1992 300E will start and run but will quit in gear after 3 - 5 seconds - PeachParts Mercedes-Benz Forum

Swifter53 · #1 02-27-2024, 02:36 AM

So this car has been sitting for 7+ years, and I've been trying to get it running lately...originally when it first started sitting, my dad told me it was a water pump that needed replacing, but as time went on he said it might need a new wire harness (Cali rodents are ruthless). He passed not too long after that and I'm left here scratching my head on why the car starts and runs but hates being in gear.

I've replaced the water pump, coolant, serpentine belt, spark plugs, oil,oil filter, and some fuses (not all) for good measure. Fuel was empty so I put some seafoam and half a tank in, and changed the fuel filter. Fuel pumps are noisy and work hard even after the fuel filter change. Before the fuel filter change, I couldn't get it to rev past 3k without dying and now it revs to right under 5k and will die.
The new spark plugs I put in are champion copper spark plugs, single-pronged, gapped at 0.032 (listed in the 89 owner's manual) the ones in the car were 4-pronged platinum spark plugs that were just a little blackish brown. New spark plugs didn't change how it ran, now it just starts a little easier. That was done before the fuel filter change though. Now I am guessing sensors are to blame, or even the OVP, but the fuse didn't blow in it either. There was also a cut wire to a plug that went to a connector under the oil filter that I fixed, but now the car burns oil (blueish-purple exhaust smoke). I've looked at some other threads similar to my issues but some don't get resolved or they point to an issue that I fixed. Maybe I missed a thread with issues just like mine and if so, can you guys steer me to it? This car does have 203,214 miles and has a lot of aluminum oxidization everywhere under the hood, so some would say give up but I would rather not. I already put work into it, and I'm not stopping now.

Also, my dad tried selling this car on these forums a longggg time ago but no one took the chance to snatch it up so I guess he racked up another 93,000 miles on it. It was under 382111-92-300e-sale-only-110-000

Swifter53 · #2 05-13-2024, 12:42 AM

I changed the OVP to some new cheap eBay one, it ran for longer and was able to get halfway down the street before it died, which is an improvement.

The ignition coil has some aluminum oxidation so maybe that is putting some resistance and strain on the ignition system as a whole?
So I will replace the ignition coil with some cheap eBay one to see if that does anything (manufactured by APWi??) and replace the fuel pumps with OSIAs fuel pumps.

I might clean the air meter plate with carb cleaner since I suspect it might be choking the engine of air since it looks like it closes too fast and isn't opening far enough sometimes. Maybe it's just acting rigid because of age and no use for so long

. I might even pull off the air flow sensor plate and check the mechanical parts that control its movement.

Duke2.6 · #3 05-13-2024, 11:25 AM

If you just let it idle until it reaches at least 60C when the fuel system goes into closed loop operation will it continue to run in gear?

Also, is the check engine light on and have you read out any codes?

Duke

Swifter53 · #4 05-24-2024, 07:54 PM

Quote:

Originally Posted by Duke2.6

If you just let it idle until it reaches at least 60C when the fuel system goes into closed loop operation will it continue to run in gear?

Also, is the check engine light on and have you read out any codes?

Duke

CEL only comes on when I unplug the little air intake temp sensor and try to watch the movement of the air plate. Also yes the engine acts the same on Benzer 5 no matter if he's cold or operating temp, hell it seems like he slightly gets easier to kill at operating temp. But he is also very easy to start back up at operating temp. Usually now the first cold start is a perfect strong start-up. I just changed the spark plug wires to the blue NGK ones. The new replacement Distributor and rotor are from Beru. The new ignition coil was made in china and faces the opposite way of the original but works perfectly fine it seems. I haven't put in the new fuel pumps yet, hopefully they do something or actually fix the problem.

Sugar Bear · #5 05-24-2024, 10:48 PM

Reasonable chance the fuel pumps will help, they do fail and yours are noisy. A strong dose of Techron or better yet BG fuel cleaner will help. The BG will probably have to be ordered online.

Sugar Bear · #6 05-24-2024, 10:49 PM

This is an M103 car correct?

Swifter53 · #7 05-26-2024, 12:50 PM

Yes this is a m103 SOHC, I just changed the fuel pumps yesterday and it revs like it should, I wasn't able to move it (my aunts van was in the way and I had to get to work) but it doesn't die now revving so it probably won't die moving. The new osias fuel pumps are already screaming like little bagpipes so I'm going to get a rebuild kit for the KE-Jetronic fuel distributor. I'm guessing it's clogged up in there with grime after sitting for so long. The new fuel pumps are slightly bigger too so they seem to be able to keep up since it was able to rev to redline almost (dont worry benzer 5 was operating temp)

Sugar Bear · #8 05-26-2024, 01:03 PM

I think there is a screen at the fuel inlet at the fuel distributor which may need to be cleaned.

rayhennig · #9 05-27-2024, 11:20 AM

Quote:

Originally Posted by Sugar Bear

I think there is a screen at the fuel inlet at the fuel distributor which may need to be cleaned.

Sounds like a good place to start.

But you mentioned the coil. Is it ancient? I'd change that for an MB original.

And, of course, verify that the entire HT system is AOK.

RayH

Swifter53 · #10 11-18-2024, 02:41 AM

Not too long after my last post I replaced all the things mentioned but nothing stopped the car from dying...
until I replaced the fuel pumps, from there Benzer 5 ran strong, the fuel pumps I replaced the old ones with though were Oasis E-85 fuel pumps, not regular gas ones, so for 10k miles I had this annoying wine from the fuel pumps no matter how much gas was in the tank (Yes Premium gas only), I also did a distributor rebuild not too long ago, but that thing was clean, wasn't really needed.

So about maybe 3k miles ago I replaced the fuel pumps again but this time they were normal gas fuel pumps. Performance wise I don't think the car is any different, maybe just slightly more low end torque and little more of a gas guzzler, but that's it.
I also just replaced the O2 sensor and it seems to be running way better at idle, no more hunting idle. The old O2 sensor was cooked, white and orange looking. Benzer 5 hasn't passed smog though in the 15k miles I've driven him, even with the new O2 sensor I just put on, the smog guy says that with the stories of my dad I've told him, he wouldn't be surprised if the Cat was hollowed out on Benzer 5. Honestly the more I thought about it, the more it made sense, since in this car we were in one of the last road rage incidents before he passed, I remember finding a thread not too long ago that he started about getting cheap power out of the car without too much work, since this was our main running car, it couldn't be down for too long. He said in the thread that a low 16s car just couldn't hold it's own in Cali anymore. Not a lot of people replied to that thread and the ideas were more extensive/expensive so I guess he went with stock-ish mods like just cutting certain parts off the exhaust system. He must've welded the resonator and muffler back on when he went to sell it since there are weld points right after the Cat. This is just a guess though since I haven't seen inside the cat.
Main issue at smog was Hydrocarbons, Benzer 5 puts out about 185 PPM at idle and the limit is 120 PPM at idle. Funny thing tough is at 2k RPM he passes