Fuel pump/wiring issues......I just keep trying

Alright, here we go again, this time with a new Truck... 4.0/AX15/4x4

My 90 Eliminator had stalled out at idle and will not restart, the fuel pump is not priming as the key is turned to the "on" posistion. I had the truck running about and hour prior to this, just a sitting idle while I seafoamed through the TB and some Vac. Lines, it did its usual smoking and was running great. I was working on bleeding my brakes (via proper procedure) and fired it up 1 other time to check the pedal. I shut it off and now it will not restart.... :dunno:

It has spark, besides the vac lines from the airbox all others are in tact. As mentioned I'm not getting any activity outta the fuel pump, i bypassed the Ballast resistor to no avail as well. Is it possible the Seafoam job gummed up the 02 sensor bad enough that it won't run? I will check for power at the fuel pump tomorrow.

I'm lettin it sit overnight and see if it manages to fire up tomorrow as well.....Thanks for any Help! :roll: :oops:

no you can cut off the o2 sensor and the truck will run....

Since you can't hear the f/pump prime , check the power supply to the pump , if you have no power , check your fuses/relays . If you got power , you know what you have to do :(

Yep, ill check power 2 the pump today.....If it comes to a bad pump atleast i have 2 Others on the shelf waiting ;)

Alright, with a few free minutes this afternoon i plugged in 1 of my spare Sending unit/pumps and gave it a try, I didnt get any power to that 1 either. So I'm pretty sure I have a bad relay, loose connection, ect.....

Any ideas where to start 1st?

alright well this mornin she didnt wanna fire up again, its acting like its starved for fuel......I'm leaning towards the fuel filter, this truck wasnt run much at all for a few years and now that Ive been cleaning up the fuel system and for all i know the filter is factory installed, I think the pump is priming till it feels pressure back 2 it than quits, meanwhile the engine doesnt have any fuel to it... meaning clogged filter...

I have a spare filter laying around so ill swap it tonight and see what i find, meanwhile ill keep hunting for the culprit. :wrench:

:dunno: ^^^

This is a very intermittent problem. Once its running it runs great but occasionally just while sitting at idle it stalls out and will not restart...

I have bypassed the Ballast resistor and tested starting 6-8 times and each time the pump primes and the truck runs fine. I drove it 8 miles tonight, parked it applied the parking brake and it slowly stalled out and no longer had power to the pump to restart. Ill try to fire it up in a few hours to drive home.

I'm really at a loss for this now, its very intermittent. I'm 90% sure its a fuel pump power issue but may just replace the CPS as well, it seems to be more of an issue after the truck is drivin and up to tempreture, cause itll sit there and idle all day long once up to 210+ degrees. :wall:

Check for a loose/broken wire over near the battery and fusible links. Next time it won't start, try messing with those wires and see if it starts.

Well after another 20 mins troubleshooting @ 11pm I think i finally found the culprit. This orange wire had seperated, i quick fixed and twisted it back together and wa la the fuel pump came on and the truck ran again.....this was probably the problem all along, atleast I hope so. ill get it repaired properly this evening and go from there.

sorry for the bad pic, but this was on the distribution block behind the battery.

Well its been about 2 weeks since i though this issues was resoved after repairing the connection. After about 50 or so miles of driving and replacing the alternator that had crapped out I went to fire up the truck this morning and boom....No more power to the fuel pump, alright so i went back under the hood to the previous trouble spot and noticed my repair hadnt held up. No problem, I just sperared the orange wire from the eylet and made up a new wire onto its own connection on the Master Soleniod, all back together but Still Nothing :huh???:

Ill try my best to describe where i am now with words. Any I did some tracing and when I run 12v direct to the pump its runs

The pump checks out!

Now here's where it gets tricky, there is a red wire that runs from the connector right above the relays to an eylet connected to the master soleniod, with 12v applied to that wire AND the fuel pump jumper wire the truck will start and idle, only for a few seconds then that connector begins to heat up quick, i kill the 12v to that connection and the truck dies (all this is done under the hood, no input from the key to kill the engine) The orange wire (fuel pump power i assume) and the red wire both are able to get ot the point where they begin to melt, I didnt let em get there but thats opointing to a short or else a larger amount of power flowing through them than there should be (extra 12v?) Anyway thats the only way the truck will run...

Put back to the normal way all the wired are hooked up, when the key is turned to the "on" posistion there is no priming of the pump and the truck does not start, If straight power is applied to the pump with the pump running the truck still doesnt not start. the only way to start the truck is to connect the 12v fuel pump jumper inline with that red wire, while leaving all others hooked as they should be., in turn overheating that and another circuit......

Ive been over the wiring diagram as well as my uncle, he has traced out a few ideas for me and i also have been though a few topic on here and have a few more tests to try.

Truck has spark, just no power being sent to the fuel pump :help:

Thanks for any help or ideas you guys may have, I'm not giving up ;)

Well its been about 2 weeks since i though this issues was resoved after repairing the connection. After about 50 or so miles of driving and replacing the alternator that had crapped out I went to fire up the truck this morning and boom....No more power to the fuel pump, alright so i went back under the hood to the previous trouble spot and noticed my repair hadnt held up. No problem, I just sperared the orange wire from the eylet and made up a new wire onto its own connection on the Master Soleniod, all back together but Still Nothing :huh???:

 

 

Ill try my best to describe where i am now with words. Any I did some tracing and when I run 12v direct to the pump its runs

 

The pump checks out!

 

Now here's where it gets tricky, there is a red wire that runs from the connector right above the relays to an eylet connected to the master soleniod, with 12v applied to that wire AND the fuel pump jumper wire the truck will start and idle, only for a few seconds then that connector begins to heat up quick, i kill the 12v to that connection and the truck dies (all this is done under the hood, no input from the key to kill the engine) The orange wire (fuel pump power i assume) and the red wire both are able to get ot the point where they begin to melt, I didnt let em get there but thats opointing to a short or else a larger amount of power flowing through them than there should be (extra 12v?) Anyway thats the only way the truck will run...

 

Put back to the normal way all the wired are hooked up, when the key is turned to the "on" posistion there is no priming of the pump and the truck does not start, If straight power is applied to the pump with the pump running the truck still doesnt not start. the only way to start the truck is to connect the 12v fuel pump jumper inline with that red wire, while leaving all others hooked as they should be., in turn overheating that and another circuit......

 

Ive been over the wiring diagram as well as my uncle, he has traced out a few ideas for me and i also have been though a few topic on here and have a few more tests to try.

 

Truck has spark, just no power being sent to the fuel pump :help:

 

 

Thanks for any help or ideas you guys may have, I'm not giving up ;)

Red or Orange wires, aren't those fused links there?

Yes, that red (was orange at the very end post fusable link) wire came together at the solenoid with the green wire on the same eyelet.

I bypassed the fuable links for those 2 and still had nothing so I ruled them out as well...

*Update*

This problem was solved by running a whole new wire from the harness plug near the relay center to the fuel pump, somewhere in the system the main power wire to the fuel pump was severed. i just replaced it and cut the old 1 outta the setup and wa la, problem has been gone for a few weeks now :D

Glad to hear you solved it. And thanks for posting the fix.

I know this is REALLY dredging up the past, but its near identical to my problem.

With mine the issue is that pump does not prime, turn key on, nada. But the truck does start and run, albeit breifly. I have found that the in the row of 4 large black relays the rear most relay is the fuel pump relay. The relay checks out and the pump is good. I have found also that there is no 12v going to said relay, while there is to all others. Which pin is supposed to carry the 12v?

Id check again u have a/c? http://www.akaqa.com/question/q19192122378-Where-is-fuel-pump-relay-on-a-1990-jeep-cherokee-located?page=1

Check what again?  Yes i have a/c. If you are thinking i have the wrong relay, i know its the right relay because when you put a jumper 12v wire on one of the tabs you can hear the fuel pump kick in.

I'll take some pictures, maybe that will clarify things.

Rear most relay is usually the a/c weird. Yea take some pics of it and the starter motor relay where all the positives go and post back on ur post ill try the best i can.

The relay that is pulled is the one that powers my fuel pump.

This is the pin that I would think 12v would be coming in on, at least that is true for the two next to it.

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But, if you run a jumper wire from this pin. . .

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To this pin you can hear the fuel pump running and see the pressure increasing on my guage.

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I am wondering if there is somekind of pressure sensor that tells the fuel pump whether or not to run based on the PSI in the lines.

On relay at pic 2 thats pin 30 now looking at the pic in line with that not the center pin but one behind is 87 jump with wire should hear fp. Now if it doesnt work please humor me try it same way to relay in pic four.

Another development. . .

The wire for this pin is the orange wire you see directly below it. 

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This wire run down behind the battery and joins with another identical orange wire, which then carries on as a single orange wire.

The wire wraps around the front of the truck going over to the driver side, where it runs into this. . .

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It is NOT a plug as you can see, i actually think it is some kind of fuse. :dunno:

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The bottom orange wire is the one coming from, the gray wire goes to the CTS, the one in the radiator.

The other orange wire, the one in the middle goes to this. . .      This is the relay/base for the electric cooling fan. It has 12v going to it, but even with a jumper wire going from the 12v pin to the orange wire's pin there is no power at the fuel pump relay.

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The 12v stop at this contraption,  middle orange wire has 12v, bottom orange has nada

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Something else else, I cut out the entire EGR system, wire included, i traced them back to where they came from and snipped them off with 4-5in remaining, in case it needed to be reinstalled.

Thats ok as long as nothings touching metal

Ftpierce has something weird going on. Anybody know at the firewall plug what pin is for the fuel pump? He has to trace wires and if he knows what pin it will save him some time. From tracing all the way from the tank. Thanks guys.