BMW 325i 1983, fuel problem. Car runs fine for about 4 miles and then engine fades to a tick over.?

Question

Leave for a few minutes with ignition off then restarts and runs O.K. for another mile or so. Leave for 30 minutes with ignition off and then runs for about 4 miles again.
Have had most of the fuel system replaced plus new rotor arm, distributor head etc. Two different garages have given up saying they don't know what the problem is.
CAN ANYONE GIVE HELPFUL ADVICE PLEASE.

Answer 1

Its does not sound electrical, so ignore the rotor arm etc.

It sounds like fuel flowrate to me, resulting in a drop in pressure, have you checked the fuel pump and all the lines?

It seems either the pump cannot keep up with the flow required or there is a blockage restricting the fuel flow rate.

Alternatively maybe it relates to temperature. I think BMs reduce fule pressure when the engine overheats so, if the engine temp is ok, it might be that sensor thats faulty. disconnect or short it out, it depends if its "open on fault", or "close on fault"

If you run the engine at 1500, 2000, 2500 RPM etc, does it fail at all these values. I wonder if it runs ok at 1500 then the fuel pump can keep up with that flow rate, but not higher.

Answer 2

If you haven't already contacted your local BMW dealer, what are you waiting on? The older BMW's have sensors located in different areas than the newer models, and the sensors also have different functions. It may just be that your fuel sensor is acting up in which case you wont get enough fuel or the problem could be larger. Rather than continue to muck about with it, I'd say save yourself the explosion that will occur if you actually have a leak and that fuel hits your HOT manifold and seek professional help in the form of your Local DEALER!

Answer 3

I have come across this with a few motorbikes and cars, and eventually a mechanic sussed it on one of them, and it is worse than you were hoping.
Cylinder heads, and especially alloy ones, sometimes develop hairline cracks between the inlet and outlet valves. As the engine warms up, the head expands, the crack opens and the engine starts sucking in extra air, making the mixture far too lean to run on. It overheats, loses power and forces you to stop. While you wait for the mechanic to arrive, it cools down, the crack closes up and you look stupid when it starts perfectly for him.
This is a big, expensive job to do on a 23 year old car, so unless it is otherwise in superb condition and also you are planning to keep it for years and years, scrapping it is the smart option at this point.

Answer 4

Hi, I have a 520i on a 91 plate and I have a similar prob, have been told that it is the manifold? The big connection box directly under the **** pit on the exhaust. Apparently, if you can't get a second hand one these can cost in the region of £600 to fix, hope this helps.

Answer 5

I had same problem, on mine it was the Engine Temp Control Sensor....A small electrical fitting that tells the engine that it is runnng to hot and will not let it rev over about 1500 rpm..If your temp guage says that everything is ok, then it could be a faulty senser. It cured mine and costs me £14.00 & £10.00 to fit

Answer 6

Fuel pipe blockage/ broken hence fuel starvation, does it have a cat if so it might be breaking down making the engine lose compression.

Answer 7

sound like your theft device are shorted or do you have a original key came with the car or your E C U may be bad have a dealer do diagnostic on it that should tell you exactly what is wrong with your car.

Answer 8

Try asking your question on this site,
http://bmwland.co.uk/
lots of enthusiasts on there (and some BMW Technicians as well) - maybe able to help you.

Answer 9

the car is gettiing old