Fuel Pump Module - 1996 Jeep Grand Cherokee Laredo 4x4 4.0 S6
I recently had quite an adventure diagnosing and replacing a fuel pump module on my 1996 Jeep Grand Cherokee Laredo 4x4 4.0 S6. The truck would run perfectly for about 20 to 40 minutes after startup but the engine would then start to miss at any speed, or from a stop, highway or city, and it would then run OK again if you didn't ask for much power. It went away after stopping for a little while, 20 to 30 minutes, but then the next time out the same thing would always happen. I replaced the spark plugs, spark plug wires, distributor cap, ignition rotor, fuel filter, air filter, oil, oil filter, and wiper blades (I didn't think they were the problem).
I finally gave in and paid the $100.00 for my local Jeep dealership to run a complete diagnostic on it. They came back with nothing because the problem didn't trip the OBDII diagnostic comuter for the Check Engine light to come on. They test drove it and the problem didn't occur. I told them that they needed to drive it for a longer period of time, and eventually it did it to them too, thankfully, because otherwise I may not have found out the problem. They told me that it was definitely the fuel pump and proceeded to ask for a total of $845.00 for the job! Don't get depressed about the cost yet, keep reading.
This pump must be replaced as a module that includes a huge plastic housing with the fuel debris strainer inside along with the fuel level float and electrical sending unit all wrapped around the pump itself. No auto parts chains have this fuel pump module as of 7/9/02. I tried NAPA, AutoZone, Advance, CarQuest, and Pep Boys. Of course my local Jeep dealership had it, for $535.00! This is where it gets good. I was able to acquire an entire gas tank from an identical model at a local auto salvage yard. What a great place. If you've never been to one, you should go before you need to, just to check them out. Find a yard with computerized inventory, and they're likely to have what you need for just about any late model Jeep. The entire plastic fuel tank, including the expensive fuel pump module, only cost $200.00, instead of $535.00 for a new fuel pump module alone at the dealership. And if you have fuel pump problems, there's probably gunk in your tank anyway, so that worked out great for me. I paid a couple of genius mechanic friends of mine to come to my house and rip my skid plate and gas tank off, and put the new tank in. That was about 1.5 hours work for two of them, half of that time waiting for the loosening spray to ease up the nuts and bolts. If you can, spray them at least half of an hour before beginning work.