Fuel Relay/engage. Start issues. Patience appreciated.
 

89 Jeep Cherokee 4x4 auto 98,xxx miles.

Well, I'm back friends. Have already and currently doing research.

Last week I went out to drive my Jeep and it did perfect. The next morning I went out to drive it and it would not start. It turned over fine. 12 volts at battery. Noticed pump not engaging when turning key to on. 12 volts at pump on red and black wire when turning key to start but 0 volts on yellow and black wire when turning key to on. Family member had turned key 5-10 while I was checking and double checking all this. (Important later). Anyways I changed out the relay with my AC relay and it engaged and started right up.

Everything did fine until today. Wouldn't start and fuel pump not engaging. Thought it was just another bad old relay. Grabbed 4 relays out of my 94 parts jeep. No relay would engage the pump. I checked voltage at 85 & 86 and gpt right at 12 volts. I then jumpered 87 & 30 and the fuel pump kicked on and ran as long as held the jumpee wire there. Maybe 5 seconds but more than 2. Key was off at this point by the way. Checked some of the relays again, still no engage.

Rode up to my brother in laws and checked some of the relays in his. His started fine.

Came back and put one in my jeep. Turn key and the fuel pump engaged as it should. Key had probably been turned to on position about 5-10 as before. Not sure if thats important but wanted to be sure to include it.

What could this be pointing to? Could it still be the relays? What could be wrong that makes it take 5-10 of turning key to on to make the pump engage or is that coincidence? Sadly, I know this will most likely happen again and I won't be able to see if all acts the same until then.

I will do my best to answer any questions that I can.

Possibly the ignition switch going bad? Maybe its not making a good connection and turning it a bunch of times gets it to work briefly.

What's the voltage at each side of the fuel pump ballast resistor on Start and Run?

I have the ballast resistor by passed. The two wires are connected. I did that 2 years ago.

Edit: the volatge back at the fuel pump harness near the tank is;

12 volts on the red and black when turning over to start. And is 12 after it starts.

0 volts on the yellow and black when turned to on. Unless the fuel pump primes. Then it has voltage of course.

It went a week and half in between doing this again. Now its back fine again. So it's not all the time (yet).

And somebody above mentioned my ignition switch could be the cause. In cold weather my ignition switch does stick and it has just got colder and started to do it some.

I can drive it for 20 minutes or 5 minutes. Go to turn it off. And it does this. It turns all the way past on (nothing is lit up) but just not quiet far enough for me to pull the key out, unless I wait for a number of minutes. The it will turn back the rest of the way and the key will come right out. The colder it is the longer I have to wait it seems.

It never does this in Summer. It has always done this in the winter but has never really bugged me that bad.

Hmm sounds like an issue i had, is the cps wire okay? when was the last time you replaced it? Mine was touching or getting close to the engine that it started to melt. That gave me problems.

Then you might want to check the connectors that are by the kick panel on the driver side? these connectors connect the wires from the front to the rear. If they seem fine, i would try cleaning them, and putting some dielectric.

This is probably an exaggerated thing to do but take out your ECM and open it up, there might be a corrosion build up like i had. On mine i also had a couple of diodes even off the board.