 Fuel Pump Troubleshooting, I'm stumped |
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| ThinAir |
 Sep 17 2019, 07:12 PM
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Best friends  Group: Members Posts: 2,555 Joined: 4-February 03 From: Flagstaff, AZ Member No.: 231 Region Association: Southwest Region 
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Trying to get my car on the road for Red Rock Classic. It's not looking good.
I had an intermittent problem with the fuel pump not running, which at the moment seems to be no longer intermittent. I've successfully tested the pump by connecting it to a battery charger. I've followed the steps in the two fuel pump diagnostic documents at Jeff Bowlsby's site (http://bowlsby.net/914/Classic/zTN_FI_FPChecklist.pdf and http://bowlsby.net/914/Classic/zTN_FI_FPChecklist2.pdf). They both fail at the point where it says I should wrap a wire around pin 87 and reinsert the relay. I get no power on the wire. Following the steps in the Brad Anders document, I don't have 12V on pin 86 and when I test pin 8 on the plug I have power so that means I have a faulty relay board trace. My board was rebuilt last year by a member here who has a great reputation so I don't have any reason to doubt my relay board. I have also tested with 2 other relay boards as well as multiple relays - all with the same result. It just doesn't make sense to me that 3 boards could all have the same issue. I'm stumped. Can anyone provide some additional things to check? |
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| dr914@autoatlanta.com |
Sep 18 2019, 01:40 PM
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914 Guru Group: Members Posts: 8,120 Joined: 3-January 07 From: atlanta georgia Member No.: 7,418 Region Association: None |
no all three cannot be bad and relay boards rarely fail. make sure you have power to the fuse on both sides of the holder
Unplug and plug the power relay with the key on the coil wire to the condenser unplugged and with two good known relays (you can test them in the rear relay slot for the heater blower motor. Each time the main fuel injection power relay is plugged in (second from the front, front most is the rear window defrost relay slot) two injectors should click and the fuel pump run momentarily and stop. If the two injectors do not click, check the ground leads at the back of the block, if they do, then pop off the front harness cover cap and put a test light to the first left front pin the black with the red and repeat the plugging and unplugging. If the test light goes on and then off for a moment, the fuel pump wiring or plug or ground lead is faulty QUOTE(ThinAir @ Sep 17 2019, 06:12 PM)  Trying to get my car on the road for Red Rock Classic. It's not looking good. I had an intermittent problem with the fuel pump not running, which at the moment seems to be no longer intermittent. I've successfully tested the pump by connecting it to a battery charger. I've followed the steps in the two fuel pump diagnostic documents at Jeff Bowlsby's site (http://bowlsby.net/914/Classic/zTN_FI_FPChecklist.pdf and http://bowlsby.net/914/Classic/zTN_FI_FPChecklist2.pdf). They both fail at the point where it says I should wrap a wire around pin 87 and reinsert the relay. I get no power on the wire. Following the steps in the Brad Anders document, I don't have 12V on pin 86 and when I test pin 8 on the plug I have power so that means I have a faulty relay board trace. My board was rebuilt last year by a member here who has a great reputation so I don't have any reason to doubt my relay board. I have also tested with 2 other relay boards as well as multiple relays - all with the same result. It just doesn't make sense to me that 3 boards could all have the same issue. I'm stumped. Can anyone provide some additional things to check? |
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Posts in this topic
ThinAir Fuel Pump Troubleshooting Sep 17 2019, 07:12 PM
TravisNeff I would also suspect the relay board. When you tu... Sep 17 2019, 07:26 PM Spoke You can isolate the fuel pump drive circuitry from... Sep 17 2019, 08:44 PM
ThinAir Thanks, Spoke. I'll give that a try in the mor... Sep 17 2019, 11:50 PM ThinAir Grounding pin III does indeed cause the pump to ru... Sep 18 2019, 12:53 PM rhodyguy Can you use the carb jumper wire trick to power th... Sep 18 2019, 12:58 PM ThinAir
Can you use the carb jumper wire trick to power t... Sep 18 2019, 01:06 PM SirAndy Can you use the carb jumper wire trick to power th... Sep 18 2019, 01:09 PM SirAndy Is your fuel pump fuse OK? (91) in the pic below.
... Sep 18 2019, 01:12 PM ThinAir
Is your fuel pump fuse OK? (91) in the pic below.... Sep 18 2019, 01:22 PM ThinAir It works again!
After reviewing the diagram, ... Sep 18 2019, 01:40 PM Spoke
It works again!...I'm thinking that I jus... Sep 18 2019, 07:25 PM ThinAir :driving: WooHoo!!!!
Just got ba... Sep 18 2019, 03:46 PM SirAndy Red Rock Classic 2019 - here we come!
Pack sp... Sep 18 2019, 04:52 PM jim_hoyland A spare pump is cheap insurance... :) Sep 18 2019, 04:33 PM |
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