1989 4.0 Comanche, Fuel Supply System-crash course needed

[Dal3]

 

This is a personal utility truck I've owned 8 years that I don't use frequently.  Until this morning, the engine had generally performed satisfactorily.

While running errands in town, on the 3^rd start, the engine sounded a bit rough.

As I drove about 1/10 mile more it ran worse stalling frequently. Finally, it wouldn't restart. It would just sputter during cranking.

As I thought about it, I realized I hadn't heard the fuel pump cycle on, as it has normally when turning the ignition on.

 

Trying to confirm my fuel supply hunch, I dumped some fuel into the air intake hose. Cranking confirmed the problem was fuel supply. And, I surmise, the non-running pump was the likely source.

However, I'm unfamiliar with the system and don't know how test the various components.

 

So I need to take a crash course learning to:

identify, name. understand, locate and test system components 

To isolate the cause of the fuel pump not running.

I don't have a repair manual.

I just watched a video about changing the fuel pump, so I know the pump's location and how to locate it's power connection.

 

About the only other thing I know about the pump is the location of the ballast resistor.

That is because I was having some fuel trouble immediately after I bought the truck.

I was advised to bypass the ballast resistor, which did and that solved the problem.

I was also told the ballast resistor was only present to make the pump less noisy and didn't need to be replaced. And I haven't replaced it (In case this might be related to the problem I'm having now.)

One question I have is the identity of a black plastic component near the ballast resistor "Whether it is related to the pump and, if so, its name and function. It is connected to wires from the same harness sheathing as the ballast resistor wires.

 

I'd appreciate knowledgeable information

Dale

[pizzaman09]

The black plastic component you speak up, which should be forward of the ballast resistor on the fender, should be a vacuum valve that controls the EGR valve.  So it doesn't have anything to do with the fuel system.  

 

The fuel system is fairly simple in these trucks.  For what you are suggesting, I'd start by checking the ground for the fuel pump at the drivers side tail light and confirm your ballast resistor bypass still works.

[Dal3]

After making my original post I decided to take the little I had learned about the system from a youtube video (Location of the fuel pump and electrical connection) back to the truck in daylight.

 

This morning I returned to the truck and found that someone had cut 2 of the wires, then reconnected them with wire nuts. One of these had shaken loose and that was the source of my problem.

Thanks for the information provided. I'm going to try to learn a  more about how the the system is lid out  in case of later trouble

Thgaks,

Dale

[Salvagedcircuit]

1 hour ago, Dal3 said:

This morning I returned to the truck and found that someone had cut 2 of the wires, then reconnected them with wire nuts. One of these had shaken loose and that was the source of my problem.

I found plenty of taped over wire nuts in my engine bay too. A quick but terrible long term fix.

[AZJeff]

22 hours ago, Salvagedcircuit said:

I found plenty of taped over wire nuts in my engine bay too. A quick but terrible long term fix.

Wire nuts have NO place on automotive applications.  For starters, they don't hold well in high vibration environments such as vehicles.  Secondly, they are not sealed from the elements at all.   Moisture will get into such joints and cause corrosion of the individual strands of the conducting wires and eventually create an open connection.

 

The BEST connection of two wires is solder, with an outer coating of heat shrink tubing.   Barring that, a crimp type connector with an outer covering of shrink tubing that contains adhesive is the next best choice.

[Salvagedcircuit]

16 minutes ago, AZJeff said:

Wire nuts have NO place on automotive applications.  For starters, they don't hold well in high vibration environments such as vehicles.  Secondly, they are not sealed from the elements at all.   Moisture will get into such joints and cause corrosion of the individual strands of the conducting wires and eventually create an open connection.

 

The BEST connection of two wires is solder, with an outer coating of heat shrink tubing.   Barring that, a crimp type connector with an outer covering of shrink tubing that contains adhesive is the next best choice.

Absolutely! I ended up cutting out all the wirenuts and hand-twisted wires in my wiring harness from the PO then soldered up the joints and covered with adhesive lined heatshrink.