scottintexas

I think my fuel pump died. Problem is I can't get to the right stuff for troubleshooting. For example; Haynes says the fuel pumpt test terminal is located near the brake distribution and the brake booster (arrow pointing to photo in manual). I can't find anything that even resembles a test terminal. I pulled the relay and checked that power was present in the socket with the key on. I need more than two hands to test the relay. Maybe get some help in a while. There must be a way to test the fuel pump without having to remove it from the tank. Any advice, help or information will be greatly appreciated.

EvansBlue

You should have a fuse for it as well as a relay. Check the fuse and get back to me.

scottintexas

I can't find a fuse for it. The wiring diagram says fuse 9 so I looked in the fuse panel inside the truck but fuse 9 is for HVAC. There is nothing else in the under hood panel that gives any clue of being the fuel pump fuse. When the key is turned on I can feel and hear the relay work. So I rule that out. The problem now (may have always been) is I may have a bad positive cable. Although the hood has been open for quite a while I can't see it draining the battery so much that I can't even get the engine to turn over. My trip counter is also reset as well as the radio. I tried to get the vehicle up high enough to fit under it to see if I could get to the wiring at the tank, but my jack wont go up that high. I need a new floor jack. Yesterday as I was driving home from the store the engine just died. I coasted to the shoulder and as soon as I decided I couldn't restart it it started and I coninued to drive home wihtout a problem. Checking all the grounds I could fins they all appear to be in good shape and tight. There is some corrosion at the positive cable though. If I can get enough light under the truck to remove the cable from the starter I'll replace it and see if there is any change. Of course we now have Christmas duty to attend to.

Thanks for your response. I'll get back as soon as I do something different.

EvansBlue

What year model do you have?

scottintexas

I thought I included that, sorry. It is a 98, 4.3 ltr. The manufacturing date is 9/97 so it could still fall under the 97 model, I don't know.

dewey

Check your fuel pressure. A fuel pressure gage is a basic tool for a fuel injected vehicle. If this has the csfi fuel system, they are noted for problems. Fuel pressure is critical.

My information shows, the 97 has a prime connector for the pump and the 98, doesn't. You can always run voltage to the pump from the relay. Most relays I've seen, have wiring diagrams on them. The ISO type (bosch type) relays, the terminals should be numbered. Some of these vehicles have an oil pressure switch in the pump circuit, once you crank it and oil pressure comes up, the switch closes, and the pump should run, regardless of the relay. The o/p switch and relay are in parallel to each other, not series, so, low oil pressure won't kill the pump, as long as the relay is functional.

RCars2

Iwant to say that its probably not thepump.You can hear and feel it moving fluid so it doesnt seem like thats itthough it can sound fine and be crapped out. Normally if the pump isweak you can hear a sound difference compared to normal(ie it sounds kinda half dead). To be safe you can check fuel pressure off the schrader valve and make sure you are getting fuel when cranking (forgive me for not knowing the exact pressure at crank off the top of my head, its around 50 or so PSI if i remember right,but i can get that for ya in a bit).

Now ya said as well that you thought it might be the positive cable, which might explain why it just up and died going down the road (i had the cables fall out of the terminal when goingdown thefreeway once so i know it will kill the motor if it goes)but you wouldnt be able to get it to crank if it was the cable not supplying power, so thats kinda out.

Something tells me it its probably more fuel related than anything. Hit up your local parts house and rent a tool to test the pressure and check it against the normal pressure level.

EvansBlue

The PSI shouldn't be that high!!! I think its like 12-17 thats normal.

Ann Mitchell Ingersoll

how do i test fuel pressure in pump 97 blazer 4 dr.