1990 Ford Bronco Turns but won't start, fuel pressure probl

Tiny
MRNICGUY00
  • MEMBER
  • 1990 FORD BRONCO
  • V8
  • 4WD
  • AUTOMATIC
  • 170,000 MILES
I'm having the same problem as mentioned on the Dec 1st diagnosis question. I knew about the ether or starter fluid method. It does have spark. I tried with the help of a friend to see if the fuel pump was pressurizing before turning it over and got no responc from the pump. So thinking that the fuel pump was out, we replaced it. We replaced the fuel filter at the same time. When installed and we tried to see if the pump would charge, it did. We tried to start it and it tried to kick over but didn't start. Then discovered that the new pump wouldn't charge. Curiously we checked the old pump on the battery and sure enough it worked just fine. So why isn't the pump charging when I turn the key into the on position? We think that the battery is low from trying to start it before we changed the pump and the pump isn't getting the charge it needs. But if the pump was fine before why woudn't it start? NEED HELP on this one, Thanks.
Wednesday, December 3rd, 2008 AT 8:21 PM

7 Replies

Tiny
DAVE H
  • MECHANIC
  • 13,384 POSTS
Have you checked fuel pump relay?

Fuel Pump Relay. Under shield at air cleaner support bracket
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Wednesday, December 3rd, 2008 AT 8:58 PM
Tiny
MRNICGUY00
  • MEMBER
  • 6 POSTS
I just replaced the fuel pump relay and that wasn't it and the new pump still isn't kicking on. When we applied ether it will run as long as ether is being sprayed into it and stalls when we stop. So far I've replaced the fuel pump, fuel filter and fuel pump relay. What else could it be? And how do I check it?
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Wednesday, December 10th, 2008 AT 3:30 PM
Tiny
DAVE H
  • MECHANIC
  • 13,384 POSTS
I should have asked this sooner. But you have checked the inertia fuel cut off swtich? I see no mention of it in your post?

FUEL PUMP SHUTOFF SWITCH
This switch stops the flow of fuel to the engine after a collision. The impact does not have to be great to trigger the switch. To reset, press the white reset button on the switch located on the floorboard, to the left and above where the steering column passes through the floorboard.. If this needs reset. Then try to start vehicle. If it still doesn't start check if you are getting power supply to the pump?
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Wednesday, December 10th, 2008 AT 8:30 PM
Tiny
MRNICGUY00
  • MEMBER
  • 6 POSTS
I completely forgot about the inerta switch, which I will check next. We checked the pump to see if it was getting voltage and it reads 11.5 which is at spec I believe. Would there be no power to the pump if the switch was off?
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Thursday, December 11th, 2008 AT 11:13 AM
Tiny
DAVE H
  • MECHANIC
  • 13,384 POSTS
You will still have power going to the switch. It trips the contacts inside the actual switch?

On the pump you should have a red wire which is live from fuel pump relay via inertia switch. Yellow/white wire going to instrument cluster. An orange wire and a black wire which are both grounds.4 wires in total off pump connector. If your getting 11.5 volts to the pump. Then your not getting a ground otherwise you would hear the pump running
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Thursday, December 11th, 2008 AT 11:34 AM
Tiny
MRNICGUY00
  • MEMBER
  • 6 POSTS
Well we figured out the problem and you were correct. There's a short somewhere along the wiring harness. Most likely due to the major exhaust leak I had that super heated the undercarrage for a very short while( it had backfired so bad at one point it split the seem on the muffler from end to end). So we ran 2 new wires 1 lead, 1 ground through a toggle switch in the cab and straight wired to the battery directly. Without disturbing the other 2 wires to the cluster. Vs finding a needle in a haystack in the wiring harness. Which is the better choice when the truck is parked on a city street in 15 to 30 degree temps outside. Now it runs fine, I just have to flick a switch now. It also doubles as a kill switch if anyone where to try and steal my truck. Thanks for all your help.
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Thursday, December 11th, 2008 AT 9:56 PM
Tiny
DAVE H
  • MECHANIC
  • 13,384 POSTS
No problem. Anytime we can help. Spread the word

Happy motoring

Dave H
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Thursday, December 11th, 2008 AT 10:08 PM

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