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Fuel Pump Not Energizing Intermittendently
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NewfGuy
New User
Dec 19, 2008, 9:33 PM
Post #1 of 7
(1597 views)
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Fuel Pump Not Energizing Intermittendently
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Hello there,
I have a 1996 Safari with 4.3L that has served me incredibly well. Just about 1.5 years ago the fuel pump suddenly failed for the first time. It happened while driving and had been after it had been getting noticeably noisier. Had shop replace pump and was fine till recently.
Just about a month ago she wouldn't start and I noticed I wasn't hearing the fuel pump energizing with turning the key. Towed to shop and a new pump was installed and worked fine for about two weeks then same problem, wouldn’t start, not energizing, after fueling up at a gas station. Towed to shop and started fine next morning when they went to bring it in shop. They put it on the computer anyway and couldn't find any problems and said had to be not working to really find the problem.
I went ahead and replaced the fuel pump relay thinking that must be the problem and drove it for about a week then same thing wouldn't start one morning, not energizing. Never has happened while driving.
I actually had kept the 1.5 year old pump that was replaced a month ago. and I decided hook it to a battery and sure enough it worked fine. When talking to the shop they said "yah but it wasn't supplying the right pressure when they checked it". Somehow that seems fishy to me because when I was originally stuck a month I could tell the pump was wasn't kicking in period. I wonder if the low pressure thin is a crock and whilst working on it what ever intermittent problem simply righted itself as it has done recently.
The only work that was done just prior to these problems was a new ignition installed that had a new key as well as the guy didn't have the proper tumbler pieces to match my old key.
When I turn the key everything else lights up like it should and the starter turns over just fine but still no pump energizing.
Is there a way I can jump some juice and see if the pump can be energized separately?
Any wiring in the ignition area that is specifically for the energizing of fuel pump he may have damaged?
Is it likely a faulty computer be causing this?
I got under it and moved all the wiring harnesses and cleaned the ground wire and no luck.
Will try tomorrow unplugging the harness connector along the chassis rail and see if power is at least getting to there. I'm a fairly experienced backyard mechanic but electrical is not something I've done a ton of.
Really would appreciate any help as we're having one of our coldest winters on record here in Vancouver, minus 12 Celsius, and I use this for my home based small business.
Thanks and a Merry Xmas!
Glen
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Dec 20, 2008, 12:01 AM
Post #2 of 7
(1594 views)
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Re: Fuel Pump Not Energizing Intermittendently
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Just some ideas and thought Glen:
GM wiring connectors are junk and replacement parts sometimes come with pigtails and are required for warranty. Relays must also be made by a bone head as those are frequently the root cause of intermittent problems too.
Try to make sure wiring plugs for pump are clean - not showing corrosion. Some relays will respond if you tap on them if you catch one down and that works a new one is in order.
Check battery votage and make sure it stays above about 13.5 when running. They don't want plain battery voltage for some things but like the operating voltages. Of course pump should be able to pump full pressure before engine starts.
I know it stinks but if battery is older consider a new one. They just don't age well (IMO 3 years is getting old) and can throw tantrums especially when cold and do intermittent problems like this that you'll never find if they don't stay broken. You just gotta know that the battery is good and staying that way. Is gauge showing steady, even volts when running? Belt properly tenioned - all that stuff counts and won't give you a code but matters.
Merry Christmas to you too!
T
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Loren Champlain Sr
Veteran
/ Moderator
Dec 20, 2008, 1:59 PM
Post #3 of 7
(1588 views)
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Re: Fuel Pump Not Energizing Intermittendently
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Glen; As Tom mentioned, the harness connections at the fuel pump are a known problem. Yes, check to see if you are getting voltage at the pump. But, you gotta be quick , as the fuel pump will only run for a few seconds when you turn the key to the 'ON' position. Also, if you have a helper, you can have them start cranking the engine while you 'smack' the tank with a (preferably) rubber mallet. You may have to smack it rather hard, multiple times with the engine cranking. If it does start, it is more than likely a faulty pump or connection problem, either of which will require dropping the tank. Are you buying GM fuel pumps, or aftermarket brands? We quit selling aftermarket brand fuel pumps 15-20 years ago because they just don't last.
Another consideration; The Vortec motors are very persnickity when it comes to pressure. If it doesn't have 50psi
during crank, it probably won't start.
If you don't already know, you should always keep at least 1/4 tank of fuel. The fuel pump depends on the fuel to keep it cool. And, a plugged fuel filter will shorten the pump life, as well.
Loren
SW Washington
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NewfGuy
New User
Dec 20, 2008, 2:19 PM
Post #4 of 7
(1582 views)
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Re: Fuel Pump Not Energizing Intermittendently
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Thanks guys,
Was a Carter pump that was put in but as I'd mentioned the fact that the old one seems to work fine makes me think this isn't a fuel pump issue but instead electrical. Filter was changed at the time and don't think it has anything to do with low pressure as the pump simply doesn't kick in at all when turning the key to on position. Always has happened after van was shut off, never while running.
I had alreday wiggled all the harnesses,cleaned the ground wire to frame and thumped the tank to no avail.
I'll check with my meter if the harness connector before the tank is getting juice and then check what's getting to the fuel pump relay.
Does anyone know if this could have been brought on by the changing of the ignition? I'm getting power to dash and starter when turning key.
Cheers!
Glen
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way2old
Veteran
/ Moderator
Dec 20, 2008, 3:55 PM
Post #5 of 7
(1578 views)
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Re: Fuel Pump Not Energizing Intermittendently
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Maybe a mis-adjusted ignition switch? Since it doesnt work immediately but comes on later, I just about have to agree on electrical. Maybe even a relay. Not sure just ideas.
Being way2old is why I need help from younger minds
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americanmusclegurl
User
Dec 29, 2008, 7:17 AM
Post #6 of 7
(1555 views)
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Re: Fuel Pump Not Energizing Intermittendently
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i know exactilly what it could be haha .. because it just happened to me in my boyfriends transam .. we put race gas in his tank and it must have been contaminated .. so we had to replace the whole fuel system pretty much lol. so what you need to do is get a new strainer for your fuel system .. if it gets clogged then it will not suck enough fuel through to feed the engine.the second thing that could be wrong is you need to look,at your fuel pump and make sure that the mechanic that worked on your car to replace the pump did not cross the wires on the fuel pump .. if that happens .. exactly what you are describing is what happens haha~. also you should definitly eaither drop your gastank and drain the gas yourself .. its fun actually haha.. just heavy. if you have gas that is contaminated from sitting in your tank for so long it contaminates your whole system .. also if the wires are crossed when you check .. i would just get a new fuel pump .. it probably means your fuel pump is shot
(This post was edited by americanmusclegurl on Dec 29, 2008, 7:19 AM)
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americanmusclegurl
User
Dec 29, 2008, 7:24 AM
Post #7 of 7
(1547 views)
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Re: Fuel Pump Not Energizing Intermittendently
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 your fuel could be either too rich or not rich enough .. if it isnt rich enough .. before you drop your gastank and do all that work .. fi you havnt already .. try adding a fuel additive :) and see if that cleans your system out :) lucas is the best brand :)
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