low voltage @ pump

[hubdawg]

HI everyone. The other day I turned on my 96 eb explorer and did not hear the fuel pump sound as i have for the last 7 years. So i got the Haynes manual checked all the wiring check the inertia switch.. put 12 volts right to the pump and it will work. I only get 11.2 volts at the pump and it will not come on.. I have exhausted all my ideas. I am not real great at auto electric.

On the fuel pump relay I bought a new one.. because it was cheap /emoticons/[email protected] 2x" width="20" height="20" />

Anyway I read in the manual about the voltage dropping down from 12 to nothing on one of the terminals at the pump relay.. but when i turn the key to on.. I get the steady 12 on one terminal 12 on two others 6 on one and ground on the last.

The voltage at the inertia switch when I turn the key on peaks at 11.2 and drops back to 6 about one second after the key turns on. Anyone can help me please.. I have traced wires and checked continuity to the best of my ability but when it comes to the pcm and stuff I am stumped.

TIA .. good day

I though I might add the this is the V6 4.0 efi engine with 4wd. It is a southern built and kept truck with no rust or corrosion and is very clean car.. so I am not thinking it is wiring or a short, rather some other issue. I hope you guys can help me out.

 

[scubacy]

I'm not an expert by a long shot, but I had a similar problem with my B2. I could have sworn it was a fuel supply problem because I didn't hear the fuel pump either, but it turned out to be a pick-up coil in the distributor. The symptoms were it would start up and run cold every time but would die after a few minutes of driving and warming up. After it cooled down it would start and run again for awhile.

It would help to know what is going on. Does it start and not run? Does it start at all? RE: testing your inertia switch - it depends where you have your meter leads when you get your readings. There should be batt. voltage, roughly 12v in and 12v out. If you have both leads on the 2 terminals with power on you should get the potential difference of 12 -12 = 0v which is good. If your getting 6v across both terminals means you have a 6v drop in voltage across the inertia switch which would indicate a bad switch. The 11.2v at your pump should be enough to run it, but the pressure might be good so the the fuel press. regulator is not calling for fuel so your not hearing it spin. At least that's what I assume goes on with the FPR and pump /emoticons/[email protected] 2x" width="20" height="20" />

After the couple days of cussing and getting to know all the folks at Napa, I learned to keep to the basics - check the fuel pressure, see if it sparks. I could have done without dropping the tank!

Happy hunting!

HI everyone. The other day I turned on my 96 eb explorer and did not hear the fuel pump sound as i have for the last 7 years. So i got the Haynes manual checked all the wiring check the inertia switch.. put 12 volts right to the pump and it will work. I only get 11.2 volts at the pump and it will not come on.. I have exhausted all my ideas. I am not real great at auto electric.
On the fuel pump relay I bought a new one.. because it was cheap /emoticons/[email protected] 2x" width="20" height="20" />

Anyway I read in the manual about the voltage dropping down from 12 to nothing on one of the terminals at the pump relay.. but when i turn the key to on.. I get the steady 12 on one terminal 12 on two others 6 on one and ground on the last.

The voltage at the inertia switch when I turn the key on peaks at 11.2 and drops back to 6 about one second after the key turns on. Anyone can help me please.. I have traced wires and checked continuity to the best of my ability but when it comes to the pcm and stuff I am stumped.

TIA .. good day

I though I might add the this is the V6 4.0 efi engine with 4wd. It is a southern built and kept truck with no rust or corrosion and is very clean car.. so I am not thinking it is wiring or a short, rather some other issue. I hope you guys can help me out.

 

[Seabronc]

The voltage at the inertia switch when I turn the key on peaks at 11.2 and drops back to 6 about one second after the key turns on.

Sounds like a possible high resistance short from a wire insulation rub through. Pull the wire to the pump at the inertia switch and see what the voltage indication is.

If it is OK then work your way to the pump. Since the pump works when you jumper it, there are two possibilities that come to mind, + line or bad ground; providing the voltage reading in the previous step is OK.

If not OK , work your way back to the source.

Good luck,

>-

 

[hubdawg]

Seems crazy but it looks to have been the short wire that feeds power to the pump inside the tank had gotten short and brittle.. I chopped it short and put a new piece of wire and connectors in there and the damn thing works now. Mostly I believe the truck was jealous because we got a new car and it has had to stay outside the last month. After i kept it in the garage for a week she was happy. go figure. Thanks for all the great suggestion. we can close this thread now.