diagnostic testing. The gray wire from the sensor has 3-wires inside which go to the Diagnostic Test Plug.

Thanks for mentioning the starting fluid in the oil, I need to consider anything I do with this car. The starting fluid wasn't in the oil, it was gasoline. The engine will fire once or twice, but then totally ceases any ignition in the cylinders.

This is my first MB, love the ride and quality of these cars, but dislike all the extras that can stop a car. For lack of stress I have a 64 Pontiac Bonneville Station Wagon that is my number one car, the MB comes in second.

You mentioned fluid leaking down into the intake plenum. When I was able to get the engine to run on the starting fluid it would run until I stopped squirting the fluid. I kept the spraying to a minimum, just not best for the engine.

When I turn over the engine it RPMs very well, has new battery installed. I try not to crank it unless they are short and only a few tries.

I got a late start today on the Cold Start, but will post tomorrow after I know something. Thanks for the pointers. This has been a learning process for me, just NEVER had a car baffle me as this one has.

nagsusansmith

ChamaRiver, I am having the same problem with my 1985 MB 380SE. Will you please let me know if you were able to correct your problem and if so what you did? Thanks. Below is my description of what is happening to my car.

The engine would begin stalling and being hard to start up after my initial start up and turn off of the engine.

I replaced the ignition coil, ignition rotor and distributor cap. It continues to do the same thing.

When someone would push on the larger (of the two) boots(plug ins) on the Magnetic Pick up plate, it would start right up but then stall again.

I purchased a Magnetic Pick Up, but the car would not start at all. The engine turns over but would not catch to start.

Is it possible there is a break or loose wire in the cable that goes to the larger(of the two) boots(plug ins) on the Magnetic Pick Up plate? OR do you have any suggestions as to what is causing this? I'm so frustrated right now, any thoughts would be appreciated. Thanks Susan

tony-ontario

ChamaRiver, I also have been having a very similar occurrence with my 84' 500SEL and would be willing to experiment with any ideas you have, as my car is in my shop and I have a few days to research again before going back up there this weekend.

RyanRichter

Any luck?

Do you have any warning lights when the car is running?