Engine won't run, too much fuel

BimmerSchnitzel · Post by **BimmerSchnitzel** » Wed May 13, 2015 3:28 pm

Trying to make a ChumpCar from a 1978 530i. We gutted the interior and removed as much emissions equipment as we could. Upgraded to a E28 radiator.

Anyway, we can't get it to start and run normally. At this point, it will start and run for a few seconds then die. It won't restart unless we disconnect the fuel pump, and then it will run for a couple min until it runs out of fuel.

We can see it pouring fuel out the exhaust when we try to start it and the ignition system and timing have been checked repeatedly and seem to be close enough to run.

What would cause the fuel computer to dump so much fuel, or what might be wrong keeping the injectors open? I feel like there has to be a sensor or wiring problem, but I'm not sure where to look.

Any tips to diagnose would be great. Thanks in advance.

GripGreg · Post by **GripGreg** » Wed May 13, 2015 9:04 pm

Injected engines don't generally need to be primed using the go pedal.
Try starting it by turning the key only?
After it sits a while so the injectors aren't flooded.
Hope this works,,,,Greg

Mike W. · Post by **Mike W.** » Thu May 14, 2015 12:12 am

First check the fuel pressure regulator, the FPR can fail in at least a couple of different ways, one of which is the diaphragm failing which results in fuel going thru the vacuum line to the intake manifold. Next look at the starter wiring. I'm pretty sure all 530s used the same setup where there were two push on leads going to the starter along with the large battery cable one. One of them is to engage the starter, the other is actually an output to give increased voltage to the coil on starting. If you get it miswired, and I did when I injected a Bav a thousand years ago, you can get full starting enrichment, which is just pig rich, all the time it's running. I'd have to look at the wiring diagram again to see how it works, but I remember clearly when it happened. I didn't see gas out the pipe, but I did see black smoke.

Other possibilities, but that's where I'd start.

D. · Post by D. » Mon Jun 01, 2015 10:26 pm

It's probably the fuel pressure regulator. If it's the original one, it's time.

YouTube · Post by **Peter Florance** » Tue Jun 02, 2015 8:03 pm

Also open connection to coolant temp sensor. I think that can causing flooding

BimmerSchnitzel · Post by **BimmerSchnitzel** » Thu Jul 16, 2015 7:44 pm

Checked the starter wiring, since we did replace the starter. Seems like it is correct, reversing it the car won't turn over. Not sure how to check the FPR. I think it is a wiring issue. A lot of stuff got taken off or disconnected. I think a sensor is missing or unplugged.

Here is a link of pics showing some of the wiring. If anyone could look and see if something important is unplugged or wired wrong, it would really help. Thanks.

https://www.dropbox.com/sh/ozszjrcgc0wk ... h0Z-a?dl=0

Mike W. · Post by **Mike W.** » Thu Jul 16, 2015 11:03 pm

BimmerSchnitzel wrote:Checked the starter wiring, since we did replace the starter. Seems like it is correct, reversing it the car won't turn over. Not sure how to check the FPR. I think it is a wiring issue. A lot of stuff got taken off or disconnected. I think a sensor is missing or unplugged.

Here is a link of pics showing some of the wiring. If anyone could look and see if something important is unplugged or wired wrong, it would really help. Thanks.

https://www.dropbox.com/sh/ozszjrcgc0wk ... h0Z-a?dl=0

No pics of the wiring, but the starter replacement did raise a possibility. There will probably be a small, 1/8", maybe 3/16" push on connector. Not the 1/4" one. Remove the small push on connector. IIRC that goes to both the ballast resistor by the coil and the ECU to provide for starting enrichment while cranking. If that is hooked up wrong you can have it backfeeding to the ECU telling it is cranking all the time and creating a massive rich condition.

Hefeweizen · Post by **Hefeweizen** » Thu Jan 11, 2018 11:52 am

Did this ever get resolved?