91 RT turns over but doesn't start, has no codes but no injector pulse

[Force Fed Mopar]

Trying to get a 91 RT going, it spins over good, has no codes but doesn't start. Haven't been able to check spark yet but I put a noid light on 2 different injector plugs and got nothing. Where do the injectors ground on a TIII? It's not at the rail bolts like an 8v. Everything worked a few years ago but it had really low compression. I just tore it apart replaced rings, bearings, water pump etc and reassembled. Tried to start and now no injector pulse.

If cam or crank sensor weren't working it should throw a code, right?

[c2xejk]

On a long crank, does the tach bump up? It should if the cam and crank sensor work. Also a scan tool should eventually register some RPM...

[Force Fed Mopar]

I'll have to check, I don't remember if it moved. I'll the scanner next time too.

[Force Fed Mopar]

No spark either. Thinking bad crank sensor maybe, it was a bit sketchy looking. There's power to injectors and fuel pump, so assuming to coil pack also (same circuit). May try swapping it out tomorrow, I have an old one out of my car that worked when removed. Has to be either it or cam sensor, it's seeming. Tach doesn't bump when spinning.

[cordes]

The injectors should be grounded by the computer. If it's anything like the 8v cars, the car won't energize the ASD relay to allow it to start unless it's seeing the sync signals coming from the crank and cam(?) sensors. Of course, both signals are in the dist for the 8v cars. If you jump the ASD relay, do you get power at the coil?

[Force Fed Mopar]

The injectors should be grounded by the computer. If it's anything like the 8v cars, the car won't energize the ASD relay to allow it to start unless it's seeing the sync signals coming from the crank and cam(?) sensors. Of course, both signals are in the dist for the 8v cars. If you jump the ASD relay, do you get power at the coil?

Haven't checked that yet, but ASD seems to be working fine. Fuel pump buzzes on with the key. Not sure if it's working while spinning over or not. Injectors get power while spinning over though, and that's the same circuit.

I swapped the cam sensor today, no change. Put the scan tool on it and it does register rpm, shows about 60-80 rpm while spinning over. Unplugged and replugged the engine harness plugs and the PCM plug, no change. My scanner doesn't have the able to look at individual sensors though, and I don't know if it gets an rpm reading from the crank or the cam, I'm assuming crank sensor? I pulled the rail off and verified there's no pulse at all, not even a prime shot, no fuel spraying from the injectors.

I kinda feel like it's not seeing the cam signal for some reason. It's spinning fine and should have enough voltage, I put the battery charger on it at 20a rate, it was showing 13v on the scanner.

[cordes]

That's interesting. I don't know about the SBECII stuff, but I thought the LM/SMEC/SBEC would give a prime shot without seeing a signal at all.

[c2xejk]

If you are getting RPM, then at least one of the position sensors is working. If the other one is failed it should be setting a code. (ie. it is faulting the primary RPM source and using the secondary. or if it is only seeing one it should then fault the other... May take a really long crank) This is a generic analysis, somebody with specific information on these controllers may disagree... This is where a scope would be super helpful.... Note that it could be a wiring harness issue too.

[rx2mazda]

Pressure plate isn't blocking the crank sensor knotches on flywheel correct?

[Force Fed Mopar]

Pressure plate isn't blocking the crank sensor knotches on flywheel correct?

No, that was good.

Turns out the crank sensor I swapped in at the beginning of the troubleshooting was bad. Put the original one back in and now have injector pulse and spark. Has a fuel leak at the filter though, so I think fuel pressure is low. It tried a time or two but didn't catch. Gas is also pretty old. Guess its time to drop the tank out and drain, fix leak, and try again.