centralnc Posted April 18, 2010 Share Posted April 18, 2010 I finally bought a Comanche. It is a 1988 4x4 5sp complete with a camper top. It has not been cranked in several years, so I towed it home yesterday. The fuel gauge does not work, but the owner told me it was almost out of gas. I added about 5 gal of 93 octane. I installed a new battery and turned the engine by hand a few times at the crank. I then hit the ignition. The engine turns over nicely, but it does not fire. I pulled the spark plugs and they are dry as a bone. I checked for spark I found I have plenty of fire at each plug. Since I have fire and air, I assumed that the problem was with the fuel. I installed a jumper wire at the ballast resistor and turned the engine over a few more times. I checked the pressure port on the fuel rail and there was no fuel pressure at all. It seems that no fuel is being pumped up from the fuel tank. The Haynes manual says to replace the fuel pump, but I am hoping that there is something easier that I should try first. Maybe a wire or a fuse? Any suggestions would be appreciated. Link to comment Share on other sites More sharing options...
88pioneer Posted April 18, 2010 Share Posted April 18, 2010 could just be a clogged fuel filter, especially since its been sitting, or the fuel pressure regulator Link to comment Share on other sites More sharing options...
Yesterday's Danish Posted April 18, 2010 Share Posted April 18, 2010 Check the fuel pump relay under the hood. Swap it with another relay to see if the fuel pump turns on. Link to comment Share on other sites More sharing options...
jimoshel Posted April 18, 2010 Share Posted April 18, 2010 When you jumped the ballast did you hear the pump? If not then it's probably bad. If you did hear it then the fuel strainer is bad. There are 2 of them. One in the the fuel line and the other in the bottom of the tank. Just off hand I would suspect the strainer in the tank. Just sitting all the crud gathers there. Also if the pump doesn't work quite often it's full of crud. I've flushed them out and cleaned them and they worked. Your probably going to have to remove the Fuel pump assy. Dropping the driveshaft will make it easier. Good luck, Jim And welcome to the madness. :banana: Link to comment Share on other sites More sharing options...
centralnc Posted April 19, 2010 Author Share Posted April 19, 2010 Thanks for the advice guys. I will swap the fuel pump relay and see if that helps. That is quick and easy. I did not hear the fuel pump come on at all. Nothing clicked and I did not hear the noise. The MJ wiring is not in the best shape. The fuse box needs some serious work as well. I was just hoping that I might find an easier solution to pulling the pump out of the tank. My neighbor is going to help tomorrow afternoon. I am hoping we can solve the problem and get it running. It is nice to be a Comanche owner again!!! Link to comment Share on other sites More sharing options...
Pete M Posted April 19, 2010 Share Posted April 19, 2010 check for power at the tank directly after someone turns the key to start. the pump should get power for like a second. Link to comment Share on other sites More sharing options...
Oizarod115 Posted April 19, 2010 Share Posted April 19, 2010 fuel pump in the manche is no big deal, don't worry about that. but definitely get a multimeter and check for 12v at the pump either when cranking or when first turned to run for 1-2seconds. Link to comment Share on other sites More sharing options...
ParadiseMJ Posted April 19, 2010 Share Posted April 19, 2010 Have you taken the driver's side tail light out and checked the rear harness ground that shares the fuel pump? Has that been covered here? Link to comment Share on other sites More sharing options...
centralnc Posted April 20, 2010 Author Share Posted April 20, 2010 I checked the relay and jumped the ballast resistor this evening with no luck. I tested the circuit just before the fuel pump and had power reaching the pump, but nothing was happening. I guess I will need to replace the pump!! I had never heard that the ground in the drivers tail light is shared with the pump. Maybe I should give that a look tomorrow. Thanks for the advice!! Link to comment Share on other sites More sharing options...
centralnc Posted April 21, 2010 Author Share Posted April 21, 2010 I didn't get home in time today to work on the MJ. After thinking about it I believe I am going to go ahead and drop the tank when replacing the fuel pump. If the tank has enough sediment to mess up the pump then maybe I should clean it out. Would you guys suggest dropping the tank or just replacing the pump? Autozone has the Airtex for $72 + $12 for strainer. I appreciate all of the advice!! Link to comment Share on other sites More sharing options...
glundblad Posted April 21, 2010 Share Posted April 21, 2010 Congrats on the new truck. :clapping: FYI my fuel pump on my '87 is pretty loud even with the engine off and the ignition turned on. It was like that when new. Almost sounds like a bilge pump on a motor boat or a significant air leak. Oh, and one more thing, don't forget to post pics of the new truck. Link to comment Share on other sites More sharing options...
Pete M Posted April 21, 2010 Share Posted April 21, 2010 if you pull the pump, take note of the condition of the little rubber hoses. if they are degraded enough, it'll leak and lose pressure. Link to comment Share on other sites More sharing options...
centralnc Posted April 22, 2010 Author Share Posted April 22, 2010 I pulled the fuel pump today and it was really gummed up. I guess I am going to need to drop the tank and clean it out as well. The bigger problem is that the aftermarket pump I bought does not fit the bracket at all. Advance Auto Parts gave me the Airtex E7006 fuel pump and strainer. It is very close, but it doesn't fit well in the brackets. The Jeep dealership is giving me a price of $400 for a fuel pump and telling me that only 1 pump is left in the whole country!! The pictures of the fuel pumps at RockAuto, Autozone and Napa all show the same basic pump. I am not sure what to buy. Which pump have you guys used in the past? I might try to post some pictures of the old vs new fuel pump. Any comments would be greatly appreciated. Link to comment Share on other sites More sharing options...
glundblad Posted April 22, 2010 Share Posted April 22, 2010 I know there are aftermarket fuel pumps. Anyone? I don't know if these guys can help or not: http://www.wholesalemopar.com/ Link to comment Share on other sites More sharing options...
Wildman Posted April 23, 2010 Share Posted April 23, 2010 Most, not all, of the OEM fuel pump in the MJ were Bosch pumps. If you look on rockauto.com, they list this - CARTER Part # P74155 More Info {In Tank Fuel Pump and Strainer Set} w/Bosch OE Pump Part Image $84.79 *notice the ......w/Bosch......* The other pump spec'ed, which I've never seen in an MJ was the Walbro pump. Where this "Airtex" is coming from :dunno: I see Rock also has it listed. Unless, you have really deep pockets, and want to buy the only OEM pump left in the country and be proud of that fact........go for it :D Oh, and if your sock filter was gummed up, Yes, clean out the tank the best you can, before you install a new pump. And change the frame filter before any major running. Link to comment Share on other sites More sharing options...
centralnc Posted April 23, 2010 Author Share Posted April 23, 2010 I appreciate the advice. The pump I pulled from the tank was a Bosch. The problem with the Airtex wasn't necessarily with the pump. It was the rubber gaskets that mate the pump to the holder unit. The round rubber gaskets would not seat into the fittings on the holder. I will try Napa first and look for the Bosch pump and then I will try RockAuto for that Carter you mentioned. I sure hope I can find one!! thank you. Link to comment Share on other sites More sharing options...
Wildman Posted April 24, 2010 Share Posted April 24, 2010 I understand that, others have used the Carter replacement pump with out any problems with fitment in the sending unit brackets. All I asked, why this Airtex is coming up, I've never bought one, and I don't know anyone else that even tried one :dunno: For what's it worth, you could go with the Bosch pump from rockauto, and know it will fit the sending unit bracket :yes: Link to comment Share on other sites More sharing options...
centralnc Posted April 26, 2010 Author Share Posted April 26, 2010 Thanks for the advice. I ordered the fuel pump and some other miscellaneous things from RockAuto today. I used your Discount Code from the other fuel pump thread. It saved me almost $10. I really appreciate it!!! :cheers: Link to comment Share on other sites More sharing options...
Wildman Posted April 26, 2010 Share Posted April 26, 2010 No Problem :D Glad you caught that other topic and got the discount :brows: See........it pays to read all of this forum....... :teehee: Link to comment Share on other sites More sharing options...
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