88 no start problem.
Senior Member
Joined: Sep 2014
Posts: 896
Likes: 2
From: Phoenix, A-to-Z
Year: 1988
Model: Cherokee
Engine: 4.0
99%+ of us have taken our vehicles to other mechanics for one reason or another; be it more convenient, faster, time saving, because we don't have all the tools we need, because we don't know what to do or simply just don't wanna do it. Here in Phoenix in the summer, it is just way too sucky hot to be fuxing with that son-of-beach car unless it be sending us some nice cool waves to surf on!
I don't mind working on the car most of the time, but I am gonna pay somebody to fix my car if I can when it is hot as Ph(oenix)uck out...lol! I'd pay even more if it were cold!
If you don't need to drive it, then spend as much time with your beautiful new child as you can and don't fret too much about it.
If you were my neighbor, I would gladly drive out help with however I could for free or beer.
Maybe some Ohioans could drop by to help?
I don't mind working on the car most of the time, but I am gonna pay somebody to fix my car if I can when it is hot as Ph(oenix)uck out...lol! I'd pay even more if it were cold!
If you don't need to drive it, then spend as much time with your beautiful new child as you can and don't fret too much about it.
If you were my neighbor, I would gladly drive out help with however I could for free or beer.
Maybe some Ohioans could drop by to help?
CF Veteran
Joined: Aug 2011
Posts: 10,489
Likes: 24
From: Nor-Cal Coast
Year: 90,84
Model: Cherokee
Engine: 4.0,2.5
Not to disagree with the above, but I'll stay with you. (this is better than watching TV, and I learn Jeeps, typing, and spelling in the deal!)
While I was away (6 weeks) I left my phone under a leak, dumped a pot of lentil soup in my HP notebook, got rear-ended (doing about 45 in a 45 mile zone), so hard it totaled my Jeep, both our hats landed in the back, and both front seats bent back. Then a couple weeks later slipped a disk in my lower back, as the storms came in. So....
88 doesn't have an ASD relay. (the fuel pump relay seems to fulfill those functions) Freedgr mentioned the latch relay..Idk, news to me!
Do I gather correctly that the fuel pump will not run unless you jump it's relay? I believe the ECU grounds that relay (to activate the pump), and that wire goes through your C-101 connector. If it's not activating, I might trace that all the way back to the ECU. I think it is the A5 terminal on the ECU that grounds/activates the fuel pump.
While I was away (6 weeks) I left my phone under a leak, dumped a pot of lentil soup in my HP notebook, got rear-ended (doing about 45 in a 45 mile zone), so hard it totaled my Jeep, both our hats landed in the back, and both front seats bent back. Then a couple weeks later slipped a disk in my lower back, as the storms came in. So....
88 doesn't have an ASD relay. (the fuel pump relay seems to fulfill those functions) Freedgr mentioned the latch relay..Idk, news to me!
Do I gather correctly that the fuel pump will not run unless you jump it's relay? I believe the ECU grounds that relay (to activate the pump), and that wire goes through your C-101 connector. If it's not activating, I might trace that all the way back to the ECU. I think it is the A5 terminal on the ECU that grounds/activates the fuel pump.
Senior Member

Joined: May 2012
Posts: 925
Likes: 5
From: Fort Erie, CANADA
Year: 1987
Model: Cherokee
Engine: 4.0
So i went out and rechecked everything. Went on ahead to make sure all me electrical connections were refreshed, verified the elimination of the C101 connector just to make sure i didnt mess anything up. Fuel pump is running when i turn the key over, and i have pressure at the fuel rail. my distributor is connected all good with all the spark plug wires on in the right order with 1 being at "5" so on so forth. I have a new coil, CPS VAC is in spec according to everyones requirements. All my vacuum lines are good including the MAP sensor line. No tape whatsoever. I cleaned the throttle body and the intake box. I just dont know where to go now. I really am lost. I can see why people dont like these engines. But im not known for ever giving up so im going to keep pressing on. So if anybody knows what i missed or somthing please just pipe in. I really could use some expert advice right now.
In this post you say you verified the C101 connector, the fuel pump was running and you have fuel pressure. Please check the fuel pressure with a gauge and let us know the PSI reading.
CF Veteran
Joined: Dec 2011
Posts: 1,050
Likes: 2
From: Roanoke, VA
Year: 1990
Model: Cherokee
Engine: 4.0
Not to disagree with the above, but I'll stay with you. (this is better than watching TV, and I learn Jeeps, typing, and spelling in the deal!)
While I was away (6 weeks) I left my phone under a leak, dumped a pot of lentil soup in my HP notebook, got rear-ended (doing about 45 in a 45 mile zone), so hard it totaled my Jeep, both our hats landed in the back, and both front seats bent back. Then a couple weeks later slipped a disk in my lower back, as the storms came in. So....
88 doesn't have an ASD relay. (the fuel pump relay seems to fulfill those functions) Freedgr mentioned the latch relay..Idk, news to me!
Do I gather correctly that the fuel pump will not run unless you jump it's relay? I believe the ECU grounds that relay (to activate the pump), and that wire goes through your C-101 connector. If it's not activating, I might trace that all the way back to the ECU. I think it is the A5 terminal on the ECU that grounds/activates the fuel pump.
CF Veteran
Joined: Aug 2011
Posts: 10,489
Likes: 24
From: Nor-Cal Coast
Year: 90,84
Model: Cherokee
Engine: 4.0,2.5

There is a Yellow, which is the switched from the ign, to the relay coil, (86), then a red from a fused link, (30), provides the power the relay then switches to pump, (out 87), when the ECU grounds 85.
The wire that needs to be grounded by the ECU when the yellow is juiced by the key is orange/orange black and comes from relay socket 85. It ends up at A5 on the ECU.
Disclaimer! I've seen the diagrams incorrect before!

86 should power up when the ign. is turned on.
Last edited by DFlintstone; Dec 14, 2014 at 01:55 PM.
::CF Moderator::
Joined: Aug 2011
Posts: 43,971
Likes: 1,578
From: Prescott, Az
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
CF Veteran
Joined: Aug 2011
Posts: 10,489
Likes: 24
From: Nor-Cal Coast
Year: 90,84
Model: Cherokee
Engine: 4.0,2.5
Not sure how he jumped the fuel relay, but a pretty common ign. stitch failure could leave 86 dead with the ign on. Didn't fully read through, but of course both that and the coil ground 85, need to get past the C-101....
Sooo much can be learned at a relay socket. If he went 30, 87, theirs that direct. If he simply hit 87 there's that.
On the SPDT relays. No argument we can swap them at will. I have gathered some are rated for different AMP's, and some have a diode, (one way valve), somewhere. (my "Bedrock Sense" tells me the diode would only require the relay coil is activated when activated in the "normal" direction), IE, energizing 85 and grounding 86 won't trigger it.
If he does not have power at 86, thinken ign switch.
Trov, please resolve this relatively simple fuel pressure issue. I wanna get to funner stuff!
Sooo much can be learned at a relay socket. If he went 30, 87, theirs that direct. If he simply hit 87 there's that.
On the SPDT relays. No argument we can swap them at will. I have gathered some are rated for different AMP's, and some have a diode, (one way valve), somewhere. (my "Bedrock Sense" tells me the diode would only require the relay coil is activated when activated in the "normal" direction), IE, energizing 85 and grounding 86 won't trigger it.
If he does not have power at 86, thinken ign switch.
Trov, please resolve this relatively simple fuel pressure issue. I wanna get to funner stuff!
Senior Member

Joined: May 2012
Posts: 925
Likes: 5
From: Fort Erie, CANADA
Year: 1987
Model: Cherokee
Engine: 4.0
Thanks-I thought they were but I see different part numbers on Rock Auto but maybe that's the manufacturer PN. I was thinking of telling him to just swap the FUEL PUMP relay for the A/C clutch relay as a test of the relay itself. That would check to see if the pump primes with the different relay and then it's just a bad relay.
I guess you could put a jumper wire in the socket to see if you can get the fuel pump to run but there's always the risk you short something by doing that.
I still can't tell if he has the fuel pump running or not from his posts.
::CF Moderator::
Joined: Aug 2011
Posts: 43,971
Likes: 1,578
From: Prescott, Az
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
Thanks-I thought they were but I see different part numbers on Rock Auto but maybe that's the manufacturer PN. I was thinking of telling him to just swap the FUEL PUMP relay for the A/C clutch relay as a test of the relay itself. That would check to see if the pump primes with the different relay and then it's just a bad relay.
I guess you could put a jumper wire in the socket to see if you can get the fuel pump to run but there's always the risk you short something by doing that.
I still can't tell if he has the fuel pump running or not from his posts.
I guess you could put a jumper wire in the socket to see if you can get the fuel pump to run but there's always the risk you short something by doing that.
I still can't tell if he has the fuel pump running or not from his posts.
Thread Starter
Junior Member
Joined: Mar 2014
Posts: 72
Likes: 0
From: Ohio
Year: 88'
Model: Cherokee
Engine: 4.0 IL6
OK..............
So yes i jumped the pins 86 and 30 on the fuel pump relay port. When i turned the ignition over the fuel pump started. So i know i have power to the fuel pump with the relay unpluged and jumper wires in. That tells me the relay was bad. I did a jumper on the power latch relay just to see if it would start up. No it didnt. As with the coil im only showing 4-5 volts out the wire that goes to the distributor. I even pulled a plug wire with plug on it and attached it to the coil straight up and tried for spark.....nothing. Now i havnt been able to get to advanced to rent a fuel pressure guage but ill try to somtime this week.
So yes i jumped the pins 86 and 30 on the fuel pump relay port. When i turned the ignition over the fuel pump started. So i know i have power to the fuel pump with the relay unpluged and jumper wires in. That tells me the relay was bad. I did a jumper on the power latch relay just to see if it would start up. No it didnt. As with the coil im only showing 4-5 volts out the wire that goes to the distributor. I even pulled a plug wire with plug on it and attached it to the coil straight up and tried for spark.....nothing. Now i havnt been able to get to advanced to rent a fuel pressure guage but ill try to somtime this week.
CF Veteran
Joined: Aug 2011
Posts: 10,489
Likes: 24
From: Nor-Cal Coast
Year: 90,84
Model: Cherokee
Engine: 4.0,2.5
First please understand post my post #110. I realize I dumped a s-load if info in a few sentences. You are going to need to "get on the page" with that. With lectrics you gotta break it down, take it one step at a time. The whole deal is way too complicated, but is actually a bunch of little things we can check/and fix, one at a time.
Jumping 86 to 30 only provides power to the relay coil, (instead if the ignition switch)
If I were you, I'd see if 86 powers up when the ign switch is turned on.
Jumping 86 to 30 only provides power to the relay coil, (instead if the ignition switch)
If I were you, I'd see if 86 powers up when the ign switch is turned on.
Last edited by DFlintstone; Dec 14, 2014 at 11:08 PM.


