m50nv Cranking but wont start - Fuel pump/fpr/dme??

[Kristoge]

Hey guys I need some help badly. On my way from SF to LA a couple nights ago the car all of a sudden died under power in 4th gear with about 70 miles left to go. Dashboard lit up like a christmas tree cel, oil light, etc.. car cranks all day but never seems to even begin turning over even 2 days later.. Searching seems to suggest fuel pump or fpr as most likely culprit? Ill be honest my skills are limited at best otherwise I would have figured out how to test the fuel system by now. Before I go out and waste $200 on a new pump there's another unfortunate embarrassing factor to consider. Before setting out I was topping off the oil when the hood collapsed on me causing a 1/4 qrt or more to spill all over the dme casing and general passenger strut area of the bay 😩 I did my best cleaning up as much as I can quickly but now I'm starting to worry this could be very well be dme related. Is there a way to test the dme? Also is there a ground wire in that area? I'm about to go try a stomp test and open the dme casing. I need to figure this out today as the car needs to be moved to clear the driveway for tomorrow. Any help/advice is much appreciated! 😞

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[Mixzzz]

Firstly I would try pulling out a spark plug and checking whether there is spark. A bad CPS could also cause no start situation. You can also try pulling off the fuel line to the fuel rail. If the gasoline pours out of it with pressure then the fuel is getting to the injectors. Just be careful not to get it everywhere...

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[Kristoge]

i was just able to get it started for a few seconds before it dies. im getting a lot of responses pointing at the cps. trying to figure out how one would test it

[zubbie]

i was just able to get it started for a few seconds before it dies. im getting a lot of responses pointing at the cps. trying to figure out how one would test it

You need to locate the connector, unplug it, check resistance value. It's all in the "Bentley"

https://wiki.bentleypublishers.com/d...specifications

[Kingpin025]

I had a similar situation with my '93 M5 last fall on my way home from a BMW meet no less. In stop and go traffic, far left lane on the 210 east four lanes in my direction, a stutter and then dead. I managed to get it started and creep over to the right shoulder stalling and starting a few more times along the way. I had the car towed to our good buddy M5 Jed's place who just happened to have a spare fuel pump. He swapped it out and no more issues. As I was making the painful ride in the tow truck I recalled a moment on our caravan to the meet that morning where I felt a stutter at about 85mph and then all seemed fine, well you know until it wasn't.

I kind of see your situation as it's most likely the fuel pump and the $200 will probably fix the problem. If it doesn't you've still fixed an issue that was more likely than not going to leave you stranded so I wouldn't call it a waste. Fuel pump failure is a little/no warning failure. My factory original M5 fuel pump lasted over 240,000 miles, but I've read other instances of them going out at less than 150k.

As far as the DME goes I'd doubt oil would find it's way though the seal, they are screwed together pretty well. It would have to have been opened at some point and the seal would have had to have been damaged when being reassembled. I'm not saying it's impossible, just not likely.

[Kristoge]

yup im trying to figure out how to work this old multimeter to test the cps and fuel pump but I'm completely incompetent when it comes to electrical.. and thanks zubbie was searching all over the bentley manual just what i needed

[Mixzzz]

To test fuel pump, you may just turn it on by putting a wire in place of relay and hearing whether it is working. If you want to be more accurate, get a T fitting and attach it to the fuel line with a fuel pressure gauge.

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[Kristoge]

Stomp test throwing code 1215 which is the air mass sensor...?? Completely confused now is this possibly not a fuel issue after all?

[Kristoge]

shit also shows 1261 which is fuel pump relay control and but i dont hear the pump working at all even when jumping the relay

[Junglenut]

Testing CPS with ohm meter should be a few hundred ohms. It's only 2 of the 3 pins required to get a reading. Try first pin and third pin on the plug.

Could also try key on to position 2 then off, repeat 5 times.

Check fuses under hood for popped ones.

You should be able to hear the fuel pump prime when key is on position 2.

[Kristoge]

Well for anyone that cares it turned out to be the fuel pump after all. After days of mis-diagnosing and fiddling with a multimeter I finally gave in after replacing the CPS and it still not starting, and had it towed to a local shop down the street. Paid $120 for a oem bosch replacement shipped overnight on Amazon, $60 for them to swap it out, and all is well