lvcherokee

Hello!
I have a 1987 XJ with the 4.0, pretty much stock for the purpose of this question. The jeep ran fine, but sat in the driveway for 2 weeks while we were on vacation, now it won't start. It's 112 degrees in the desert, and the fuel pump sounded quieter than usual, so I suspected a fuel issue.

Bled fuel at the rail and there was pressure (sorry, no gauge). Good pressure when first turning on the key, but after the initial burst of pressure, the flow slowed to nothing. The pump is an Airtex (all we could find at the time), so I suspected that may be the issue.

After reading a few threads here, I decided to check the voltage going to the pump as a double-check. Well, the voltage is 6.8 (battery is 12.2) so not sure what's going on!
Any help or ideas to check would be appreciated.

Batman33165

Do you know if the ballast resistor is still in the jeep? that is supposed to lower the voltage to the fuel pump.

You could also try renting or purchasing a fuel pressure gauge from harbor freight to check the reading

cruiser54

Airtex is junk.

Where are checking for voltage?

Try removing the 4 relays on the passenger fender well and cleaning their terminals with some abrasive and spraying out their receptacles with contact cleaner.

lvcherokee

not sure if I have a ballast resistor or not, where would I check for that, and what kind of voltage should I expect to see at the fuel pump if there is a resistor?
I checked the voltage by disconnecting the harness at the fuel pump, figured that would be a way to prove that the Airtex was bad. But with 7 volts, what should I expect??
So today tried switching the relays and cleaning their contacts - same result. I could feel the relay clicking when the key was turned, voltage up a little to 7.2 - but I did have the battery charger on it at the time.
Hit it with starting fluid and it didn't even try to run at all. Lifted the air filter hose off and shot it straight down the throttle body, still no go at all. Pulled a spark plug and have spark, but thought it was kinda weak. Bought a new coil, spark looks a little better, but still no go - even with starting fluid.

lvcherokee

oh, and have 11.8 volts at the supply to the coil.
thanks for the help!

6Cylinder

Whats wrong wit Airtex?

cruiser54

Ballast resistor should be mounted near the air cleaner on the fender well. 87 may or may not have one.
Here's a photo:

cruiser54

Whoops.

cruiser54

Did you put the relays back in their original slots?

If so, move each one down one slot.

Batman33165

Hmm... im having a similar problem but it starts and turns over with starting fluid and no power to the fuel pump... working on the wiring harness

Have you checked your CPS?

lvcherokee

Didn't check the CPS, will have to search the forum to see how to do that. I figured if I had spark, everything else was ok - but with no start on the starting fluid, maybe that's it.

To check spark, I pulled a plug, grounded it on the shock tower, and turned the engine over. Old school, hope that's a good indication.

Borrowed a fuel pressure gauge and got 38 psi after the turning on the key for the 2 second prime. It did bleed down, maybe 10 psi in 15 seconds. Held firm at 38 psi while cranking.

Didn't see the ballast picture until now, will check for that tomorrow.

lvcherokee

oh, and for the relays, I checked the voltage at the fuel pump wiring harness with three of the four relays, they all gave the same reading - about 7 volts.
Pretty sure they are not in the original slots, but we were kind of playing the cup game with them. I started off knowing which came from where, but my son helped while I was checking voltage, so not really sure. Think I have a spare in the toolbox, will break that out too.

lvcherokee

freeze frame from video of spark.

cruiser54

So, you should have battery voltage at those relays, not 7 volts.

Check voltage at the lug with the nut. Should be battery voltage. Then check the other terminals while cranking.

lvcherokee

from the ground terminal to each of the other terminals, had 12.2 volts with the key off, and 11.9 volts with the key on.

I do have a ballast resistor, it measured 10.5 volts on one side, and 6.2 volts on the other

for further testing, I pulled the fuel pump relay and checked the voltages across those terminals. All zero voltage with key off. With key on 30-86, 30-87, 30-87A all measured 11.1 and 30-85 was 0.4

the battery was getting slow to crank from all the non-starts, so pulled and am charging it up.