This is more of a story that I hope will help others. If someone wants to chime in on the single question I have near the end, feel free.
About four years ago I had an issue with my car where it would lose a bunch of power up top for weeks at a time. But it was never a sudden lose. You know that "jump" you feel around 3.5K? My car had basically zero change in feel past 3K. It would run like it needed major spring maintenance. But the engine was smooth, consistent, and seemingly had nothing wrong with it.
This symptom would come and go for days at a time. It seemed to always "fix" its self right before a weekend I had free. And never fell ill while driving. So this continued for months. and months. Everything appeared to check out, many parts were replaced over the course of a year. Specifically, a fuel pressure test revealed good results, and fuel pump electrical tests produced the correct resistance.
Finally, one day, I went for a drive without the back seat and cover over the fuel pump. And I heard it. The fuel pump changed pitch for a second while driving at a constant throttle position. I reached back and wiggled the plug for the pump, this changed the pitch of the pump some more. I took her home and with the car running, put a volt meter to the fuel pump prongs with the plug still attached. 12.x volts, right within spec... I wiggled the plug and wires...the pitched changed, 5.x volts. BINGFUCKINGGO!
Turns out the ground wire was not always acting as a ground. The connector was the culprit. The fuel pump its self was apparently grounded just enough to operate the pump even when the ground wire was disconnected, and produce the correct fuel pressure while at idle.
But I had to know for sure.
I went to NAPA and bought a long length of fuel pressure hose. I attached my fuel pressure tester to the fuel line and snaked it up to my windshield, and taped it down so that I could see it from the drivers seat (I love living in the country). I then went for a drive armed with the ability to effect the fuel pump voltage at will. Sure enough the pump could provide enough pressure when at lower RPMs, but as soon as the car was floored the pressure dropped off when only powered by 5.x volts. A make shift connector using crimped wire connectors later, and it ran brilliantly.
So ended a year long ghost in my car. It was nice to have it running like a 325i again, and not a 318 :grin:
Fast forward a few years. I sensed that my car was having "good" and "bad" days again. Nothing so major as before, almost at the point that I wasn't sure if it was the car having an off day, or myself. I had forgotten my lesson from years before. So I lived with this for the winter.
The other day I was digging through my electrical tool box and saw some electrically conductive grease, and remembered my cars "off" days, and that problem I had long ago. I thought, what the hell. I went out and popped the fuel pump cover off. Wiggling and a voltmeter showed nothing odd, but I pulled off the aging hack of a connector I made long ago anyway. I added some grease and put her back together. Since then, my car hasn't had an off day.
I wish grease would solve my off days :)
In my years on BMW forums (not just this one) I've never heard anyone talk about a partial failure of the fuel pump. Usually either the pump dies, or the positive wire dies. Or, perhaps on most cars the pump isn't grounded enough to keep it running after a loss of the negative wire. In any case, hopefully someone doing a search might pick up on this thread and diagnose their pump as being partially grounded.
And now for the question you've all been waiting for, what is the proper connector for the fuel pump? I'd love to replace my ghetto crimp connector with the real deal so I never have to deal with this again!
About four years ago I had an issue with my car where it would lose a bunch of power up top for weeks at a time. But it was never a sudden lose. You know that "jump" you feel around 3.5K? My car had basically zero change in feel past 3K. It would run like it needed major spring maintenance. But the engine was smooth, consistent, and seemingly had nothing wrong with it.
This symptom would come and go for days at a time. It seemed to always "fix" its self right before a weekend I had free. And never fell ill while driving. So this continued for months. and months. Everything appeared to check out, many parts were replaced over the course of a year. Specifically, a fuel pressure test revealed good results, and fuel pump electrical tests produced the correct resistance.
Finally, one day, I went for a drive without the back seat and cover over the fuel pump. And I heard it. The fuel pump changed pitch for a second while driving at a constant throttle position. I reached back and wiggled the plug for the pump, this changed the pitch of the pump some more. I took her home and with the car running, put a volt meter to the fuel pump prongs with the plug still attached. 12.x volts, right within spec... I wiggled the plug and wires...the pitched changed, 5.x volts. BINGFUCKINGGO!
Turns out the ground wire was not always acting as a ground. The connector was the culprit. The fuel pump its self was apparently grounded just enough to operate the pump even when the ground wire was disconnected, and produce the correct fuel pressure while at idle.
But I had to know for sure.
I went to NAPA and bought a long length of fuel pressure hose. I attached my fuel pressure tester to the fuel line and snaked it up to my windshield, and taped it down so that I could see it from the drivers seat (I love living in the country). I then went for a drive armed with the ability to effect the fuel pump voltage at will. Sure enough the pump could provide enough pressure when at lower RPMs, but as soon as the car was floored the pressure dropped off when only powered by 5.x volts. A make shift connector using crimped wire connectors later, and it ran brilliantly.
So ended a year long ghost in my car. It was nice to have it running like a 325i again, and not a 318 :grin:
Fast forward a few years. I sensed that my car was having "good" and "bad" days again. Nothing so major as before, almost at the point that I wasn't sure if it was the car having an off day, or myself. I had forgotten my lesson from years before. So I lived with this for the winter.
The other day I was digging through my electrical tool box and saw some electrically conductive grease, and remembered my cars "off" days, and that problem I had long ago. I thought, what the hell. I went out and popped the fuel pump cover off. Wiggling and a voltmeter showed nothing odd, but I pulled off the aging hack of a connector I made long ago anyway. I added some grease and put her back together. Since then, my car hasn't had an off day.
I wish grease would solve my off days :)
In my years on BMW forums (not just this one) I've never heard anyone talk about a partial failure of the fuel pump. Usually either the pump dies, or the positive wire dies. Or, perhaps on most cars the pump isn't grounded enough to keep it running after a loss of the negative wire. In any case, hopefully someone doing a search might pick up on this thread and diagnose their pump as being partially grounded.
And now for the question you've all been waiting for, what is the proper connector for the fuel pump? I'd love to replace my ghetto crimp connector with the real deal so I never have to deal with this again!
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