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Old 07-04-2012, 11:39 AM   #16
j cAT
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Re: 1998 k2500 4x4 fuel pump problems

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Originally Posted by rusnamps View Post
Also as far as the wiring I removed the old butt splice and soldered and heat shrinked it as well (as a electrician i hate butt splices) and the filter did not show light through it b4 i cut it in 1/2 however it did not have much if any crap in the gills...it was a light brown color with a few dark green spots.
if you could not see brightness thru the filter media use another gas station... what is the brand name of the fuel you buy ?

I would also check pressures after a month and see how they look compared to todays readings. if slow to rise then replace filter and cut open to inspect for more debris.

buy a locking gas cap .
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Old 07-04-2012, 12:39 PM   #17
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Re: 1998 k2500 4x4 fuel pump problems

Ok cool thanks J cat, the gas brand is BP more times then not.
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Old 07-04-2012, 12:59 PM   #18
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Re: 1998 k2500 4x4 fuel pump problems

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Ok cool thanks J cat, the gas brand is BP more times then not.
I had issue with a citgo gas station several years ago. they had old steel tanks. my filters got dirty fast . after avoiding that station, the problem stoped.

new type tanks should not be a problem.
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Old 07-07-2012, 08:23 PM   #19
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Re: 1998 k2500 4x4 fuel pump problems

Ok, After replacing the Fuel pressure reg, filter, relay, wiring, and pump with a AC delco/ Delphi replacement pump......it shows 24 psi on the fuel rail......new pump it started once ok but after i let it sit all night it did not work again....I thought maybe a voltage problem since it stated with the old pump some times and others i would have to cycle the key .......but i get 12.34 vdc to the pump connector and no volts on the ground (so I think that means it is a valid ground)....new pump 1 start and now it can't pump up more then 24 psi........ i read 2amps on the pump circuit, is it me or did i get a bad pump?
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Old 07-07-2012, 08:51 PM   #20
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Re: 1998 k2500 4x4 fuel pump problems

the fuel pump is running and the pressure is 24psi. if this is correct then what can occur is the pump hose to the lower pick up screen has a leak,this will cause low pressures and many have had this occur on installing a new pump. you could be sucking air instead of fuel.

also remove the fuel filter and hook up the fuel pressure guage to the pipe coming from the fuel pump cycle ignition and the pressure should shoot up over 60 psi and hold. if so the pump is good.

also pinch the return line at the engine/reg area see if the fuel pressure rises above 60 psi. .

post back what occured.
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Old 07-07-2012, 09:15 PM   #21
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Re: 1998 k2500 4x4 fuel pump problems

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Originally Posted by rusnamps View Post
i get 12.34 vdc to the pump connector
12.34 volts with the pump RUNNING???

If the pump was running, but the engine is off, that's nearly 1/2 of a volt of voltage drop. Excessive.
If the pump was not running, the battery is not fully charged. Charge the battery. AFTER the charger has been disconnected for an hour, the battery no-load (open circuit voltage, OCV) should be 12.6--12.7. Then re-test the fuel pump voltage with the pump RUNNING.

If you're getting 12.34 with the pump and the engine RUNNING, you've got close to 2 volts of voltage drop. Totally un-acceptable.

If the testing was done with the pump running and a fully-charged battery, it seems that the pump is starving for proper electrical supply.

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and no volts on the ground (so I think that means it is a valid ground)
Depends on how it's measured. I'd need to see how you're connecting your meter. Proper procedure would be to ground the voltmeter AT THE BATTERY negative terminal.

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i read 2amps on the pump circuit, is it me or did i get a bad pump?
I have thought all along that you had a faulty electrical supply to the pump, that it wasn't any of the nine fuel pumps themselves.

2 amps is far too low. Typical would be 6--7 amps. Sure your meter is accurate?

If you can find a digital oscilloscope and a low-amps probe, you'd have this figured out in no time. See post #2:
http://www.thirdgen.org/techboard/tb...p-upgrade.html

Low voltage, low amperage, low fuel pressure all point to electrical (wiring) problems. Sucking air would not cause low voltage; although it could reduce amperage draw and fuel pressure.

This is why I made the comment about nine fuel pumps and no proper diagnostic work. Glad we're getting that handled now.
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Last edited by Schurkey; 07-07-2012 at 10:00 PM.
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Old 07-08-2012, 07:53 AM   #22
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Re: 1998 k2500 4x4 fuel pump problems

well the school I went to a 12 volt battery sitting at rest fully charged should read 12.6 volts +/-.2volts.

if the engine is not running that 12 volts on the fuel pump connector at the fuel pump sounds extremely good. this when considering its path from the battery thru a relay to the rear of the vehicle .

when cranking an engine the battery voltage will drop to about 9 volts. the fuel pump should still produce enoungh pressure to get the engine started.

what I do to reduce cranking time is to place key to ignition on, wait 2 sec. then crank. that way the fuel pump has the full 12 volts not a lower cranking voltage.

the problem is it is NOT RUNNING !
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Old 07-09-2012, 06:45 PM   #23
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Re: 1998 k2500 4x4 fuel pump problems

Schurkey, J Cat I just tried a test ...proly not the correct way but this is how i did it..took jumper cables from my other car removed the truck connector and attached the hot to the #14 hot wire from a spare pump connector and the gnd to the #14 gnd.. so the pump would run constant..a instant 63psi and the truck started and ran perfect. ..pulling 6.86 amps......so then I hooked up the connector that is wired into the truck...and attached my jumper cable to the ground and the other end of the cable to the battery ground...it worked like a champ..so here is what i think i am going to do......I am going to take a tap and tap the frame with a new lead and hook it into the wiring harness and maybe for kicks and giggles run it too the battery ground as well. any thoght as to this course of action?
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Old 07-09-2012, 06:48 PM   #24
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Re: 1998 k2500 4x4 fuel pump problems

Also, by pinching the return line the psi jumped to the mid 70s before i let it lose..so i think the pump is fine its just the electrical system. I don't know how the 3 dealerships I payed good money to missed it....
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Old 07-09-2012, 07:18 PM   #25
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Re: 1998 k2500 4x4 fuel pump problems

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Originally Posted by rusnamps View Post
Also, by pinching the return line the psi jumped to the mid 70s before i let it lose..so i think the pump is fine its just the electrical system. I don't know how the 3 dealerships I payed good money to missed it....
your an electrican there not ! that why they missed it . when it is an electrical problem in the car body wiring the dealership is not the place to go.

well before you stated 12 volts at the pump ..this may be a bad ground connection.

pinching the return getting that much higher pressure your good with the wiring jumped. also the 6 amp draw sounds good.

now you got to find this voltage drop or bad ground .

loose fuses [bad socket] other thing like this will do it.
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Old 07-09-2012, 08:39 PM   #26
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Re: 1998 k2500 4x4 fuel pump problems

Quote:
Originally Posted by rusnamps View Post
Schurkey, J Cat I just tried a test ...proly not the correct way but this is how i did it..took jumper cables from my other car removed the truck connector and attached the hot to the #14 hot wire from a spare pump connector and the gnd to the #14 gnd.. so the pump would run constant..a instant 63psi and the truck started and ran perfect. ..pulling 6.86 amps...
Sounds good.

Quote:
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...so then I hooked up the connector that is wired into the truck...and attached my jumper cable to the ground and the other end of the cable to the battery ground...it worked like a champ..so here is what i think i am going to do......I am going to take a tap and tap the frame with a new lead and hook it into the wiring harness and maybe for kicks and giggles run it too the battery ground as well. any thoght as to this course of action?
If I'm understanding this correctly, all the voltage drop is on the ground side of the circuit.

Cleaning/re-tapping the connection is wise. VERIFY THAT THE GROUND AT THE BATTERY-to-FRAME cable IS ALSO CLEAN AND TIGHT on both ends.
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