Cutting out

Christopher

Christopher

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Took my car out for an enjoyable run yesterday, and whilst cruising at 90 got a loss of power. i managed to coast to the hard shoulder to a stop. Tried to start it but it wouldn't fire. Tried again a couple of minutes later and straight back into life, and no problems all the way home. This is the second time it's happened.My immediate thoughts are that it's likely to be a fuel supply issue, and more specifically a relay. On checking the fuel pump relay by the ECU (mine's a csi) it felt hot, but given its an intermittent issue this might be a tricky one to nail. To further complicate it appears that this relay in NLA. (please BMW keep these vital parts available !). How can i test an intermittent fault (that doesn't appear to be wiring related at the terminals) ? any thoughts would be appreciated.
 
I had the same problem after an engine overhaul. After a lots of troubleshooting the problem proved to be a badly earthed distributor. After installation of a new cable and connectors between the body and the distributor the problem dissapeared.
 
While you are probably correct on the relay being the issue, I had a similar experience with my 81 320i years ago. Would just die, just like the ignition was switched off. An old timer said the distributor has a copper coil that can get a microfracture in the wound and cause this. He was right as I changed it and drove happily for 3 years till I sold the car.

Look on Bimmerforums under e24, somewhere there, there is a nice write-up on relays which may help you replace the one you believe may be faulty.
 
Connect pin 30 of the relay to pin 87. Use a 15 amp fused jumper wire.
If you blow the fuse your pump is seizing.
If the car quits running check for fuel pressure at the fuel rail after checking the fuse.
 
Thanks for the feedback chaps - Bavbob & Henrik - when you say you had the same issue, did your cars start again with no problem after a couple of minutes and run fine OK until it happened again ? The distributor is one component (apart from the trigger points and electronic ignition) that hasn't been replaced in my ownership, so it's possible it could have an issue.

Thanks too SFdon for the tip on testing the relay. I'll give it a go. my issue is that's it's an intermittent and rare issue, so given the car is running ok now, i'm guessing the relay would check out. i'd like to try to figure out what running condition would make this occur in the first place ?

If anyone could point me in the right direction to find a NOS fuel pump relay this would be an inexpensive place to start. Injection distributors are a fortune ...
 
besides the relay or fuel pump overheating it could also be your coil overheating. Then when it cools off after a while, it works again. Perhaps check condition and that ballast resistance is ok.
 
Yes. The car could sit for a time, ranged from a few minutes to hours, then restart as though nothing had happened. Then again, when I had a bad relay on my e24, it acted this way also.
 
Christopher:
If you can't find a NOS relay, don't despair. You can use any type of relay as long as it can handle the fuel pump amperage which is the same as the fuse rating (i.e. 8 amps, in my '74.) Any auto parts supplier will have something that works.
 
I have posted this before but it is worth checking. As others have said the coil can overheat if the ballast resistor has the wrong rating or isn't working. The standard coil uses an 0.8 ohm resistor, the current replacement coils, either red or silver, use a 1.8 ohm resistor which is stated on the label. It happened to me several times on a 69 2002, suddenly dies at speed but would restart after one minute.
 
Try another coil.
Typical behaviour of a bad coil. Also check whether you get 12 Volts at the coil when starting but only 9 Volt when running (thorugh balast). I once had a bad starter motor solenoid that would put constant feed on the 12 Volt circuit it should only feed when starting (a feed that circumpasses the balast). That then fried the coil while running. Would start up again after coil was cooled.

Other possibility on the D-Jet: The pulse generator in the distributor. The inset that has mechanical switches to send impulses to the ecu in the dizzy body. I once changed a sorry looking one for a better looking used one. Car ran great until it warmed up It then just died and would only restart after a cool down.
Try a known good one if you can (new ones are available but expensive)

Fuel pump going bad should be audible. Bad fuel pump relay could be diagnosed by simply bridging it. If it´s a bad fuel pump relay and it´s NLA: There´s nothing exiting about these. Should be reapairable by a guy with a voltmeter and a soldering iron. Most likely a relay from another model would work with some wiring mods.

If it´s a bad pump: Don´t shell ourt for an original replacement. They are $$$. There´s plenty of generic pumps out there that will work fine in this application. Pressure is regulated by the regulator anyway. You´d need a pump that delivers slightly more than 2 bar (about 2.5 to be safe) but relatively high volume. There´s cheap replacments out ther (look for anything offered for E3 and E12 L-Jet, these will work) or if it makes you feel better go through the bosch catalogues, there should be a recommended generic bosch replacement (which is a relabeled cheapo pump from the same factory in china anyway - but it´ll work fine). OR get a better pump from a motorsports outfitter. Still half as expensive as the original. But much nicer to look at.
 
Thanks for all the words of advice. Stan kindly forwarded me an article detailing this issue, with the symptom of the tacho dropping to zero at the same time, which mine did. Looks like the coil and it's connections could be the likely culprit, so will take a good look at this first.
 
It's always a pain when these things happen and potentially dangerous too.

When you turned on the ignition to try to restart the car, does the fuel pump buzz up as it should to pressure? You know the noise and if it does't then at lest you know it is fuel or fuel controls as opposed to ignition.

Good luck with the problem.
 
An update to my issue. I took a look at the wiring to the coil and one of the wires had worn insulation, exposing bare wire for about an inch. i taped it up good an neat and have spent 3 hours driving today (in glorious sunshine) without incident. With luck this was it, and a simple fix. Thanks to Stan for the heads up.
 
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