Topic: 97 tj 2.5 cranks but no fire

[aw12345]

Doesn't the cam sensor just sync the injectors? Might be of topic somewhat but just trying to get the Jeep specifics straight, they are a bit of an odd beast
Even with out the cam signal it should have ingintion spark right, so it would point back towards pcm/ ignition module?

[andrew383]

not knowing if it would work i swapped in a 95 zj 4.0  ecm and i still have no spark....i still need to retest the injector pulse tho

[sharpxmen]

Doesn't the cam sensor just sync the injectors? Might be of topic somewhat but just trying to get the Jeep specifics straight, they are a bit of an odd beast
Even with out the cam signal it should have ingintion spark right, so it would point back towards pcm/ ignition module?

not sure but i see what you mean - since the crank would alternate tdc for pistons 1-4 and 2-3 you could be right that it does not actually need the cam sensor to give spark, however according to that article that i posted the link for in this thread if the cam/crank are not seen in sync by the pcm it will not give spark, so by that account i assume that if there is no cam signal at all there shouldn't be a spark either.

[sharpxmen]

not knowing if it would work i swapped in a 95 zj 4.0  ecm and i still have no spark....i still need to retest the injector pulse tho

don't think so since is programmed to see 3 groups of 4 teeth at the crank for 1 cam signal - if it gives you spark then you know it's the pcm, if it doesn't you're at square zero as you don't know if it is because it's a 6cyl pcm or not.

[andrew383]

ok i have 12v with key on at inj but no pulsing on any of them when cranking.When i turn the key on the asd relay will click twice and 5 sec apart.Is there a way to bypass the asd relay?Im fixin to do the camsensor test that was posted.   

[sharpxmen]

you don't need to bypass the asd to test the camsensor - make sure your multimeter is a needle one and not a digital.

[andrew383]

tested the cam sensor and i have 5v on both out side wires and the middle is ground.The one outside wire will light the test light and the other wont but they both read 5v with a meter.

i went and bought an anolog meter this morning just for injector testing  i still didnt get any pulse from the injectors BUT the inside of the intake manifold is wet with gas so not really sure whats up with that.

Im really at wits end here guys i just dont know whatelse to to do but change the ecm...      

[sharpxmen]

did you use the analog multimeter to test the cam sensor? go thru the testing procedure and see if you get a pulse while crancking on the cam sensor as per testing instructions.

EDIT: while you're at it test the crank sensor as well (you can find the testing procedure in the same pdf as the cam sensor test)
you could test with another ecm, that would be a quick rule-out or confirmation if that's the problem. btw, do you see voltage between the injector terminals? you shouldn't, you should only see a quick spike while cranking.

[andrew383]

ok retested the cam sensor and i get the pulse from it.The injectors still have NO pulse!!I do however have fuel IN the intake manifold. What else is there?

[sharpxmen]

ok retested the cam sensor and i get the pulse from it.The injectors still have NO pulse!!I do however have fuel IN the intake manifold. What else is there?

test the crank sensor using the same method. not sure how you got fuel in the intake. if your crank generates a pulse/signal then it is likely to be the PCM (unless you've got that weird situation where the crank and cam are out of sync). Not sure what to tell you, would be great if you could borrow a pcm and test with it - that would be a quick way to evaluate it (or maybe take your ecu and put it on another vehicle to see if it works, that might be even quicker). keep us posted.

[andrew383]

OOOOOOOOOOOKKKKKKKKKk whole new batch of cookies   
ok so i went back out and started messing with the coil power/ASD.I bypassed the ASD with a jumper and BAM fired rite up  .

Sooo put the relay back in and no fire,swapped with the FP relay and still no fire,jumped it again and fired rite up.

When it fired up it wouldnt idle without me pressing on the pedal,after it ran for a min and a few rev's it idled but has a dead mis.The mis IS NOT constant but happens about every 5 sec.

Sooo what is the ASD not seeing that it needs to?

[sharpxmen]

didn't you say you were getting 12v at the injectors (i think that is given by the ASD)? or am i mixing this with another thread. did you check to see if you have 12v at the coil side of the ASD (pin 86 or 87, can't remember) - my recollection is that the ecu is controlling it by ground to one of those 2 pins and the other one has 12v when you turn the key in run position. since it runs it means you have crank signal, otherwise you wouldn't have ignition/spark. interesting is that your FP relay is working and the ASD not.

[sharpxmen]

i looked at the diagrams for the 94/95 wrangler in FSM - look at pages 44 and 50 in the 95YJ_8W.pdf file. the coil side of the relay is the same (both positive and ground) for both ASD and FP relay. even more the feed for the contacts side is the same. so unless there is a wiring problem and assuming the connections are the same for your year you should have power at the asd when your FP relay gives power. i would check to see if there is a wiring prob there and if you have 12v on the coil and contact side of the ASD (again, assuming that your model is the same with 94/95).

from that document this is the description of how ASD operates

AUTOMATIC SHUT DOWN (ASD) RELAY
When the ignition switch is in either the START or
RUN position, it connects circuit A1 from fuse 4 in
the Power Distribution Center (PDC) to circuit A21.
Circuit A21 powers fuse 5 in the fuse block. Circuit
G50 from fuse 5 splices to power the coil side of the
Automatic Shut Down (ASD) relay. The Powertrain
Control Module (PCM) provides ground for the relay
on circuit K51. Circuit K51 connects to cavity 51 of
the PCM.
When the PCM grounds the ASD relay, contacts inside
the relay close and connect circuit A14 from fuse
1 in the PDC to circuit A142. Circuit A142 splices to
the generator field terminal, fuel injectors, ignition
coil, and heated oxygen sensor. Circuit A142 also connects
to cavity 57 of the PCM.
Circuit A14 from fuse 1 in the PDC supplies battery
voltage to the contact side of the ASD relay.
HELPFUL INFORMATION
˛ Along with supplying voltage to the ASD relay
contacts, circuit A14 supplies voltage to the contact
side of the fuel pump relay.
˛ Circuit G50 also supplies battery voltage to the
coil side of the fuel pump relay.
˛ Circuit A14 also connects to cavity 3 of the PCM.
J 8W-30 FUEL/IGNITION—YJ VEHICLES 8W - 30 - 1
BATTERY FEED
Circuit A14 from fuse 1 in the Power Distribution
Center (PDC) supplies battery voltage to cavity 3 of
the Powertrain Control Module (PCM).
HELPFUL INFORMATION
Circuit A14 also supplies power to the contact sides
of the Automatic Shut Down (ASD) relay and fuel
pump relay.

[andrew383]

well its fixin to go on the scanner :)

[neale_rs]

I don't think you need a scanner at this point.  Just check the wiring to determine why the relay is not being activated.  Looks like you are pretty close to fixing it.  If the FP relay is working, that would mean the computer is providing the ground so you don't need to worry about that any more.