94 4.0 4x4 no start after rebuild

Finally got everything buttoned up with my stock 4.0 rebuild, but now I'm stumped! The engine cranks over strong and the battery is fully charged but it won't start. (Motor ran good before rebuild)

I think I've ruled out a fuel delivery problem as I'm getting a strong 35psi on the fuel rail while cranking, , I'm reading 12v on the injector hot wires (the 3 that I could get to at least), I know the injectors are all good as I bench tested/cleaned each one, spraying starter fluid into the intake does nothing.

As far as spark goes I seem to be getting spark according to my spark test light (the kind that goes between the wire and plug), but I only tested cylinder 1. I also read 12v from the power wire to the ignition distributor box. But I suppose the box could be bad (worked great before rebuild).

My thinking is that the CKP sensor may be bad, but I'm unsure how to test them, as I understand the CMP sensor only controls sequential fuel injection so even if it's misaligned it shouldn't cause a no start? Or finally the distributor box could be bad, but I'm also unsure hot to test this.

I know this is a long question but I'm trying to get this done today if possible, I'm looking for anything I may have missed that could cause a crank no start with solid fuel pressure, thanks all in advance!

Correct, CMP, cam position sensor can't cause a no start.

CKP, crank position sensor can cause a no start

If you added fuel manually to the intake, sprayed in starter fluid, and it didn't fire then you have no spark.

After cranking pull out a spark plug, if it is dry then you have no fuel either.

If you have no spark and no fuel then could be CKP sensor or EDIS module
Spark plug wires are plugged into the Coil Pack, that's all that is, 3 coils in one case, no 'brains' in there.

CKP sensor reads a tone wheel behind crank pulley.
It has 35 "teeth", and 36 "places for teeth", so there is 1 "tooth" missing, that gap tells EDIS module when #1 is at TDC, that starts the spark.
EDIS module is the 'brains" for spark.
EDIS module passes that #1 TDC on to the computer which uses that to time the fuel injectors.

If during the rebuild the tone wheel got hit and lost another tooth then EDIS module won't start the spark.
EDIS module looks for 35 "pulses" the a gap, then 35 "pulse" then a gap....from CKP sensor.
If there are 2 gaps before 35 "pulses" then EDIS doesn't know which one is TDC so doesn't do anything.

Check tone wheel carefully make sure there is only 1 gap(missing tooth)

EDIS module on my '94 4.0l is on the front side of the rad support Drivers side.
You can see it looking up from under the bumper.
EDIS modules rarely fail, only time they are usually replaced is when there was a front end collision, and they are physically damaged, but check the plug in

CKP sensor wires run up from passenger side to above water pump and next to Thermostat housing, then become part of main harness on top of lower intake.
You can use sewing pins to pierce the 2 wires and then use a Volt Meter set to AC Volts.
You should see .5 to 1v AC while engine is cranking.
This will NOT tell you if a tooth is missing, just that the CKP sensor is generating its own power as teeth pass by, so it is working and close enough to the tone wheel

Thanks for the quick reply, I checked the balancer and it's not missing additional teeth, I did paint it with engine enamel, but it shouldn't be thick enough to interrupt the magnetic pulse. From why you indicated I may now be able to rule out the CKP as if that were the fault then I would be reading no fuel pressure while cranking as the ECM would not be receiving the signal for TDC. Since I'm reading 35psi while cranking I don't think this is the cause.

I'm going to check all of the spark wires while cranking to make sure they are all getting spark, if they are then I can soundly rule out the CPK as well. I'll look at the module on the radiator support and see if I possibly disconnected it, but if I'm getting spark then that's also not the cause.

Suppose after that it's a compression test.

One final thought, when I first tried starting it I had cylinder 5 and 6 plug wires out of order, I cranked it several times before I realized this, is it possible this alone would cause a no start? If so then it could be possible that I flooded the engine, it was turning over a little fast towards the end, guess I'll also be checking/drying plugs.

What a headache, and it's probably something really simple.

Thanks again!

Fuel pressure is unrelated to CKP/EDIS/injectors

It is a simple ON/OFF relay that turns on fuel pump when key is on.

Check spark plug for fuel after cranking, no fuel = no injector pulses from computer.


You just need to press gas pedal down to the floor, and hold it down, then Crank engine, that will dry off the spark plugs.
Gas pedal to the floor with 0 RPMs tells computer to shut off fuel injectors, it is called "Clear Flooded Engine" routine, all fuel injection computers have this routine.
Key on
Gas pedal to floor
Crank engine
As soon as you release gas pedal injectors will start up, even while still cranking

But if you add fuel manually to intake and it doesn't fire then you have no spark, doesn't matter what spark "tester" shows.
yes compression under 90psi would cause a no start but Starting Fluid is ether, and a working spark plug would ignite that causing at least a back fire.

Thanks for the clarification, I was under the impression that fuel was also contingent on a signal from the CKP.

All said and done I tried drying the plugs as you described and as I suspected it fired right up and went to idle. Seems the mis-ordered wires caused a the no start and I flooded it with repeated cranking. Now runs smooth as silk, albeit quite smokey, but that's probably the enamel on the exhaust manifolds curing.

On a side note, I've tried plug drying on other vehicles before but was hesitant on this one as prior to the rebuild I did a compression test and cranking with the pedal at full throttle the car started right up and jumped to full throttle, it did the same thing tonight, pedal depressed to floor,, cranked for a few seconds then raced to redline, never took my foot of the pedal (which is what should allow the injectors to start), scared the piss out of my wife. Either way it seems to be sorted, tomorrow I'll have to check for leaks and make sure the smoking is just the paint, the fact that it started is enough to let me sleep tonight.

Thanks again!

Sounds like your throttle cable is stretched some. Search: zip tie mod.

Should fix you right up.

jeremysdad said:

Sounds like your throttle cable is stretched some. Search: zip tie mod.

Should fix you right up.

Click to expand...

I've actually done the zip tie mod, made a big difference, could just be time for a new cable though, if that wasn't enough, either way it's running now so I'm happy.

Good work on getting it running

Clear flooded engine routine is based on TPS(throttle position sensor) voltage.
TPS gets 5 volts from computer
TPS sends back .69-.99 volts, under 1 volt, if throttle is closed, the return voltage
As throttle is opened the return voltage increases.
When throttle is wide open(WOT) the TPS return voltage needs to be above 4.5volts.

WOT voltage is important for a few things, one, of course, is that it enables Clear Flooded engine routine.
It also puts computer into "balls to the wall" mode, computer ignores O2 sensors and pushes in as much fuel as MAF(mass air flow) sensor allows, fuel economy be damned, lol.
If vehicle has AC, WOT voltage also shuts of AC compressor for more power to the rear wheels.

So yes throttle cable can effect WOT, or not getting full WOT voltage from TPS

i was also thinking the TPS may be off, I'll check the voltage on it later today and see. Even if the cable is stretched I'd be surprised if it really stretched beyond the 1/2-3/4" that the zip ties compensate for. As you said, if the TPs was off that could mean the ECM is never reflecting WOT even if the throttle cable allows for it. I was getting 18-19mpg before though so I never though twice about it, guess I'll see.

Center wire on TPS is return voltage

Just use a weight or stick against the seat to hold gas pedal down to the floor and then check if you can open the throttle linkage more, if you can then you are not getting WOT, for the engine or the TPS/computer

Well I checked the voltage on the TPS and all looks good, .97v at closed throttle and 4.53 at WOT, pedal fully opens the throttle plate when fully depressed as well so I have no idea why it won't do the dry flooded engine mode without going nuts, but I'm not overly concerned, never seemed to cause any drive ability issues before.