525tds starting problems

[cmoura]

Hi everybody
I have a '95 E34 525tds touring and my problem is that the engine starts great when it's cold but when it's warm most of the times it is difficult to start I must keep the key on start for 5~10 seconds. Is there anyone who knows what might be the problem.
Thanks a lot for any help you can give me
Best wishes from Portugal

[shuny]

I've had the same problem with my tds. It could be either your fuelpump, but more likely it will be your injektors. Sometimes they start leaking a little bit when the car is hot and was just driven. Then the fuel gets pushed through the injektor by the pressure. Now that that has happened the engine needs a couple of turns to build up compression again. That is why it takes a while for it to start. Another symptom that indicates that is that you will have smoke coming out of the exhaust. Only right after the engine started though!! Hope that helps.

P.S.: The injektors have an estimated lifespan of about 100000-150000 kms

[SimonP]

Mine is the same.
Fully cold, two shots of the glow plugs allows an instant start.
Fully warm, starts within about 5-10 seconds.
Just-about warm, temp gauge just above the blue zone (glow plugs do not come on), need to crank engine for 20-30 seconds. A cloud of smoke is emitted when the engine fires because fuel has been injected but not burnt.

Different people have told me it is a tired fuel pump, one has said the injector spray pattern could be poor.
However, one has said that it is possible to increase the startup fuelling value in the ECU. He has done this successfully on a few occasions. I will be getting that done first as it's the cheapest option.
Unlike a conventional setup, you can't control the startup fuelling with the throttle pedal.
I can't see it being the injection system losing pressure, as the engine would be difficult to start when cold too.

Please see my post about the injection warning lamp

Si

[shuny]

Hi everyone,

I have just replaced the engine in mine. It ws due. The reason for this was a loud ticking noise. Well, anyways. The hard starting problem was from one of my injectors being burned out. When the car was hot the fuel would trickle into the combustion chamber and make it hard to ignite. The symptoms you can see from that are that when you start it the engine will smoke for the first 1-2 seconds. The reason, as I said before, why the engine starts so bad is that the engine has to build up enough compression to ignite the fuel. Also the turbo was bad, which these engines are notorious for. Also one of my piston Jackets was broken of. Well, all I can say is that the new rebuilt engine runs smoother and better then the original.

Cheers,
Shuny

[paul1776]

Hi,

I have a 525 tds tourer, 98, and I think the fuel pump has failed (starts and runs for a few minutes, then cuts out, wait a while then same again) Where is the fuel pump located ? Can't get fuel to spurt out through the filter when turning over. Local garage wants 2 k for a a new injector pump, but I think it's the fuel lift pump

[SimonP]

Hi!
The lift pump is located inside the fuel tank.
The access to it is from a removable panel in the boot floor, between the spare wheel well and the rear seats.
Before removing the pump/sender assembly from the tank, test for voltage at the pump:

If you pull back the rubber boot from the electrical connector, you will see a green/purple wire, which is thicker than the others. This is the power for the pump.

The fuel pump is fed through fuse 23 under the bonnet on E34 models.

The relay for the fuel pump is energised under TWO conditions:
1: Terminal 86:
A feed is tapped off the glow plug relay output to cylinder 6. This allows the lift pump to prime the fuel system from a cold start.
This supply is present when the glow plugs are being operated (the glow plug light is on), and during "afterglow" - the glow plugs may be intermittently energised after starting, to aid the clean running of a cold engine)
2: Terminal 86b:
A feed is taken from alternator terminal "D+". This is a safety feature - if the engine stops rotating, the alternator stops producing output and the fuel pump relay will be de-energised.
You should have this input whenever the charge warning lamp is NOT lit with the ignition on.

My guess is that your fuel pump relay is not responding to the alternator, therefore once the afterglow phase has finished, the fuel pump will not run, and your engine will stall.
Once the engine temp is outside the blue zone, the glow plugs are not activated, so this sounds like why the car will re-start if left to cool.

The fuel pump relay is a special-purpose relay - it has two diodes in it so that it can be energised from any of the two sources as above. A standard relay is not suitable.

Make up a test strap from a piece of wire with a 1/4 inch male blade each end, to mimic the relay pins.
Remove the fuel pump relay and insert this test strap between the sockets which correspond to terminals 30 and 87 on the relay.
Start the engine and see if it will stay running.
If it does, you need to check for voltage on the relay socket which corresponds to relay pin 86b.
If you have this, the fuel pump relay is faulty. You may however just be able to replace the diodes, as the relay appears to be working from the glow plug input. It may even just be a poor solder joint that wants re-making.
If you do not have voltage on terminal 86b with the engine running, there is a disconnection in the wiring loom.

Simon.

[paul1776]

Thanks,

Have changed the filter meantime, and got engine started but can hear a louder then normal noise from under the back seat. The fuel pump is not under the bit between boot and seat, so will have to unbolt rear seat squab to check it out

[paul1776]

OK, it's running, but pump noisy. Can't locate a pump here (I am in Ireland) except the local BMW rip-off mob. ASnyone know a good mail order that will send to me in Ireland, or should I replace it with a different pump ?

[SimonP]

Some people have used a "Facet" fuel pump, (originally intended for carburettor applications on petrol engines) to replace the original type.
The pressure is in the range 5-7psi.

You MUST NOT use a type intended for petrol injection, as the pressure is way too high at about 45psi.

Have a look on the forums relating to vegetable oil conversions, because this thicker oil soon causes the OE pump to fail.

Before replacing the pump though, you should examine the pipework to and from it - any small holes in this and the pump will either be sucking in air, or spraying the fuel back inside the tank.

Simon.

[handyman68]

I have just the same problem, but I can`t locate the relay for the fuel pump. Anyone who knows where it is?