Still crank and no start. 91 850i

[2001740il]

Been trying to get this car fired back up but so far no luck. I replaced the EML no change I replaced the fuses in the trunk no change.

I know it is not energizing the fuel pump when it does the crank no start. It was intermittent but now it just will not start.

Still wondering if anyone else has solved this problem.

[8eights]

All sensors under the oil fill cap pushed down and seated correctly?

And when you turn the key to the start position without cranking, DK's Buzzing?

[2001740il]

DK's are buzzing away. I will double check the connectors under the oil fill but it is effecting both banks. I know for sure the fuel pumps are not getting energized when it cranks but no start.

[8eights]

Had a sensor under there not fully locked, Car wouldn't start, The fuel pumps also share a ground wire on the fuel pump carrier, If there's a issue with said wire, The pumps will not work! Have you tried feeding current directly to the pumps?

[dragon850]

Have you tested the crank sensors, 540ohms between pin 1 and 2 is good.
You replaced both fuses in the trunk??
What does the diagnostics say what code??

[koenig d]

My poorly fitted aftermarket alarm somehow stopped 1 pump from working, maybe DWA. related??

[2001740il]

No Codes.
I will check the ground wire.
I have not energized the pumps with a jumper wire yet. I was thinking of working backwards to see where the open was located rather than just running a separate wire to them.

I do know when it will not start the fuel pumps are not energized.

[6speeder]

I know it is not energizing the fuel pump when it does the crank no start...

There is only 1 way to confirm 100% if the pumps are energized... by getting to the pump harness, disconnecting it, and putting a voltmeter to the pins inside the harness. while cranking you should get 9.0 - 10.25v on both positive pins. put the ground lead from the voltmeter inside the harness too, not on the chasis. there is an easier way to do this (but not as conclusive) by putting the voltmeter over the fuel pump fuses while cranking but this method wont confirm the wiring is ok from the fuses in the engine bay to the fuel pump harness, the harness to the ground, or the harness itself which is why you really should get to the pump harness to test the voltage.

When you say you know the pumps are not energized do you know this because you tested as above?

Note that if you get voltage to the pump harness while cranking you just confirmed that all the following work:
both fusible links, both crankshaft and both camshaft position sensors, eml, both dme, dme relay, fuel pump relays and fuel pump fuses.
and therefore is mostlikely bad fuel pumps, or less likely clogged fuel filters.

[2001740il]

Everyone thanks for sharing.

I took the back seat out and connected a fuel pressure gauge to one of the pumps. And I could hear them run when they ran with pressure car started. When they did not run and no pressure no start. Since both of them would either run or not run I did not check the voltage at the connector since I did not have an easy way to do that alone at the time.

So the common ground could be an issue I am going to check that next.

I will update any results thanks again.

It use to be an intermittent problem now it is at least consistently not starting I think that is actually a good thing. lol

[6speeder]

the common ground is in the trunk, passenger side above the tail light.

you need to test voltage, if you get voltage AND no pressure directly at the pump it MUST be an issue with the fuel pump assembly. non working pumps, poorly working pumps that run but dont produce enough volume, or alot less likely the fuel pump strainer is clogged. i know you only tested one pump cause the 2nd access hose clamp is a pain to get to so you can test both pumps by connecting your pressure gauge under the car at the fuel filters (do it before the filter not after). you can test voltage by yourself, get a few inches of inside electrical wire 12/2 residential. make 2 short jumpers from the voltmeter to the fuel pump harness... you can fold over the ends of the wire that go inside the harness, it will make them thick enough to stay put inside the harness while you crank.

your batteries may also be not strong enough to supply the right amount of current to get the pumps to run to produce enough volume. you cant go by the battery voltage when not under load so without checking the voltage while cranking at the fuel pumps you will never know and your gona be chasing your tail.

[imola38]

I would start with just replacing both fuel pump AND main relays if they are 20+ years old.

I know it sounds like suggesting "throwing parts at it" but in this case, they are cheap to replace and can absolutely leave you stranded and cause intermittent start/no start conditions.

Sounds like you also need to get a voltmeter and begin testing for power at the pumps as previously suggested as well.

Ben

[bruinbro]

Hate to say this but it sounds like you may have the same problem I had. There is a fairly large harness with a butt load of wires in it that connect the relays on the passenger side of the engine bay to the fuse box on the left side. It runs against the firewall. What happened to my car is the insulation on the individual wires became brittle through age and cracked and fell off allowing the conductors to short against themselves and any other metal objects. The fuel pump relays and fuses are connected by these wires. Had to have the whole bundle undone and each wire wrapped. Car started fine after that.