1998 k2500 4x4 fuel pump problems


rusnamps
07-02-2012, 06:21 PM
Ok, I have a 1998 chevy k2500 with the 5.7L vortech and what keeps happening is my fuel pump stops pumping...I have tried taking it to a dealer and they said that the only thing wrong is the fuel pump and changed it (that pump lasted 2200 miles)......I am on my 9th pump I have tried EVERY brand....it runs perfect for the 1st 15 starts after that you have to cycle the key 3-10 times to build up pressure so it will start. Once started it runs great no fuel problems..let it cool and you have the same problem again...... on the last stages of pump failure you have to spray a 1 sec burst of starting fluid to get it over the hump then it will run....also as it begins to fail the normal whine of the pump gets quieter till it makes no noise at all (at that point it it bad)..if any1 can take a stab at what might cause it to go out so often I would appreciate it.

thanks James

Bob B
07-02-2012, 06:52 PM
Hi,
The wire harness to the pump at the tank has a wire that goes to the frame rail for a ground. has it been checked? Or unscrew it next and check. Clean t5he metal on the frame and the connector then retighten.
My 97 was on the left.
Bob B

rusnamps
07-03-2012, 10:18 AM
I replaced the connector from the pump did not see the ground screw/bolt to the frame, I will look tonight and see if that will fix it.

Thank you for your post Bob.

Schurkey
07-03-2012, 10:37 AM
I am on my 9th pump I have tried EVERY brand....it runs perfect for the 1st 15 starts after that you have to cycle the key 3-10 times to build up pressure so it will start.

Nine pumps and no diagnostic work done?

1. Sediment in the tank destroying the pumps. Thoroughly clean or replace tank. You are replacing the inlet prefilter, right?

2. Electrical supply to the pump is defective. Test voltage (as close to the pump as possible), current, and if possible, use automotive oscilloscope with a "low amps" probe to check pump instantaneous current draw and motor speed.

2B. Earlier vehicles have a known problem with the wiring of the sending unit; perhaps yours also. The wires INSIDE THE TANK on the sending unit get burned from poor design and excess current. Many fuel pumps come with a replacement wire harness. Did your pumps have a wire harness, and was it installed?

3. Plugged fuel filter, or restricted plumbing creates excess pressure; prematurely wears out pump.

j cAT
07-03-2012, 03:17 PM
If the dealership replaced the pump and it failed after 2500miles what did the dealership say ? do you ask for any free fix for their failure to correct this ?

the fuel pressure need be tested. 60-65psi is what is required. when replacing fuel pumps on old vehicles like this the relay also must be replaced. obviously the fuel filter.

the pump to use would be the delphi pump. if this is an air tex pump then this would explain all these failures.NEVER USE AIRTEX.....

WHEN A PUMP IS REPLACED YES YOU DO THE FUEL PRESSURE TEST AGAIN ! make sure all is good.

the frame rail ground next to the fuel tank driverside is the ground for the pump etc...

cut open the fuel filter to examine for contamination.

rusnamps
07-03-2012, 05:28 PM
Ok in reply to Schurky.......I Have had Diagnostic work done on it as well as testing the fuel PSI (before and after the new pump) new is allways around 65psi old is in the low 20s or lower more times then not. The tank has been repalced for shi** and giggles so its not a crap in the tank problem that i know of..........all filters are replaced every time the pump is. Now my first thought was that the return line was blocked making the pump work harder to keep the proper PSI on the return side however according to the dealership that is not the case. Also, I did not list EVERY time that the 3 dealerships in 2 states have run tests on the truck for sake of running on.......but at least 6 full work-ups have been done (i payed for 3 because I kept dealer hopping). Now to reply to J Cat, Like i mention above the filters have all been change or atleast I was billed for them as I was not the one replacing them. I will try replacing the relay and will cut open the "old" filter and see if anything is in it, I am allmost to the point of scrapping the truck but it has under 50k miles on it......Oh and the wiring harness that connects to the pump has been replaced twice as I was told that was a common problem...

rusnamps
07-03-2012, 05:33 PM
I forgot to mention that I Did find the ground and it was a little worse for the wear so I replaced it and sanded the frame where it attaches (it did have continuity so it was not compleatly bad).

j cAT
07-03-2012, 06:47 PM
I forgot to mention that I Did find the ground and it was a little worse for the wear so I replaced it and sanded the frame where it attaches (it did have continuity so it was not compleatly bad).

the return line if restricted will cause high pressures. this is restricted when testing to see if the pump can produce pressure above 65 psi. for a very short time. pinching the return line.

so check the filters for contamination. also find out if the pump was a delphi pump.

the other thing is make sure at all times you keep the tank at 1/4 or more of fuel as this will damage the pump if running low on fuel will overheat the pump.

a bad relay or even a loose fuse socket will cause the pump to run hot and not at the proper speed. so too a bad corroded ground..

since the fuel tank was replaced then debris like a piece of plastic wrap is not the cause of low pressure. one time I had a person find a condom in the fuel tank causing this type issue.

it is possible the fuel tank venting system is plugged up creating a high vacuum. could be cannister or and lines full of charcoal . this occurs from overfilling fuel tank and then parking rather than burning off the excess fuel before it can expand into the cannister . if liquid fuel enters the cannister this is bad..

777stickman
07-03-2012, 07:45 PM
I forgot to mention that I Did find the ground and it was a little worse for the wear so I replaced it and sanded the frame where it attaches (it did have continuity so it was not compleatly bad).

Continuity is one thing. Running volts and amps thru a "not completely bad" connection is an entirely different thing. Sure hope that you get this figured out.

One other thing that hasn't been mentioned is to keep your tank above 1/4 full. Less than that causes the pump to loose cooling from the fuel.

rusnamps
07-03-2012, 08:47 PM
the replacement pump was a Bosh... I have a Delphi that i plan to replace it with....I also just installed a new presure regulator (major pain in the butt to put in) and filter, the old one seemed semi clean when i cut it open. I hope by replacing the pressure regulator and ground connection my problem will be fixed.

Blue Bowtie
07-03-2012, 09:58 PM
Did you set the FPR when you installed it? Most come out of the box a few PSI off the optimal setting. Once the intake is opened, adjustment is pretty easy:

http://www.wwdsltd.com/files/CFIPressureRegulatorAdjust.jpg

Schurkey
07-03-2012, 10:29 PM
the other thing is make sure at all times you keep the tank at 1/4 or more of fuel as this will damage the pump if running low on fuel will overheat the pump.

One other thing that hasn't been mentioned is to keep your tank above 1/4 full. Less than that causes the pump to loose cooling from the fuel.
I see this mentioned frequently, and I do not understand it.

The pump has nice, cool fuel being pumped through the middle--how can it overheat just because the outside isn't submerged?

j cAT
07-04-2012, 07:49 AM
the replacement pump was a Bosh... I have a Delphi that i plan to replace it with....I also just installed a new presure regulator (major pain in the butt to put in) and filter, the old one seemed semi clean when i cut it open. I hope by replacing the pressure regulator and ground connection my problem will be fixed.


with all the different pump manufacturers used, the wiring at the pump and splices into the OEM wiring should be soldered and heat shrink with electrical insulation to insure a good electrical connection for the pump power which does draw a few amps.

the fuel filter should look slightly dark if it has a few thousand on it . remove the filter from the frame and you should see light thru the filter media. it you cannot see any brightness when placing a light at the other side of the media then the filter is restricted. with a filter this little used perhaps the fuel supplier used is to be avioded.

rusnamps
07-04-2012, 08:57 AM
Blue,
nope...i just took the default fpr..hope it won't be a problem, the truck seems to run ok with the new pump in...the pump sounds different then the old bosh, sounds stronger and more consistant. thank you for the pic too, wish i had that yesterday would have saved me a lot of time finding the fpr.

rusnamps
07-04-2012, 09:03 AM
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.

j cAT
07-04-2012, 11:39 AM
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 .

rusnamps
07-04-2012, 12:39 PM
Ok cool thanks J cat, the gas brand is BP more times then not.

j cAT
07-04-2012, 12:59 PM
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.

rusnamps
07-07-2012, 08:23 PM
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?

j cAT
07-07-2012, 08:51 PM
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.

Schurkey
07-07-2012, 09:15 PM
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.

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.

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/tbi/612473-tbi-fuel-pump-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.

j cAT
07-08-2012, 07:53 AM
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 !

rusnamps
07-09-2012, 06:45 PM
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?

rusnamps
07-09-2012, 06:48 PM
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....

j cAT
07-09-2012, 07:18 PM
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.

Schurkey
07-09-2012, 08:39 PM
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.

...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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