Fuel pump whines at ON & doesn't shut off, circuit opening relay AFM harness
Mar 13, 2018 | 04:19 PM
#1
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Fuel pump whines at ON & doesn't shut off odd circuit opening relay AFM harness
Hello,
When I turn the key ignition switch to ON I can hear a whine/buzz from the Gas filler neck area. I'm assuming that's the fuel pump. The audible doesn't go away unless I turn the key to ACC or LOCK.
Based on my search of the forum using a ohm meter I tested the Circuit Opening Relay, EFI Relay and AFM per the FSM and all were within spec. So I checked the wiring harness for both the COR and AFM.
According to the FSM section FI-65 and FI-56 for my 85 efi extra cab auto 2wd on the AFM wiring harness and Circuit Opening Relay wiring harness E1 is supposed to go to ground and FC is the connection between both harnesses.
COR wiring harness:
What's supposed to be E1 is the white/black wire and it grounds. What's supposed to be FC is a green wire and it's open.
AFM Wiring harness:
What's supposed to be the E1 in 2nd position is the green wire and it's open. What's supposed to be FC in the 1st postion is white/black wire and it's grounded.
Confused. What am I doing wrong? See pics from my 85 truck and 85 FSM
When I turn the key ignition switch to ON I can hear a whine/buzz from the Gas filler neck area. I'm assuming that's the fuel pump. The audible doesn't go away unless I turn the key to ACC or LOCK.
Based on my search of the forum using a ohm meter I tested the Circuit Opening Relay, EFI Relay and AFM per the FSM and all were within spec. So I checked the wiring harness for both the COR and AFM.
According to the FSM section FI-65 and FI-56 for my 85 efi extra cab auto 2wd on the AFM wiring harness and Circuit Opening Relay wiring harness E1 is supposed to go to ground and FC is the connection between both harnesses.
COR wiring harness:
What's supposed to be E1 is the white/black wire and it grounds. What's supposed to be FC is a green wire and it's open.
AFM Wiring harness:
What's supposed to be the E1 in 2nd position is the green wire and it's open. What's supposed to be FC in the 1st postion is white/black wire and it's grounded.
Confused. What am I doing wrong? See pics from my 85 truck and 85 FSM
Last edited by ocyota; Mar 14, 2018 at 11:23 AM.
Mar 13, 2018 | 04:49 PM
#3
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Thanks for the reply. No jumper wire in the FPCC.
What if I swapped the position of the green wire with the white/black wire on the AFM wiring harness ?
is the FC wire supposed to be the same color from the AFM wiring harness to the COR wiring harness?
the COR wiring harness seems to match up with the FSM. And E1 is grounded as it should and FC
is open as it should.
Is it pure coincidence that at the AFM wiring harness that the E1
pin is open and FC is grounded yet the color of wire doesn't match the wires at the COR wiring harness?
What if I swapped the position of the green wire with the white/black wire on the AFM wiring harness ?
is the FC wire supposed to be the same color from the AFM wiring harness to the COR wiring harness?
the COR wiring harness seems to match up with the FSM. And E1 is grounded as it should and FC
is open as it should.
Is it pure coincidence that at the AFM wiring harness that the E1
pin is open and FC is grounded yet the color of wire doesn't match the wires at the COR wiring harness?
Last edited by ocyota; Mar 13, 2018 at 04:56 PM.
Mar 13, 2018 | 05:02 PM
#4
Sounds like you've located the issue and someone has altered the wire location in the plugs.
Does the pump shut off with the vafm unplugged? If not you have a short somewhere else.
Double check your printout for the correct layout..
There is an internal connection between e1 and e2, if I'm not mistaken, si having fo hooked into e1 location hot wires the pump.
Mar 14, 2018 | 11:19 AM
#5
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Yes. Just got this truck. And know little about it.
1985 FSM FC is in the 1st position and E1 is in the 2nd position on the AFM.
1986 FSM E1 is in the 1st position and FC is in the 2nd position on the AFM.
I'm looking at my AFM wiring harness connector in my 85 right now (see pics above) and it matches the 86 FSM diagram. What gives ? Lol
1985 FSM FC is in the 1st position and E1 is in the 2nd position on the AFM.
1986 FSM E1 is in the 1st position and FC is in the 2nd position on the AFM.
I'm looking at my AFM wiring harness connector in my 85 right now (see pics above) and it matches the 86 FSM diagram. What gives ? Lol
Mar 14, 2018 | 12:59 PM
#7
You did not answer if unplugged AFM shuts off the pump..
None of these show an internal connection of the ground circuit inside the vafm. It shouldn't matter if these two wires are reversed.. You could test for internal shorts, ohm reading, the two pins for the fuel pump should show as open with the vane closed and have no other connections.
None of these show an internal connection of the ground circuit inside the vafm. It shouldn't matter if these two wires are reversed.. You could test for internal shorts, ohm reading, the two pins for the fuel pump should show as open with the vane closed and have no other connections.
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Mar 14, 2018 | 02:14 PM
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You did not answer if unplugged AFM shuts off the pump..
None of these show an internal connection of the ground circuit inside the vafm. It shouldn't matter if these two wires are reversed.. You could test for internal shorts, ohm reading, the two pins for the fuel pump should show as open with the vane closed and have no other connections.
None of these show an internal connection of the ground circuit inside the vafm. It shouldn't matter if these two wires are reversed.. You could test for internal shorts, ohm reading, the two pins for the fuel pump should show as open with the vane closed and have no other connections.
I did conduct the AFM test via the FSM twice but maybe I'm conducting that test wrong.
Mar 14, 2018 | 02:30 PM
#10
^the point above is unless you tell us what you did, what the book says your results should be and what your results actually were. You have left out information needed. This makes it more difficult for people to help. It is an incomplete ...
went ahead and checked the FSM inspection, neither of the vafm inspection pages have you test the fuel pump circuit. The fuel pump section doesn't either.. Guess 4crawler has this check but not going to look..
..
Yeah bad vafm, test it no continuity between the E1 and F pins is what you should have. Make sure the vane is closed and not stuck open. If the vane is closed and the fuel pump switch is closed also, its time to pry the cover off and see if it's something you can fix like a loose wire, a PO hack, or time to buy a refurbished one.
went ahead and checked the FSM inspection, neither of the vafm inspection pages have you test the fuel pump circuit. The fuel pump section doesn't either.. Guess 4crawler has this check but not going to look..
..
Yeah bad vafm, test it no continuity between the E1 and F pins is what you should have. Make sure the vane is closed and not stuck open. If the vane is closed and the fuel pump switch is closed also, its time to pry the cover off and see if it's something you can fix like a loose wire, a PO hack, or time to buy a refurbished one.
Mar 14, 2018 | 04:15 PM
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Thank you for your input.
I swapped out the bad AFM with a good AFM from my 85 4x4 and sure enough the fuel pump doesn't whine when the key is ON.
For poops and giggles I put the bad AFM in my 4x4 and it made the fuel pump whine when the key was in the ON position and wouldn't shut off.
I did notice that while looking into the air chamber side of the bad AFM that the compensation plate was slightly open. It did move freely, however.
Will crack the AFM open and investigate further.
Last edited by ocyota; Mar 14, 2018 at 04:16 PM.
Mar 15, 2018 | 02:16 PM
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heres the result. I noticed the E2-Vs range when the measuring plate goes from fully closed to full open ranges from 300-1500 ohm. The FSM calls for a range of 20-1000.
How do I repair this AFM back to spec?
Last edited by ocyota; Mar 15, 2018 at 02:29 PM.
Mar 15, 2018 | 02:28 PM
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From http://www.4crawler.com/4x4/CheapTricks/AFM/index.shtml#AFMtesting:
- The resistance measured in Test 3 should add up to the resistance measured in Test 2 plus the resistance measured in Test 0.
- The resistance measured in Test 1 should be less than the resistance measured in Test 2.
Mar 15, 2018 | 02:47 PM
#14
Seems pretty good results, and you found the FC test chart also..
You will need to insure a good clean connection (use a fine emorycloth on the plugs copper), that you aren't touching the probe ends, and the flap is fully closed. Wiggling probe wires doesn't cause fluctuations. Test multiple times, test from both sides of the exposed copper ect.. Basicly that what you see on the meter is acurrate and not skewed.
You will need to insure a good clean connection (use a fine emorycloth on the plugs copper), that you aren't touching the probe ends, and the flap is fully closed. Wiggling probe wires doesn't cause fluctuations. Test multiple times, test from both sides of the exposed copper ect.. Basicly that what you see on the meter is acurrate and not skewed.
Mar 15, 2018 | 06:36 PM
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From: Cedar Park, Texas
Your on the right track...
You will have to open up the AFM to see if the fuel pump switch is in the closed position. If I recall there is an adjustment for the fuel pump switch or the pin can be bent, it’s been a while.
That means cutting the silicone around the black cover and removing the cover.
Good luck.
That means cutting the silicone around the black cover and removing the cover.
Good luck.
Mar 15, 2018 | 06:56 PM
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Your on the right track...
You will have to open up the AFM to see if the fuel pump switch is in the closed position. If I recall there is an adjustment for the fuel pump switch or the pin can be bent, it’s been a while.
That means cutting the silicone around the black cover and removing the cover.
Good luck.
That means cutting the silicone around the black cover and removing the cover.
Good luck.
Mar 16, 2018 | 12:12 AM
#17
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Seems pretty good results, and you found the FC test chart also..
You will need to insure a good clean connection (use a fine emorycloth on the plugs copper), that you aren't touching the probe ends, and the flap is fully closed. Wiggling probe wires doesn't cause fluctuations. Test multiple times, test from both sides of the exposed copper ect.. Basicly that what you see on the meter is acurrate and not skewed.
You will need to insure a good clean connection (use a fine emorycloth on the plugs copper), that you aren't touching the probe ends, and the flap is fully closed. Wiggling probe wires doesn't cause fluctuations. Test multiple times, test from both sides of the exposed copper ect.. Basicly that what you see on the meter is acurrate and not skewed.
I think maybe the black resistive strip that's shaped like an arc might be worn out. See pic.
Mar 16, 2018 | 10:31 AM
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The wiper is glued in place into the black mounting block so it can't be moved forward. Buttoned it back up and the truck still has same symptoms. The e2-fs test result lowered dramatically to 160ohms. It's above my pay grade now. Lol
Time for a replacement AFM. CHEERS!
