4.0HO No Start, No Spark

[ihscoutlover]

I know this is kind of off IH, but I have run into a situation with EFI, that I am not sure what I should be checking, so Bill chime in here if you get a chance.

Vehicle: 1994 J**p Cherokee, 4.0 AW4, 242, D30, 8.25

Problem: No start, no spark, no fuel pressure at fuel rail.

Tested: Relays are testing according to specs. Still checking grounds to verify all sensors and computer are grounded correctly. All fuses are good and have continuity.

Replaced: Crank Position sensor(which is a common issue on these vehicles), swapped out various relays as well, all which give me nothing.

I have no spark at the coil. I am manually starting the solenoid via a remote starter switch. This is due to either a bad NSS, or the one in place is needing adjustment. The cranking is being done with the ignition in the on position. I am wanting to know whether I should be chasing down sensors, and verifying they are operating within their specs, or am I missing something else. I can and am willing to get the other parts off JY units in an attempt to fix this. I know I know, its a J**p and not an IH, but this is the wintertime beater, to take some duty off Melissa's Traveler, and heck I only paid $375 for it, so I don't have but $450 into it now. Thoughts and or suggestions??

Jeff

[Mt Hood Carl]

I have a copy of the factory diagnostic procedures for '94 Jeeps. Are you able to pull OBD trouble codes stored in the PCM?

Check that ASD relay is providing voltage to the coil. Cavity one (DG/OR wire) of the two pin connector at he coil should be above 10VDC.

[Bill usn-1]

As Carl said, I would start with the ignition side.
Most systems will not run the fuel if there is no spark.

IIRC Jeep also has the ignition in the PCM. I have heard of work arounds to run an external ignition bypassing the one in the PCM.

I have also found some good troubleshooting and diagrams on autozone.com under the repair section. And it's all free. Just log in and select your vehicle.

1991-98 Jeep vehicles are not equipped with an ignition control module. However, the functions of the ignition control module are performed by the Electronic Control Unit (ECU), also known as the Powertrain Control Module (PCM).

The Crankshaft Position Sensor, or CKP sensor provides the PCM with information about engine speed and crankshaft position. It is located near the bellhousing.

The CKP sensor contains a Hall effect device which sends either a 0.0 volt or a 5.0 volt signal to the PCM depending on the position of the distributor shaft.

The PCM uses the CKP sensor signal to determine fuel injection event time among other things. The engine will not run without the CKP sensor signal.

http://www.autozone.com/autozone/rep...00c152800a9b52

[Isa Ismail]

The Jeep came with a factory security system,(It triggers the auto shut down) If you pulled all the electrical from the Jeep to transplant, You will need to include the security system module and bypass it.
It will not work otherwise with out doing so.

[Bill usn-1]

Isa,
It's still in the original cherokee.

[IH64Scout]

ray cass EFI'd his 258 with the stuff off my '95 GC 4.0. he wired it all in, had some security issues, he may be able to help!

[ihscoutlover]

Originally Posted by ihscoutlover

Problem: No start, no spark, no fuel pressure at fuel rail.

Tested: Relays are testing according to specs. Still checking grounds to verify all sensors and computer are grounded correctly. All fuses are good and have continuity.

Replaced: Crank Position sensor(which is a common issue on these vehicles), swapped out various relays as well, all which give me nothing.


Jeff

Per my first posting, (12-25-11 @ 19:01hrs) See above ^^^

I have replaced all of the following:

Crank Position Sensor
Distributor/Cam Postion Sensor(Pickup Coil)
Ignition Coil


I have tested all the relays prior to starting this thread. The ones I have been testing/using all are the ones I have tested and that tested per specs.

Everything on the vehicle appears to be original, to include the Crank Position Sensor, Ditrtibutor/Cam Sensor/Pickup Coil, the ignition coil, engine, tranny, etc.... Vehicle has 155k miles, and from the gunk buildup of oil grease and grime, its all original, and will be cleaned with the steam cleaner to verify leaks.

On Thursday the 5th at 11:57hrs, i posted that I had spark, which told me that now I need to concentrate on fuel delivery. This part is going to be a go no go exercise. I know the tank has approximately 5 gallons of fuel in it. I am going to first replace the fuel filter, since 1 it isn't going to hurt it, 2 it probably hasn't been done for a very long while(like some of the other things on this J**p, and 3 its cheap, easy and will work to lessen any load on the fuel pump if there is crud up in it, preventing some of the flow of fuel to the fuel rail.

I am trying to track down one of my test lights to verify pump is getting power, and I am going to bypass the relay, by jumpering #2 and #4 relay positions, to see if I am getting power at the pump wiring connection.

The Crank Sensor was the first sensor/component replaced. Per the FSM, with a bad Crank Sensor no fuel or spark event will take place.

On the 5th I was also able to pull the trouble codes off the ECM, and since it was after Cam Sensor/Pickup Coil/Distributor replacement, the #54 code for checking the Cam Sensor Circuit, has since gone away. So there are only 2 codes stored, the battery power loss to the ECU since the last 50 key on cycles, and 55 which is the end of codes.

I haven't had time yet to finish working on it as of yet, but once I get the pump and wiring checked for proper operation then we will know what's going on. I am also going to check the pump for infinite resistance, as per the FSM, if that is the case, the pump is bad. All this checking can be done through the wiring connection that I am going to use for the diagnosis of the pump and power to the pump. I will also be applying 12v to the pump to make sure that with a dedicated source of power that it functions correctly.

What is getting me is the low fuel level, with 5 gallons in the tank, that's just at 1/4 tank(21.0 gallon tank), so the gauge should have gone up, and the light out, but I am thinking that the ground here is bad, or needs cleanup, and once good, the light should go out, and the gauge should start to read correctly.

Hopefully this clarifies anything that I may have missed. Post up any other questions or concerns, and thanks for the help with this. This just adds to my edumacation to adding FI to at least one of my Scouts later, but helps me get a better understanding of operation of the system and some of its corresponding sensors.

Jeff

[ihscoutlover]

I am in the process of checking the grounding on the fuel pump and sending unit. Apparently the sending unit on this vintage Jeep uses a basackwards setup to read fuel level. I am going to check my grounding first, then see if I actually reground the unit, if that changes the operation of either the sending unit(and gauge) or at least gets the pump to work. I keep getting the code for the fuel pump circuit, which occurs when I jumper the contacts in the relay bay to provide a constant powering of the fuel pump just to see if the unit is bad or good. I'm almost there on the diagnosis of the "issue" per se.

Jeff

[Bill usn-1]

Sounds good Jeff.
Trouble shooting is cheaper then buying and swapping parts.

[ihscoutlover]

Yes it is Bill. All the parts I have replaced to date have all been out of factory specs. One of my other forums indicated that IF(all caps here), the guage is pegged at empty, with gas in the tank(I have added 5 gallons and no change to the guage reading) that is an indicator of a bad ground. If the pump or sending unit's ground is bad, then its gonna seek ground where it can, and in this case, through the gauge. And since that is the first stop to find out just why the pump isn't working. I will post up my findings once my helper and me have time off together so I can troubleshoot parts of it with her help turning the key on and off. We are almost there that's for sure, and its definately paving the way for at least one or two of my IH's to go FI.

Jeff