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Fuel pump fuse blows when you shut down. Replace fuse it runs.

Tiny
GROG247
  • MEMBER
  • 1992 GMC VAN
  • 300 MILES
With the common ground on the fuel pump / sending unit. Is it possible that the reostat is shorting out sending juice back through the ground when shut off? Other than putting the fuel pump in a gas can and seeing if it still blows the fuse on turn off. We don't even have an ohm/volt meter to test anything. Arggghhhhhhh!
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Friday, May 11th, 2012 AT 5:13 AM

19 Replies

Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
I'd try cleaning the ground first and making sure it has good contact and not rusty corroded. You really need to see if the relay may be sticking causing this as well.
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Friday, May 11th, 2012 AT 2:02 PM
Tiny
GROG247
  • MEMBER
  • 14 POSTS
We clipped and isolated the power side of the sending unit. Still blows fuse on shut down. The relay is new. Still blows fuse on shut down
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Sunday, May 13th, 2012 AT 12:12 AM
Tiny
GROG247
  • MEMBER
  • 14 POSTS
Ground looks clean and tight. It's a soldered connection
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Sunday, May 13th, 2012 AT 12:20 AM
Tiny
GROG247
  • MEMBER
  • 14 POSTS
Still for the life of me can't figure how the pump can work and then short on shut down.
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Sunday, May 13th, 2012 AT 12:26 AM
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Check the relay or disconnect it and see if it does the same
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Sunday, May 13th, 2012 AT 1:12 AM
Tiny
GROG247
  • MEMBER
  • 14 POSTS
Old relay or new relay, neither one blows the fuse on shut down.
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Sunday, May 13th, 2012 AT 12:54 PM
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
That's not what I said, disconnect the relay to see if it stops the pump. You cold have a hsorted wire in the harness making it do that. If it continues then you know you have ahsorted wire and will have to find out where it is together getting the power from.
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Sunday, May 13th, 2012 AT 1:45 PM
Tiny
CADIEMAN
  • MECHANIC
  • 3,544 POSTS
U will need to buy a short tester.U install the breaker in the fuse panel and when it blows use the gauge to follow the the way the needle goes. Just hold it the taped up harness. When u get to the short the needle will shake violantly
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Sunday, May 13th, 2012 AT 3:03 PM
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
You can do the same with a small compass
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Sunday, May 13th, 2012 AT 3:19 PM
Tiny
GROG247
  • MEMBER
  • 14 POSTS
Started up, disconneted relay, stays running. Shut down, restarts and runs without relay in !
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Sunday, May 13th, 2012 AT 3:49 PM
Tiny
CADIEMAN
  • MECHANIC
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U dont have the right relay then
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Sunday, May 13th, 2012 AT 10:05 PM
Tiny
CADIEMAN
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Compass is ok but u will still need 10 amp circuit breaker to hook to the fuse panel.
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Sunday, May 13th, 2012 AT 10:22 PM
Tiny
GROG247
  • MEMBER
  • 14 POSTS
Correct relay ! RUNS WITHOUT IT IN LINE ! Short in the harness I believe. Now just to find it. Thanx guys
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Tuesday, May 15th, 2012 AT 2:15 AM
Tiny
CADIEMAN
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  • 3,544 POSTS
Remove the relay panel and test the relay pins how many have power? Ive never of this problem.
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Tuesday, May 15th, 2012 AT 4:38 PM
Tiny
GROG247
  • MEMBER
  • 14 POSTS
1. ORANGE "ALWAYS HOT". STILL CHECKING FOR SHORT UNDERNEATH. HOPEFULLY IT'S OUT IN THE OPEN BETWEEN ORANGE AND GREY
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Thursday, May 17th, 2012 AT 5:36 PM
Tiny
HMAC300
  • MECHANIC
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Theorange wire has to be touching the gray wire to make it runlike that.
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Thursday, May 17th, 2012 AT 10:20 PM
Tiny
CADIEMAN
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Hook a meter up on the orange wire at the tank. Put it on continuity. Probe the relay wires the orange wire should show cont. Probe the other wires. If you have cont. On any other wires thats the wire shorted to the orange.
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Thursday, May 17th, 2012 AT 11:34 PM
Tiny
GROG247
  • MEMBER
  • 14 POSTS
Two shorts found so far. Connector to fuel/ oil pressure switch was wet and fouled with gunk, no more blown fuses and starts every time. Grey wire chaffed on column near ignition.
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Sunday, May 27th, 2012 AT 5:33 PM
Tiny
CADIEMAN
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Good to hear
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Sunday, May 27th, 2012 AT 9:36 PM

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