M50 wont start.. Plz help

[haggardfab]

So im just about done my m50NV swap in my 92 e30 convertible.. Im to the point where im trying to start it before i finish tieing up wires etc and i cant get it to fire..
I bought the whole swap from a salvage yard out of a lightly hit 92 525i 5speed car.. I used the entire swap..

This isnt my first time at the rodeo so ive covered all the obvious things, batteries fully charged, the main relays have a constant B+, the engine harness is grounded to the strut tower at the B- post, engine ground goes from the block to the oem spot on the frame rail, fuse box is powered, crank sensor reads 490-500ohms (which i read was correct?) ive triple checked my x20-c101 swap.. And last night i tried my ecu in a friends 92 e36 and her car fired rite up..

What am i missing here? The ecu does not prime the fuel pump and the trigger to the coil packs is only .7v when cranking it.. If i run a jumper to pin 13 in the c101 the fuel pump fires rite up..

I drove the e30 for several months prior with the m20 with zero issues so im leaning towards something in the e34 harness

Any input is appreciated, thanks

[haggardfab]

Also the car was claimed to be a running car as it was in a side lot and the drivetrain could only be purchased complete

[MR E30 325is]

You shouldn't have to jumper pin 13 to get the fuel pump to prime. Are you 100% confident in your wiring connections?

Check your fuel lines. Fuel should be coming from the tank to the front of the fuel rail (input closest to the radiator). Also, make sure you have a fuel pressure regulator on your fuel rail. Some were mounted to the body.

I will post more as I think of potential solutions.

[haggardfab]

Im just saying that the fuel pump works, seems like in all the threads ive read that the fuel pump was usually the issue why it wouldnt run, mine works fine..
Fuel lines are hooked up properly and all the connections at the c101 seem to be correct, ive even refrenced them back to the oem wiring diagrams.. The ecu is seeing voltage and it turning on because im getting a "check engine" light on the dash

My regulator is on the rail but i have no power going to the pump period..

Im to the point where i think im just going to pull the entire harness out of the looms and check for possible breaks.. Theres no physical damage to the harness but im running out of ideas..

[haggardfab]

The only grounds on the engine harness are the main two coming out of the loom on the ecu side (e34 harness) and the one at the thermostat housing correct? I cant find any more that i may have over looked

[e30austin]

There should be a ground on the back of the valve cover for the coil packs. Very important that you have that.

It isn't as big of a deal on the E34 harness, but probably a good idea to ground out your DME. E36 has less physical grounds than the E34 harness, so a lot of it grounds through the DME. There should be the harness loom ground, the engine block ground, the injector rail ground and the coil pack/valve cover ground.

I had a very similar issue once. There is a little green wire under the dash that runs into one of the C104 connectors that loops (maybe 1/2" in length) into itself, which gives power to the fuel pump and coils. Somehow, that came unplugged while we were swapping the booster (methinks), and caused hours and hours of frustration and headache. I would look into that.

Maybe try posting a picture of your power distribution block, just so we can make sure that everything is connected properly.

[haggardfab]

I have two grounds on the coil packs, one on front and one on the rear that go from the coil pack to one of the valve cover bolts.. I have the main harness grounds (two 10g wires), the engine block ground and the injector ones.. I wasnt aware of the c104 wire since ive never seen that in any of the swap threads but now that i google it i see alot of people having issues with that so ill look at that tomorrow when i get there, thanks alot for the help man

[e30austin]

Good luck, sir.

[haggardfab]

So i still have nothing, we ended up pulling the intake manifold off to diagnose the wiring easier and found out that the original oil level sensor in the pan was not grounded, we cut that and temporarily grounded it and everything worked, fuel pump fired, injectors sprayed etc.. So we pulled the harness back out to tape it back up, reassembled what we took off and now the car is back to doing nothing..

This is honestly one of the most frustrating things ive ever dealt with in the car world, does anyone have a list of parameters the ecu has to see for it to be happy and fire..
Like..
Oil level needs to see ground
Oil pressure must see ground
Etc..

This is my personal car so i dont mind hardwiring things to bypass unneeded sensors and possibly save me from headaches in the future

Im close to just buying another harness but im not having much luck finding a non vanos m50 harness on this side of the country :(

[e30austin]

Could there possibly be anything else in there you touched? Are you running an E34 harness? I've never heard of an oil level sensor ground causing that issue...

[NickL]

Between what pins does the crank sensor ohm out around 500? I had the same issue on an e36 I had. Try another sensor. It was the most frustrating thing when I saw mine ohmed out correctly but I ran out of ideas and decided to try another one. And it worked.

[haggardfab]

Austin, the car was bone stock when i got the swap, i pulled the harness before the yard pulled the motor so i know nothing was cut.. We've checked almost every wire from sensor to pin on the ecu plug and theres no breaks we can find..

[haggardfab]

Nick, the original sensor read 494 ohms on a wooden bench so there was no interference.. Tried another known good one that read 519ohms and i even bought a brand new one to try which read 845ohms.. None made a difference.. Even checked the ohms at the ecu pins (with sensors connected) and got very similar readings