Fuel pump (?)

[Dammerung]

So, just got my Comanche, and it won’t start. It turns over, but we have no fuel. The pump will sometimes turn on , and the truck will start, but it mostly doesn’t. The truck will also sometimes partially start and sound horrible, and then it’ll die off. I think it might be a pump issue, maybe a bad ground or crank sensor like some others have said on here, but I’m not sure. Any help or options I might have would be appreciated.

 

 

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[87MJTIM]

Do you hear the pump prime EVERY TIME when you turn the key on (engine off)?  If not, check ballast resistor.

 

Check and clean the pump ground wire (behind left tail light).

 

Yr? Engine? 

[Dammerung]

Do you hear the pump prime EVERY TIME when you turn the key on (engine off)?  If not, check ballast resistor.
 
Check and clean the pump ground wire (behind left tail light).
 
Yr? Engine? 

It does not. The ballast resistor was bypassed by a PO. I’ll check ground and replace the resistor. It’s an 88 4.0


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[eaglescout526]

You could always apply direct power to your pump and see if it stays running to eliminate the thought of a bad pump. 

[JMO413]

http://cruiser54.com/

 

Do steps 1-6 and save yourself allot of time and effort.

Step 7 how to check the CPS.

If you know how to solder just delete the C101 connector. It is faster than cleaning it if you truly get it clean. 

[JMO413]

Tip 29 is the fuel pump ground improvement.

[Dammerung]

Investigated my grounds, did not like what I saw


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[Dammerung]

This is what it was connected to

 

Also, anyone know what this wires for? It was disconnected when I got to it.

 

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[JMO413]

The top one is the ground for the rear lamps and fuel pump. No idea on the bottom one. What does it connect to at the light socket?

[Dammerung]

The top one is the ground for the rear lamps and fuel pump. No idea on the bottom one. What does it connect to at the light socket?

Not sure, but a PO installed a trailer brake unit, so I think there might be some extra wires or something. Just a guess.


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[JMO413]

I would agree, it shouldn't be there.

[Dammerung]

Does anyone know what the three wires coming from the fuel pump connector to the wiring harness are? I know black is ground, but what about the other 2? I know orange is probably a positive wire, but not too sure about the middle one. Does anyone know where they run too as well?


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[cruiser54]

CRUISER'S MOSTLY RENIX TIPS

IMPROVING THE FUEL PUMP GROUND

JANUARY 3, 2016 CRUISER54 49 COMMENTS

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.

[Dammerung]

CRUISER'S MOSTLY RENIX TIPS

IMPROVING THE FUEL PUMP GROUND

JANUARY 3, 2016 CRUISER54 49 COMMENTS

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.

Cruiser, do you know how I could test my pump? I’ll redo the ground later today though. Also, I just strip the wire on the harness side, no cutting correct?

 

 

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[JMO413]

4 hours ago, Dammerung said:

Cruiser, do you know how I could test my pump? I’ll redo the ground later today though. Also, I just strip the wire on the harness side, no cutting correct?

 

 

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Correct you just strip the wire and solder on the new jumper.

This is mine.

You can test the pump by running a wire back to the connector.

Put 12V + to the orange wire eat the connector and the pump should run.

Extra ground picture also.