Trouble with starting

**ajs1978** · 06-16-2008, 06:25 AM

Hello to all!

I have a 2000 GMC Sierra with the 5.3L, 145,xxx miles on it. It's recently been having some troubles with warm starts. When it's cold, as in it sat for atleast half a day or more, it starts right up. But if it has ran within the previous 5 or 6 hours or less, it will take a lot of turns by the starter to get the motor fired up and it will sputter for a second. It does start right up though, every time. Also, it will run at idle just a very little bit rough, like a miss.

I have replaced the spark plugs and wires as well as the fuel filter and tried injector cleaner and none of those things have helped. Has anyone had this problem? I can't seem to decide whether I should try replacing the fuel pump or replace fuel injectors.

Thanks in advance!

**2-bowties&abird** · 06-16-2008, 07:18 PM

Originally Posted by ajs1978

Hello to all!

I have a 2000 GMC Sierra with the 5.3L, 145,xxx miles on it. It's recently been having some troubles with warm starts. When it's cold, as in it sat for atleast half a day or more, it starts right up. But if it has ran within the previous 5 or 6 hours or less, it will take a lot of turns by the starter to get the motor fired up and it will sputter for a second. It does start right up though, every time. Also, it will run at idle just a very little bit rough, like a miss.

I have replaced the spark plugs and wires as well as the fuel filter and tried injector cleaner and none of those things have helped. Has anyone had this problem? I can't seem to decide whether I should try replacing the fuel pump or replace fuel injectors.

Thanks in advance!

i wouldn't think injectors, fuel pump is very likely. i have 140,xxx on my '99 z71 and fortunately haven't had any problems at all but i know from past exprerience with other silverados i have owned that thats about the life span of a fuel pump and other small things as well.

**ajs1978** · 06-17-2008, 03:17 AM

I'm assuming that by checking the fuel pressure(which I haven't done yet) would be a tell tale sign of the fuel pump taking a crap. It does sound a little strange when I turn the key. It sounds like it doesn't prime itself very well like I've heard in the past. I just didn't know if it could be injectors or not since it still has a small hesitation during idle like it's not injecting fuel as well.

**2-bowties&abird** · 06-17-2008, 05:23 AM

yeah thats kind of strange, the hesitation that is. on my old silverado when the fuel pump went up it just totally crapped out on me, no signs of it getting ready to go at all.

**ajs1978** · 06-17-2008, 07:18 AM

Thanks for the help!

I'm probably just going to pull the trigger on the fuel pump and do that. Did you find it easier to drop the tank or to pull the bed off to replace the fuel pump?

**Tim the Tool Man** · 06-20-2008, 03:47 PM

I have a 2001 5.3 Silverado that I am dealing with the same issue. I doubt it's the fuel pump since it starts fine cold. There are no electronics or other components in the pump that should be affected by a warm engine. It seems like it should be a fuel system issue, but it's been too many years since I've been a mechanic for me to make an educated guess. However, it almost seems like the fuel system doesn't maintain pressure when the system is warm, which would make me think it's a pressure control valve. There should be a return valve at the engine to prevent high pressure. if it leaks by, then the injectors may not have enough pressure to operate properly.

I agree with 2-bowties&abird that fuel pumps typically work or fail.

Are you getting any codes on the computer?

**Tim the Tool Man** · 06-20-2008, 04:40 PM

I've checked another site and the tech says to check the fuel regulator vacuum hose for fuel. Then check fuel pressure, then check for a leaking instake gasket. I just checked my regulator and it's spewing fuel like old faithful.

**SPRT2H** · 06-24-2008, 06:33 AM

i have a 00 gmc 5.3 z71 same issues --- bought it w 145000 miles with the starting issues -- fuel gauge would not read int so i replaced the fuel pump assembly for that (was making loud whining noises as well) did not fix starting problem replaced fuel filter - nope - replaced regulator and that just made it consistant --- went from every other time to every time -- truck will int. start on the first attempt but very seldom my fuel mileage is 14.5 on the highway driving 65-75 mph and the performance just isnt what i expected out of it. no faults no warning lights no leaks k&n oem filter

what is fuel pressure supposed to be?
is there any adjustment to it or do they offer an adjustable regulator ?

**Tim the Tool Man** · 06-24-2008, 04:54 PM

I think the fuel pressure should be around 30-35psi. I'm not aware of adjustable pressure regulators or other adjustments to help with starting. The function of the regulator is to make sure the fuel pump has flow. Low fuel flow can damage a pump and potentially vapor lock the pump. Are the symptoms the same. Cold starts are okay, warm starts require a lot of engine turns? Have you checked the intake gasket for leaks. If it's sucking air, then you'll be lean and the truck will be hard to start.

If your pressure is good and you don't have intake leaks, then you may need to have the injectors cleaned, but that's a guess. Have you pulled some plugs to see if the engine is running ricj (or lean)?

You could have a faulty regulator - new parts don't mean good parts.

**SPRT2H** · 06-25-2008, 05:08 AM

Originally Posted by Tim the Tool Man

I
You could have a faulty regulator - new parts don't mean good parts.

that aint no joke ...

plugs and wires are new delco, old plugs looked good on all 8 did that 2 weeks after i picked it up -- didnt change a thing performance, starting, or mpg --- starting condition does not matter hot, cold, no matter how long you crank on the first key cycle it will not start sometimes it will sputter but will almost always fire on first hit of second key cycle ---

thanks for the help

**Tim the Tool Man** · 06-25-2008, 05:04 PM

"Poor fuel economy, hard/no starting first crank, performance below par, no codes".

Poor mpg: that should be a rich or lean problem. Rich creates excess CO and should set critical codes. Lean, results in lack of power and low economy but no CO. You should have high NOx with excess O2, but the egr system may be masking that - you probably wont get a code for a lean mixture. A lean mixture would also account for had starting like a carburated engine without a choke. I'm guessing at some of this because I haven't been a professional mechanic since the late 80's (decided engineering was the path I wanted).

I would guess fouled injectors if there are no intake or vacuum leaks. One other issue you could have is a fouled catalytic converter, but I think that is pretty rare plus I think the O2 sensors would catch that. If your egr system is stuck open, then the recirculation could create a similar problem or at least account for hard starts, but that doesn't account for starting on the second crank plus most of these systems should fail closed or at least that is my experience.

If you've checked the intake/vacuum system/gasket and found no leaks, then you might try cleaning the injectors or having them professionally cleaned if you don't have the equipment.

My best suggestion is to spend a few dollars at justanswers.com (http://car.justanswer.com/). They claim to have ASE certified techs making a few extra bucks and they helped me evenhtough I diagnosed my problem, but was too dum to act on it (I had no idea they were still running vacuum operated pressure regulators).

If you choose to go to JustAnswer I would like to know what they said and what you find just in case I run into the same problem.

**SPRT2H** · 07-12-2008, 07:32 AM

havent tried justanswer yet but i did check my fuel pressure -- 0 on first crank would build up on second crank and finally fire at 10psi and be grumpy ... swapped relays then on first key switch on 20psi --- so bad relay for starting issue (yes forgot to check the simple stuff first) -- but still have a feul pressure issue -- at idle im running at 14psi higher rpm no more than 19... block off fuel line return and get up to 35psi ... it ran for several minutes with fuel return blocked and never went over 35 --- working on that issue now ... will keep you posted

**SPRT2H** · 07-12-2008, 07:56 AM

p.s. did find an adjustable regulator

made by accel pt #74750

**Tim the Tool Man** · 07-20-2008, 03:33 AM

Thanks for the info. It's easy to skip the KISS principle. I know I've done it a few times and then kicked myself. I'll keep the part number handy for when I need one.

Thanks again.

**ajs1978** · 07-30-2008, 07:25 AM

That's what my problem was, fuel pressure regulator. It had an internal leak, which is why I never saw any fuel spilling outside anywhere. I replaced that, and now, fires right up everytime.