No power to ballast resistor or fuel pump

Hey guys I need your help.
I spent all day searching posts on this topic before I decided to post.

1991 XJ 4.0 Auto W/ ballast resistor

Here is the story:

wife takes xj to drop off the baby at the sitter on her way to work, she comes out and the jeep would not start. i had left the tank sorta low, but not less than a quarter tank, so we both assume it may have ran out of gas. I leave work grab a can and come to her aid. put the gas in and the jeep would not start. I had the jeep towed home, so I could get back to work.

Fast forward to yesterday afternoon

Get home and get on this site. I try and check everything that has been posted before from others having this problem. Still no start. So now im beginning to think the fuel pump is toast. I pull it from the tank and wire it directly to the battery = gas in my face. So at least i know the pump still works. I get out the test light and check for power to the fuel pump relay i have power there. i get under the jeep and test the harness, no power there, but the sender still works fine. (I had noticed that after putting gas into the car earlier when we thought it was just out of gas)

Test the ballast resistor, no power there either.
So i just don't get it. I've read and read, checked for corroded wires, fusible links, relays, (spend 35.00 on a bunch of them just to swap out) And I can't get it going. This would not be a big deal if I didn't have to take it to get to work Monday, but I do.

So I'm kinda at wits end with this thing, Can't understand why I get NO power to the ballast and either side.

Just looking for some direction before i bypass the harness power supply and relay it directly to the Battery so that I can drive the damned thing.


Thanks to all that can help in advance, sorry so long

to help with ideas, try checking the following:

do you get any sound from the pump if you turn key on and don't start?

do you get spark at plugs when you're cranking?


post results and we'll see what we can do to help:looney:

--Shorty

Well as it stands no sound from the pump(been this way since yesterday)
and no spark at all....

Now im totally confused

It could possibly be the crank position sensor. When it dies, you have the last known good code on the ECU...until you shut the engine off. After that the engine will not fire.

Does the '91 have the same starter relay as the Renix years? Or at least a similar circuit? If so, the fuel pump ballast resistor runs off of that. But, that wouldn't explain no spark. We're trying here...

could it be the ECU?
I need to get this going

Thanks for the help so far guys

any more ideas on this?

try jumping fuel pump relay and see if the pump will run. CPS signal is necessary for the ECU to trigger fuel pump AND ignition module on these things-- I'd check it carefully as well.

Does the check engine light come on? I had the same problems, no fuel, no spark & no cel. Ended up being the CPS. JIM.

I got no check engine light, so I will check into jumping the relay.
Are there any guides on how to do this correctly?
thanks for all the help guys.

If you get no check engine light, no spark and no fuel pump relay activate, it's likely like shorty mentioned the CPS is toast. The fuel pump relay may activate for a second or two (prime) (you can feel this with a finger tip on the relay), as you turn the key to run on the way to start, but the relay won't stay engaged unless there is a CPS pulse signal.
Jumping the fuel relay may get you fuel, but there will still be no spark. When the check engine light fails to illuminate when the key is turned on, this can be a short in the CPS, instead of an open circuit. It can also be a short in the sync sensor but less likely. Something is likely messing with your 5 volt sensor supply circuit, most likely the CPS.
Try unplugging the CPS and see if your check engine light illuminates as soon as you turn the key to run. If you still get no light unplug the sync sensor.

Okay, well I did some more searching here and found the trouble coded list, so im going home at lunch to see if I can get the cel to give me the trouble code. Then ohm test the cps. I will post results when i get back here to work. I will try all of these tips at lunch. The fuel pump makes absolutely no noise at all. Thats how I first new I had a problem, and mistakenly thought it was the fuel pump.




Thanks guys

Well I tested the cps plug at lunch and got 0 on the meter. No ohm spec at all. At first i thought I was doing something wrong since it gave no reading, but then I pulled a surplus 4 ohm speaker out of a pile o crap that i had and tested it and got a positive 4 ohm reading. So I guess the CPS is toast.

Weird thing though is my CEL never came on, even after disconnecting the sync plug, Im thinking a bad bulb there??

So I couldn't get trouble codes at all.

Correct me if im wrong here guys, But I think if i replace the cps all should be good .....right??

Thanks again

until proven otherwise, I'd say you've got it!!!!arty:

I would double check that your CPS is being tested correctly. The CEL having a burnt bulb would have no effect on there being no codes.

I recently had this same problem and it turned out to be a bad PCM. Same exact symptoms, same test results.

I'd turn my key on and I wouldn't even get a CEL on with all the other lights. It's as if the whole PCM was toasted. I bought another one on ebay for $60, plugged it in, and she fired right up. My A/C even started working again. Turns out my original PCM was pretty much a paper weight at that point.

When you turn your key to the on position and all the dash lights come on, is the CEL one of them? If not, then you probably have a problem with your PCM like I did.

Hope this helps.

You can check my past posts to find my thread about my problem and solution details.

waxer-

when I turn the key I get no CEL at all, All I get is washer fluid, because it's empty. I turned the key a bit past acc, almost to crank , and the brake light lit up, but still no CEL.....

So youre thinking PCM???

also can't find your post on the subject..

Yes Im thinking PCM. You are experiencing the same symptoms I had when my PCM was dead.

Start looking on ebay for a PCM. You'll have a 7 digit serial number on your PCM. Input that serial number into the ebay search field to see if there is one currently for sale. You will need to use a PCM with a matching serial number to be certain it's compatible with your jeep.

Click on my name, click on "Find all posts by waxer" and look for the post titled "Starting problems after hammering fenders"
*Edit* Disregard that... It's been deleted it seems. Why I don't know. There was excellent information there that you could have benefited from.
Oh well.
*Edit* *Edit* Forgot that there was a server crash and some of the posts were lost. Looks like my post was part of that lost data.

well i got home and pulled the pcm to check it out, it smells fried. I've never smelled one before, but this one smells like fried electronics. I will hit ebay after hitting the JY tomorrow, there were a few there with my engine/trans combo, and within the correct year range that I pulled the fuel pumps from. ( i pulled 3 fuel pumps when i thought that the Fuel pump was the problem)

Has anyone ever smelled their PCM?

The circuit board is encased in Gel, so it would be hard to smell it I would imagine.

Just make sure you get one with the same serial number.

If I remember correctly, it's the number on the bottom (closest to the fender when the PCM is mounted).