 Strange Fuel Pump Ground III Problem |
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| LukeD |
 Aug 31 2015, 02:58 PM
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#1
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Member  Group: Members Posts: 254 Joined: 14-November 04 From: Atascadero, CA Member No.: 3,117 Region Association: None  |
Came around a hard corner Saturday and the car just died, figured out pretty quick the fuel pump wasn't running so hot wired it to the battery and drove home. after some troubleshooting with a volt meter I determined that ground III on the relay board wasn't grounding, so I ran a ground wire from that to the post ground above the relay board and fuel pump is back working, although it no longer runs for 1.5 seconds like it used to just runs when the key is on.
Looking at Pelican wiring diagrams I can see ground III runs to Pin 19 on the ECU, I have yet to take the ECU harness out and test continuity on that wire (will do so tonight after work) but I can't wrap my head around how it just went bad (other than its 42 year old wiring) (IMG:style_emoticons/default/WTF.gif) Other than that no other negative symptoms when this happened (IMG:style_emoticons/default/confused24.gif) -Luke |
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| SirAndy |
Aug 31 2015, 03:54 PM
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#2
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Resident German Group: Admin Posts: 41,644 Joined: 21-January 03 From: Oakland, Kalifornia Member No.: 179 Region Association: Northern California |
How does the bottom of your relay board look? They can (and do) fail.
The FI brain grounds the fuel pump through the relay board, which is why the pump now runs all the time with the key, since you bypassed the brain ground ( (IMG:style_emoticons/default/biggrin.gif) ). There are several threads here on how they fail (soldered connections coming lose) and how to rebuild them. (IMG:style_emoticons/default/popcorn[1].gif) |
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| JeffBowlsby |
Aug 31 2015, 04:36 PM
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#3
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914 Wiring Harnesses Group: Members Posts: 8,510 Joined: 7-January 03 From: San Ramon CA Member No.: 104 Region Association: None 
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Maybe a corroded electrical terminal? :dunno:
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| LukeD |
Aug 31 2015, 06:48 PM
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#4
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Member Group: Members Posts: 254 Joined: 14-November 04 From: Atascadero, CA Member No.: 3,117 Region Association: None |
QUOTE(SirAndy @ Aug 31 2015, 02:54 PM)  How does the bottom of your relay board look? They can (and do) fail. The FI brain grounds the fuel pump through the relay board, which is why the pump now runs all the time with the key, since you bypassed the brain ground ( (IMG:style_emoticons/default/biggrin.gif) ). There are several threads here on how they fail (soldered connections coming lose) and how to rebuild them. (IMG:style_emoticons/default/popcorn[1].gif) Forgot to mention I have 2 other relay boards and tried both, I'm going to pull off the ECU harness and test for continuity |
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