bucketheadben Posted February 23, 2009 Share Posted February 23, 2009 I've swapped the entire drivetrain from my 99XJ into my MJ, now I have to figure out how to get fuel to it. Id really like to keep the tank in the stock MJ location, but he XJ tank will not fit naturally. So I'm wandering if anyone knows the measurements of a TJ or Grand Cherokee gas tank. Maybe one of those will fit. Or if there is no other option, I'll put a fuel cell in the bed. Has anybody been faced with this issue or have any ideas. Thanks Ben Link to comment Share on other sites More sharing options...
Geonovast Posted February 23, 2009 Share Posted February 23, 2009 What's wrong with the MJ tank? I'm putting an XJ tank in the bed of my 4.0. Link to comment Share on other sites More sharing options...
bucketheadben Posted February 23, 2009 Author Share Posted February 23, 2009 I need to use the 99 fuel pump and it won't mount in the mj's tank. Link to comment Share on other sites More sharing options...
JeepcoMJ Posted February 23, 2009 Share Posted February 23, 2009 use a 91-92 H.O. comanche fuel pump and sending unit. it puts out enough pressure to run your 99 xj properly. hell, a renix fuel pump works just fine as well, but will make your fuel gauge read backwards Link to comment Share on other sites More sharing options...
bucketheadben Posted February 24, 2009 Author Share Posted February 24, 2009 use a 91-92 H.O. comanche fuel pump and sending unit. it puts out enough pressure to run your 99 xj properly. hell, a renix fuel pump works just fine as well, but will make your fuel gauge read backwards Is that all that I have to do? That is too easy! :bowdown: I thought they ran at two completely different PSI's. Link to comment Share on other sites More sharing options...
HOrnbrod Posted February 24, 2009 Share Posted February 24, 2009 The 99 and early 91-92 fuel pump pressure ratings are slightly different, but the rail regulator should handle it w. no problems. It's commonly done on stroker engine applications in different models. Worst case is you may need an adj. MAP to even the A/F ratio under WOT, but that's no biggie. Link to comment Share on other sites More sharing options...
bigd44889 Posted February 24, 2009 Share Posted February 24, 2009 :agree: :hmm: Link to comment Share on other sites More sharing options...
JeepcoMJ Posted February 24, 2009 Share Posted February 24, 2009 yup that easy. pay attention to don on this type of topic. he does know his performance $#!&. it's just like using a renix fuel pump with a H.O. motor...the regulator adjusts pressure accordingly. I did this with no issues...the only reason I swapped to a H.O. pump/sender is that my fuel gauge now works properly without me having to dick with a ton of POT ratings and stuff that I don't understand. Link to comment Share on other sites More sharing options...
bucketheadben Posted February 24, 2009 Author Share Posted February 24, 2009 That's excellent news guys. Thanks. I do have one other question. I was looking on the the Renix fuel pump and it has a return line. Should I just cap it off? Ben Link to comment Share on other sites More sharing options...
JeepcoMJ Posted February 24, 2009 Share Posted February 24, 2009 That's excellent news guys. Thanks. I do have one other question. I was looking on the the Renix fuel pump and it has a return line. Should I just cap it off?Ben um. I'm pretty sure the 97-01 cherokee still had a return line....so you NEED to use it if that is the case. personally I would find the 91-92 fuel pump and sending unit. if you use the renix sending unit your fuel gauge will read backwards, if at all. Link to comment Share on other sites More sharing options...
bucketheadben Posted February 26, 2009 Author Share Posted February 26, 2009 um. I'm pretty sure the 97-01 cherokee still had a return line....so you NEED to use it if that is the case. personally I would find the 91-92 fuel pump and sending unit. if you use the renix sending unit your fuel gauge will read backwards, if at all. Nope, no return line. I'm sure of it. It has one fuel line and a vent line. So should I just cap the return? I will be buying a 91-92 pump tomorrow. I just had a renix pump handy so I was using that as a reference. Thanks again for the help. Ben Link to comment Share on other sites More sharing options...
HOrnbrod Posted February 26, 2009 Share Posted February 26, 2009 Nope, no return line. I'm sure of it. It has one fuel line and a vent line. So should I just cap the return? I will be buying a 91-92 pump tomorrow. I just had a renix pump handy so I was using that as a reference. Thanks again for the help. Ben You know I been thinkin' about this, and I don't think the 91-92 fuel pump is going to run w/o a return line; it will probably vapor lock. I could be wrong, but I really don't think it'll work. Prsssure regulation might be a problem too. To play it safe, a good solution is to get a 91-96 fuel rail w. regulator and pressure relief valve, use the 91-96 injectors (they'll plug right into your 99 intake) and grab the engine bay lower fuel rail supply and return lines and plumb them up to the lines coming from the tank. I KNOW that will work. :cheers: Link to comment Share on other sites More sharing options...
bucketheadben Posted February 26, 2009 Author Share Posted February 26, 2009 You know I been thinkin' about this, and I don't think the 91-92 fuel pump is going to run w/o a return line; it will probably vapor lock. I could be wrong, but I really don't think it'll work. Prsssure regulation might be a problem too. To play it safe, a good solution is to get a 91-96 fuel rail w. regulator and pressure relief valve, use the 91-96 injectors (they'll plug right into your 99 intake) and grab the engine bay lower fuel rail supply and return lines and plumb them up to the lines coming from the tank. I KNOW that will work. :cheers: I just went out and looked at the renix pump. The return line dumps in to the tank. It doesn't got into the pump. If the H.O. pump is plumbed the same way, would it vapor lock? :hmm: Ben Link to comment Share on other sites More sharing options...
HOrnbrod Posted February 26, 2009 Share Posted February 26, 2009 I'm not sure. The 99+ pumps had a pressure relief on the pump itself; the earlier systems has the Schrader valve on the rail. I know a lot of folks who have built stroker engines. Most use the earlier block/head combos because of the infamous cracking issues on the 99+ heads. But all those I'm aware of who have used the 99+ blocks also use the 96 and below fuel rails IF their stroker is in an older rig. My 91 rail has pressure and return lines on it, and it uses the same fuel pump you will be using. Pretty sure you will need to do have this setup too IF you use the 91-92 HO pump/sender. Link to comment Share on other sites More sharing options...
bucketheadben Posted February 27, 2009 Author Share Posted February 27, 2009 Well I had a good day at the junkyards. I scored wiring for the H.O. injectors, 2 fuel lines, mounting hardware for the tank, the locking ring for the pump and the carpeted interior panel behind both seats. All for $20. I already have the H.O. fuel rail and injectors so now I just have to hook it all up. On the down side the fuel pump auto zone order was wrong. I had the check and it has the same part number as the Cherokee fuel pump. Does anyone have the part number for a 91-92 Comanche fuel pump or do you know where I can purchase one? Until then I'll hook up the renix pump I have and get it running for the time being. One other question. The 99 fuel pump has 4 wires, and the renix has 3. How many wires are in the H.O. fuel pump? And does anybody have wiring diagrams so that I can splice everything together? Thanks again for all your help. Ben Link to comment Share on other sites More sharing options...
bucketheadben Posted February 27, 2009 Author Share Posted February 27, 2009 Oh, I forgot to mention that the problem with the fuel pump from auto zone was that it would not mount in the MJ tank. The pump would hit the slosh tray. The renix pump that I have goes into the tank at an angle and into the tray. The auto zone one just goes down and hits the tray. Link to comment Share on other sites More sharing options...
HOrnbrod Posted February 27, 2009 Share Posted February 27, 2009 Well I had a good day at the junkyards. I scored wiring for the H.O. injectors, 2 fuel lines, mounting hardware for the tank, the locking ring for the pump and the carpeted interior panel behind both seats. All for $20. I already have the H.O. fuel rail and injectors so now I just have to hook it all up. On the down side the fuel pump auto zone order was wrong. I had the check and it has the same part number as the Cherokee fuel pump. Does anyone have the part number for a 91-92 Comanche fuel pump or do you know where I can purchase one? Until then I'll hook up the renix pump I have and get it running for the time being. One other question. The 99 fuel pump has 4 wires, and the renix has 3. How many wires are in the H.O. fuel pump? And does anybody have wiring diagrams so that I can splice everything together? Thanks again for all your help. Ben The HO fuel pump will not work with the Renix fuel sender and vice-versa. And both the XJ and MJ HO pumps are the same, but the senders are not. So to use the HO pump you are going to have to find a MJ sender from a 91 or 92 HO model. But both the HO and Renix pumps have three wires; one hot, one ground, and the float output to the fuel gauge. Link to comment Share on other sites More sharing options...
bucketheadben Posted February 27, 2009 Author Share Posted February 27, 2009 The HO fuel pump will not work with the Renix fuel sender and vice-versa. And both the XJ and MJ HO pumps are the same, but the senders are not. So to use the HO pump you are going to have to find a MJ sender from a 91 or 92 HO model. But both the HO and Renix pumps have three wires; one hot, one ground, and the float output to the fuel gauge. Sorry, I should have said "fuel pump assembly." That is what I ordered from autozone. I've checked autozone, advaced, napa and pepboys for a MJ fuel pump assembly, but they all have the same part number as the XJ. Link to comment Share on other sites More sharing options...
mvusse Posted February 27, 2009 Share Posted February 27, 2009 The 91-92 COmanche pump is the same as the 91-??? Cherokee pump. The sender unit assembly is different, but the pump is the same. I know the 86 through 90 (Renix) is the same, and see no reason for that being changed in 91. Link to comment Share on other sites More sharing options...
bucketheadben Posted March 2, 2009 Author Share Posted March 2, 2009 Well, I'm almost there. Since I can't find a MJ H.O. sending unit, I stuck the Renix assembly in the tank. So far I've got the tank and pump back in it's original location, installed a fuel filter, H.O. fuel lines, fuel rail and injectors. I've spliced the wires so that the fuel pump adapts to the 99 harness. I've got the pump working and the fuel rail is pressurized. Now all I have left is to splice in the H.O. injector wiring harness and fire it up. Link to comment Share on other sites More sharing options...
bucketheadben Posted March 7, 2009 Author Share Posted March 7, 2009 I just finished splicing in the wires for the fuel injectors. The fuel rail is full of gas and I'm getting spark to the plugs but it will not start. It turns over and it sounds like it's trying to fire but all it does is sputter while the starter is engaged. Any ideas? Thanks Ben Link to comment Share on other sites More sharing options...
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