Won't start - no spark, no fuel...

I swapped the engine and automatic tranny from my '91 XJ to my '87 YJ so mechanically/electrically wise this is just an '91 XJ. It fired right up the first time I started the engine but then I put a stroked engine in it and now it won't start. So this is what I've done so far:

- Reindexed the distributor
- Checked the NSS
- The ignition coil has good ground
- There's no spark
- The fuel pump does work
- The spark plugs (brand new) haven't seen any gasoline so there's no fuel coming in the engine
- The MAP sensor does get 5 volts input, don't know how I can check the output voltage???

What I think might be wrong:
- CPS, how do I check it? Do I have to buy a new one and check if it works...
- I had to replace the oil pressure sending unit (damaged it doh!). Might a bad sending unit be a cause?
- MAP?

Are there anymore sensors then the NSS, CPS and the MAP that might be acting up? Anything else I should be checking?
If theres something wrong with the ignition system (given the CPS is OK? which I don't know) would that affect the injectors?

cps could be a problem or even the flexpate/flywheel. the flexplate/flywheel must be the one that matches the ecu. for example on an xj, a 91 engine will not work in a 90 xj unless the 91 has the 90 flexplate/flywheel.

Yeah it's the '91 flexplate. Any chance I might have installed it wrong?

i would also check the fat ground on the passenger side of the block.
If i remember right, it is near the oil dipstick mount bolt

I have checked the grounds and replaced the battery, made no difference. I also changed out the crank sensor, no difference. What I'm now looking at is the sensor in the distributor but can't figure out HOW to get it out... :S

the 91 Computer and wiring harness I assume?

Yeah I swapped the whole engine harness from the XJ to the YJ and it worked fine on the old engine...
Right now the suspect is the ignition coil, next time I work on the Jeep I'm going to test if I can get a spark plug to spark with the wire from the ignition coil... if not I'm totally lost!

first you say no spark, now you say I'm gonna check a plug

title says no fuel , then you say the pump works.

I think we are all lost, and can not further help you.

Check for power going TO the coil.

What I mean with no fuel, is that the injectors aren't spitting any fuel inside the cylinder. And when I try to get a spark plug to spark I don't get any spark. It's just like the crank sensor is bad, but it's brand spanking new! I think there must be something causing the PCM to cut on spark and fuel... but how the PCM works is a mystery to me.
What I'm going to try next time is if the ignition coil actually works, then the problem might be with the distributor or the timing??? If anything is wrong with that, might that cause the PCM to cut out the fuel?

Thanks for reminding me, I checked the power going to the coil. With the ignition switch on, I got 5.5 volts, is that normal?

You may want to check you ASD relay. That will also cut the grounds from the PCM causing a no start condition. In my case the PCM got fried, and someone wound up putting in the wrong one in. Now I have the right one in and it runs like a top. Victor

Thanks for the advice, I found this on the ASD relay:

The ASD relay supplies voltage to the ignition coil, and fuel injectors. It is not located inside the SBEC, but it is turned OFF and ON by the SBEC (controls the ground). The Crankshaft Position Sensor (CPS) signal goes directly to the SBEC II, and in the event that the SBEC II sees no signal, the ground is removed from the ASD circuit. If the ignition switch is ON and the engine is OFF, the SBEC II will allow the ground to be applied to the ASD for approximately 3 seconds, then if no Crankshaft Position Sensor (CPS) signal is sensed the SBEC II removes the ground from the circuit. If the ground is removed from the ASD relay circuit, then the ASD relay acts as an OPEN switch in the power circuits to the fuel injectors, and ignition coil causing a no start condition.

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So I was thinking about just grounding the relay permanently... or atleast try and replace it first and see if it helps...

All right, I just jumped the ASD relay (wire straight from 30 to 87), made no differance. Which leads me back to the crank sensor... but it's brand new, original Mopar!

Any chance the sensors on the throttle body might be the problem?

Found 3 wires right by the oil dipstick and grounded them, PROBLEM SOLVED!!! But I still have to reset the ignition... I must have put it 180 degrees off LOL

Doublehead said:

I have checked the grounds

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:nono: LoL

Glad you got it solved!

RyanM said:

:nono: LoL

Glad you got it solved!

Click to expand...

yeah I know didn't realize there were MORE grounds then just the basic straps!!!