1998 yukon, Is my fuel pressure regulator bad?

[OilBurner2003]

Good evening everyone! Long story short, Decided to do a fuel pressure test. Key on is 60-62, Idle is 55-54. When the engine is off it loses about a pound of PSI every 10 seconds, I've had people say that it's my fuel pressure regulator inside the intake manifold. Brand new Fuel pump, we actually thought we fixed the fuel pressure issue but turns out we didn't lol. My question is, Is there a sure way to tell if it's my fuel pressure regulator? I've been chasing rough idle and a misfire for a bit and thought it was injectors, but then I started thinking wouldn't only a couple cylinders be affected if it was only injectors? There's no way they all/1 went bad suddenly! (Although you never know,) Code is P0300, heavy gas smell, rough idle, Looks like it's a 4-5 hour job for someone who's never done it before, It does look simple enough! I hope.

With spark and air being pretty finely tuned, It leads me to this issue, I'm just looking for confirmation that says this is it. Any advice is appreciated! I know I've flooded the Yukon 98 section with my username by now haha.

 

[east302]

What are the misfire counts on each cylinder? A good scanner should be able to show that so you’d know if it is specific to one or more cylinders.

To isolate a pressure loss, and assuming that no lines are leaking, you’d need to put a ball valve in the supply and return lines. One goes in place of the filter, the other in the adjacent return line, disconnecting at the union that GM installed there.

To detect a leak back into the pump, you’d put the valve in the supply, prime it, close the valve, quickly turn off the ignition (since you’re dead heading the pump) and watch the pressure gauge. If it drops, then it’s either the regulator or an injector. If it holds, it’s at the pump.

Move to the valve on the return. Prime the system, close the return valve. If pressure drops, then it’s through an injector. If it holds, it was through the regulator.

GM diagnostic tables for 1998, should be applicable to any Vortec 350…

 

[east302]

 

[OilBurner2003]

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I appreciate this greatly sir! This should really narrow the problem down hopefully. This is why Tahoe Yukon is where I always go looking for answers haha

 

[B-train]

Those spider injectors were known for having issues. Sometimes a good fuel system cleaner can clean them up, but since they are a poppet style, it usually means you need to replace the line to the cylinders with misfires.

Luckily they are pretty reasonable nowadays and the repair isn't too bad. Have to pull off the upper plenum. Depending on mileage and price, just do all 8 while you are in there. Takes only a few minutes each to do.

 

[OilBurner2003]

Those spider injectors were known for having issues. Sometimes a good fuel system cleaner can clean them up, but since they are a poppet style, it usually means you need to replace the line to the cylinders with misfires.

Luckily they are pretty reasonable nowadays and the repair isn't too bad. Have to pull off the upper plenum. Depending on mileage and price, just do all 8 while you are in there. Takes only a few minutes each to do.

Funny you should mention it, I actually would like to Upgrade Fuel Injectors. Would you happen to know of a specific brand that sells reliable ones sir?

 

[B-train]

Just stick with OEM or ACDELCO. Anymore for most repairs I do, I stick with genuine GM or AC Delco. I've been burned too many times thinking I could get by with (name your chain auto parts store here....) I don't want to redo jobs......just done right the first time. Spend the little bit extra up front.

Try VALLEY AUTO PARTS or other online GM stores to get the best pricing. Sometimes you can luck out with specific part numbers on Amazon as well and get genuine GM.

 

[OilBurner2003]

Just stick with OEM or ACDELCO. Anymore for most repairs I do, I stick with genuine GM or AC Delco. I've been burned too many times thinking I could get by with (name your chain auto parts store here....) I don't want to redo jobs......just done right the first time. Spend the little bit extra up front.

Try VALLEY AUTO PARTS or other online GM stores to get the best pricing. Sometimes you can luck out with specific part numbers on Amazon as well and get genuine GM.

Awesome, Thank you!

 

[east302]

I’ve used the GM (Delco) MPFI part for two of mine and had no issues over four or five years. I’d agree - skip the miscellaneous brands that tend to be popping up more frequently now.

 

[OilBurner2003]

I’ve used the GM (Delco) MPFI part for two of mine and had no issues over four or five years. I’d agree - skip the miscellaneous brands that tend to be popping up more frequently now.

Do you happen to have a link to the delco? I seem to only find them for 700$