1987 325e surging/hesistation

gejettest · 10-02-2006, 07:13 AM

Hello,
I've had this car for about 8 yrs. Had a subtle surge/hesitation during light throttle acceleration when I bought it, I've troubleshot the symptom, found many things wrong, fixed them, and still have this problem. One of the major findings was the in-tank fuel pump not working. Voltage ok, replaced pump, surge seemed to disappear. Surge back again with a vengeance, checked in-tank pump, sure enough, dead again.
What is the life expectancy of these units? I bought the previous one from bavauto, vdo brand, still lasted only about 4 yrs. Is this normal?
Any other suggestions about the surge problem?
Thanks,
I appreciate this knowledgeable forum, I've seen others, but this is the best!
Thanks again
Henry

Wayne 962 · Wayne 962's Garage

Hi Henry, welcome! If you're having fuel pump failures, it could be that there's some crap in your tank that is clogging the pump and causing it to fail. In fact, that's almost the only plausible explanation for multiple failures like that. VDO is the OEM supplier of these, and is usually a good brand. I would carefully inspect the inside of the tank to see if you can see any debris in there before installing a new one...

-Wayne

LiquidBMW76 · 10-04-2006, 08:14 PM

When was the last time you changed the fuel filter?

gejettest · 10-05-2006, 09:26 AM

Yes, fuel filter was changed regularly, and especially for this problem. A lilltle bit of history for ya. I changed the O2 sensor, found the pins in the quick disconnect were bent on the old one. installed new one making sure pins went in correctly. Found fuel tubing under car pinched, repaired same, no help. Found the resistance reading on the mass airflow sensor erratic, replaced, no help. Replaced engine coolent temp sensor (the one the DME reads to know whats going on) no help. Checked for vacuum leaks, none. Replace idle air solenoid, no difference. Checked crankshaft sensor at the DME, reads good. At the time my daughter had here 1986 325e at the house, so I took advantage of the opportunity to swap parts for troubleshooting, such as the injectors, fuel rail, fuel regulator, DME, idle control circuit box (next to the DME), none of these made a difference, I am at the end of my rope. I took the car to an independant BMW shop for some advice. I had just replaced the timing belt and adjusted the valves. Well, the car would stall whenever the clutch was depressed as in downshifting. He asked what I the valves at and I said .010" cold. He said he would go .012" hot, he said if you gave us the car to troubleshoot that is what we would do right away and go from there. He checked for a vacuum leak by pulling my oil dipstick out, and noted a decrease in the idle speed along with roughness, and said "if you had a vacuum leak you wouldn't see that change". I changed the adjustment, and yes, it does run better, less stalling. The is no pressure at the pre-pump in the tank, verified it is not working. Voltage ok, just no life.
Wayne, I did order one from your parts dept, nice guys, and I believe in support you guys. I'll post further as soon as I install the pump.
Thanks for all the replies, I'' be around for awhile as I have a long list of fix-its to do to this car.

Wayne 962 · Wayne 962's Garage

Hmm, it might be low fuel pressure - there's a reason for that pump. Please let us know what you find out...

-Wayne

gejettest · 10-13-2006, 07:51 PM

Hi, I'm back,
Replaced the in-tank fuel pump, verified pressure, runs about the same. Before I changed the pump I connected a pressure gauge to see what the car was running at the fuel rail. I drove the car with the old pump (not working one) and it was reading about 40 psi. When I felt the surge/hesitation there was no drop in fuel pressure. Replaced the pump, read the gauge, same.
I did take apart the old pump just to see why it didn't work. The strainer at the bottom of the pump had very little debris, checked bottom of tank in the sump area, found little, vacuumed it out with the suction side of spray gun, being careful to capture the atomized fuel and debris. Not too bad overall. The pump doesn't lend itself to being taken apart, so hacksaw to the rescue. The problem was one carbon brush had about 1/4" of material left, while the other one was worn down to the spring. Oh well, I guess that can't be helped.

Any other suggestions?
I am going to test the engine coolant sensor (to DME) again, as well as the idle control solenoid.
Any thoughts on the adjustment on the air bypass screw on the mass airflow sensor box?
Thanks,
Henry

Wayne 962 · Wayne 962's Garage

On some blower motors, you can buy new "brushes" which you have seen worn down here. Unfortunately, I don't know of any "fuel pump repair kits." I suppose the manufacturers would rather sell brand new ones than repair kits.

-Wayne