SG Mason

I can't edit the title but the jeep is a 98

Last night the jeep died without warning. Quick diagnostics showed no fuel pressure so we towed it to my brother's and put it in the garage. This morning I went there with a new relay and some fuses. I also took a good look at the connector at the tank. The insulation was worn away on 2 wires and one of those was corroded through. I spliced the wires back together. But haven't shrink wrapped them yet.
With a new fuel pump fuse and relay it still won't kick on the pump, but if I jump pins 30 and 87 the fuel pump kicks in and it will run.
I get battery voltage across 30 and 87as well as battery voltage across 85 and 86 when the key is on. Both the old and new rrelays trigger on 12 volts.
What is the next thing to test?

I have spark and the CPS is only a few months old. Bought from Chrysler dealer.

AutobotXJ

what year do you have? there might be a ballast resister on your jeep. try bypassing it (connect the two wires) and see if it starts. it is located near your brake booster.

SG Mason

Oops forgot to mention that, it is a 98

I am thinking of bypassing the relay and wiring it to a switch. Something that will only be live with the key on.

CCKen

Did you separate the pump electrical connector to see if there's corrosion in the connectors? If you have corrosion on the wires the connector pins and cavities may be corroded.

Next, The ground for the fuel pump is behind the spare tire mount. You have to remove it and the carpet to get at it. There's two grounds screwed into the structure there. Crappy ground techniques from the factory. You may want to check to see if the grounds are secure and see if there's continuity between the ground and the ground wire pin at the pump connector.

CCKen

Pump ground behind spare tire:

CCKen

The ground circuit wire is a Black 12 gauge wire.

The power wire from the relay to the pump connector is a Dark Green/White tracer wire.

SG Mason

I checked the grounds before coming home, they are good. I could not get the connector apart at the tank to check the condition of the pins or check for continuity. I am actually thinking about cutting out the connector and just joining the wires directly to take it out of the picture. There is more than enough slack wire to allow me to do this without putting stress on the joints. the breaks in the wires were on the pigtail side and very close to the connector

I will follow your instructions to the letter, but wouldn't the fact that I can jump the fuel pump mean that the connections at the pump are good?

Using this picture and the number it provides


If I jump 8 and 2 the pump turns on and supplies pressure to the fuel rail. Voltage reading across those is battery voltage.

I tested my relays, both new and original, and they will click when 12v is applied to 6 and 4, can't remember the actual numbers on the relay Voltage on the power distribution for those pins is 6.7-7.3v The variance is because it is cold and I was having a hard time holding the probes.

When I first started trying to figure this out this morning first thing I did was check for blown fuses. The fuel pump fuse was blown, but someone had jumped it with a few strands of wire. I replaced it with a new 15a fuse and it has not blown.

I had to chase down my OBD2 reader and didn't get it till I was ready to come home. I am pulling two codes P1282 (Fuel Pump Relay Control Circuit Malfunction) but I have had the relays out with the key on so that may be triggering that code

I am also getting a 1694 (No CCD message from PCM- Aisin transmission) I hope that I didn't loose a TCM again and that the code is just being triggers by my tests.

Time for me to cook some supper and head back out to try fix this. I will be bringing my laptop with me, it will be so much easier to try communicate with it than on the dinky screen and keyboard of a smart phone.

Final thoughts, I did go ahead and check the CPS and it passed the simple ohms reading. I do have spark and gauges. If I jump the pump the Jeep does run so when the pump runs it supplies enough pressure.

Would it do any harm to just put the fuel pump on a switch and bypass the relay as a temporary solution? I need to be back up and running by tomorrow evening so I can get to work

SG Mason

OK CCKen while waiting for your next step I have been going over things on my own, and it just dawned on me how tired I really am. All this time I have been focused on the power distribution center under the hood and didn't even think to check the fuse diagram inside the cabin Is it possible that all the problems that have popped up are related to the interior fuse #11? In my owners manual is says it is for Run/Start ignition, day time running lights. Yet on lunghd.com it says Transmission control module, powertrain control module, automatic shutdown relay, fuel pump relay. If that is true it could explain why I am getting the P1694 and P1282 now. Also why I can jump the relay socket at 30 and 87 to turn on the fuel pump and be able to actually start the Jeep. With 30 and 87 jumped it starts up almost right away.

Any how I am done beating my head against the wall for tonight, it is time for bed First thing in the morning I am going to check fuse #11 on the interior panel, fingers crossed it is my problem.

Oops just realized that i didn't mention it here, but the previous owner had bridged the fuel pump fuse with a few strands of wire. I removed the blown fuse and the strands of wire, then replaced everything with a new 15a fuse. I am sure the PO was having problems with the fuse blowing from the bad wires in the pigtail and this was his solution. I have not blown the fuse yet.

CCKen

You should get battery voltage (12V) at the Fuel Pump Relay PDC pin cavity D4 with the key turned to RUN. Using the battery negative post for your meter ground.

I have checked the relay control coil wiring (pin cavity D6) and PCM output before on my Jeep.

Here's how:

Probe pin cavity D6 (meter + probe) and batt negative post (meter - probe). With your voltmeter set to 2 VDC, key OFF, you should see around .02 volts. With key to RUN you should see a slightly higher voltage, such as .03 volts.

If you don't see any voltage at all the wire between the relay D6 and the PCM is open or the PCM fuel pump relay control driver is bad.

If you want, you could repeat this test on the Radiator Fan Relay D13.

If you don't see battery voltage at D4 some other unit on fuse F11 may be dragging it down.

The '98 has the following on F11:

ASD relay
AC Compressor Clutch relay
NSS
TCM
Duty Cycle Evap Purge Solenoid
PCM

SG Mason

I am getting 0v on both d6 and d13 in both key on and key off. I guess the next step would be to check for continuity between them and the PCM harness?

I do get battery voltage at D4 and D13 with the key on and 0v with it off.

Cabin fuse #11 was good,, but I put a new one in any how and did the test again with the same results

CCKen

Check continuity might be a good idea.

Morris4x4Center

Man, you Cherokee forum members don't mess around! LOL

You'd give NASA a run for their money!

:-) :-) :-)

Well done






...

SG Mason

trying to find the pin out diagram right now, but it is a little cold out here in the garage, maybe -6 with the heater on so the laptop and my fingers are a little slow. I will let you know the results once I find them.

It is all CCKen, he knows his stuff and always seems ready to offer advise. I refer to him as the cherokee whisper to friends and family

CCKen

Maybe you should put a hyperlink to our Forum on the Morris4X4Center website. LOL

SG Mason

I hope I figured out what I needed to test continuity. I have good continuity from D6 to C19.