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Intermittent failure to start - 1995 E320 W124

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bolide

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Oct 8, 2005
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BMW E39 525 Diesel Touring
1995 E320 W124 estate. HFM injection, 3 coil packs, no distributor. RCL remote locking (infra-red) probably with automatic immobiliser. Standard car. No history of starting problems or any other problems. Car runs smoothly, pulls very well, no contra-indications

Intermittent starting problems reported - car cranks but won't fire, just as if the immobiliser was active. I haven't been able to repeat the problem but on my first attempt to start the car it didn't fire. On the second attempt I waited for the underbonnet kit to come live (about a second), then the fuel pumps (about a second more) and then it started first turn. Subsequent starts were 100%. ABS light is off

I don't suspect the immobiliser as the fault is not consistent. I am thinking OVP, CPS or fuel pump relay

Questions: where is the fuel pump relay? Are there any other usual suspects? Is there a good way to nail this down to a particular culprit?

If it happens again, or happens when the car is being driven, I think I'll replace all three items

Nick Froome
 
ive had the exact same problem for a year

so thinking it was the old nackerd alarm (would not work more than 6" from side indicator) i got the new A1606

all fine for a while now doing it daily

last weekend we tried until the battery was dead

my mate borrowed it (a mechanic) and he ended up flattening the battery too

the ex borrowed it yesterday and gave up after attempts

seems if you lock the car and then leave it for a few mins that sometimes does it

other times we have gone under the bonnet

then in the engine bay just infront of the windscreen there is a big black pipe going horizontaly and that has a thing the size of your thumb in it and if you removed that and blew it and then put back in it sometimes worked

i too would love to know why it does it

mainly when the weather is very hot
 
First questions to both:

Any codes set? (you do have a blink tester, don't you....)

Do you hear the fuel pump come alive when you turn the ignition on (but not to the start position?

Is the issue just when (engine temp) cold, just when hot or both?

Any issues with wobbly tickover when warm (or cold)?
 
The fuel pump relay and OVP relay are located beside the engine and ABS ECU s. Its located behind a flexible black plastic shield behind the battery. The fuel pump relay will have "kickdown + 6 zyl "or similar marked on it- the OVP will have1/ 2 fuses on the top of it its often silver coloured and sometimes mounted on the bulkhead. PM sent also- edit can't send a message for some reason sorry.

other possibility is a dodgy ignition switch
 
Last edited:
Thanks, chaps. I don't have a blink tester but I do have a Car Surgeon with a Star machine about a mile away...

There's not enough history to this problem to answer some of the questions. It idles & runs perfectly

This is the first electronics / injection problem I've ever had on a W124 so I don't know what to suspect first. Some good suggestions, though

If the problem resurfaces I'll report back. My inclination then would be to have the fault codes read and possibly swop the OVP & FPR

The only curious thing is that, at about the same time as the fault was reported, the Becker stereo speaker outputs stopped working. It turns on, selects stations & plays CDs but gives no audio output so I suspect the output amp chips have blown. The 10 amp fuse on the back panel of the Becker was blown

I wonder if there was a voltage "event" that popped the Becker and tripped the OVP? I didn't check the OVP fuse as it ran perfectly and the ABS lamp went off. Maybe I should have done

Nick Froome
 
Exactly the same thing happened to my E320 coupe. Very intermittent non-starts, that would usually start on the second or third attempt, then finally it wouldn't start at all. The OVP relay was the culprit.
 
If your OVP has one fuse on the top then it's the old style and probably should be replaced....new version has two fuses.

OVP and FPR tend to give erratic starting problem symptoms...
 
On UK spec cars I think the number of fuses in an OVP has to do with what options are on the car.
 
Nick, the stereo on my old estate seemed to be working okay but every once in a while it would turn off whilst it had been running for a while and I'd lose windows, seats, wipers, mirrors at the same time. After I while (30 mins) the SRS light would glow (as per start up) and everything would come back.

I decided that maybe the unit was overheating so I swapped the stereo out and hey presto I never had a problem again.
 
yes thanks from me too

not sure what OVP means but the other is fuel pump relay non?

anyway if this works ill supply everyone with pointy sticks if i come to a meet and you can poke away and my ample chubbyness
 
The G.F.P said:
yes thanks from me too

not sure what OVP means but the other is fuel pump relay non?

anyway if this works ill supply everyone with pointy sticks if i come to a meet and you can poke away and my ample chubbyness
Click to expand...

OVP is the Over Voltage Protection relay....that along with the fuel pump relay are usually the first components to check when you find the car is hard to start.
 
just paid £25 for a new fuel pump relay from mercedes and as soon as the car played up we put the new bit in and it made no difference

so put the old one back in and no difference

then left it for 5 mins and it started!

any ideas
 
The G.F.P said:
just paid £25 for a new fuel pump relay from mercedes and as soon as the car played up we put the new bit in and it made no difference

so put the old one back in and no difference

then left it for 5 mins and it started!

any ideas
Click to expand...

Could be the crank position sensor. They can go faulty as the engine heats up and then be OK when everything cools back down. More common on later model cars tho.
 
I had exactly this when the engine harness on the 190 fried

All I did was to check and clean the plugs and this caused an intermittant short in the coilpack harnesses, eventually it led to an ECU failure and a total refual to start.
Now I am rewiring the whole engine bay with DTA management ready for the turbos :D


Before anyone asks the DTA and building the new harness was a lot cheaper than a new S class engine harness and recon ECU and eminently more suitable to the engine application
 
Have you tried replacing the OVP yet?
 
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