A Jeep Cherokee Fuel Pump Problem
Your Repair Questions Answered on a 1997 Jeep Cherokee.
Learn how to handle a 1997 Jeep Grand Cherokee with no fuel pump power in Vincent Ciulla's latest auto repair article.
This weekly Q&A session answers your questions about cars and trucks. This week explores a 1997 Jeep Grand Cherokee and a Ford Mass Air Flow Sensor.
Question: 1997 Jeep Grand Cherokee
Here's the scenario: I drove home and parked the car. The next morning the car would turn over but not start. I noticed no whirring noise at the fuel pump. Sprayed a shot of ether in the air cleaner box tube and it fired up for about 1 second. When turning the key to the on position, after about 3-4 seconds the low fuel indicator light would come on "ding." There was approximately 17 gallons of fuel on board.
More investigation revealed no power to the fuel pump. I checked the relays by swapping them out 2 at a time, no luck. Since the fuel gauge never gave an accurate reading anyway, I changed out the fuel pump and fuel position sensor, and no surprise, same problem.
Where do I go from here? Some suggestions so far were
- Replace the battery
- Replace the PCM [whatever that is]
- Replace all the black relays in the fuse box.
- Short in the system somewhere. Ugh!
Any help would be appreciated.
Thanks!
Mike
Answer:
Power for the fuel pump is supplied by fuse #16 in the Power Distribution Center (PDC), goes through the Fuel Pump Relay and then to the Fuel Pump and the ground completes the circuit. Power for the Fuel Pump Relay coil is supplied by fuse #18 in the PDC and the Powertrain Control Module (PCM) supplies ground. It is a fairly simple circuit to check.
The first thing to do is check all the fuses, especially #16 and #18. If you have they are good then you will need to pull the fuel pump relay and check for power, with the key ON at the dark green/black wire and orange wire. The DG/BK wire is the power for the fuel pump and the OR wire is the power for the relay coil. If you have power there connect a jumper between the DG/BK wire and the dark green/white wire. You should hear the fuel pump running. If not there is a problem in the DG/WT wire from the relay to the pump.
Okay, lets assume that checks out fine, the next thing to do is replace the fuel pump relay and ground the dark blue wire. You should hear the fuel pump running. Okay? Good, now go to the PCM located on the firewall in the engine room. It has three large connectors, black, white and grey. There is a DB wire in cavity 19of the grey connector. Ground this wire and you should hear the fuel pump running. If it does then the wiring for the fuel pump circuit is all good and the PCM will need to be replaced. If it doesn't run, then you have a problem in the DB wire between the relay and the PCM.
That’s all for this week. Feel free to browse the archives for past topics.
