Intermittent failure to start - 1995 E320 W124

[The G.F.P]

Have you tried replacing the OVP yet?

not yet

as GFP4 works fine we will swap bits till we find the problem then buy a new bit

thanks for all the ideas peeps

 

[The G.F.P]

3 weeks ago i bought a new battery and then for a week it started 1st time every time

then it sat for a week and when i tried to start it it would not until the 4th attempt

then did a 100 mile run and for the next week it started fine

seems that unless the battery is fully charged it does not like to start

does this make sense?

 

[grober]

You could have a combination of 2 faults. First you have some form of parasitic load which drains the battery over time while the car isn't running. Second you have a slightly dodgy OVP or other control unit that is susceptible to low voltage-i.e. doesn't function below a certain voltage-hence the no start. I would certainly try changing the OVP. Might also be worth monitoring battery or OVP output voltage over a period of time to see if you can correlate voltage levels/drop with the failure to start fault.

 

[macabethiel]

I would replace the OVP if its the early one, later one has extra fuses as stated by others, then the fuel pump relay.

A simple test I found from an American website that sounds really basic was when next it will not start remove the fuel pump relay strike it with a metal spanner, re-fit relay if it starts its the relay. It is an intermittent issue that gets worse as the solder joint fails.

You get dry jointing on the printed curcuit you can open the relay and re-solder them if you are good with a small soldering iron but the printed circuits are quite delicate and brittle with age.

If its a case that the engine only starts after loads of cranking then its the fuel pressure diaphragm that hold the fuel pressure in the line. This seems more of a problem in hot climates or with starship mileage. Fuel pump relay failure is more to do with time & mileage

 

[gabhainn]

W124 start failure (E220, HFM)

I'm trying to chase down the same problem ... changing fuel filter didn't help (thought a blocked/fouled filter was causing the fuel pump to stop early), beating the fuel pump relay hasn't help - thanks for the tip about the OVP relay / battery voltage guys, that will be tomorrow's entertainment.

Does anyone know if there's a *factory* manual for the injection system anywhere? I got one for the LandRover EFi system and it saved me a fortune ... they usually give test flowcharts and processes which will help with testing sensors (temp, airflow, crank pos, lambda ... testing these by swapout can be expensive without a "spare car" to swap bits in and out of)

Interestingly, my car is 1995/96 as well - it does look very like an electrical failure related to age as a couple of folks have mentioned.

 

[GP801]

Ours had similar issues. It was the OVP relay. The OVP seems to be involved in many systems on a 124. Also needed a new ECU but that was for a different problem.