guest02

It ran Great until it sat for 4 months. Now it doesn't have any Fuel Pressure!!!

What are the chances of the strainer and or lines could just be gummed up? If so what could we use to clean it up?

How do we test the Fuel Pump Relay?
What is the purpose of the Ballast Resistor?

Should we just dump $120 on a new Fuel Pump?


Any Suggestions?

5-90

More symptoms, please.

Are you able to hear the fuel pump running? Have someone stand near the rear of the vehicle while you turn the key to ON (don't crank.) If you can hear the fuel pump, suspect the pickup/strainer or fuel pressure regulator on the rail - differentiate by checking for fuel delivery at the Schrader valve on the rail (if you're getting fuel volume, replace the regulator. If you're not, check/clean/replace the pickup "sock.")

Are you not able to hear the fuel pump? Try the following:

1) Pull the wires off of the fuel pump ballast resistor and bridge using a jumper lead. If this corrects the problem, just connect the two leads permanently (the FPBR was a voluntary recall for NVH, and was added in early 1988.)
2) I don't recall which one it is, but you can test the fuel pump relay by substitution with a known good DIN relay (which you should have around anyhow - along with spare fuses and small bulbs. Quality - read: Bosch or Hella - DIN relays should be easy to find for a skosh under ten dollars a copy.) The contacts on the relay may have burned out.
3) Last option - the three-wire Weatherpack connector on the front of the fuel tank is where the fuel pump gets power - a wiring diagram should tell you which wire is which (I'll give you the colours for 1990 shortly,) and you can patch in there directly using 12VDC. WARNING - have a fan going on the area while you're doing this! Just in case you have a fuel vapour leak, you want to make sure they're fully dispersed!

If (3) doesn't work, you either have a loose connexion on the fuel pump proper (as I recall, it's done with screws) or the fuel pump is shot. You need not drop the tank to remove it, but you do have to make sure you're below half-full so you don't get a faceful of fuel.

WIRING COLOURS (Per 1990 FSM):
Fuel Pump Relay will have RED/YEL/ORG/ORG underneath it.
Fuel pump connector at tank:
ORG - Fuel Pump Power Supply
VIO - Fuel Level Sensor Signal
BLK - Common Ground

Colours for 1990 XJ w/242ci I6. 150ci I4 may be different.

svt cobra

put some gas down the throttle body . if it starts, then its your fuel pump.

dont get one from autozone , spend a few extra and get a quality pump. you dont want to do it again.

guest02

Thanks 5-90!!!

The Fump doesn't run at all!
It has the exact symptoms as Always89's thread, "Did It, Still Doesnt Start"...

We'll give all of your suggestions a shot!

5-90

Then, unless it's a wiring fault (probably isn't, but don't rule it out yet...) you've got three possible causes:
- Open fuel pump ballast resistor (don't replace, just bypass.)
- Burned contacts in the fuel pump relay (replace with quality piece. DIN relays are common.)
- Failed fuel pump (get a quality unit. Don't get the cheapest one you can find.)

perez1989

Also check the fuses.

guest02

Red/Yel/Org/Org?

There's a row of 4 Relays on the Fender Well, behind the Battery om my friends '88 XJ. I can't really see what color the wires are underneath. Is one of these the Fuel Pump Relay?

Sorry, no pics yet...

5-90

You should be able to blast underneath the relay block using electrical cleaner (carburettor cleaner isn't recommended here - it can be too aggressive for the wiring insulation...) and you can then see the wiring.

RED = Red
YEL = Yellow
ORG = Orange

They're standard abbreviations, but I sometimes forget that not everyone knows them (I've been looking at wiring diagrams labelled things like "14 YEL/BLK" for so long I just automatically translate, same as I do with a 24-hour clock.)

A little hook work can get the wires to where you can see them (don't pull too hard!) and a little screwdriver or wedge work can get the relay block tipped back a bit so you can get better light under it.

BillyBoy

Can't he also unhook the fuel line after the filter?
(Never done this on a Cherokee, but this worked on my F-bird and truck.)
It's (the F-Filter) located on the inner rail/driver side/ under the vehicle.
If you unhook it, (from the engine side, so it's still connected to the fuel line coming from the tank) put a bucket underneath it, turn the key forward, and see if it starts pumping... (shooting out of the filter)

Remember,

Number 1.) Be ready to shut it off when it shoots out, if it does.
Number 2.) DO NOT smoke or have an open flame/heat source near-by.
Number 3.) if it (gas) doesn't come out, turn it off, take out the fuel filter, and try it again... the Fuel Filter might be clogged.
If you have the line from the tank unhooked, and the tank is less than 1/2 full, no fuel should come out of the line with the key in the off position.


Either way, you might waste some gas, but you have to get some out if you're gonna change the pump anyway.

Can anyone elaborate/correct me if I'm wrong?
Thanks-
Billy