Only Runs with Bypasses Resistor

[Discoman9001]

Hello everyone, I’m going to try and be as thorough as possible because my jeep has me stumped. I have an 88 comanche. 4.0 auto trans that I’ve owned for the last 30k miles. Until recently it never missed a beat but I’ve done repairs since I’ve owned it. As of late it’ll intermittently just not run. Start. Run for 5 seconds and die. It has a brand new fuel pump, crank sensor is about 5 months old, I’ve tried the new and old ballast resistor, checked fuses, checked wiring, cleaned the C101 connector, ran some new grounds, changed the fuel pump ground as suggested by cruiser54s website. And the only way this truck will run is to bypass the ballast resistor with a jumper wire, then it runs fine. Does anyone have any suggestions of what it might be? Or should I just say screw it and leave the resistor bypassed. 

[JZLAJeep]

Sounds similar to an issue we had. This was our temporary solution. Haven't gotten back to a more permanent solution.

 

[gogmorgo]

New ballast resistor could have been bad out of the box. Have you checked it for continuity? Or excessive resistance?

[Discoman9001]

22 minutes ago, gogmorgo said:

New ballast resistor could have been bad out of the box. Have you checked it for continuity? Or excessive resistance?

I’ve tried 2 different ballasts and ohm tested them before and after and they checked out. It just refuses to run if there’s a ballast resistor. I’m stumped. I even put a MSD resistor that was only 0.8 instead of 1.2 and it still wouldn’t stay running 

[fiatslug87]

I have the same issue on my ‘90. Resistor checks out fine but fuel pump will not run unless jumped. My assumption was something in the connection but I haven’t looked at it any further, just have it jumped. Hope someone has figured out what it is.

[Discoman9001]

54 minutes ago, fiatslug87 said:

I have the same issue on my ‘90. Resistor checks out fine but fuel pump will not run unless jumped. My assumption was something in the connection but I haven’t looked at it any further, just have it jumped. Hope someone has figured out what it is.

Radical. I kind of have no choice but to leave it for now and hope for the best. The jumper wire doesn’t get warm and it runs excellent with it jumped so. Idrk anymore 

[Ωhm]

Connect DVOM across the ballast resistor with both Fuel Pump connectors connected. Polarity doesn't matter (+/-), just looking for the number (vdc). CRANK engine. Should read between 3-4vdc.

[cruiser54]

Bad ground at fuel pump?

 

Here ya go.

 

CRUISER'S MOSTLY RENIX TIPS

IMPROVING THE FUEL PUMP GROUND

JANUARY 3, 2016 CRUISER54 60 COMMENTS EDIT

The fuel pump and fuel tank sending unit ground at a sheet metal screw up behind the spare tire on an XJ, and behind the driver’s taillamp on an MJ.

Not only is a sheet metal screw a lousy way to ground things, this ground path is long and travels through some connectors that are prone to corrosion and moisture.

Locate the black wire on  the HARNESS side of the fuel pump/sender 3 wire connector. Remove a 6″ length of the split loom covering. Strip back about 1/2″ of insulation from the BLACK wire.

Take your new ground wire, preferably at least 14 gauge and 12 to 18 inches long as needed, strip it about 3/4″, and wrap it around the exposed part of the harness plug wire.Solder the connection. Tape it up and reinstall the split loom covering.

At the other end of your new ground wire, add a crimp on eyelet. Attach the eyelet under a bolt that goes directly into the chassis. Be sure to clean the attaching point til shiny and apply OxGard to the contact surfaces.

[Discoman9001]

1 hour ago, cruiser54 said:

Bad ground at fuel pump?

 

Here ya go.

 

CRUISER'S MOSTLY RENIX TIPS

IMPROVING THE FUEL PUMP GROUND

JANUARY 3, 2016 CRUISER54 60 COMMENTS EDIT

The fuel pump and fuel tank sending unit ground at a sheet metal screw up behind the spare tire on an XJ, and behind the driver’s taillamp on an MJ.

Not only is a sheet metal screw a lousy way to ground things, this ground path is long and travels through some connectors that are prone to corrosion and moisture.

Locate the black wire on  the HARNESS side of the fuel pump/sender 3 wire connector. Remove a 6″ length of the split loom covering. Strip back about 1/2″ of insulation from the BLACK wire.

Take your new ground wire, preferably at least 14 gauge and 12 to 18 inches long as needed, strip it about 3/4″, and wrap it around the exposed part of the harness plug wire.Solder the connection. Tape it up and reinstall the split loom covering.

At the other end of your new ground wire, add a crimp on eyelet. Attach the eyelet under a bolt that goes directly into the chassis. Be sure to clean the attaching point til shiny and apply OxGard to the contact surfaces.

Goodmorning to the legend himself. I’ve already done this tip, as well as several others from your website, not all at once but over the last year and a half of owning the rig. I did the fuel pump ground 4-5 months ago and i checked it to make sure it was still good and solid ground during this whole debacle and it’s still good. At the moment the jumper wire bypassing the resistor seems to work. Doesn’t get warm to the touch or anything and well, I need to be able to drive the manche so for now it’s the fix I guess. 

[cruiser54]

I'd be curious about the voltage at the pump while running.