OBD-I s52, has spark and fuel, but won't start

[JGood]

Trying to get an s52 running in a 91 318ic. Engine ran in another e30. OBD-I harness was bought pre-wired from Zionsville. It's OBD-I, and has the EWS delete. We are getting spark and fuel (plug sparks while cranking when grounded, and fuel is dumping out of the return side of the rail).

While cranking, it's backfiring a lot, but nowhere near starting. After pulling the plugs, they looked wet.

CPS reads 540ohms.

I don't know how to test the cam sensor, can I measure resistance across the pins? I tried every combination, and couldn't get any reading of resistance. The meter didn't say 0 ohms, it basically said no connection at all... as if none of the pins are even connected through the sensor. I thought that was strange, but don't know how that sensor works.

We also tried a different FPR, and a good 413 ECU from a running m50 e30.

Another thing that was weird to me was the fuel pump fuse was only getting 10v while cranking. Shouldn't it be 12? Other fuses read 12v. I don't think that would effect anything though, as the return side of the rail was dumping fuel, which means the injectors should have had full pressure.

[flyboyx]

well, if you are indeed getting spark and fuel, the engine would run. those are the two components required along with air to support combustion. did you check your fuel pressure? it should be about 50lbs. there is a schrader valve on the fuel manifold where you can check this. pull the #1 spark plug, ground it against one of the bolts on the valve cover, crank it over to see if you do indeed have spark.. if your cam sensor were bad, you likely would not have spark because the dme would not know when to send the signal to the coils.

[JGood]

well, if you are indeed getting spark and fuel, the engine would run. those are the two components required along with air to support combustion. did you check your fuel pressure? it should be about 50lbs. there is a schrader valve on the fuel manifold where you can check this. pull the #1 spark plug, ground it against one of the bolts on the valve cover, crank it over to see if you do indeed have spark.. if your cam sensor were bad, you likely would not have spark because the dme would not know when to send the signal to the coils.

That's what we did with the plug, watched/heard it spark while cranking. I didn't put a gauge on the fuel line, but while cranking, I ran a hose from the 'out' side of the rail (after the regulator) to a container, and fuel dumped pretty fast. So if the pressure regulator is allowing fuel past, shouldn't it be at 3.5 bar, and then some? And the fact that the plugs are wet, and it's backfiring, shows that the injectors are at least spraying some fuel.

[Danny]

Are the coil packs plugged in in the correct firing order?

[JGood]

Are the coil packs plugged in in the correct firing order?

Yep.

[Danny]

Maybe the plugs aren't grounding when placed inside the head? Have you checked compression? I too, am stumped.

[JGood]

Maybe the plugs aren't grounding when placed inside the head? Have you checked compression? I too, am stumped.

The engine ran in the previous e30 it was pulled out of. The only thing that was changed was the engine harness.

If the cam sensor is not reading any resistance values, I don't see how that isn't a problem... I just don't know what values it should be. I don't want to buy a new one until I prove that it's bad, as I don't see how it would go bad since it worked fine in the previous car.

[Danny]

Well has the engine harness been messed with? Are all the connections connected? I know I'm asking obvious questions and you know what you're doing but it can't hurt to double and triple check.

[JGood]

Well has the engine harness been messed with? Are all the connections connected? I know I'm asking obvious questions and you know what you're doing but it can't hurt to double and triple check.

The harness was replaced before it was dropped in this car, the old one was spliced for a late model m20 c101. So he bought this one from Zionsville that came pre-spliced for his m42 connector. Thing is, it's getting spark and fuel, the the c101/x20 has to be right, and even the rest of it should be good.

We triple checked all connectors and tried swapping some around. The ICV and CPS are the only 3-pin connectors that can be swapped, and they are correct since the ICV buzzes with the ignition on. None of the two pin connectors would cause a no-start AFAIK, but they all appear to be hooked up correctly anyway. It sounds like a serious timing issue since it has spark and fuel, and it backfires, but it won't start.

The only 2 clues I have at this point are the 10v at the fuel pump fuse issue, and the apparantly non-functioning cam sensor issue. Still can't find a value for the cam sensor, to test it. Are those Hall sensors different then the VR sensors that the crank uses as far a how they are tested for failure?

[e30s50dan]

are ALL your plugs firing, maybe you have a bad coil pack or two..if you are near a Harbor freight,they have a spark plug tool that has a light, so you can see if they are firing....its like$5-$10 bucks.worked for me ..I ended up having two bad coils...just a thought. Good luck

[JGood]

are ALL your plugs firing, maybe you have a bad coil pack or two..if you are near a Harbor freight,they have a spark plug tool that has a light, so you can see if they are firing....its like$5-$10 bucks.worked for me ..I ended up having two bad coils...just a thought. Good luck

I suppose it's possible, but I'd be damn surprised. The coil packs haven't been touched since the last time the car ran. I'll check it out though.

[Wh33lhop]

My M50 started up just fine on 4 cylinders. If it's your coil packs, 4-6 of them failed at the same time. Are you absolutely sure it's getting spark? I'd look a little further into the cam sensor, is it possible that instead of outright failure (no spark) it's somehow malfunctioning and throwing your timing way off?

[7pilot]

The back firing (through the intake??) suggests that the engine is out of spec for static timing. I understand that it ran prior to installation.

I would treat the engine as an unknown and start from square one. Check the static timing, check the engine position/rpm sensors, check spark quality, fuel delivery, and add a new set of plugs(or burn off the fuel varnish on the current ones with a torch).

m
Oh, make sure that there are no rags or objects stuck in the intake tract to keep foreign objects/critters out.

[JGood]

Are you absolutely sure it's getting spark?

It's sparking, I'm not sure how I can be any more sure, haha. I saw and heard sparking as we held the plug against a valve cover bolt and he cranked it over.

[JGood]

The back firing (through the intake??) suggests that the engine is out of spec for static timing. I understand that it ran prior to installation.

I would treat the engine as an unknown and start from square one. Check the static timing, check the engine position/rpm sensors, check spark quality, fuel delivery, and add a new set of plugs(or burn off the fuel varnish on the current ones with a torch).

m
Oh, make sure that there are no rags or objects stuck in the intake tract to keep foreign objects/critters out.

It sounds like a static timing issue to me too. But he pulled this engine out of the car running, then put it into this car. He didn't even pull the valve cover. Timing doesn't change itself on these motors, AFAIK. Even if Vanos was locked the whole way to one direction, it should still start. Going through the process of removing the vanos and retiming the engine just brings more variables into the equation, considering I've only timed a vanos engine twice, so I'm not an expert by any means.

I'd love to test the cam sensor as you suggest, but nobody can tell me how.

New plugs is a good idea. Not sure how to check for spark quality though. I'll also check fuel pressure.