intermittant hard start and miss

[bcnya]

Hi all, My '88 325 iX has been doing things lately that are probably fairly common and I am wondering what the most probable cause (s) are.

When starting, warm or cold, occasionally the engine will fire briefly, just long enough to burn off the residual fuel pressure then die. I have to try several times and then wait a few minutes before the engine will start. Once it does there is no problem.

The other problem that I've noticed just 3 times in the last week is that the car momentarily dies while driving. The tach goes to zero but within 1 - 2 seconds the car is running fine again.

To the first problem I feel that the fuel pump relay may be at fault but perhaps both problems are related and there is another relay at fault. Or not.

Can anyone relate similar instances and what the fix was?

Thanks,
Roy

[KC Ron Carter]

intermittant stalling is electrical, 100%.

The starting is can be a simple issue.
The fuel pumps have built in check valves to retain fuel pressure.
As pump wears the check valve starts to allow pressure drop.

Replace the pump or I have a real deal fix.

Fuel pump check valve.


I could replaced the fuel pump for $200 but I fixed the problem by putting in the fix from BMW for about $3.50,
part # "16 14 9 068 988"

Now the engine starts on first turn, hot or cold, overnight or after
standing for a while.

Diagnosis:

The check valve in the main fuel pump was leaking allowing the fuel injector rail residual pressure to bleed off resulting in formation of a huge fuel vapor bubble in the fuel rail and back down the fuel line toward the pump.

The extra cranking time was needed by the fuel pump to recompress and eliminate the fuel vapor bubble in the line and repressurize the fuel injector rail.

Installation can be anywhere in the fuel pressure line but next to the main pressure pump is best.

It is a two screw clamp job.

Later,

[Masterpeaker]

My 325i touring had the same problem. Just installed a new check valve next to the fuel pump en now it starts right away.

Perfect solution for only 10 euro's

Masterpeaker

[jase007]

Roy:

I agree with what the others have said but ... with similar issues (firing .... running briefly .... then not refiring) I ended up replacing the main and fuel pump relays (with the extras I had in glove box) and never had to install the check valve. I have replaced my spares with more relays ... in the glove box. Cheap insiurance. I was back up and running in moments from the gas station where it decided to fail.

my iX died a few times while running and I think replacing the main relay cured that. I also rebuilt the throttle body after chasing down some air leaks b/c I was in there.

Here is the thread on sealing vacuum leaks.

Jason

[Masterpeaker]

Originally posted by Masterpeaker
My 325i touring had the same problem. Just installed a new check valve next to the fuel pump en now it starts right away.

Perfect solution for only 10 euro's

Masterpeaker

Oeps, i was confinced to quick. Again it took a long time to start the car after standing for a while.

I did some more investigation and i think i found it. The hard plastic connection in the fuel line just under the inlet manifold was leaking and one fuel hose was cracked. I replaced the hose and refitted the other hoses on the connection using new clamps. Now everything seems to work fine again. If i get trouble again i will replace every hose and all the things that are related.

Masterpeaker