Help Fuel line issues

Bean Swank

Bean Swank

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Hi all,

Wondering if anybody lse has encountered this issue.
When I was driving along yesterday the car started to misfire and felt like something was clogging the fuel lines. Luckily I was near a servo so I pulled up there as my engine was overheating.

I let the car cool down and then went to start it again. It started fine but was doing the same thing. and blowing a bit of smoke.

This had happened to me some time before hand (about 2 or months ago)
which funnily enough was the last time (before this day) that my petrol level was below half way.

So I filled it up (being at the servo already) and started it up. worked fine..drove it home without an issue.

Now its a CS with an aftermarket i, which is a Haltech Injection system.

Talking o my mechanic he thinks that air is getting into the send unit or the lines. I will have to check that first, but also he mentioned that it did not have a pre supply pump in the tank. He thought I should be able to get one from an old 3 series and install that (say an e21) and it might be a simple conversion.

Has anybody come across this before or done it themselves. And if so what is involved?
 
so you think it might b coincidence that it happens only when the fuel tank is below halfway?

or does this contribute?

can't say i noticed a smell, it did start to blow a bit of smoke though
 
Could be coincidence - but its relatively easy to check the pickup so its a good place to start. The overheat and smoke are more difficult to explain by just fuel starvation.
 
I had an 85 535i which had the in tank pump go out and, when I was down to about 1/4 of a tank, it had similar symptoms; surge and die like it was running out of gas. I kept the tank full until I got around to replacing the pump which fixed the problem. I think however, there are some people on this board that have done the FI conversion with out an in tank pump and haven't had problems?
 
If your CS has been modified to EFI and the original CS gas tank was retained then it is probable the fuel pickup and return line device is the culprit.

The original CS tank lacks a fuel return line for the EFI conversion so usually a donor pickup device which usually incorporates both fuel feed and return line is used. These units also contains the fuel sender unit so essentially, this device serves 3 different functions. I believe some have used the VDO unit from the early 530i, there may be other cars that used a similar fuel pickup unit. The problem lies in the fact that the CS tank is of a really deep design and the donor fuel pickup unit is usually not long enough to pickup fuel from the bottom of the tank. Therefore, even though the tank is about 1/4 to 1/3 full, the fuel cannot be suck out due to the overly short suction device. Also, the fuel level reading on the tank gauge will give a false and really inaccurate reading.

If this is indeed the case then you can either find an original CSi tank with proper sender and fuel pickup units or use the oem CS tank with the correct length sender/pickup unit and somehow fabricated a return line right into the tank.

Bert
72 3.0 CSi
88 M6
 
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