no power to fuel pump

[thisfords4u]

Helping a friend out, hes got a 91 ranger 4.0. He was going down the freeway and he said it was like someone shut the key off, the engine just died. no sputter just off. We've replaced fp relay w/known good one. by passed the inertia switch. Checked for power at pump and theres none. hot wired pump and it works. so whats in between, what am I missing, some help/advise please guys.

 

[zukirider21]

i am having this exact problem now! hope you find an answer...

 

[Sasquatch_Ryda]

Do you have power at the relay with the key on?

 

[thisfords4u]

to be honest my test light bulb broke. but I can feel it powering up/clicking when the key is on, so iwould say yes. getting a new bulb and using multimeter today. thank you all for help.

 

[noahkenny]

A little word of advise. If your gonna use a test light, make sure it is a circuit safe test light. Old style test lights pull current and can damage modern day electronics, even make air bags deploy. I either use a multi meter or a power probe III. Dont even own a test light anymore. Ive been a mechanic for about twenty years. Dont know about your fuel issue but from my experiences never assume that just because its an electric fuel pump it either works or it dont. Electric fuel pumps do wear out just like mechanical ones do and cause all kind of crazy issues like you are having.

 

[thisfords4u]

its not a regular test light not that stupid. Iknow the fuel pump works because we bypassed all wiring to pump and ran power direct and it works fine.

 

[ranger_mclaren]

Check to see the wires are bad I had a similar thing happen to me it kept just shutting off. Sometimes it would restart right away other it wouldn't then finally one day it finally died. I took it to the repair shop they said the positive wire was bad they put a new one on and it work great afterward. Check your grounds too. I've had a engine ground wire go bad before too.

 

[thisfords4u]

he said there were no warning signs, no acting up etc. just died.

 

[ranger_mclaren]

he said there were no warning signs, no acting up etc. just died.

When my motor ground went bad I had no signs I just drove to work shut it off later when i went to leave it wouldn't start I first thought silonoid, so i through one on real quick cause I had a extra one. but still nothing so I checked my wires to the battery and i found the ground from the frame to the engine was to the battery was bad. I replaced it worked fine afterward. I know thats not the fuel pump but just an idea.

 

[thisfords4u]

well Im fairly certain the lack of power to the fuel pump is a coincidence, because of the way it died. to me if fuel is the issue it would have sputtered and died not just off like turning off the key. thanx for the ideas though.

 

[thisfords4u]

update: Joe is getting antsy. He's swapped parts back and forth from his other running ranger to test them from the non running ranger. It all works on the known runner. After following wiring diagrams and going cross eyed reading them, I'm finding that the EEC relay has a blk/wht wire that says its supposed to go to ground. With the relay hooked up we have voltage at that wire, is there supposed to be voltage there? Both the eec and fuel relay are brand new. I can jumper the fuel pump terminal w/relay removed and the pump turns on, so now its spark. Power seems to be at the appointed wires, and switched with he key, but the relays arent "clicking". HELP PLEASE.

 

[Earl43P]

The PCM relay has to energize to send power to the fuel pump relay.

If you have no spark, the PCM relay is the bad actor.

Here's a representative diagram: http://www.therangerstation.com/tech_library/EDiagrams/files/Diagram_Enginecontrols4_0_3_0_1of3.JPG

If that BK/W wire has power on it, Ground 101 is bad. It is either on the radiator support or on the inner fender. Sometimes the small wire from the Neg Battery terminal is the problem for those symptoms. (edit: Just confirmed G101 is from B- to the Rad support - that WILL be your problem area).