All right I posted on a few other boards with no luck so I am need to know if you have any ideas. Heres the deal. I bought a 73 cj-5 that had a 4.0 swapped into it from a previous owner. I have drove it for about 6 months no problems until now.

I went to start the other day and it had no power so I went and charged the battery and started it and drove a few miles and as I pulled in the driveway it dies. It has no power again so I open the hood and checked the posative cable was loose and arcing on the silinoid when I tried to start it. I wiggled the wire and it broke off. Rusted apart. So I replaced that and now it will roll over but when I turn the key on I do not hear the fuel pump kick on. I ran a jumper wire from the battery direct to the pump and it turns on but it does not stop like when you turn on the key. Not sure if should build pressure and stop like when you turn the key on or keep running. So the fuel pump seems good so I traced the wires from the fuel pump up to the motor and down the fuel rail wiring to the starter relay and I replaced that and still no power to the pump. There is a green black wire that goes from relay to fuel pump and it does not have power. There is a red white wire off the relay that goes into the black box that is vented on the firewall I thinks its the computer not sure? There is also a yellow white and blue white wires that go from relay up to the fire wall box as well but they both have power when the key is on.

So the question is could I have fried the computer from the arcing of the cable making the computer turn on and off or surging power?? What else can I check?? I think the pump is good because it runs from jumper and the relay is good. I am not sure if there is a in line fuse? Who ever did the swap never put in a fuse block. If I have to get a new computer I will have to find out what year the motor is and how would I go about finding this off the castings? Thanks

Well yes you can fry a computer by improper jumping and/or causing power surges etc. Definately don't hook the battery up wrong or jump it wrong. However its rare. I would jump your fuel pump and try to start the engine. If the engine starts then most likely your computer is fine. Do you know what kind of 4.0 fuel injection it has? If it has an egr valve on the intake then its the early renix 87-90, if there is no egr then its the later HO motor 91-97?. I would then try to find a wiring diagram of the fuel pump circuit.

How are you verifying that there is no power to the fuel pump? Have you checked your computer grounds and body grounds? It sounded like you might have some sketchy electrical connections and I would check them all first. No power or ground to the comp and it won't turn anything on.

Kevo

Something else is amiss. A bad ground or bad + wire somewhere. Check all the relays and fuses in the box. Check them and double-check them.
If you can't figure it out, let me know...I've got schematics here and can look it up and probably tell you exactly what your problem is. ;)

Thanks guys I will have to check and see what I have if its a older swap or newer swap. I don't think it has a fuse box because when I had issues with my lights I tore into it and only found in line fuses and no fuse block unless it is on the fire wall in the black steel box that all the wires go into.
I will also have to try starting with the jumpered fuel pump.
I checked too see if the fuel pump had power going to it with a meter. I used the red lead from meter and pushed it into the relay where the green black wire comes out and goes back to the fuel pump and then used the black to a ground on the frame and then turned the key on and nothing. If it had power it would have regitered on the meter for a few seconds I would think. not sure? Thanks this is a start. None of the other boards I posted on have a clue.

turn on the key and see if the pump is getting power from your electrical wires. if not, then reverse trace the wires. where the pump wire goes in, check and see if there is power on the reverse side. if there is power going into the box but not out, then you have isolated the fault. another trick is to wire a switch into your jumper wire so you can control it from the Cab.

When you first turn the key to RUN, most (almost all) relays are energized, as is the fuel pump relay. After a short delay (1-2 seconds), the ASD relay (automatic shut down) de-energizes and, since it's tied into the fuel pump relay, de-energizes that one.

Ok I went out and first hooked a jumper wire from the battery direct to the fuel pump and tried to start it and it just turns over and does not start.
I then started looking at the wires to the relay and trace them back and one wire from the relay goes into another relay and this is one that has power with the key on. The green black goes back to the fuel pump and the other two go into the box on the fire wall. My haynes manual that I had for a wrangler I once owned said the box is the Engine Controler. Is this the computer?? I pulled it off the fire wall and disconnected the block of wires to it and cleaned it up( It was all muddy from previous owner).

Ghetto Fab-- I looked for a EGR valve on the manifold and I could not find one. When I pulled out the controller I noticed a tag on the side that has some numbers and a bar code and a date of 12-04-92. This would make me think it may be out of a 93 or so model. So it will be the HO model. Not sure if it is a cherokee or a wrangler.

I also have the diagnostic pig tail that is on the harness just before it goes into the controler. Will this help me find the problem if I get a code reader and will it just plug in to the connector?? If so where can I pick one of these up at and about how much??

Also I think I want to get a Factory service manual for this but I need to find out what year and vehicle it came from. Any ideas on finding this info?

Thanks

check your latch relay......

also try crossing over the relays and see if you get any power to the pump

have you checked to see if it is firing either?

if the engine is a 92 and has a diagnostics port you might be able to have advance auto hook it up for free to see whats wrong with it

What and where is a latch relay????

Also I have not crossed the relay to see if it powers the pump because not sure which ones to cross.

The engine will turn over but not fire.

I may have to put the tow bar on it and bring it to advance auto but I was wondering if the small testers will work on this?

you should have a row of probably 4 relays...... could be ASD,FP ,Latch and A/C relays

you could also check the fuseable links ..if they were used in the swap

so it has no spark when turning the engine over?...... if the latch relay is bad it wont fire...... and sometimes it can draw power from the FP relay to where you would have to cross them both over to get it to run

When you first turn the key to RUN, most (almost all) relays are energized, as is the fuel pump relay. After a short delay (1-2 seconds), the ASD relay (automatic shut down) de-energizes and, since it's tied into the fuel pump relay, de-energizes that one.

Geez, is it TUESDAY already????????

All of the previous replies except for Damage's quoted above are absolutely useless.

You can jumper crap all day long and not find the source of your problem, you're just creating more problems. Before you really burn up something expensive, stop using a jumper wire.

When you turn the key to the "ON" position, the PCM (computer) awakes and waits until a signal is sent from the CPS. As part of the wake up, the ASD, and Fuel Pump relays are engergized for 1-2 seconds. You should hear the relays click. If you don't, you've isolated your problem. If you do hear the relays click, then you've isolated your problem. The relays are the key to chasing down your problem. Let us know if you hear the relays.

Ok I just replaced the other relay that is tied to the one that goes to the fuel pump. They are cheap so I did it anyway to be sure. Yes I do hear a click coming from at least one. The one that runs to the fuel pump I can not feel click. I plugged it into another and still no click on the fuel pump relay.

When it ran I would turn the key on and yes the fuel pump would kick on for a couple seconds.

I have a single red wire going from the battery along the fire wall to a seperate blade fuse. I checked the fuse and its good and I have constant power tgoing through it. This wire then goes up and enters into the rest of the wiring harness and then splits into five seperate wires. One goes to the fuel pump relay and it is the red white wire and has power to the relay all the time. Anoter goes to the other relay that is also tied into the fuel pump relay. Anoter wire splices into a green and yellow and geen and grey wire and go back in by the fuel rail. The last wire goes along the harness all the way up to the engine controller and has power up to the controller all the time. So power goes into the controller how can I make sure it is coming out of the controller?

I also took and checked to see if I had spark and I have none. So it has to be the controller or a bad ground somewhere.

Okay...listen closely.

The ECM *grounds* those two relays (ASD and fuel). +12V is constantly provided; the ECM then grounds (sinks, technically) the relays to energize them. In layman's terms, the ECM is providing the ground (switching the ground on and off), not providing the +12V.
If you hear the ASD relay energizing (when you turn on the key), then de-energizing after a couple of seconds, the ECM is okay. If the fuel pump relay isn't engaging with the ASD relay, then there's something wrong with the fuel pump circuitry.
*VERIFY* all fuses. Find the one that says 'fuel pump' and check that it has 12V on both sides. Look HERE (http://www.teamrocs.com/technical/pages/relay_basics.htm) for relay basics. In the case of your fuel pump relay:
85 - ECM provided ground
86 - +12V when ignition is in RUN
87 - Output to fuel pump
30 - +12V Constant

To verify everything, remove the fuel pump relay, get a buglite (+12V tester) and do the following:

Ground the alligator end of the buglite:
Verify +12V at '30'
Verify +12V at '86' when you turn the key on (will only be 12V for a couple of seconds)
Verify +12V at '87' when you turn the key on (will only be 12V for a couple of seconds)...I don't think you'll get +12V here; this is the problem.


Connect the alligator end of the buglite to +12V (*at* the battery!!!):
Verify +12V at '85' when you turn the key on (will only be 12V for a couple of seconds).

Let me know the results. ;)

Oh yeah...the stuff above, that's looking down into the 'hole' left by the relay. ;)

So you've allready replaced both relays and it still doesn't run. Is it getting any spark at the plugs at all? If not then its starting to sound like the usual crank sensor failure. No engine crank signal and the asd shuts everything off. Sounds like you need to get a good wiring diagram also.

Kevo

it could also be the ignition control module under the overflow bottle. I have had 3 burn out in 16 years.

Damage- I did exactly what you said

I first removed the relay and got a bug lite and grounded it to the battery and checked #30 first and Yes I have power to it

Next I checked #86 whilke turning on the key and Yes I have power but it stays on.

Next on #87 I turned the key and NO Power just as you suspected

Then I took the bug light and hooked to the (+) side of the battery and checked #85 with the key on and I have NO power there.

Where should I go from here :)

Damage- I did exactly what you said

I first removed the relay and got a bug lite and grounded it to the battery and checked #30 first and Yes I have power to it

Next I checked #86 whilke turning on the key and Yes I have power but it stays on.

Next on #87 I turned the key and NO Power just as you suspected

Then I took the bug light and hooked to the (+) side of the battery and checked #85 with the key on and I have NO power there.

Where should I go from here :)


Also I run the casting numbers on the intake and motor and found it is from 91-96. I also know the side of the computer has the date of 12-92. I think the motor is from a cherokee because the power steering resivior is mounted at the pump and not seperate like the wranglers.

Where should I go from here :)

With the buglite connected to battery +, check #85 on the ASD relay. When you first turn on the key, you should get 12V (ground, technically) there, then it should go away after a couple of seconds.

If it does, the ECM is working fine. This signal from the ECM (ASD Relay Output) feeds *both* the ASD relay and the Fuel Pump relay and grounds them both. There's a splice in the wiring harness somewhere. If the ASD relay is getting the signal and the fuel pump relay isn't, it's this splice or something similar.

Let's take this to PM. ;)