No getting fuel delivery to rail

Tiny
WILLIAM TESENE
  • MEMBER
  • 1988 FORD BRONCO
  • 5.8L
  • V8
  • 4WD
  • AUTOMATIC
  • 180,000 MILES
I have replaced both fuel pumps, all relays, but still am not getting fuel to rail. Pumps work when relay is bypassed, but still no start. Hooked a pressure gauge to shrader valve and with pumps running, reads zero pressure. The fuel pump relay doesn't engage when key is on but the PCM relay does. This is driving me nuts. Also will start momentarily with ether. Please help.
Wednesday, August 26th, 2020 AT 5:57 PM

9 Replies

Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
We need to rule out a physical blockage in the line. So I would start at the pumps and unhook the supply line and energize the pump and run a rubber line off the supply line into a bucket and make sure the pump is pumping when it is turned out. We can't rule out a faulty pump until we confirm that when you hear it running that it is actually sending fuel.

Once you do this, just hook the line back up and move up the line and disconnect it again, and do the same thing. Basically just work your way up to the rail until you are not getting fuel. Then we know where the issue is.

Let me know what questions you have and we can go from there. Thanks
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Wednesday, August 26th, 2020 AT 6:19 PM
Tiny
WILLIAM TESENE
  • MEMBER
  • 8 POSTS
Thank you for replying. Would a blockage cause the fuel pump not to come on? As I said earlier, if I bypass the relay, both pumps run. There is a small amount of fuel in the rail but obviously not enough pressure to register on the gauge. I will try disconnecting the outgoing side of the pump to check volume.
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Wednesday, August 26th, 2020 AT 7:18 PM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
Maybe I misunderstood. I thought the pumps came on normally. I didn't read that closely enough.

It would not cause that but with that info, you may have two issues. If you can jump the relay and still get no fuel when the pumps come on, then I suspect you have a blockage or a failed pump. Due to the pump being new, you would think there is a blockage which is why we need to confirm it is coming out of the pump. Once we solve that issue and you are getting fuel to the rail and proper pressure, even with jumping the relay then we can tackle why you are not getting power.
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Wednesday, August 26th, 2020 AT 7:31 PM
Tiny
WILLIAM TESENE
  • MEMBER
  • 8 POSTS
Okay. So I disconnected the output side of the primary pump and energized them by bypassing the fuel pump relay. They are definitely working. Hooked it back up and reinstalled the pressure gauge to the shrader valve energized the pumps again and read 38# pressure. Disconnected my jumper and watched for drop in pressure and it was marginal, maybe 2# over 5 minutes. I have replaced the relay 3 times with the same issue each time. The EEC relay is closing because you can feel it clicking when the key is turned on. Still wont start even with jumper over fuel pump relay. Any ideas?
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Thursday, August 27th, 2020 AT 3:48 PM
Tiny
WILLIAM TESENE
  • MEMBER
  • 8 POSTS
  • 1988 FORD BRONCO
  • 5.8L
  • V8
  • 4WD
  • AUTOMATIC
  • 180,000 MILES
Okay, so I disconnected the output side of the primary pump and energized them by bypassing the fuel pump relay. They are definitely working. Hooked it back up and reinstalled the pressure gauge to the schrader valve energized the pumps again and read 38# pressure. Disconnected my jumper and watched for drop in pressure and it was marginal, maybe 2# over 5 minutes. I have replaced the relay 3 times with the same issue each time. The EEC relay is closing because you can feel it clicking when the key is turned on. Still wont start even with jumper over fuel pump relay. Any ideas?
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Friday, August 28th, 2020 AT 11:28 AM (Merged)
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,176 POSTS
Hi,

When you provided power direct to the pump, did you check to see if there was power in the harness? If you are jumping at the relay and the pump doesn't run, then you have an open circuit between the two locations.

Let me know if you checked to see if there is power to the pump. Also, let me know if you checked to see if the inertia switch needs reset.

On F-series, the Inertia Switch is located at the far Left part of the toe-board, near the parking brake assembly.

Let me know.
Joe
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Friday, August 28th, 2020 AT 11:28 AM (Merged)
Tiny
WILLIAM TESENE
  • MEMBER
  • 8 POSTS
Hi Joe. Thanks for the response. I have been using a jumper wire at the back of the fuel pump relay to power the pumps. The inertia switch isn't tripped and to cross check it I ran a jumper across it, in essence bypassing it. I have power to the relay with key on, but no power out of the relay. If I jump the relay I get power to the pumps, 38# of pressure at the test port, but still no start. I know I have fire from the distributor because it will try to start on starting fluid. I'm pretty stumped.
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Friday, August 28th, 2020 AT 11:28 AM (Merged)
Tiny
WILLIAM TESENE
  • MEMBER
  • 8 POSTS
It actually wound up being a broken ground wire for the pump. Located right next to the battery of all places! Couldn't have got it without all your guys' help!
Thanks a million!
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Saturday, August 29th, 2020 AT 6:54 AM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
That is great information. Thanks for that update and I am sure that info will help others. Please come back to 2CarPros the next time you need some help. Thanks
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Saturday, August 29th, 2020 AT 5:03 PM

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