97' 4.0 Dead

I got a 97 ZJ yesterday (I know this is :shhh: ) and I have not been able to get it to fire. When I picked it up from the PO the battery was flat dead from sitting for 3 months and had all the gas siphoned out. I tried to jump start it but the battery was too far gone. On the way home I put about 3 gallons in it and a fresh battery. Went to start her up and all it dose is crank. Never fires. I have no spark, no fuel pressure and my gauges are dead. When you turn the key to "on" you dont hear the fuel pump or any relays. Ive checked all the fuses and swapped around the relays with no avail. He says it was driven to where he parked it and that it never gave him any troubles. Im wondering if I fried the PCM when I tried to jump start it. Any Ideas? The GC forums are not very useful. I figure someone on here can help.
Thanks!
97' ZJ w/ 4.0

if the ignition key causes the starter to turn over then there should be power going into the PDC, but if there is no fuel or crank then something is wrong after it. I would get hte FSM and multimeter and start testing outputs, then test the computer.

If the PO says that it was sitting for 3 months, it's probably closer to a year. Check all your wiring to make sure that no critters have been chewing on them.

Took the volt meter to it today and this is what I found. Ive got power running threw the fuses and relays and Ive got 5.14v going to the CPS and 5.12/8.15v going to the fuel pump. Fuel pump is still not cycling and the relays are not tripping. Its still sittin in the shop with no fuel to the rail, no spark and dead gauges. Theres no way that I could have fried the CPS and the fuel pump just by trying to jump start it. All the wiring looks good. Im missing something stupid or I did burn up the computer. Any other ideas?

check the fuel pump relay operation? relays go bad...

redneck said:

Ive checked all the fuses and swapped around the relays with no avail.

Click to expand...

That was one of the first things I tried. I guess ill have to wait till pay day and go up to the JY and get myself another ECU, fuel pump and CPS and start throwing parts at the problem. I hate doing that but thats the only thing I can think of to do. Im at a loss.

there are ways to check the ECM by testing ground on some pins, but I don't know what they are for that model

maybe ask a shop for help, or buy an alldata personal subscription for that model?

I pulled the battery off for about an hour and reconnected it. When I did i noticed that some relay in the cruse control servo it tripping when the power is applied. Is that meant to happen? I also have no "check engine light" when I turn the key to "on" just the fuel light, ABS light and brake light.

You say you have power to the fuel pump, so if it has a ground the pump MUST run or it needs to be replaced. Power plus good ground pump operates.

You may have multiple problems. Check and fix ONE thing at a time. Or, just throw parts at it.

I guess I need to specify a little. The cannon plug going to the fuel pump has 4 wires in it. 2 of them are dead. One has 5ish volts (top left) and the other 8ish volts (bottom right). Im wondering if the computer supplies power to the other 2? I dont think its the pump because I dont hear any relays like I do in my XJ when I hit the key. Thats why I keep leaning twords the ECM.

I finally got another computer and threw it in. Solved all my problems. Fuel pump came on cranked and fired up. I have another problem now... It will fire right up and run great for about 5 seconds then it will shut off. Im thinking that this new computer is one from a ZJ with a security system. The part numbers are different between the two but they are from the same year. Is there any way to bypass this on the computer? Thoughts?