My 1993 325i has just developed starting problems.
It will almost start but won't. To me it seems like a fuel problem so I started to look in that direction.
I have found that the fuel pump relay is not operating. 12v is present on the primary winding when the key is on but no earth is present on the primary winding so the relay does not energise.
I have manually operated the relay (by removing the cover) and I can hear the fuel pump operate but when the engine is turned over it still will not start.
Tracing the primary side of the relay that should have an earth on it, it goes into an ecu of some sort.
The Haynes manual doesn't have a circuit diagram that shows the fuel pump circuit so I am stuck.
Any help greatly appreciated.
The module is fitted under the left hand bulkhead accessed from under the
bonnet, behind a plate held in place by about 7 small bolts. There is a large
bundle of wires going through this plate into the module.
Can you tell me what the DME is?
The DME ( Digital Motor Electronics ) is basically the central brain behind the Engine electronics and also shares other duties. This is just about the most simplistic way to tell you. There are so many things that the DME does but triggering your fuel pump is what matters here. There must be a reason that the fuel pump is not triggering the pump and most certainly is the obvious thing to figure out here. Have you been able to pull any fault codes?
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Unfortunatly I cannot get any fault codes at all.
I have turned on the igition and pressed the gas pedel 5 times in 5
seconds but the check light does not light at all
Is this a bad sign?
Is there any other check I can do?
Today I managed to borrow a secondhand working DME from a broken 325i and got exactly the same results.
My car is a European model so the check light indication is not likely to work, apparently that is for US spec models only!!
The fact that the fuel pump is not priming / the fuel pump relay does not operate when the ignition is turned on suggests that something very basic is not happening. What could stop the fuel pump relay from operating if it is not the DMU?
I have a spark at the plugs when the engine is cranked!
I got a mechanic to come round yesterday this his diagnostic eqpt and the electronics all check out.
The only fault code that was displayed was code 26 - ECU batt voltage - 1 amp.
I have already checked the pins on the harness that should have batt voltage and they are ok.
The mechanic seemed th think that the BMW immobilizer may have gone faulty.
I suppose that could make sense and as I have a Cobra immobilizer fitted as well I could by-pass the BMW one if I was able to find a diagram or if anyone could tell me the pinouts.
Apparently, the immobilizers are coded to match the vehicle and so are not interchangeable.
If anyone has any knowledge of the BMW immobilizer that they can pass on to me I would be very gratefull.
Well I have now put the bcar back together and found that the engine will fire and rev up to 1500 - 2000 rpm and then cut out. It will do this every time I try to start it after putting it back together!!!
After deciding that the problem now seemed to be that the car would not idle I tried starting the engine and pumped the trrottle to see if I could keep it from stalling - and I could - it backfired a bit but I could keep it on.
I then thought I would test the idle control valve.
I found it hidded behind the throttle on the inside of the inlet manifold.
IT HAD FALLEN OUT OF ITS MOUNTING.
Gaping 1" hole in the inlet manifold was the reason it would not start / run.
Live and learn - it has been a hard week.
I had checked for any loose hoses when I started with this fault but I didn't realise there was a hose where this one was.
I think the lesson is: check the obvious most basic things first, then check them again. Don't assume that because the car is full of fairly complex electronics that they are at fault.
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