whatis42 Posted March 20, 2007 Share Posted March 20, 2007 As the title says starts then stops? I was going to try replacing the cps but I can't figure how to get to it! :mad: New wires plugs cap rotor.. New ceramic fuel pump ballast resistor [broke that the other day] I replaced brake mc and booster last night. ummm not sure what else well thanks.... Link to comment Share on other sites More sharing options...
Rokhound Posted March 20, 2007 Share Posted March 20, 2007 lower the back of the tranny down so that you can get to the bolts Link to comment Share on other sites More sharing options...
fiscus Posted March 20, 2007 Share Posted March 20, 2007 I think it's not the CPS, possibly IAC or TPS? I just did a CPS on an XJ, I just stuck my arm up there & took the bolts out; (removed front driveshaft first) is it harder to get to on an MJ? Link to comment Share on other sites More sharing options...
Pete M Posted March 20, 2007 Share Posted March 20, 2007 Bypass the new resistor by touching the wires together and see if that works. It could be a bad resistor. Link to comment Share on other sites More sharing options...
feerocknok Posted March 20, 2007 Share Posted March 20, 2007 Like crankity-crankity-crankity-vroom-poom? Or crankity-crankity-crankity-vroom-vrom-vrm-poom? Have you tried holding down the gas pedal once it starts for a couple seconds if it's the second one? Link to comment Share on other sites More sharing options...
87manche Posted March 20, 2007 Share Posted March 20, 2007 I still think you've got a fuel pump power problem. When you turn the key to start the ignition bypasses the ballast resisotr, giving 12V to the pump. When it goes back to run it runs it through the adition circuit for the ballast resistor. Link to comment Share on other sites More sharing options...
DirtyComanche Posted March 20, 2007 Share Posted March 20, 2007 I agree on bypassing the resistor to rule it out. That's normally what causes that. Link to comment Share on other sites More sharing options...
Eagle Posted March 20, 2007 Share Posted March 20, 2007 I agree on bypassing the resistor to rule it out. That's normally what causes that. Agreed. If it starts, it isn't the CPS, and probably not the IAC or TPS. As noted, the START circuit bypasses the fuel pump resistor. Once you release the key to the RUN position, the power is routed through the resistor. Either the resistor is bad, or there's another problem in that part of the fuel pump circuit. You could also try running a hot wire directly to the fuel pump. If it starts and stays running, do NOT leave it that way, because you won't have a pressure switch to shut the pump off when there's sufficient pressure in the fuel rail. Hot wire it only as a diagnostic aid. Link to comment Share on other sites More sharing options...
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