George's 2003 Sub "lucky7"

[Georgeb]

The only outlying issue may be how tight the nut is on the pinion. It was pretty loose when I went to take it off. I would say it was maybe around 20-30 lb-ft to get the marks lined up. In approximatly 1/4 turn from there it snugged up. I was holding the yoke with an 18” pipe wrench and using a standard 12” rachet. Probably around 80-90 lb-ft but no more. I don’t believe I could crush the sleeve further by hand so I assume the preload is close to correct. I hope.

 

[Honky Kong jr]

That’s the suck part about crush sleeves over time the loosen up and once crushed and pounded on for 100,000 miles or so they crush a lot easier.

 

[Georgeb]

Hey guys,
Long time no see! I have been busy with life and not much fun. Wife and kids are good and growing. Looking for some help with my 03 Burb. I am at my wits end with an occasional hard start. It always starts right up cold and usually restarts fine within a few minutes of shutting down. When it is at operating temperature and it sits for 15min to an hour it will randomly start hard. It will crank and try to start, kick the starter back and try again. Usually takes two or three tries. Once running it is perfect.

I originally assumed it was the fuel pump check valve or regulator. So, against my better judgment I replaced both before ever putting my pressure gauge on it. Needless to say I still have an issue $300 later. I have since connected my pressure gauge to watch what is happening. Currently my fuel pressure is at spec for the 5.3Z. When it acts up the engine is warm, It will loose fuel pressure slowly after holding steady for 15 minutes and slowly drop to zero over the next hour. If I try to restart too soon it has trouble. let it cool off and it starts up fine. I suspect an injector leak but it happens so randomly I doubt I will find it by pulling the rail and pressurizing it.

Looking for some ideas here.

 

[bucket]

You replaced the regulator on the fuel rail? Those are easy to test for the symptom you describe... simply pull off the vacuum hose after the truck has been running and check for fuel in it. If the diaphragm leaks, it sucks excess fuel into the plenum, making the mixture too rich.

If you give it just a little throttle while cranking, dies it start easier?

 

[Rusty Nail]

@Old77
I forgot this thing even existed lol

Hey guys,
Long time no see!"

Good to see ya.Happy New Year.



"When it acts up the engine is warm, It will loose fuel pressure slowly after holding steady for 15 minutes and slowly drop to zero over the next hour.

Looking for some ideas here.

has this been verified? loses fuel pressure -where?- at the rail ? is it pass. side engine or?
More importantly loses pressure at what rate?
Better yet George, I bet it holds the pressure for exactly 120 seconds after key off
eh?


Seems like I know this one. Problem persisted through '05 I think. Is this the one about the...
well, let me know when u got another $300..
your better judgement indeed!

 

[Georgeb]

You replaced the regulator on the fuel rail? Those are easy to test for the symptom you describe... simply pull off the vacuum hose after the truck has been running and check for fuel in it. If the diaphragm leaks, it sucks excess fuel into the plenum, making the mixture too rich.

If you give it just a little throttle while cranking, dies it start easier?

Yes, replaced the regulator on the rail. I have tried applying throttle but can’t say if it helps or not. It usually starts on the second or third try every time it acts up without throttle. If I get another chance I will try that again and report back.

 

[Georgeb]

@Old77
I forgot this thing even existed lol





has this been verified? loses fuel pressure -where?- at the rail ? is it pass. side engine or?
More importantly loses pressure at what rate?
Better yet George, I bet it holds the pressure for exactly 120 seconds after key off
eh?


Seems like I know this one. Problem persisted through '05 I think. Is this the one about the...
well, let me know when u got another $300..
your better judgement indeed!

I had that coming! Well, at least my fuel gauge reads correctly now too.

I have verified that it loses pressure but I don't know where. When I shut it down the pressure will rise from the running 42PSI to 48PSI and hold rock steady for 15 minutes. It will slowly drop from there over the next 15-30 minutes. I was planning on doing some tests to try to isolate the leak but when I have time it isn’t acting up.

 

[Rusty Nail]

does the truck have the black plastic EVAP mailbox under it?


can you duplicate that drop in pressure timing with the gas cap off?

 

[Georgeb]

does the truck have the black plastic EVAP mailbox under it?


can you duplicate that drop in pressure timing with the gas cap off?

Yes it does. I will have to check if it does. What are you thinking the relationship to the EVAP system is?

 

[bucket]

Imho, that drop in pressure is perfectly normal and doesn't hurt a thing. As long as it builds right quick when you turn the ignition on.

 

[Rusty Nail]

What are you thinking the relationship to the EVAP system is?

costs about $300... sad face

 

[Georgeb]

Imho, that drop in pressure is perfectly normal and doesn't hurt a thing. As long as it builds right quick when you turn the ignition on.

It does and it usually starts right up. In the morning there is zero pressure and she fires up without even priming first. just turn the key.. When it sits for a bit after reaching temperature it will start hard sometimes.

 

[Rusty Nail]

i'm thinkin fuel return.
that's why EVAP and a noted, repeatable TIME. Part of the programming that returns fuel killing the starting pressure. Pressure regulator-switch. sticking . or some similar ****. a frozen pintle.
ya?
$300 plastic mystery Vortex box.


after you exhaust your current line of thought, that's mine.
if you decide you're barkin up the wrong tree, try down the frame rail there.

or you could just swap the gas cap.

 

[Georgeb]

i'm thinkin fuel return.
that's why EVAP and a noted, repeatable TIME. Part of the programming that returns fuel killing the starting pressure. Pressure regulator-switch. sticking . or some similar ****. a frozen pintle.
ya?
$300 plastic mystery Vortex box.


after you exhaust your current line of thought, that's mine.

or you could just swap the gas cap.

I understand what your saying.

My understanding of the fuel system is the pump sends fuel to the rail with is regulated and excess returned by the regulator. When the key is off the pressure should be held in the rail by the check valve in the pump and the return pressure setting of the regulator. There are three paths of normal fuel travel 1. return line, 2. supply line from pump, 3. injectors. I feel it is going in one of these three directions. Hith a new pump and regulator and no change in the issue I was thinking an injector leak.

The evap consists of the vent and purge valves with the purge in the normally closed position and the vent in the normally open position with the key off. Both have checked ok in this state. I was wondering if the evap system was pushing fuel vapor into the plenum but I haven't confirmed or excluded the possibility.

 

[bucket]

I don't suspect the evap system to be the cause. About the worst an evap failure can do is cause a minor vacuum leak and the driveability issues associated with that (would still start fine).

I suspect a faulty MAF, CTS, dirty throttle body or something like that. Maybe a leaking injector, but normally that would just cause a misfire on startup.