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2001 8.1 Running Rough When Hot


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#1 smokefan2214

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Posted 18 July 2010 - 10:36 AM

hope someone can help. I changed my fuel pump last week but i am still having issues. just driving to and from work I have zero issues (12miles each direction). If I get stuck in traffic or have to make extra stops on the way home the truck starts to run like crap! rough idle, horrible throttle response as i was pulling in the driveway yesterday the truck died, but fired right up like nothing was wrong. some times the truck takes a little bit longer to start than normal. The fuel filter was changed as well, the fuel coming from the old filter was filthy, I would say rust. any input would be appreciated.

#2 coloradoSkiCountry

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Posted 18 July 2010 - 11:42 AM

Not sure if the 8.1 was equipped with a fuel pressure regulator, but that would be my next guess. The FPR was very common for crapping out on the 4.8s, 5.3s, and 6.0s, on the GMT-800s.

hope someone can help. I changed my fuel pump last week but i am still having issues. just driving to and from work I have zero issues (12miles each direction). If I get stuck in traffic or have to make extra stops on the way home the truck starts to run like crap! rough idle, horrible throttle response as i was pulling in the driveway yesterday the truck died, but fired right up like nothing was wrong. some times the truck takes a little bit longer to start than normal. The fuel filter was changed as well, the fuel coming from the old filter was filthy, I would say rust. any input would be appreciated.


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#3 dewfpo

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Posted 18 July 2010 - 03:54 PM

Are you getting black smoke from the tailpipe?, soot on the tailpipe? Pull an easy spark plug and check the color.

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Edited by dewfpo, 18 July 2010 - 03:55 PM.

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#4 smokefan2214

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Posted 19 July 2010 - 02:58 PM

replaced the fuel pressure regulator and cleaned the throttle body. everything seemed fine, then i noticed the "service engine soon" light on. went down to vatozone to check codes, 4 codes, all of them said something about the fuel pressure. disconnected the battery for a min, fired right up with no SES light. hope it stays that way!!
As far as the black soot at the tail pipe, negative. havent had a chance to pull a plug yet, playing Mr. MOM right now, I'll check in a couple hours.

#5 jro909

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Posted 19 July 2010 - 10:15 PM

what brand of pump you put in?
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#6 Chevyboy86

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Posted 20 July 2010 - 08:37 AM

did u change the pump urself? if so, did you drop the tank or slide the box back and go from above? i ask cuz ive seen where a guy dropped the tank, were not careful and bent the lines a bit, causing the same issues...might be worth takin a peek at. pray you didnt cuz that job is a PITA!! and also when you dropped the pump in did you clean the top mounting surface good and apply the "special" silicone?? ive changed two of my own pumps on an 00 and an 02. and helped with about 5 other pickups, i ALWAYS recommend to go from above, not risking bending those fuel lines....ive done one by myself in like 4 hours (with the help of a forklift) by takin the box off. its easy. like 8 bolts and like 5 electrical plugs...

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#7 smokefan2214

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Posted 20 July 2010 - 10:19 AM

I was actually thinking that pinched lines was a possibility. guess I'll be dropping the tank to double check. This should be fun the high temp is only supposed to get to 110 today!!

#8 smokefan2214

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Posted 20 July 2010 - 03:02 PM

no pinched lines that i could see. hopefully this crap is over with. we will see in the next couple of days. Thank you guys for all of your suggestions, they all help.

#9 Chevyboy86

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Posted 20 July 2010 - 04:32 PM

If it ran fine before ur pump went and now it doesn't with a new one. It's something to do with the pump or the pump itself...maybe you got abad one...? Or get ur fuel pressure tested, that will tell you. Just sounds like it's losing prime to me. Sounds like a bad pump.

Edited by Chevyboy86, 20 July 2010 - 04:34 PM.

2007.5 Sierra SLT 2500hd Duramax, Loaded, Leather, Sunroof, 6" Lift, DVD, Billet S475/stock twin kit (60psi), Suncoast Gmax-6 tranny built by Husker Diesel, 1058 suncoast triple disc t/c, AFE cold pipe, M/A transfer case brace, EFI LIVE DSP5 by idaho rob, 35x12.5r20 Toyo's on BMF Novakanes, Amp Research Steps, Premier H/U, 3 JL audio amps, 2 JL woofers,  Focal components, Cobalt Gauges, HID's all around, bullet proof bumper, air dog 150 and all kinds of other little fuel mods. Soon - 40 over sticks, S3xx/S475 Fixed Vane twins, Motor currently under the knife! Shooting for 700+  In Loving Memory of TC 84-12
collage

 

 


#10 StoneyPgh

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Posted 20 July 2010 - 04:48 PM

I would suggest having a close look at the crankshaft position sensor. Mine went bad and caused a no-restart if I shut the engine down when it was up to temperature. When it cooled off for 4 or 5 hours, it would start right up.
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#11 smokefan2214

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Posted 21 July 2010 - 04:35 PM

If it ran fine before ur pump went and now it doesn't with a new one. It's something to do with the pump or the pump itself...maybe you got abad one...? Or get ur fuel pressure tested, that will tell you. Just sounds like it's losing prime to me. Sounds like a bad pump.

The truck started running like crap and the pump noise was getting louder and louder, so i replaced it. I really noticed it when pulling a hill and kicked down a gear to bump up the rpms it would run horrible.

I would suggest having a close look at the crankshaft position sensor. Mine went bad and caused a no-restart if I shut the engine down when it was up to temperature. When it cooled off for 4 or 5 hours, it would start right up.

I've been through the crankshaft position sensor deal and this is nothing like it. had it replaced maybe a year and a half ago. I never had to wait 4 to 5 hours though. 1 to 2 minutes is all and ran perfect, till it happened again of course.

#12 smokefan2214

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Posted 21 July 2010 - 08:37 PM

On the way home today, rolling at about 45, when i got into it at about 3400 rpms, it fell on its face, flat, no power, runs fine at lower rpms. If I sit at a long light, when i give it gas rolls forward then starts to pop, fart, no power. pump the gas a few times rolls forward a little bit more, let it sit for a minute, fires right up runs fine til the next long light. pops, barely rolls forward, then dies. of course in the middle of the intersection!!! wait a minute then fires up with me pumping the gas, runs fine the rest of the way home. when I got out of the truck, it reeked of gas.
Pulled a plug, looks like it is burning only on one side, the ceramic actually looks like it is flaking off on that side a little bit.
I actually thought the truck was running great this morning on the way to work, WRONG!!!!

#13 Chevyboy86

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Posted 22 July 2010 - 08:48 AM

Man I bet it's a bad pump, might have dried out an Injector. Not good to run ur truck like that if you know ur having fuel issues. Take it to a dealer.

2007.5 Sierra SLT 2500hd Duramax, Loaded, Leather, Sunroof, 6" Lift, DVD, Billet S475/stock twin kit (60psi), Suncoast Gmax-6 tranny built by Husker Diesel, 1058 suncoast triple disc t/c, AFE cold pipe, M/A transfer case brace, EFI LIVE DSP5 by idaho rob, 35x12.5r20 Toyo's on BMF Novakanes, Amp Research Steps, Premier H/U, 3 JL audio amps, 2 JL woofers,  Focal components, Cobalt Gauges, HID's all around, bullet proof bumper, air dog 150 and all kinds of other little fuel mods. Soon - 40 over sticks, S3xx/S475 Fixed Vane twins, Motor currently under the knife! Shooting for 700+  In Loving Memory of TC 84-12
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#14 smokefan2214

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Posted 28 July 2010 - 12:27 PM

what brand of pump you put in?



Man I bet it's a bad pump, might have dried out an Injector. Not good to run ur truck like that if you know ur having fuel issues. Take it to a dealer.


I used an Ebay fuel pump, which I have used a couple of other times on other vehicles (not mine) and still no problems. I should have known this would happen to me!!! new fuel pump only put out between 42- 50psi. should be 55-62.
Shame on me for trying to save some money on my own vehicle. Never again!

#15 Chevyboy86

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Posted 28 July 2010 - 12:50 PM

what brand of pump you put in?



Man I bet it's a bad pump, might have dried out an Injector. Not good to run ur truck like that if you know ur having fuel issues. Take it to a dealer.


I used an Ebay fuel pump, which I have used a couple of other times on other vehicles (not mine) and still no problems. I should have known this would happen to me!!! new fuel pump only put out between 42- 50psi. should be 55-62.
Shame on me for trying to save some money on my own vehicle. Never again!


see...im not just a pretty face :lol: :confused: :lol: :D

2007.5 Sierra SLT 2500hd Duramax, Loaded, Leather, Sunroof, 6" Lift, DVD, Billet S475/stock twin kit (60psi), Suncoast Gmax-6 tranny built by Husker Diesel, 1058 suncoast triple disc t/c, AFE cold pipe, M/A transfer case brace, EFI LIVE DSP5 by idaho rob, 35x12.5r20 Toyo's on BMF Novakanes, Amp Research Steps, Premier H/U, 3 JL audio amps, 2 JL woofers,  Focal components, Cobalt Gauges, HID's all around, bullet proof bumper, air dog 150 and all kinds of other little fuel mods. Soon - 40 over sticks, S3xx/S475 Fixed Vane twins, Motor currently under the knife! Shooting for 700+  In Loving Memory of TC 84-12
collage

 

 





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