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skills4lou

By skills4lou
in Ask A GM Technician

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skills4lou Enthusiast

skills4lou

Posted
Posted

I recently bought a used 98 K3500, 454, 4X4 CC, 108K miles. It fires right up when cold, and if I shut it off and start it right back up. The problem comes when I shut it down after driving a while, let it sit for ~1hr, then go to fire it up. That's when I have to crank for 10-15 seconds before it fires up. It did that on my test drive, and I had the dealer check things out. They said it was the fuel pressure regulator, and replaced it (and gave me a line about it being a $400 fix). :D

I bought it for a song, figuring I'd have to put a little money into it. I'm just not sure where to start spending the money. It's still doing the hard-to-start thing after the regulator swap, so where do I start? It acts sort of like it gets flooded. I'm thinking maybe I've got an injector that's leaking fuel when it's shut off and sort of just dripping fuel into a cylinder. Sound crazy?

If that's the case, can I just get some good injector cleaner and run it through the tank, or do I need to have the injectors removed and cleaned?

Thanks in advance!!

GM-Tech Senior Enthusiast

GM-Tech

Posted
Posted

That does sound like a fuel pressure regulator, and if it has already been replaced, the odds are it's not that. Though we had one just a few weeks ago that one of the techs had put a brand new regulator just several hundred miles before and it was leaking again.

 

Can you put a fuel pressure gauge on it and she what's going on with pressure when this is happening?

 

I doubt it's an injector leaking. Possible, but unlikely.

skills4lou Enthusiast

skills4lou

Posted
  • Author
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The only pressure gauge I have is for low pressure (carbureted engines). How much does a pressure gauge cost, and where should I hook it up? Can the regulator leak into the manifold, causing a 'flooded' condition?

I'm fairly familiar with TBI, but this is the first MPI engine I've owned. Where is the fuel pressure regulator located on the '98 454?

Thanks again! This site is awesome!

GM-Tech Senior Enthusiast

GM-Tech

Posted
Posted

No idea how much a gauge will cost you. There should be a pressure tap on the fuel line near the manifold. Don't see many 454's around here, so I don't have direct experience, but I doubt it's much different than a small block. The requlator is on the main injection housing, internally. Yeah, if it leaks, it'll leak right into the manifold making for a rich condition.

skills4lou Enthusiast

skills4lou

Posted
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Posted

I did have a Firebird with TPI several years ago, and it had a schrader valve on the fuel rail. Am I correct in assuming the fittings will be the same? Also, what pressures should I be looking for? And the last Q for this post, if I fire it up and I'm getting lets say 60psi running, how fast should it bleed down? Thanks again!

GM-Tech Senior Enthusiast

GM-Tech

Posted
Posted
I did have a Firebird with TPI several years ago, and it had a schrader valve on the fuel rail. Am I correct in assuming the fittings will be the same? Also, what pressures should I be looking for? And the last Q for this post, if I fire it up and I'm getting lets say 60psi running, how fast should it bleed down? Thanks again!

 

 

 

 

 

Yep, exact same fitting. Pressure should be 55-62 psi with the pump running (but not the engine running). Make sure you bleed the air out of the gauge, cycle the key a couple times to get max pressure. After the pump shuts off, the pressure shouldn't drop much below 50 psi. It won't hold forever, but it should hold for 5 minutes or so and VERY slowly drop. It will probably never get to 0. If it instantly drops to 0, you have a problem.

skills4lou Enthusiast

skills4lou

Posted
  • Author
Posted

I found the fitting, it's on the front of the engine on the passenger side of the thermostat housing. Should be easy to check, once I get a gauge. Thanks for the help!!

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