More Fuel Related Problems

Well, to make a long story short....

87 xj died this weekend, we narrowed it down to a fuel problem. No fuel pressure at the rail, and we couldn't hear the pump turn on. So we checked it for voltage. It was 6.6 volts in the on position, don't know what it was in the crank position.

I did some searching and found they switched to the ballast resistor in 87. Not sure if mine has one, didn't check. But when we were at the parts dealer he said there were two pumps listed, If I had this vin number I had to use this one, If i had the other Vin I needed this one. They only had one in stock so we took it. Hooked it up, and no go can't hear the pump fire up.

So when I run back up there (50 miles away) I'm gonna run 12 volts back there to see if i can get the pump to spin up. I'm pretty sure that since the 87 didn't come with a ballast resistor, It would be okay to simply bypass the resistor if it is found bad.

I'm also going to bring a spare relay with me to swap that out if it is needed.

Anyone have any Advice?

thanks,
Hodge

well, looks like we are just gonna throw it on the trailer and bring it home. Be a bit easier to work on it than trying to troubleshoot it on the trail.

:repair:

Not sure if this helps but my 1990 did the same. It turned out that it was a combination of a bad fuel pump and a bad fuel pressure regulator.

What you're saying is most likely what I'd do too....
Good luck. Hope it's just a bad connection.

Okay, Got the jeep home and sitting in the driveway. Started tearing into it. Its an 87 XJ RENIX. I jumped the pins in the Diagnostics connector as said in the FSM. Pump fired right up. So I cracked out the wiring diagrams and started to trace it back.

I first removed the relay and started to check for voltage. 12v from battery good. Jumped the relay and pump fired up. Long story short, the ECU is supposed to supply a ground for the fuel pump relay, and the 12v comes from the Ignition control unit. I get 12v from the ignition fine. the problem is with the ground that the ECU is supplying. I hook the multimeter upto it and it registers about 8.5-9 volts. I took the ECU out of the dash thinking it could be a corroded wire, and am getting the same thing using the ECU + and fuel pump relay ground.

Right not the onlything I can think of is that the ECU is toast. Am I correct on this? The relay doesn't trip, but I can use a 9 volt battery to trip the relay.

Any insight would be greatly appreciated.

Thanks,
Hodge

HRm.. Can't seem to figure it out. I'm thinking I could just by pass the ECU ground and apply the ground manually VIA a switch.

Anyone think thats a bad idea? :fuse:

HOdge