Starting Problem

I have a 1994 (M) 525TDS ASE which runs perfectly except for the following annoying fault.
Left overnight or longer, the starter initially starts the engine which then immediately stops although
the starter keeps turning the engine. It then requires prolonged turning over on the starter until the
engine evenually starts (sometimes reluctantly) From then on, the engine will start perfectly all day.

The car has had new glow-plugs, new battery, and new alternator. The main problem is that the over-use
of the battery in starting flattens the battery very quickly.

There is no fuel leak, but the symptoms might suggest that there is a (slow) "run-back " of fuel in the fuel filter
or fuel lift pump overnight which has to be replaced before the engine will start.

What type of fuel lift pump is used on these cars, and where is it located?

Any help would be appreciated.

The lift pump is located in the diesel tank. It is this part here. http://www.realoem.com/bmw/showparts.do?model=HA02&mospid=47379&btnr=16_0305&hg=16&fg=15

From memory, access is available via the boot by removing a cap to expose the unit.

A common problem with these are the o ring seals which fail and can cause symptoms you describe. Have you changed the fuel filter and seals as a matter of course? It is certainly worth doing so if you have'nt as this may present problems such as air leaks. But i would have to agree with your theory on a worn lift pump. They retail, depending on the brand for give or take £100.

slinky

Many thanks your prompt reply.
The position of the fuel lift pump in the tank means it is electrically operated, and probably blows my theory that
turning the engine over with the starter was needed to restore the fuel supply, unless it has something to do with
a necessity to re-bleed the engine after the fuel loss has reached a certain level.
However, your remarks are most helpful, and I will investigate the filter, O-rings, connections, and the fuel lift pump itself
and let you know the outcome

Once again, many thanks

Hi, I agree with slinky about the fuel filter, it is definately worth changing. As for the lift pump, it is electrically operated, and so there is a relay as well... Although, i dont think in your case the relay is at fault, it is worth testing it after standing over night just in case it is sticking...

The lift pump maybe weak, It only needed in operation when the engine is cold and the fuel is unprimed... once the fuel is primed and reaches the diesel injector pump, it is then the pump that takes over the pressurising of the system.... So that is still a possibilty....

Another issue in addition to slinky's post, which is linked to the above is the leak off pipe. Check these are not corroded and in need of changing, again this can cause similar problems...

As you have no other problems once it has started, you probably can discount air leaks, injector seals can fail, but you will experience starting problems and running problems all day... but if you find non of the above solves the problem, you could try getting the fault codes read in case you have a sensor issue...

hope this helps,
mightybmw

Hi
I located the fuel lift pump, cleaned it up and checked the connections. I then renewed the fuel filter (which I think has not been touched
for a long time.)
Result?
Car has started perfectly for the last three mornings. I did'nt realise the fuel filter could have such an effect - but general relief all round.

Many thanks, Slinky and MightyBMW, for your very helpful advice.

Oldfella

Im glad its now running properly.

The fuel filter needs changing with the service interval really, it collects water and impurities that are naturally found in diesel.

good luck.

slinky.