Topic: 97 tj 2.5 cranks but no fire

[sharpxmen]

i shouldnt have 12v at the injectors should i?When the key is on there shouldnt be any voltage correct?
i did check out the wire(s) back to the ecm and there ok and the other wire was ground.Thge asd relay is clicking when the key is turned on and the fuelpump is also coming on.

when you crank it you should get 12v - you're correct, the injectors are powered by the ASD, so whenever that closes you will have 12v at the injectors, coil and O2 sensor.

[andrew383]

one other thing is when the ASD relay is pulled the fuelpump STILL kicks on

[sharpxmen]

one other thing is when the ASD relay is pulled the fuelpump STILL kicks on

the fuel pump relay is separate - the feed is the same (circuit A14), they are controlled by different circuits - page 18 and 15 of 95YJ_8W.pdf from FSM (or by their numbering page 8w-11-6 and 8w-11-3)

[andrew383]

the fuel pump relay is separate - the feed is the same (circuit A14), they are controlled by different circuits - page 18 and 15 of 95YJ_8W.pdf from FSM (or by their numbering page 8w-11-6 and 8w-11-3)

yes but with the ASD relay pulled and the FP relay still in shouldnt the FP be dead when the key is on?

[sharpxmen]

yes but with the ASD relay pulled and the FP relay still in shouldnt the FP be dead when the key is on?

mine clicks in when i turn the key on and turns off after a couple of seconds. Once you start cranking it should power the pump. There is an ASD sense pin on the ECU, not sure what happens when you pull the ASD relay if the fuel pump will still spin, if i have time i'll test and see what happens on mine.

[andrew383]

ok i rechecked a few things today.The coil HAS 12v at the plug,the injectors also HAVE 2v at the plugs,but i still dont have any spark through the coil.The cam/crank sensors have 5v at the plug which is what the haynes calls for.Soooo ill test/swap the coil,and cam/crank sensors AGAIN.
What else is there to check?If the coil and the sensors check out what else what not spark?

There is ONE problem i didnt mention before but when i put the gas tank skid on about 4 months ago i messed up the check valve and have had to do the "turn key 3 times" deal and havent had a problem other wise.I did have the FP checked and on the  key on its 32psi and 2nd is 50psi.If i was getting spark but no fuel then i would think that was the problem but since there is no spark i dont think it is.

[sharpxmen]

did you check if your distributor is rotating/spinning?

[andrew383]

yes checked with cap off...

[sharpxmen]

 this is for sure interesting (unless is the ecu/pcm). keep us posted with what you find.

[BarneyJeep]

sorry i didnt get back with you andrew, the batt temp sensor shouldnt have anything to do with the starting circuit...you could track the wire down and unplug it and try that. As far as i know there are only 2 sensors that tell the computer to fire the coil...but if you're holding a constant 12v TO the coil then i'd say those sensors are working. I wouldnt think you'd have voltage at the coil if they werent. I would prolly try the coil first. How do the contacts on the rotor button and cap look? worn? corroded? nicked?

[aw12345]

You still haven't answered this question, when you crank the engine do the asd relais and fuel pump relais engage and do the injectors pulse?
IT's not all that important that those relais turn on when you cycle the key
If they come on when cranking it means the ecm gets a signal from the cranksensor
Then if the injectors pulse it means that the ignition module works saves a lot of time. Instead of measuring voltage here and there. Check the basics keep it simple if it does all that and there is no spark the coil or the wiring to or from it is faulty.
All of the above can be checked with a simple test light and should not take all that long.  Even if the distributor for some reason is way out of time due to say a jumped timing chain, as long as it turns it should make spark. Probably will not run but you should have spark

[andrew383]

You still haven't answered this question, when you crank the engine do the asd relais and fuel pump relais engage and do the injectors pulse?
IT's not all that important that those relais turn on when you cycle the key
If they come on when cranking it means the ecm gets a signal from the cranksensor
Then if the injectors pulse it means that the ignition module works saves a lot of time. Instead of measuring voltage here and there. Check the basics keep it simple if it does all that and there is no spark the coil or the wiring to or from it is faulty.
All of the above can be checked with a simple test light and should not take all that long.  Even if the distributor for some reason is way out of time due to say a jumped timing chain, as long as it turns it should make spark. Probably will not run but you should have spark

i checked the injector plug with a meter and test light.When its turning over the volts just drop down to 11 but they dont pulse.Same thing with test light it just dims alittle.

[sharpxmen]

i checked the injector plug with a meter and test light.When its turning over the volts just drop down to 11 but they dont pulse.Same thing with test light it just dims alittle.

you should have 12v when cranking at the ASD side of the injectors but if you measure between the connector terminals you should have 0v and get a "pulse" once every 2 crank rotations (the ecu will ground 1 wire per cycle for each injector). The start of the sequence is given by the cam sensor (distributor sensor).

also thinking of another thread where the guy had problems with the engine interrupting and it turned out there was oil in the distributor which was causing the problem, someone else also mentioned that his engine stopped running due to the same reason, you might want to have a look just in case. They both said it worked fine after cleaning all that oil out of the distributor.

this is the camshaft position sensor test procedure from the 94/95 XJ/YJ FSM - it will tell you if the sensor is giving the appropriate signal (not sure if 97 is the same but i think the idea is similar, and most likely the same idea for the crank sensor) - this is on page 6 from 95XJ_8D.pdf

CAMSHAFT POSITION SENSOR TEST
To perform a complete test of this sensor and its circuitry, refer to the DRB scan tool.
Also refer to the appropriate Powertrain Diagnostics Procedures manual.
To test the sensor only, refer to the following:
....
For this test, an analog (non-digital) voltmeter is needed. Do not remove the distributor connector from the distributor.
Using small paper clips, insert them into the backside of the distributor wire harness connector to make contact with the terminals.
Be sure that the connector is not damaged when inserting the paper clips. Attach voltmeter leads to these paper clips.
(1) Connect the positive (+) voltmeter lead into the sensor output wire. This is at done the distributor wire harness connector. For wire identification, refer to Group 8W, Wiring Diagrams.
(2) Connect the negative (-) voltmeter lead into the ground wire. For wire identification, refer to Group 8W, Wiring Diagrams.
(3) Set the voltmeter to the 15 Volt DC scale.
(4) Remove distributor cap from distributor (two screws). Rotate (crank) the engine until the distributor rotor is pointed to approximately the 11 o’clock position. The movable pulse ring should now be within the sensor pickup.
(5) Turn ignition key to ON position. The voltmeter should read approximately 5.0 volts.
(6) If voltage is not present, check the voltmeter leads for a good connection.
(7) If voltage is still not present, check for voltage at the supply wire. For wire identification, refer to Group 8W, Wiring Diagrams.
( 8 ) If voltage is not present at supply wire, check for voltage at pin-7 of powertrain control module (PCM) 60-way connector.
Leave the PCM connector connected for this test.
(9) If voltage is still not present, perform vehicle test using the DRB scan tool.
( 10 ) If voltage is present at pin-7, but not at the supply wire:
      (a) Check continuity between the supply wire. This is checked between the distributor connector and pin-7 at the PCM.
           If continuity is not present, repair the harness as necessary.
      (b) Check for continuity between the camshaft position sensor output wire and pin-44 at the PCM.
           If continuity is not present, repair the harness as necessary.
      (c) Check for continuity between the ground circuit wire at the distributor connector and ground.
           If continuity is not present, repair the harness as necessary.
(11) While observing the voltmeter, crank the engine with ignition switch. The voltmeter needle should fluctuate between 0 and 5 volts while the engine is cranking. This verifies that the camshaft position sensor in the distributor is operating properly and a sync pulse signal is being generated.
If sync pulse signal is not present, replacement of the camshaft position sensor is necessary.

[aw12345]

i checked the injector plug with a meter and test light.When its turning over the volts just drop down to 11 but they dont pulse.Same thing with test light it just dims alittle.

you should have 12v when cranking at the ASD side of the injectors but if you measure between the connector terminals you should have 0v and get a "pulse" once every 2 crank rotations (the ecu will ground 1 wire per cycle for each injector). The start of the sequence is given by the cam sensor (distributor sensor).


Here is the answer to your problem.

If the injectors do not puls it means either the ecm does not see a signasl from the crank sensor or the ignition module does not get that info or failed.
Now if the ASD relais and the fuelpump relais engage, it means that the ecm does get a signal. If you could find a obd2 scanner somewhere it would show cranking rpm while cranking. So you would look for a signal at the ecm that goes to the coil.
From what it looks like it would not hurt to try swapping the ecm if that is a remote posibility. Since the ignition module is integrated into the ecm/pcm.
Got to hate this integrated stuff

[sharpxmen]

i checked the injector plug with a meter and test light.When its turning over the volts just drop down to 11 but they dont pulse.Same thing with test light it just dims alittle.

you should have 12v when cranking at the ASD side of the injectors but if you measure between the connector terminals you should have 0v and get a "pulse" once every 2 crank rotations (the ecu will ground 1 wire per cycle for each injector). The start of the sequence is given by the cam sensor (distributor sensor).

Here is the answer to your problem.

If the injectors do not puls it means either the ecm does not see a signasl from the crank sensor or the ignition module does not get that info or failed.
Now if the ASD relais and the fuelpump relais engage, it means that the ecm does get a signal. If you could find a obd2 scanner somewhere it would show cranking rpm while cranking. So you would look for a signal at the ecm that goes to the coil.
From what it looks like it would not hurt to try swapping the ecm if that is a remote posibility. Since the ignition module is integrated into the ecm/pcm.
Got to hate this integrated stuff

you quoted my statement but i'm not sure if you agreed or otherwise. just in case i didn't explain properly the first time: you need a cam signal or the injectors will not be open by the pcm. the cam sensor tells the pcm when cyl 1 is at compression. the injectors are opened by a ground given to the control terminal of each injector (individually) in sequence (not all at the same time). so if he sees the injectors opening it means he's got cam signal.