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Ignition or Fuel pump?

aggar

aggar

Don't tear it up!
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Location
Kirklin, In
I've got an 85 GMC that I'm trying to sell. The other day the battery was dead. Never happened before. So I jump it and get it next to the barn to charge the battery. Well went out to move it and dead again. So I put the charger on and as soon as I did the fuel pump started running without the key on. So my question is it the fuel pump just stuck or something in my ignition? ANy ideas. The fuel pump is a round inline flow through. Help me. Gotta get this thing running to sell.

Ryan
 
This is probably stuff you already thought of, but.............Disconnect the pump and see if it still loses charge. If it's an ignition problem, it would still drain eslewhere. Did you pay attention to if it kept running or if it shut off after a few seconds? Maybe it just lost prime. If it is a freak thing and for some reason that circuit only is causing the problem, you could always wire it to a switch, or a different ignition wire.
 
I had the battery charger on it and as long as the charger was on the battery the pump would sit there and run with the key off. I need to disconnect it and put the charger on it ot see what happens. I didn't here the first time b/c I jumped it with the dmax and then moved it to the barn and had noise all around so I couldn't hear it run. I'll have to check to see if it drains with the pump off but I think the pump is just f-ed up.
 
the pump should only run with the key on. mind you it should also stop shortly after it hits a preset pressure. look like you've got a gremlin to chase down. see if you can remove the fuse for the pump and check if it still has power. It almost sounds like you have a feedback loop from something else.
 
I just noticed what the years was. why does it have a electric not a mechanical one? I just wondering what was used to supply the power or it. any ideas?
 
I dunno. The guy that owned it before me put on a TBI off of a 91 burb. I'll have to unhook my battery and charge it then drive it to our shop to work on it where I've got more tools and dad can help me trace it down. I'm thinkin a relay from the ignition.
 
aggar said:
I dunno. The guy that owned it before me put on a TBI off of a 91 burb. I'll have to unhook my battery and charge it then drive it to our shop to work on it where I've got more tools and dad can help me trace it down. I'm thinkin a relay from the ignition.
Click to expand...
find out the souce of power to the pump, it should be hooked to a relay, this can be easy...on the trigger side of the relay or coil side...disconnect power, if pump still runs it is the relay (stuck closed) if the pump stops running you have to trace the trigger down as it will be the culprit. That could mean that the pressure switch could be faulty causing the pump to run all the time...never mind, if it is running with the key off that kills the pressure switch or should. I would think it would be just the relay. If it is hard wired some how you have a serious problem with the way it is wired. A good multi meter would be your best friend with this
 
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