1999 TJ 2.5 cranks but no start

[danieldb]

Hi guys,

Looking for some help on a crank no start problem in my jeep tj 2.5 1999.
No codes


- checked fuel pressure and check valve 45psi OK
- checked compression OK
- checked for spark OK
- checked for pulse on injectors OK
- checked for 5v reference at the sensors OK
- checked and cleaned grounds
- checked timing marks on crank and cam pully OK
- checked timing chain OK
- checked cam and crank sensor wiring for continuity to pcm plug OK
- checked pcm for power ground and 5v reference OK
(and ordered a new one from wranglerfix, same problem crank no start)
- soldered the connections of the cam and crank sensor eliminating a possible bad connector
- bench tested cam sensor (distributor pickup) with 5v supply
0.00-5.00v on signal wire
- bench tested cam sensor (distributor pickup) with distributor removed rotated shaft by hand
With 5v power supply
5.07v-0.00v on signal wire OK
- bench tested Crank sensor with 5v supply 0.00-5.07v on signal wire OK
- tested and checked distributor timing on TDC OK
- tested map sensor OK
- new properly gapped spark plugs
- new rotor
- new spark plug cables
- new distributor cap
- cleaned throttle body

Found a possible problem: when cam and crank sensor are mounted in the jeep and plugged into there connectors when backprobing the connector on the signal wire found a signal between 4.08v and 0.11v when turning the engine by hand.
For one rotation of the crank I get 10 pulses on all the injector ground wires and wet plugs.
Looks like the injectors fire as a batch and not sequential.
I didn’t find the info online but I think injector firing should be sequential.

both sensors bench test good but when mounted in the jeep there is a volt missing on the signal wire when turning the engine by hand.
Bench test and mounted to the jeep tested with same multimeter.

Both connectors have:
5.07v on the power supply for the sensors
Battery voltage on the ground with multimeter connected to the positive terminal of battery.

I am a bit lost about finding the solution and thought maybe this forum can help. Tried the search option but didn’t find my answer.

 

[Gollywomper]

So you have a no spark condition?
Have you checked the ignition coil?

 

[danieldb]

So you have a no spark condition?
Have you checked the ignition coil?

I have tested for spark and I have good spark on all the plug wires.

Measured resistance on the ignition coil all within limits found in the fsm.
But will give it a try by changing it.

I think the amount of pulses on ground wire off the injectors is way to much. 10 pulses on the ground wire of all the injectors for every full turn of the crank is what I find.

What I found on this forum is that
there are 2 groups of 4 notches for the 2.5 4cyl on the flywheel.

And after the 4th notch there should be an injector pulse on 2 injectors that are on compression stroke.
Regulated by the cam sensor signal.

So 1 full turn of the crank should give me 1 puls on every injector ground wire and not 10 pulses right?

 

[Gollywomper]

If you have spark I wouldn’t change it.

 

[danieldb]

If you have spark I wouldn’t change it.

Could it be that the spark is not strong enough? I am in the process of eliminating so a 50 dollar coil replacement could be an option.
If that improves spark quality it will fail some day..

I have tested for spark and I have good spark on all the plug wires.

Measured resistance on the ignition coil all within limits found in the fsm.
But will give it a try by changing it.

I think the amount of pulses on ground wire off the injectors is way to much. 10 pulses on the ground wire of all the injectors for every full turn of the crank is what I find.

What I found on this forum is that
there are 2 groups of 4 notches for the 2.5 4cyl on the flywheel.

And after the 4th notch there should be an injector pulse on 2 injectors that are on compression stroke.
Regulated by the cam sensor signal.

So 1 full turn of the crank should give me 1 puls on every injector ground wire and not 10 pulses right?

maybe someone with a 2.5 4cyl can check how many pulses there should be on the injector ground wire when rotating the crank by hand 1 turn

 

[Gollywomper]

If the crank sensor is giving out odd signals I would start there. They are known to cause a no start condition when they go bad. I wouldn’t think the injectors should be firing 10 times per revolution. That would be a huge amount of wasted fuel and super rich condition.

 

[danieldb]

If the crank sensor is giving out odd signals I would start there. They are known to cause a no start condition when they go bad. I wouldn’t think the injectors should be firing 10 times per revolution. That would be a huge amount of wasted fuel and super rich condition.

I think your right regarding those 10 injector fires that causes my plugs to be wet all the time even after 5 second try to start.

How many times does the crank sensor go from 5v to 0v for one engine revolution?

 

[Gollywomper]

I am not sure. I have not had to troubleshoot that circuit yet.

 

[danieldb]

I am not sure. I have not had to troubleshoot that circuit yet.

Found this information on this forum somewhere

 

[danieldb]

If the crank sensor is giving out odd signals I would start there. They are known to cause a no start condition when they go bad. I wouldn’t think the injectors should be firing 10 times per revolution. That would be a huge amount of wasted fuel and super rich condition.

The strange thing is when I bench test the crank sensor it gives me a solid 5v-0v.
Followed this testing procedure

 

[danieldb]

Anyone else with a possible cause of my problems?

 

[TJ4Jim]

Prior to the no start what was the recent operational history of the jeep.

 

[danieldb]

Prior to the no start what was the recent operational history of the jeep.

Bought it as a non runner, previous owner didn’t put enough coolant in the engine. Engine ran hot.

Replaced the engine block itself with one from a running donor. Used all the part: inlet manifold sensors,wiring,injectors,alternator,steering pump,pullys from the old engine, new exhaust manifold,

 

[TJ4Jim]

Bought it as a non runner, previous owner didn’t put enough coolant in the engine. Engine ran hot.

Replaced the engine block itself with one from a running donor. Used all the part: inlet manifold sensors,wiring,injectors,alternator,steering pump,pullys from the old engine, new exhaust manifold,

OK, so non-runner from the get go. I would suggest physically confirming TDC.

 

[danieldb]

OK, so non-runner from the get go. I would suggest physically confirming TDC.

Will recheck that, I checked tdc with valve cover removed and looked at the intake valve closing. Turned until marks lined up
While feeling for pressure at number 1 spark plug hole

 

[TJ4Jim]

A wood dowel in #1 spark hole is helpful. Have you tried a quick shot of starting fluid in in the TB just to record the response.

 

[danieldb]

OK, so non-runner from the get go. I would suggest physically confirming TDC.

Got it running once, but after turning it off never started again.

 

[danieldb]

A wood dowel in #1 spark hole is helpful. Have you tried a quick shot of starting fluid in in the TB just to record the response.

Tried that but didn’t unplug the injectors/fuel pump relay so flooded the engine real quick will try again tomorrow with injectors and fuel pump relay unplugged

 

[Gollywomper]

Are you sure he used the correct flywheel? Just a random thought.
I looked, they seem to be the same from 95-02’ for a wrangler 2.5.

 

[danieldb]

Are you sure he used the correct flywheel? Just a random thought.
I looked, they seem to be the same from 95-02’ for a wrangler 2.5.

Good point! I will check the notches and count them. But from what I found flywheel for 2.5 is the same over the years

how about the crankshaft sensor it’s just a Hall effect responding to the notches ? The connector is the difference between the years right?