Factory Chevy trained tech scratching his head on my truck problem.

[RiverRat4]

Background: purchased an 81 K10 with a LS3 vortec swap from a guy cuz it was ohh sooo pretty! Still an acceptable price to me but because I bought it out of a different state, I took it straight to a repair shop and had them go over it for safety issues before the trek back home in her.
That shop:
Rebuilt complete front end to include steering box, all ball joints ends, rebuilt front axle tube and reworked questionable fuel line routing. Removed aftermarket fuel pump and installed new in tank pump, replaced fuel filter, all new fuel lines. Put her on the computer and got her purring nicely.

250 miles later and weeks of fun driving around she started intermittently shutting down, hot/cold no matter, wait a few minutes and she would start up again. Occasionally crank no start, wait a few and she would start like she was ready all along.

Engine blew! Threw a rod through the oil pan. Replaced with another LS vortec 5.3 with new aftermarket harness and ECU.

Same problems now only worse. Crank/no start then start after a few minutes so much more frequent now. She’s in the shop and they are struggling to figure out what’s going on. I replaced the fuel regulator, they are going to replace the fuel filter and possibly the pump. They are saying the cheap Chinese aftermarket Amazon fuel regulator is not regulating so they are talking about replacing it as well after finding 75 lbs pressure at the Schrader valve.

Any spit balls my way would be appreciated

 

[Chevy 88]

Well, if it shuts off like that - then generally speaking its either a lack of spark or lack of fuel. So when it shuts off, immediately hit it with some starting fluid and see if it will fire up and then die. If so, you have a fuel problem.

Test number 2:

Put a permanently installed spark tester on it, and when it randomly shuts off - crank it and see if its sparking.


Then you know what system to troubleshoot.


I mean, it could be something else like timing, flooding, compression, fuel quality issues, a wiring short etc etc, but those are less likely than the basic lack of fuel / spark.

 

[Turbo4whl]

Make the checks @Edelbrock stated. My guess, from your symptoms, cheap junk fuel pump installed.

 

[TotalyHucked]

Threw a rod and 75lbs of fuel pressure sounds like it may have hydrolocked. I'd have the injectors sent out to be flow tested and buy a name brand fuel pressure regulator. What setup is it, an adjustable style regulator with a gauge or is just the "corvette" regulator? LS engines need 58psi of fuel pressure typically

 

[goldpack]

Any spit balls my way would be appreciated

if you have to do this again. ....buy a whole rust bucket that runs great....what I would pick: something 1996-2004.
and plan on keeping it, park them side by side and start transferring stuff. (so you have all the parts to use or compare,...or you can buy better if you want, )

and...in state / out of state tow the project home. (no need to 'trust" a local idiot shop to "try" to make it so you can drive it home. $$$$ ). tires / jacks/ old gas,...electrical gremlins,...all things you can fix at your leisure,...and not pay some dicks to go to the nudie bar on your nickle, knowing they will never see you again.

and as for the fuel problems. ...make sure to check your slow blow fuses / relays. (weird goings on, in the cool of the morning / and heat of the afternoon ..make me think of those $5.00 things.)

 

[RiverRat4]

Appreciate those hindsight words! I will replace the fuel relay. I have one around the garage somewhere. Im wondering if vaporlock might be an issue being that 5.3 is literally stuffed in so far back I cannot get to the cam sensor without removing a chick in the firewall for access.

 

[atlantic3777]

My Vortec engine was doing the same thing and it wound up being the crank sensor. When i removed the old one it had a slight scratch on it. Replaced with a new one and it runs fine now

 

[Ricko1966]

Buy a fuel pressure gauge, next time you are having a die no start,crank no start,check fuel pressure. No or not enough fuel pressure cold cause a no start. I find it very hard to believe that 75lbs is causing a dieing or crank no start.It would run rich. As for hydroloc even at 95lbs of pressure,it wouldn't hydroloc unless you have an injector hanging open. If you have fuel pressure with your crank no start. I would not replace the fuel pump or relay,might replace the pressure regulator,just because it's out of spec. But I'd be looking for other causes. Loosing power to the ECM. Sounds like it's loosing power( electricity + or ground) somehow some where. Whether it's power to the ECM,to the injectors,to the coils,IDK. most sensors won't shut you down they throw codes and create drivabilty problems.

 

[RiverRat4]

Ok rebuilt the fuel delivery system with ac/Delhi in tank pump, ac/Delhi filter both designed to handle a 5.3L engine. Oh yeah, re-replaced the fuel pressure regulator whixh was an Amazon Chinese POS and replaced with ac/delco FPR. While the tank was down, washed it out to remove some rust pieces floating around in there.

She still has her miss priss days of not starting till she wants to but when she runs, she’s running like a banshee! Fuel pressure is consistent at 60-65 during demands and 58-60 during idle.

Im having the engine and transmission pulled in an effort to chase a leak from the rear end somewhere, while the engine is out, I will replace the crank position sensor (CPS) and see if that solves my temperamental start/no start issue. I can’t get to the CPS now because the vortec is jammed in too tight where the CPS cant be removed cuz of the firewall. While everything is out, im wanting to replace the original 3 speed manual with a 6 speed manual. Next spring is gonna be fun when all that is done! Anyone have a line on a manual 6 speed for a 4wD? Im thinking any 99-2004 sierra or gmc anything would probably match up to that 5.3L eh?