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1981 528i Starting/Running Problem

11K views 13 replies 3 participants last post by  ryangschultz 
#1 ·
I own a 1981 528i BMW. It's been running great and I have done a lot of electrical and mechanical work on it. But now, all of the sudden, it is having an intermittent starting problem. I just replaced the fuel filter because I thought that may be the issue and I had never replaced it, but the issue is still there.

Sometimes the car will start right up, other times it will turn over but never start. After replacing the fuel filter it will not sometimes start but then stall after a second or two. Could it be an intermittent electrical problem or another fuel problem or what? I don't think it's the pump because the car will start and run, just not every turn of the key. Please help!
 
#2 ·
I own a 1981 528i BMW. It's been running great and I have done a lot of electrical and mechanical work on it. But now, all of the sudden, it is having an intermittent starting problem. I just replaced the fuel filter because I thought that may be the issue and I had never replaced it, but the issue is still there.

Sometimes the car will start right up, other times it will turn over but never start. After replacing the fuel filter it will not sometimes start but then stall after a second or two. Could it be an intermittent electrical problem or another fuel problem or what? I don't think it's the pump because the car will start and run, just not every turn of the key. Please help!
Maybe the fuel pump relay or some other electrical problem? See if you're getting fuel pressure when the problem occurs. The horn and fuel pump relays are the same, switch the two. Older cars are prone to electrical issues. Check the battery and ground connections real well and examine the fuses real carefully. I saw someone was selling a ceramic and copper fuse replacement kit for $5. Much better than plastic fuses.
 
#3 ·
Catso,

Well the fuel pump relay is actually just a fuse, so I can't switch the horn relay and fuel pump relay. But all the fuses are good. I believe I am getting fuel pressure as well because every tenth start or so the car will start and run and I can drive it around just fine until I shut it off, then it has troubles starting again. Any other ideas? I mean I've replaced all the electronics recently, I even put high performance ignition wires in it and all the spark plugs look great too.
 
#9 · (Edited)
The BMW part number is 13631272131, called Combination Relay (fuel pump relay), price $125 plus tax. Part location behind the bracket that holds the water reservoir and right above the break fluid reservoir. It's a small box, 1 inch in depth, 2 inches wide, and 2 inches lenght. The bottom of the unit has two openings for inserts (cables are attched here).
 
#10 ·
The BMW part number is 13631272131 and is called Combination relay (fuel pump relay), price is $132.90 plus tax. The exact part location is behind the bracket that holds the water reservoir and right above the break fluid reservoir. It's a small box, 1 inch in depth, 2 inches wide, and 2 inches lenght. The bottom of the unit has two openings for inserts (cables are attched here). Enjoy your classic car.
AutohausAz has the part for $50.15 shipped.
 
#14 ·
Alright, just got the car back and it's starting and running great! I had my mechanic friend diagnose it and it was the fuel pump relay, there was also some loose or broken connection he fixed under the fuse box or something too. Got the relay from bavauto for $55. Thanks a ton for the help guys!
 
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