Truck is dead, help me resuscitate

[cluricaunne]

Hey guys, hoping someone can point me in the right direction. Truck won't stay running. She'll start 20% of the time, but die seconds later. The rest of the time she is just cranking over, trying to catch life. No idea what is wrong, but maybe you guys can throw ideas at me for me to check.

 

(1988 Comanche 4x4 4.0L MT)

[MjAllTheWay]

I would try the fuel pump resistor on the side of your engine bay. Mine did the same thing.

[cluricaunne]

is that one of the relays? do you maybe have a pic of the resistor?

[Wildman]

:agree:

 

This thing -

 

 

Just make a jumper wire and connect the two female connectors together, to bypass the resistor.

 

See if you can get fuel pressure at the test port. With a pressure gauge, or just push the pin in and see if fuel squirts out. Have rags under the test port.

 

If this don't work, we'll go to the next level.

[88pioneer]

:agree: , resistor first. I went through the same issue

[cluricaunne]

Sweet, I'll give it a shot. The truck is at work (bonus that work is a wrecking yard), so I will have to tend to it later, but I think that might do the trick

[cluricaunne]

put a new resistor in in (well, used, but new to the truck) and got no results. I am going to drop a fuel pump in it this morning, see if that fixes it, otherwise I may have to try to find a brand new resistor.

[Wildman]

You should be fine with a good used resistor.

 

Can you do a fuel pressure check??? You should get 31psi with the pressure regulator connected, and 39psi with the vacuum hose dis-connect off the pressure regulator.

 

Could be a plugged frame fuel filter, or a plugged sock filter. It's has been noted that the rubber line in the tank, from the fuel pump to the sender unit hard lines can crack/rot/leak, and starving the engine for fuel.

 

Also.......did you check the CPS?? Unplug the connector and plug it back in, or do an Ohm's test on the CPS, you should get 125-275 Ohms on A & B contacts. Anything out of that range, and it's replacement time.

[cluricaunne]

Threw the pump in, truck works again, that is the fourth pump I've gone through in the last 2 years that I have owned my MJ. I have got to get the electrical work done before she gets really mad at me :dunce:

[CWLONGSHOT]

I have gone threw a couple since the orig going too. I don't think the after market pumps are very good quality...

 

CW