BimmerFest BMW Forum banner

1 - 18 of 18 Posts

·
Registered
Joined
·
463 Posts
Discussion Starter #1 (Edited)
Guys,


I am sorry for starting a new thread, it really is that important.

So.


Symptoms:

start car, drive it, with in 2 or 3 mins the car will lose power around 3000rpm. Symptom is most obvious at WOT. The car will rev up to 3000 RPM then just lose power. sometimes it even bogs. I pull over, turn off the car. re start it and it is fine, even at WOT for a few mins... then, problem all over again.


attempted fixes:
- cleaned injectors
- new fuel pump
- replaced aux fuel pump
- changed entire exhaust system
- Mass air flow sensor swapped out
- tried another ECU (not sure if it was fubar as well)
- fuel filter 2 years old
- new gas
- tank not dirty
- new rotor, distributor cap, wires,
- swapped coil
- fuel pressure regulator swapped
- new spark plugs


keep in mind, i turn the car off, and turn it back on. and it temporarily fixes it. it is not a hot vs cold issue. it seems like an electrical issue of some sort...

guys, this sucks.. i need help. I have tried everything.

I am now sourcing new crank position sensors to see WTF.

1985 325e 4 door auto....

go.
 

·
D'oh, You Kids!
1984 633CSi, 1985 635CSi, 1985 325e, 1987 325is, 1993 325is, 1995 318is, 1995 M3, 2003 F150
Joined
·
29,578 Posts
Were all the parts that your put in NEW or from other cars?

Note my signature: Guessing gets expensive. Do some diagnostics and stop throwing parts at it. Did you test the crank position sensor? Did you replace it with a NEW one? Did you test the speed sensor? (can't tell if you have the crank position sensor separate on the bellhousing or one combined at the front of the crank) What's your fuel pressure? Is the fuel pressure regulator working at idle and at full throttle?
 

·
Registered
Joined
·
463 Posts
Discussion Starter #6
update:

Seems as if further analysis reveals that over time my fuel pressure is dropping.

Replace the fuel filter. The main fuel pump was brand new last year. makes a loud buzzing noise however. The Aux pump was just replaced.


anyway, we are trying a new fuel pump, one that i know works.

IT is odd. i took the car in to get a few things fixed and it leaves with this massive error.

What other cuases would create a low fuel pressure issue, turn the car off, start it again then it is fine for a few km. hit WOT a few times and it happens again.???Q?Q?Q
 

·
D'oh, You Kids!
1984 633CSi, 1985 635CSi, 1985 325e, 1987 325is, 1993 325is, 1995 318is, 1995 M3, 2003 F150
Joined
·
29,578 Posts
The sock filter in the tank may be picking up crud while running, eventually blocking it enough to choke off the fuel flow. When you shut it off the suction is gone and the crud falls away, only to be picked up again after it's running again.

Edit: is the coil getting really hot?
 

·
Registered
Joined
·
463 Posts
Discussion Starter #8
This was my original thought. (after research)

so, i had the AUX pump changed to try to eliminate the "buzzing". I was told that the pump pick up came up clean.

So, even though some debris would fall off naturally, wouldn't some remain, indicating a major debris issue?

I suggested a new tank but was dissuaded.

So, i tried a few ideas.

How long would it take for suction to decrease upon shut down? So initially i tried a shut down of 10 seconds. and that worked.

Then after more trouble shooting i tried a shut down and an immediate restart. which also worked. That lead me in the electrical path.


the Debris issue makes more and more sense. new AUX pump then all of a sudden there is an issue.
 

·
Registered
Joined
·
463 Posts
Discussion Starter #9
the shop keeps telling me that isnt the issue. (the tank being debris filled).


it is the original tank. it must be full of debris.

He changed the fuel filter and said it was full of debris, (only 2 years old)..
 

·
D'oh, You Kids!
1984 633CSi, 1985 635CSi, 1985 325e, 1987 325is, 1993 325is, 1995 318is, 1995 M3, 2003 F150
Joined
·
29,578 Posts
The debris isn't magically appearing between the pump and the filter. Pull the tank and have it cleaned.
 

·
Registered
Joined
·
463 Posts
Discussion Starter #11
update:

The tank turns out to be clean. although, we did find the problem.

turns out the brand new bosch fuel pump i installed was faulty. it was the source of the buzz/whine. it was also causing the decrease in fuel pressure at WOT.

installing the old pump also fixed the whining.

very odd for a brand new pump...
 

·
Registered
Joined
·
463 Posts
Discussion Starter #13
the Saga Continues.

The old pump seemed to fix things temporarily. the car had power, but only 85%. but enough to drive and enjoy.

Slowly the car lost power again. Now maybe 40 to 50% power at most. I ordered a brand new pump, installed it and the problem persists.

I am leaning toward some sort of electrical issue. I am pretty annoyed and want it fixed.
 

·
Registered
Joined
·
5,550 Posts
makes me think the fuel filter got clogged again? although you said the tank is clean
 

·
Registered
Joined
·
463 Posts
Discussion Starter #15
How fast can a filter get clogged?

A New filter was replaced prior to the pump being replaced. it was only when they swapped the pump that the power came back, only temporary of course.

Makes me think that the pump replacement some how moved something or touched something that got it to work for a bit.
 

·
Registered
Joined
·
5,550 Posts
How fast can a filter get clogged?

A New filter was replaced prior to the pump being replaced. it was only when they swapped the pump that the power came back, only temporary of course.

Makes me think that the pump replacement some how moved something or touched something that got it to work for a bit.
I know,
normally it wouldn't get clogged so fast.
you said the power kept decreasing gradually, that's why i thought. however a simple restart wouldn't solve a clogged filter problem
 

·
D'oh, You Kids!
1984 633CSi, 1985 635CSi, 1985 325e, 1987 325is, 1993 325is, 1995 318is, 1995 M3, 2003 F150
Joined
·
29,578 Posts
Simple way to figure this out is test the pressure at the fuel rail! Plumb the gauge through a tee and put it on the outside of the windshield so you can read it while driving.
 

·
Registered
Joined
·
463 Posts
Discussion Starter #18
Thanks horn hospital.

Previously that was an issue. We now have strong, consistent fuel pressure.

We dropped the exhaust system and the car is back to 100%.

So it's an aftermarket cat and it's clogged. So we are chasing that issue.
 
1 - 18 of 18 Posts
Top