The M50NV (production date 3/92) in my E30 LeMons racer quit running last weekend in the middle of a race at Sears Point. The engine has been in the car for a few years and thousands of race miles with no problems until now. The car had raced all Saturday and was running great. About an hour into Sunday's racing the car suddenly lost about half its power. I limped around the track and the moment I got into the pits, the car stopped running and never fired again.
We did some diagnosis in the pits and here's what we came up with:
At that point we searched everywhere for a replacement cam position sensor but couldn't find one available in the area (the NV sensor is different than the VANOs version and only fits 1.5 years of production) so we packed it up and went home. I bought a new sensor and installed it yesterday but it still doesn't run. Oddly, I pulled the fuel pump relay to clear the cylinders of fuel (just in case it was flooded) and when I did this, the engine actually did sputter and try to run for a few seconds, but the moment I touched the throttle it died. This happened a couple of times and seems to be repeatable.
The wiring harness contains the bare minimum number of wires to run (the engine has been in 3 other cars before mine and I basically duplicated how it was in the donor LeMons racer I pulled it from), so the check engine light doesn't work, which I think means I can't do a stomp test to check codes? The car is currently being stored at my mom's house 30 miles away, so I won't have time to do any further diagnostic work right away but wanted to type this out while it was fresh in my mind to get some opinions.
Is there anything obvious here that I'm overlooking? Where's the best place to start diagnosing the problem based on what I've found so far? Thanks in advance.
We did some diagnosis in the pits and here's what we came up with:
- Fuel is getting to the fuel rail - a fuel pressure gauge is plumbed into the hose between the hard line on the chassis and the fuel rail and the pressure was normal.
- There seems to be spark. We pulled a spark plug, connected the coil to it, and grounded the plug to the strut tower and the plug fired (apparently the coil doesn't need to be grounded?)
- There are no obvious vacuum/air leaks. We double checked that the big hose that connects to the underside of the intake manifold was connected, as I had a problem with that in the past
- We swapped on a spare MAF (just plugged it in, didn't connect it to the air inlet hoses) with no change
- We swapped in a spare DME with no change. Stupid question - does the DME case need to be grounded to work?
- We checked the crank position sensor based on the specs in the Bentley manual and it tested fine. I don't remember the actual readings we got and I'll likely check them again to be sure, but the sensor is only about 2 years old.
- We tried to check the cam position sensor, but the Bentley manual doesn't have any specs on it. We found some specs online and determined it was likely bad (again, don't remember what readings we got). I wasn't the person who looked up the cam sensor specs online but I have a feeling we may have been looking at the VANOS version which is a different design IIRC.
At that point we searched everywhere for a replacement cam position sensor but couldn't find one available in the area (the NV sensor is different than the VANOs version and only fits 1.5 years of production) so we packed it up and went home. I bought a new sensor and installed it yesterday but it still doesn't run. Oddly, I pulled the fuel pump relay to clear the cylinders of fuel (just in case it was flooded) and when I did this, the engine actually did sputter and try to run for a few seconds, but the moment I touched the throttle it died. This happened a couple of times and seems to be repeatable.
The wiring harness contains the bare minimum number of wires to run (the engine has been in 3 other cars before mine and I basically duplicated how it was in the donor LeMons racer I pulled it from), so the check engine light doesn't work, which I think means I can't do a stomp test to check codes? The car is currently being stored at my mom's house 30 miles away, so I won't have time to do any further diagnostic work right away but wanted to type this out while it was fresh in my mind to get some opinions.
Is there anything obvious here that I'm overlooking? Where's the best place to start diagnosing the problem based on what I've found so far? Thanks in advance.
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