Kenosha Warrior Posted April 21, 2008 Share Posted April 21, 2008 So mine crapped out, when it gets too warm, it starts messing with my FP. CUtting in and out, along with a half-shot fuel filter, made for a $#!&ty-running 4.0. Now Ive got all that bypassed, and now I need to know something. The ballast resistor, is it ok to run without it? I just want to solder those wires together and call it good. Link to comment Share on other sites More sharing options...
Geonovast Posted April 21, 2008 Share Posted April 21, 2008 NO. It's there for a reason, if you bypass it you'll burn out your fuel pump. Just go get a new one. $7 at carquest. Link to comment Share on other sites More sharing options...
MiNi Beast Posted April 21, 2008 Share Posted April 21, 2008 $7 is the most expensive I paid $4 for mine and you can get away with it for a while, but like the man said you'll burn your pump out. So either put out $5 now or a $100 and some annoying time later. Your call bucko! Link to comment Share on other sites More sharing options...
Eagle Posted April 21, 2008 Share Posted April 21, 2008 NO. It's there for a reason, if you bypass it you'll burn out your fuel pump. Just go get a new one. $7 at carquest. Nope. It is there for a reason. The 87s (XJs and MJs did NOT have it, and people complained that the fuel pump was making too much noise. So for 1988 they added the ballast resistor to reduce the voltage to the fuel pump, which makes it run slower, which makes less noise. The fuel pump and regulator are exactly the same for an '87 and an '88. You will NOT damage anything by soldering those two wires together. Link to comment Share on other sites More sharing options...
Geonovast Posted April 21, 2008 Share Posted April 21, 2008 It is there for a reason. The 87s (XJs and MJs did NOT have it, and people complained that the fuel pump was making too much noise. So for 1988 they added the ballast resistor to reduce the voltage to the fuel pump, which makes it run slower, which makes less noise. My Dad's 87 XJ had one. Link to comment Share on other sites More sharing options...
MiNi Beast Posted April 21, 2008 Share Posted April 21, 2008 NO. It's there for a reason, if you bypass it you'll burn out your fuel pump. Just go get a new one. $7 at carquest. Nope. It is there for a reason. The 87s (XJs and MJs did NOT have it, and people complained that the fuel pump was making too much noise. So for 1988 they added the ballast resistor to reduce the voltage to the fuel pump, which makes it run slower, which makes less noise. The fuel pump and regulator are exactly the same for an '87 and an '88. You will NOT damage anything by soldering those two wires together. my 87 had one as well. Explain that? lol brain fart. Link to comment Share on other sites More sharing options...
HOrnbrod Posted April 21, 2008 Share Posted April 21, 2008 NO. It's there for a reason, if you bypass it you'll burn out your fuel pump. Just go get a new one. $7 at carquest. Nope. It is there for a reason. The 87s (XJs and MJs did NOT have it, and people complained that the fuel pump was making too much noise. So for 1988 they added the ballast resistor to reduce the voltage to the fuel pump, which makes it run slower, which makes less noise. The fuel pump and regulator are exactly the same for an '87 and an '88. You will NOT damage anything by soldering those two wires together. Yes, after the engine starts and the ballast resistor is relayed into the fuel pump circuit, it causes an operating voltage drop of about 2-3 volts that causes the pump to run slower and quieter. But running slower means less amp draw, less heat generated by the pump motor, which equates to a longer pump life. Basic electrical theory. I'll keep the ballast resistor in the circuit. Link to comment Share on other sites More sharing options...
Kenosha Warrior Posted April 21, 2008 Author Share Posted April 21, 2008 alrighty then, may as well try a new one. never hurts. Link to comment Share on other sites More sharing options...
Eagle Posted April 21, 2008 Share Posted April 21, 2008 Some '87s were retrofitted with a ballast resistor under a factory TSB. It was not standard from the factory on 1987 models. I keep it in my '88s, too, but not because I fear any problems from NOT having it. I also have an '87 MJ and that's been chugging along fine without it. I keep it because part of me is of a collector/restorer/purist mindset, and I prefer not to remove parts the factory put there just in case I enter one of the trucks in an AMC Owners Group show. You won't hurt anything by bypassing it, and you won't hurt anything by replacing it. If you replace it -- buy two and keep a spare in the glove box. That's pretty much S.O.P. for any vehicle with a ballast resistor. Chrysler was notorious for using them in their ignitions and having owners get stranded as a result. Link to comment Share on other sites More sharing options...
HOrnbrod Posted April 21, 2008 Share Posted April 21, 2008 Some '87s were retrofitted with a ballast resistor under a factory TSB. It was not standard from the factory on 1987 models. I keep it in my '88s, too, but not because I fear any problems from NOT having it. I also have an '87 MJ and that's been chugging along fine without it. I keep it because part of me is of a collector/restorer/purist mindset, and I prefer not to remove parts the factory put there just in case I enter one of the trucks in an AMC Owners Group show. You won't hurt anything by bypassing it, and you won't hurt anything by replacing it. If you replace it -- buy two and keep a spare in the glove box. That's pretty much S.O.P. for any vehicle with a ballast resistor. Chrysler was notorious for using them in their ignitions and having owners get stranded as a result. Question Eagle: On the HOs in the WOT mode, the ballast resistor is bypassed and the full 12V is applied to the fuel pump by the ballast bypass relay located near the PDC. Do the Renix fuel delivery systems have this bypass relay? Link to comment Share on other sites More sharing options...
Eagle Posted April 21, 2008 Share Posted April 21, 2008 Question Eagle: On the HOs in the WOT mode, the ballast resistor is bypassed and the full 12V is applied to the fuel pump by the ballast bypass relay located near the PDC. Do the Renix fuel delivery systems have this bypass relay? Good question. I wish I had a good answer ... but I don't. I've never even considered it. Link to comment Share on other sites More sharing options...
Pete M Posted April 21, 2008 Share Posted April 21, 2008 That should be easy enough to test. Simply pop the hood and have one of your least-liked but very gullible (and/or drunk) friends crawl into the engine compartment. Then pull out onto the street and accelerate as fast as you can. Have the guy under the hood pull the wire off the resistor while you're at WOT and see what happens. :D Link to comment Share on other sites More sharing options...
Motion Offroad Posted April 21, 2008 Share Posted April 21, 2008 Or just run some wires from the resistor into the cab and while at WOT test it with an volt meter. 8) Link to comment Share on other sites More sharing options...
HOrnbrod Posted April 21, 2008 Share Posted April 21, 2008 That should be easy enough to test. Simply pop the hood and have one of your least-liked but very gullible (and/or drunk) friends crawl into the engine compartment. Then pull out onto the street and accelerate as fast as you can. Have the guy under the hood pull the wire off the resistor while you're at WOT and see what happens. :D I've got a couple of redneck friends down here who would be happy to do that for a beer or twelve. :cheers: Link to comment Share on other sites More sharing options...
Kenosha Warrior Posted April 21, 2008 Author Share Posted April 21, 2008 well, lets hear some ideas. This is what is exactly happenig. I can start it fine, if its cold. Run it up to op-temp and then around 10 minutes later, I will give it throttle and it will sputter, like a misfire but not as violent. within as little as 5 minutes or as long as 25 minutes, it will start to make less and less power, eventually I can barely make it move the XJ in first gear. ideas? Fuel Filter is out of the equation. Link to comment Share on other sites More sharing options...
Eagle Posted April 21, 2008 Share Posted April 21, 2008 Clogged catalytic converter, maybe? Bad oxygen sensor? The O2 sensor isn't used during warm-up, when the engine runs in open loop mode. The ECU uses input from several of the sesnors only after things reach normal operating temperature and switches over to closed loop mode operation. Link to comment Share on other sites More sharing options...
chicofuentes0224 Posted April 21, 2008 Share Posted April 21, 2008 Do you know if the fuel pump has been changed recently? Link to comment Share on other sites More sharing options...
Kenosha Warrior Posted April 22, 2008 Author Share Posted April 22, 2008 yeah. it was the ballast resistor. bought a new one from crappy tire and its running good, not getting superheated and such. def the issue from day damn one. argh. I checked the FP with the schrader valve, had 34psi at idle, revving it brought me up to around 40ish. The fuel filter is brand new and I even tried it without the filter on it for a bit, no change with new filter/no filter but old filter was disgusting. I had black gas being shook out of it. Link to comment Share on other sites More sharing options...
comancheman Posted April 22, 2008 Share Posted April 22, 2008 u know napa charged me $23 for one of those which burnt out less than 4 months later. i replaced it with a $6 one from the dealer and have been good since. Link to comment Share on other sites More sharing options...
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