850 no start

[632 Regal]

Happened a couple times so far, now it cranks but no start, not even close. Batteries are at 12.74 volts but I checked it while cranking... 9.3 volts! Houston we have a problem. Off to score a couple DL-49s if anything is open tomorrow. Wish I would have checked this a few months ago.

Carry on.

[shogun]

the problem is that BOTH batteries must be good and in same condition on the 850.
Do you have a load tester? Better get one, pretty cheap from Harborfreight, I also got one.

Car and Deep Cycle Battery Frequently Asked Questions (FAQ) Section 4

Also check both fuel pumps. In case the fuel pumps did not work for some months, it could even be that both are stuck.
Plus check the fusable links in the trunk next to the batteries. We had a similar case some years back with an 850. Sometimes started, sometimes not. Tested and changed a lot. In the end it turned out that one of the TWO fusable links had a haircrack which sometimes made contact and sometimes not. Just follow the battery cable, the fusable link is hidden under plastic heat shrink usually. And remember, there ate two of them in the trunk. We checked then only one, but in the end we found that the other one was broken.

[632 Regal]

Right on man, new batteries did not help. Starting fluid (either) makes it fire. No power to fuse 23 and 24 which are both fuel pumps. Still can't figure who the fuel pump relay is. Tried jumping the fuses with 10 amps no deals. With no power to the fuses I will check the links back stairs, everything else has power however but I suppose that matters none on this car. Thats my next step.

And always, thanks Erich!

[shogun]

fuel pump relays you can see from the online ETM based on your built year.
There are pics, drawings from around page 20 usually and at the end there is the section parts view, where you can even see the part and the location.


E31 (1991 to 1995 8 Series) Wiring Diagrams

just as info/visual help. on the E32 750 the fuel pump relays are located here
Engine -- Fuel pump replacement

In case the engine was not running for some months or longer, it might be that both fuel pumps are stuck, we have that quite often in the cars in our warehouse. Sometimes you can get them alive again by removing them and whacking the fuel pump onto a wood block, and then give power in short intervals from a separate battery to the pump (outside the fuel tank), to get it lose again, once it is lose it will run again.

[632 Regal]

Zero power to both fuses. Is this car supposed to have an anti theft device that I can reset? Getting power to all fuses except the 2 in question. Starting to frustrate me. Looking at the links now.

[shogun]

I am not the expert on E31, but what I read it depends on built year. What I found
remote control - aniti-theft system - DWA IV
Drive Away Protection System (EWS)
Model: EWS I/EWS II/EWS III/EWS III D
E31/E34/E36/E38/E39/E46/E52/E53
http://www.unofficialbmw.com/images/BMW_EWS.pdf#search=

[632 Regal]

Ok it looks like my car is exempt. I found 1 post on the same exact problem and I am waiting for a reply. Whatever it is is probably staring me right in the face. We will be trying a few things tomorrow starting from simple. I am understanding that the fuel pumps only run for a couple seconds when the key is turned on so I might be missing that power on because I did not have help. The fuel gauge is working so that must be on a different circuit.

[shogun]

yeah, found your post, let's see what they tell you there. But most important is that you edit that post and tell them the exact month/year of production that they can look into the correct ETM, you even did not mention which model, just Cars: 94 530i


BMWVin.com

[Tiger]

Fuel pressure is easy to check... just put a fuel pressure gauge inline with your fuel hoses...at engine.

Have you changed your Crank Position Sensor or at least check it?

[shogun]

there are 2 crank position sensors on the M70 engine. Here is how to check them, they Bentley manual for the E32 shows the wrong set up for the connectors, the pic inside here is correct
Elektrik Kurbelwellensensor/Geber
between pin 1 and 2 540 Ohm plus/minus 10%