W124 300e Electrical Nightmare- About to give up

[natejgreene9871]

I really need some help.

I have been struggling for almost 5 months now with a 1993 300e 3.2. It has the M104 and electronic injection. It is a cheap project car.



I have an intermittent electrical issue I cannot solve. The car fires right up for about 2 seconds and then stalls. It does this about 90% of the time. See video:

[MEDIA=youtube]l3wM8KxtFgQ[/MEDIA]





Once in a blue moon it will fire up and run just fine. I went on a 20 minute drive today. Turned the car off and then it wouldn't restart.



Interestingly, when I spray starter fluid down the intake the car will always run.



It seems like some kind of issue getting correct pulses to the fuel injectors.



I put a light on one injector and the pulses seem inconsistent in brightness?



[MEDIA=youtube]gRt3cR-4vlM[/MEDIA]





Everything I have tried:

-Entire fuel system has been disassembled and cleaned from the tank to the fuel rail. New filter, rebuilt injectors, tested pumps, new fuel press regulator, all of it

-All new spark plugs, wires, coils

-I have tried 3 different ECU's, all three were known good- same behavior on all

-New OVP relay (tried 2 different ones)

-new crank position sensor

-new cam position sensor

-main wiring harness has been replaced and is not biodegradable year

-rebuilt throttle actuator from reputable vendor

-I have cut open every harness in the engine bay looking for crumbling wiring and I can find none.

-cleaned the grounds around the battery

-confirmed the alternator is charging

-Smoke tested intake for vac leaks

-tried two different MAF sensors

-cleaned fuse box

-disconnected and bypassed the alarm

-tried moving the main harnesses around, jiggling wires around the battery trying to see if there is any change


Please does anyone have any ideas?

This thing has been stuck in my garage for 5 months now and I'm starting to consider parting it out but i really don't want to.

[Scrappy]

Have you looked at the ground strap between engine & chassis?
bolted to the bellhousing then goes to the body

[dieselbenz1]

If I remember correctly your fuel pump is controlled from a relay behind the battery. When first energized by the key it only pressures the rail for 2 seconds. If it does not get a engine running status tach signal it cuts off the power to the fuel pump. Something else that escapes me is also in that relay. I recall they were fairly easy to test with jumpers I'm just not 100% certain which relay you have installed.

[Sugar Bear]

On my '93 300E 3.2 (best car I ever owned, over 360K miles) the intermittent crank but no start was either the OVP or the fuel pump relay behind the battery. IDK which it was because I threw both of them at it at the same time and the problem was gone. Hope it is that easy for you!

[lsmalley]

Originally Posted by natejgreene9871

I really need some help.

I have been struggling for almost 5 months now with a 1993 300e 3.2. It has the M104 and electronic injection. It is a cheap project car.



I have an intermittent electrical issue I cannot solve. The car fires right up for about 2 seconds and then stalls. It does this about 90% of the time. See video:

[MEDIA=youtube]l3wM8KxtFgQ[/MEDIA]





Once in a blue moon it will fire up and run just fine. I went on a 20 minute drive today. Turned the car off and then it wouldn't restart.



Interestingly, when I spray starter fluid down the intake the car will always run.



It seems like some kind of issue getting correct pulses to the fuel injectors.



I put a light on one injector and the pulses seem inconsistent in brightness?



[MEDIA=youtube]gRt3cR-4vlM[/MEDIA]





Everything I have tried:

-Entire fuel system has been disassembled and cleaned from the tank to the fuel rail. New filter, rebuilt injectors, tested pumps, new fuel press regulator, all of it

-All new spark plugs, wires, coils

-I have tried 3 different ECU's, all three were known good- same behavior on all

-New OVP relay (tried 2 different ones)

-new crank position sensor

-new cam position sensor

-main wiring harness has been replaced and is not biodegradable year

-rebuilt throttle actuator from reputable vendor

-I have cut open every harness in the engine bay looking for crumbling wiring and I can find none.

-cleaned the grounds around the battery

-confirmed the alternator is charging

-Smoke tested intake for vac leaks

-tried two different MAF sensors

-cleaned fuse box

-disconnected and bypassed the alarm

-tried moving the main harnesses around, jiggling wires around the battery trying to see if there is any change


Please does anyone have any ideas?

This thing has been stuck in my garage for 5 months now and I'm starting to consider parting it out but i really don't want to.

I know you replaced some of these parts already. Another thing to do is this: Check the wiring pinout of the components. For instance: I recently had an issue of only getting like 12-16 mpg on my w201 and I went through all the troubleshooting of the FSM. I replaced the parts with known good parts and I even checked and double checked the parts to make sure they were all within specification of the MB manual (i.e., resistance for CPS between 680-1200 Ohms, ignition coil between 8.5v-10.5v when starting, resistance of distributor to spark plug connector between 700 and 1300 Ohms, etc.) Everything checked out fine and I ended seeing a YouTube video of a guy who apparently was an expert when dealing with the KE Jetronic and the issue was the 2 pin connectors that plugged into the EHA were swapped around. So pin 1 (black wire, I think) was in the place of pin 2 (brown wire). I remember Replacing the plastic end on the connector and I must've swapped them around. You said you opened up your harness or had the harness upgraded so I would definitely check the pins against what it shows on the schematics. At this point you don't have anything to lose. Do you get a CEL error code?

[natejgreene9871]

So tonight I did the following:

-Replaced both fuel pumps including check valves
-Cleaned corrosion off main engine ground strap on transmission

-Went around the engine bay looking for electrical connectors, I disconnected EVERY connector I could find, ONE at a time, and attempted to start the car each time I disconnected one- no change whatsoever. I reconnected them as I was going

-Also I removed each fuse from the fuse box one at a time- tried starting after each fuse was removed

-tried Starting car with eta unplugged- no change
-Tried unplugging the egas module-no change
-I only see one plug micro switch type thing on the intake-tried unplugging that no change
-Tried moving around the gear selector while cranking (maybe bad NSS?) no luck-no change.

- also I have jumpered the fuel pump relay so the pumps are running constantly. Dieselbenz Are you saying there is something else aside from fuel pumps that is controlled by the fuel pump relay? My car uses the small green relay part no 0015429619

[Sugar Bear]

FWIW, mine also had the small green relay.

Are you able to constantly monitor fuel pressure to know the pressure when the no start condition occurs?

[dieselbenz1]

Did the car start and stay running with the relay jumpers? What I am saying and tried searching through the slectrical drawings but I'm heading south tomorrow to San Diego down the 101 but a storm is starting up in Calgary. Oh ya the green relay is energized by several events starting the fuel rail is pressured then the relay turns off waiting for a run signal once received from the tach the pump remains on until a roll over or normal shut down.

[natejgreene9871]

No the car will not run, even with fuel pump relay jumpered and pumps running constantly

[natejgreene9871]

other than the ECU, are there any other electrical components/modules (such as T/LLR) that affect the signal going to the fuel injectors?

[87tdwagen]

Have you tested fuel pressure at the rail?
Going out on a limb, but given all of your fuel system work, you might have air in the rail.
IIRC, you should be able to bleed at the test port.

[locry]

Throttle decel switch?

[nulu]

Maybe they put the wrong engine harness in double check the harness part number,

[nulu]

Also remove the fuse box and check under where the Phillips screws attach wiring to make sure all the wires are tight