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5.3 troubleshooting

bigbadchev84

bigbadchev84

1/2 ton status
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May 17, 2004
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Hermiston, Oregon
I will start this off by letting everyone know I am a carb guy and this injection stuff is beyond me as of now.

We bought a 2000 tahoe a year ago and had no problems with it. We just payed it off a couple months ago so of course I am starting to get some problems with it.

My biggest problem is when starting it. 90% of the time when it has reached driving temps after driving it and shutting it off it has to crank a bit before it will fire, then when it does it goes to about 500rpm and then dips way down to zero, sometimes it catches itself sometimes it dosent and dies.

Most of the time when I am cranking it i have to give it gas as well to get it to fire.

On cold starts it will almost always fire right up just reaching in and bumping the key. everynow and then it will fire and die immediatly, then it takes a while to crank to get it to run.

I just replaced the engine temp sensor today and still the same problem
 
I will ask a drive ability tech at work tomorrow, I think it's the TPS (throttle position sensor)
 
Pull the vacuum hose off of the fuel pressure regulator, if any fuel comes out of the regulator or hose then the regulator is bad and needs replaced. The diaphragms leak and force fuel into the vacuum hose which then floods the motor with fuel and causes the long crank time. Most parts stores should have them for around 70 bucks. Takes about 2 minutes to replace.

The only other thing I see that causes a long crank time when warm is leaky injectors but not near as common as the regulator.
 
bigblock72 said:
Pull the vacuum hose off of the fuel pressure regulator, if any fuel comes out of the regulator or hose then the regulator is bad and needs replaced. The diaphragms leak and force fuel into the vacuum hose which then floods the motor with fuel and causes the long crank time. Most parts stores should have them for around 70 bucks. Takes about 2 minutes to replace.

The only other thing I see that causes a long crank time when warm is leaky injectors but not near as common as the regulator.
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Where is it located?

Also forgot to mention that it has a very slight rough idle, not terribly bad, but I notice it sitting at stoplights and whatnot. After it is started, it runs great and has good power too.
 
bigbadchev84 said:
Where is it located?

Also forgot to mention that it has a very slight rough idle, not terribly bad, but I notice it sitting at stoplights and whatnot. After it is started, it runs great and has good power too.
Click to expand...



The regulator is located on the driver's side fuel rail. http://www.summitracing.com/parts/SMP-PR217/

The additional fuel from the leaking regulator will cause a slight miss (usually cyl 4) at idle, you definitely have all the symptoms I would expect to see with a bad pressure regulator.
 
I asked him and he seems to think it's the intake gaskets. Spray some carb cleaner around it and see if it changes rpm.:D
 
Intake gaskets are also a common problem but they cause a rough idle and hard starting when cold and no real noticable problems when hot.
 
bigblock72 said:
The regulator is located on the driver's side fuel rail. http://www.summitracing.com/parts/SMP-PR217/

The additional fuel from the leaking regulator will cause a slight miss (usually cyl 4) at idle, you definitely have all the symptoms I would expect to see with a bad pressure regulator.
Click to expand...


Nice Call! I went out there and pulled the hose off of it and a teaspoon or better of fuel poured out of the vacuume hose.

Ill pick up a new one and another set of plugs for it this week.

What is a good set of plugs to run in it? I believe when we first got it 12k miles ago I put some ac delcos in it.
 
Delcos only! but they are not cheap like 8 bucks a plug. GM's recommendation for the factory plugs is to be replace around 100k
 
Factory plugs are long gone, with all the extra fuel being dumped in the motor I figured it might be wise to get these plugs out. I guess I can change the regulator and see how she goes from there.
 
I prefer to run the Denso iridium plugs, they are actually the OE plug on the newer trucks. They come pregapped at .045, don't open them up to .060, they work very well and last longer then the platinums.
 
bigblock72 said:
I prefer to run the Denso iridium plugs, they are actually the OE plug on the newer trucks. They come pregapped at .045, don't open them up to .060, they work very well and last longer then the platinums.
Click to expand...

thats it, I was trying to remember it but figured they were platinums.
 
Ok I have put this off forever now, But just put a new regualtor in three days ago. Runs alot better, but started making a funny noise today. Almost like when the water faucet is partially on and makes a noise like the water squeezing by the valve.

I crawled under it and can feel it in the fuel filter everytime it makes the noise. Just picked up a new filter tonight and will install tomorrow. The fuelpump has always made the whinning noise.
 
Just an update for others to learn at my expense.........litterally.:doah:

The weather has been crappy up till recently and my 67 was in the garage getting bodywork done. gave the wife my truck and sstarted dd the blazer to work. I finally got the 67 done and out of the garage and pulled the tahoe in.

After replacing the fuel pressure regulator and it started making wierd noises I was hoping to find a bad fuel filter........no such luck. I figured it had to be a fuel pump that couldnt keep up anymore...it had been whinning anyways. After 2 trips into napa and then some research online I found that the new delphi pump from napa that had the wrong electrical connections came with a new electrical pigtail that needs spliced in........should have dug into the box a little more.

I got the new pump in and went to fire it up.......it was making the same noise as before....so I guess i can chalk the $334 fuel pump up to preventative maintenece, The wife was not happy. So back to the fuel pressure regulator....it had to be a bad one out of the box...after all it started making the funny noises after I installed it. So I ordered a delphi one from napa for $63, I didnt return the old $80 napa brand one since it had been a couple months and I couldnt find the reciept.

I got the new FPR and pulled the old one out, I noticed the old one didnt have a very small O ring on the end of it like the new one. I pulled out the dental pick and pulled out 2 small o-rings from the fuel rail. Thats right you guessed it, I missed the origainal o-ring when I replaced the fpr the first time:doah:

So its back on the road and running like a champ now.





The wife is not impressed with my diagnostic skills, that was a spendy o-ring
 
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