1986 Jeep Cherokee 2.5 TBI Fuel Pump No Power

Hi guys,

got a 1986 Jeep Cherokee Pioneer, 2.5 TBI. Manual Trans AX5

Died on the highway, towed it home. No "buzz" from fuel pump when turning the key. Threw a new fuel pump in. Still no "buzz."

Engine briefly starts when spraying engine starting fluid into throttle body. Pretty sure it's a problem with a relay or a fuse/bad ground.

I've done some looking and it looks like a lot of the late 80's jeeps have a set of four relays under the hood. Mine has two, with no cover. I tried switching them and still no luck.

I'm not great with electrical- so any kind of testing with an OHM meter is going to require some special explaining. Haha. Have to be honest...

Anyhow, could a bad ballast cause this? Is there a fusable link? Where can I check for grounds? Would anyone be so kind as to point me to where the ballast and relays/links might be located?

The leads coming out of the tank go straight up into the frame. There are three wires, FYI.

Thanks in advance for any thoughts!

Pete:worship:

Relays will reset until they blow, so if you switched and still no activity, then odds are its either a fuse in the circuit or a ground. Does anything else not work, or just the pump?

Everything else seems to work. It's only the pump as far as I can tell...

The whole system on the 86 seems pretty simple- but I have no idea if there is a fusable link or fuse somewhere in the system? I checked all the fuses under the dash and they check out.

Bump for the night crew.

Also, can anyone let me know where the fuel pump grounds to? I haven't been able to find it.

Thanks

Pete

Alright.

Cleaned every ground I could find (Oil Dipstick, weird braided wire at rear of head, large ground on block next to alternator, two small grounds; one on the left side of the engine compartment, one on the right) and one ground I found under the dash.

I tried jumping the fuel pump at the relay spot. Here's what happened.

Fuel pump spooled up. So I put the relay back in (all while the key was in the forward position, on.) and it started clicking.

Went and put the key back to off, then forward again. Heard it spool up. Jeep started right up! Let it run for a bit. Stopped it, tried to start it again. Did not hear the pump spool up. Jeep would not start.

Ran a ground from the pump to the -Terminal on the battery just in case it was a bad ground. No dice. Pump still spooled up if jumped at the relay. (30 to 87.)

Double checked the fuses under the dash. Nothing was burnt.

Tried putting starting fluid in the TBI, would not start like it did a few days ago. Pulled a plug, checked spark by setting plug against metal surface. No spark....

Replaced starter relay, ignition coil, and ICM (Ignition control module, under the coil, which tested bad at the store.)

Still no spark. Still no spool-up at the fuel pump when pushing key to forward position. Fuel pump will spool if jumped at relay, but jeep will not start of course (no spark.)

Replaced CPS. Still no dice.

I'm out of options here guys. If ANYONE has any idea what to try, I'm game.

So in all I've:

Cleaned as many grounds as I can find.
Jumped the fuel pump at the relay, and run a ground straight to the battery.
Replaced CPS, Ignition coil, ICM, checked fuses, replaced starter relay, replaced both box relays under the hood, and prayed over the Jeep.

Please help.

start unplugging sensors to the ecu.

it's possible one has a short and is killing the ecu. no ecu=no fuel or spark.

TPS would be my fisrt suspect to short out.

I'll give that a shot! Thanks.

New development.

So there are two spots for relays. The one closer to the front, when jumped, powers the fuel pump.

The one closer to the back when jumped...the jeep starts and runs like a top! (30 to 87) (Funny enough I can't hear the fuel pump spool up, but the jeep runs that way...)

Tried putting a different relay in it- no dice.

So whatever is going on has to do with that relay spot...I think.

So I tried tracing wires. One goes the the starter relay. When unplugged the jeep doesn't run (when jumped) so I'm pretty sure it's not that wire.

Two others run, eventually splicing together, and ending up at a yellow cap above the cylinder head- (I think?) that almost seems to be a dead end.

The last one ends up somewhere under the dash... I think. Best I can tell

Anyhow, I'll give the sensor deal a shot just in case.

If it doesn't work... What I was thinking was running a wire from the 30 terminal inside the jeep to a switch, and then a wire back out to the 87 terminal with an inline fuse. Just switch it when I want the jeep to run and call it good...?

from fron to back they should be:

1. O2 Sensor
2. Fuel Pump
3. B+ Latch
4. AC clutch
http://www.naxja.org/forum/showthread.php?t=944652

I'm not too terribly familiar with the pre 87, do you have the c101 firewall connector under the clutch master?

check it over well, very well. Plan on taking the fuse block loose so you can get at the center bolt and undo it. Have a good look at all the nasty brown rap in there. Get yourself many cans of contact cleaner, some brushes and an evening to clean that mess.

Also check the fuse panel itself. The clutch master enjoys leaking onto that whole area and causing havoc.

four_shot said:

Also check the fuse panel itself. The clutch master enjoys leaking onto that whole area and causing havoc.

Click to expand...

true story, the one in my 87 was a mess from failed clutch masters.

there's also some factory crimps hidden in the fuel pump circuit on the passenger side firewall.
I'm not kidding when I tell you that AMC wrapped them in duct tape....

have fun splitting the loom.

AMC was well known for their lack of thought when it came to wiring. The full size jeeps had full alternator current running through the firewall, to the gauge cluster, across an ammeter, then back to the battery to charge it. Genius. SMH.

CompleteCherokee said:

AMC was well known for their lack of thought when it came to wiring. The full size jeeps had full alternator current running through the firewall, to the gauge cluster, across an ammeter, then back to the battery to charge it. Genius. SMH.

Click to expand...

Yeah but it was only 30-40 amps.....lol

haha, yep I've seen rigs burn down because of the wire routing when the ammeter shorted out. That's why I say if you own a Jeep from the early 90's down, you NEED to carry a fire extinguisher in your truck where the driver can get to it quickly.

I'm fighting a similar issue on my 86 2.5 5 speed, only my fuel pump is cycling and I get it to start, with great effort. It doesn't run long, starts and revs to 900-1,200rpm then dies right away unless I play with the throttle a lot. It's almost acting like a nasty vacuum leak, but I can't find it. It has a new fuel pump and filter, new ignition control module and coil, new TPS, new MAP, several new vacuum lines, new battery, injector has been professionally cleaned and flow tested, new fuel pressure regulator and throttle body gaskets, new mounting gasket with black RTV (just in case the mounting surfaces weren't dead flat)... I'm at a loss. I've been a Jeep mechanic for 20 years, but have zero diagnostic experience with the Renix 2.5 system. Any suggestions or ideas where to look or go from here?

Idle Air Control?

No idle air control valve on this setup.

will it stay running if you spray starting fluid into the TB after you get it started?

Well, I did manage to get mine figured out and running. The hose for the fuel pump on the sending unit ended up being rotten and blew itself wide open. I replaced it and managed to blow the new fuel pressure regulator. The return tube on the sending unit was clogged solid with lacquered gas and rust. I didn't think to check that when I dropped it to replace the hose... Had to replace the regulator for a second time and got it running. Now I'm having to replace the low mile fuel pump, again fighting the long term sitting issue from the previous owner rarely driving it. It drives just fine for the better part of the day then when it gets a bit warm, the pump starts getting louder and fuel pressure drops off. Park it for an hour or so and it starts, runs, and drives fine again for a while.

As far as the issue the OP has with no power to the pump, have you replaced the ignition control module that sits under the coil? The pump is triggered from that on the TBI 2.5s.

glad to hear you got yours semi-sorted and running. The loud pump, if it gets louder as it heats up, I wonder if you also might have a restriction somewhere in the line?