electric fuel pump wiring

[mostwanted]

On my way to work today I almost ran out of gas before I could get to my favorite station for a fill up. It was spuddering and what not as I coasted to a stop. I filled it up and eased it out onto the road. It continued to spudder for a couple of blocks and tried to die, so I pulled off the road. It seemed to smoothe out after a few minutes so off I went again. I drove a few miles and it died again . I popped the hood and found that the fuel pump wasn't running. The power wire ran up to the drivers side of the motor, next to the distributer and attached to some sort of switch that appeared not to work with the ignition on? What is this switch? I will post pictures of it tommorrow if neccissary. My buddy stopped by and he suggested that it could be a oil pressure safety switch, but he wasn't sure. Where is the hot lead of the fuel pump supposed to hook to?

Well, we temporarely wired the fuel pump wire to the battery to get me to work, where I disconnected it for now. The motor still spuddered some after getting the pump juice. Do you think that is a different problem or did I mess up my fuel pump by running it low on fuel? It is a Holley. Not sure of the part number yet. I am thinking that it is a seperate problem with water in my fuel or a clogged fuel filter. Sometimes it would run great and sometimes it would spudder. Sorry for the long post and I thanks in advance for any help.

 

[TxasTerry]

My brother-in-law's K-5 was doing the same thing. It turned out to be low oil pressure. He had taken it to about four different shops and no one could figure it out. Turned out there is some safety switch that measures low oil pressure, and if activated, will shut off the fuel pump as a safety measure. He ended up replacing the oil pump and has never had a problem since.

 

[TxasTerry]

My brother-in-law's 1988 K-5 was doing the same thing. It turned out to be low oil pressure and a safety switch was activating shutting off the electric fuel pump. No one could figure out what was happening for a long time. Finally, the last shop he had it at replaced the oil pump and he has never had a problem since.

 

[dyeager535]

Until proven differently, I will continue to say that the '87-91 trucks are not wired up this way. The oil pressure switch is a *backup* in case the fuel pump relay fails, that is it.

If the truck dies with the oil pressure switch disconnected, it's because the relay is dead. There is no other way to interpret the wiring, The only way it could be done otherwise is for the ECM to stop activating the fuel pump relay and rely only on the oil presure switch, which is unlikely. (but as far as I know, still unproven)

 

[1979jimmy350]

i would change the fuel filter, i don't think the oil pressure switch would cause this problem like dyeager535 said it is only a back incase the fuel pump relay dies, you also might want to check the restance in the wire going to the pump you might have a pregnant wire. Because if it worked hooked directly to the battery and not normaly the extra voltage might have helped over come some restance, so check the circut for the basic problems

 

[mostwanted]

I believe that the origional 350 had an mechanical fuel pump. I don't think that there is a relay. Here is a wiring shcematic that I downloaded form holley.com it is on page 3:

http://www.holley.com/data/Products/Technical/Fuel%20Pump%20Tech%20Info.pdf

 

[Blue85]

Probably got some junk from the bottom of the tank in your fuel filter.

Obviously if the pump is turning off something is wrong. Check the fuel pump relay.

 

[mostwanted]

Here's a shot of my Holley blue fuel pump. It will soon be mounted to the inner wheel well. A new see-thru filter and the regulator will be moved to that location as well.