260E injection/ fuel line pressurisation question

[Daniel T]

My '86 260E has been intermittently (joy) playing up for a while - after 50,000 trouble free miles, and I wonder if, before I surrender it to the local garage, if someone can offer any insight into the problem. The temperature of the engine does not affect when the problem appears.

Scenario 1) The car is firing up and then immediately dying. On retrying to fire up, the engine just spins, and won't even "catch" for another 3-4 hours, when the cycle begins again.

Scenario 2) Sometimes, on a rare occasion, it will fire up, then cut out, but if the starter motor is kept engaged, the engine will fire again, and continue to run normally

Scenario 3) Sudden loss of power and engine cut-out on acceleration (Only happened 2x in 2 months). Car restarts immediately.

On the rare occasion when 2) happens, a sound from the nearside rear quarter occurs when the ignition is turned to position 2, which sounds very much like a pressurisation pump, the sound lasting only 1-2 seconds. I can't actually find what the equipment is that is making this noise, as the fuel pumps are bolted onto the floor pan on the offside rear of the car just in front of the rear wheel. This noise never happens in scenario 1).

I don't know enough about the way the fuel system is pressurised for the injectors - can anyone offer any insight?

I've ordered a new OVP Relay, which I am waiting for,but am skeptical this will do anything, as the existing one checks out fine on the multimeter.

Anyone any ideas?

Daniel

 

[piestore]

ovp

Hi

sounds like ovp to me

 

[gasara]

Two things come to mind. I also have a 260E and have, in the past suffered similar problems. Try changing the fuel pump relay (in fuse box) they have a habit of becoming un reliable when getting old. Now the more serious which I truly hope is not your case. ECU, mine intermitantly cut out then died. I managed to find a replacement at £200, stealers wanted £1600 plus VaT. Hope this is of some help.

 

[Daniel T]

Well, new OVP Relay did nothing. Won't start at all now! No noise from rear nearside quarter either - by the way do any other W124 owners get this pressurisation noise just before firing up the car, a kind of humming noise? If so, can someone let me know what it is that causes it.

Daniel

 

[paulcallender]

I would echo gasara's advice - change the fuel pump relay. Your symptoms sound similar to mine, before I changed my faulty one.

 

[gasara]

by the way do any other W124 owners get this pressurisation noise just before firing up the car, a kind of humming noise? If so, can someone let me know what it is that causes it.

Daniel

Yep its normal. Its the fuel pump pressurising the system.

 

[Daniel T]

Thanks for this help Paul, Piestore, Gasara- now I can start to make some progress - when the fuel pump pressurises the system, then the car starts, when it doesn't the car doesn't start. Sounds logical.

Gasara - I've had a look at the relay box behind the fuse box - I'm assuming the fuel pump relay is the small silver one in the attached pic -is this correct? The only thing is when this relay is removed, the fuel pump still primes. This doesn't sound right, and the haynes manual is no help in this regard.

Any further thoughts?

Daniel

 

[paulcallender]

From memory, I think the fuel pump relay is located behind the battery, near the ECU (on the other side of the car). There's 2 relays there, also its not just a relay, its a double relay and its other task is to do with kickdown. I'm sure others (with better memory!) will be able to jump in and confirm this!

 

[pascal]

Paul is correct, but my memory is not quite as good as his, so I checked back.
It is indeed a double relay, as it also controls the gearbox pressure for spoother kickdowns.

But here's the bad news, it cost about £125+vat from a dealer, because its a bigger and more complex. I'm not sure if its available from indis like Europarts, probably is.

 

[paulcallender]

It is (available from Euro Car Parts) and costs around £60!

 

[marshie001]

i would check for a loose fitting relay before purchasing a new one, as the problem is intermittent to me would suggest that the connection isn't quite right, it may well have been knocked when replacing a battery or checking the ovp relay! take it out and clean all th contacts first, usually a failure is a failure and wouln't work at all! and as you replaced the ovp relay recently it could be worth a check!

 

[Daniel T]

Thanks for all your help everyone - The relay wasn't loose marshie001, so I collected a new fuel pump relay this morning. I'll report back on the problem in a week and let you know if it appears to have solved it. No doubt something else will now bust further up or down the system, such is the way with component replacements!

cheers for now,
Daniel

 

[Daniel T]

One week later, and the starting problems have not reoccurred, so I'm confident the fuel relay was the cause of the problem.
Thanks to all who offered advice. Now I just need to get the drivers window working!

 

[pascal]

So that means the OVP relay was ok. But seing as these have a habit or going also, I would leave the new one in, and keep the old one for testing. You could put it in temperary, just two make sure it's ok first though.

Could you post a photo of the two relays behind the battery for reference, as I haven't access to a W124 any more. :cry:

Thankyou in advance
Pascal