1994 Mercedes E320 cranks but does not start

[Pete2]

I had to replace the computer on my 1994 MB E320 with an ECU from another 1994 E320. The car would start and run for about a week to 10 days and there after it would just crank but will not start. What do I need to do? Do I need to have the ECU flashed for that vintage E320? Where can I have it flashed in Northern Virginia, just outside of Washington, DC?

[Mighty190]

First check to see if it has fuel, spark, and compression.

What I always do when I have a car that cranks with no start, regardless of make, is put my timing light on #1 and make sure that's right. If that passes I will confirm it has at least some fuel pressure by poking the schrader valve on the rail. If that passes check for injector pulse. Finally check compression. Now if it has all those its time to dig deeper but 99% of the time that will reveal the problem. Once the problem is defined its a lot easier to solve it or ask the internet what to do.

My blind guess is that its the OVP/OVP fuse.

[Pete2]

Where is the OVP/OVP fuse in 1994 E320?

[TX76513]

Pelican Technical Article - Mercedes-Benz W124 - Over Voltage Relay Replacement

[Hirnbeiss]

Why would you suspect the ECU if it ran fine with it for a week+?

[bru023]

You check the harness for cracks. Deterioration? Sounds electrical. Check ovp relay.

[Pete2]

It was the OVP relay that was problematic and I replaced it. Thanks for the suggestion. The car now starts and runs. However ABS light is still on, and stays on. The A/C, heat, and fan are not working. Any suggestions?

As regards the ECU flashing, a local European car repair shop told me that it is possible that my vehicle may need a new or the old ECU flashed as I picked I had picked the replacement ECU from a salvage yard (from another 1994 E 320). Is this not true?

[Rick76]

The codes first have to be cleared and then the adaptation memory needs to be reset and reactivated.
You will need to make or buy a simple code reader (lots of info on this site).

Pin 8 of the diagnostic connector is for engine codes.

1. Clear DTC memory
2. After the DTC "1" appears (one LED flash on your home made reader), press start button (on your reader) for 8 or 9 seconds.
3. Switch ignition OFF and wait a minimum of 2 seconds.
4. Turn ignition ON, wait a minimum of 10 seconds and then start the engine.

[Pete2]

My 1994 MB E320 has OBD1 code reader. How can I make simple code reader for the Pin 8 of the diagnostic connector for engine codes? I could not find the information at this site. Please help!

[Rick76]

Lots of info in this thread:
Reading Codes

[Pete2]

I followed the procedure for OBD1 code reader and pulled out the codes from my 1994 Mercedes E320 yesterday. There were two codes, Code 6 and Code 24 were stored on Emission Built in Diagnostic Module. I think for 1994 E320 the error code relates to Code 6 - Idle speed control faulty and Code 24 - Starter ring gear segments and/ or crankshaft position sensor faulty.

On Pin 8 ECU - Code 6 - not used and code 24 - CKP sensor or magnet for position sensot not recognized

What do these error code mean and where do I go from here?

[Rick76]

Clear the codes and then drive it to see if they return.
Has the engine wiring harness been changed?
Also check for codes at pin 14. That is for the electronic throttle actuator and cruise.

[Hirnbeiss]

Of course, the code for a bad crank sensor would make sense for a cranking no-start, although they usually fail when warm.
See this for info, and also the caution to make sure you get the right style sensor for your car.

[Pete2]

Engine harness has been replaced and after replacing the OVP relay recently, the E320 is running. Where is the ETA and its wiring and Crankcase position sensor on 1994 E320?

[Hirnbeiss]

This was the link I meant to paste: 1995 E320 Wagon - Crankshaft Position Sensor Location - Mercedes-Benz Forum