I’m running 1.5 psi on mine.

 

It being tied to a hill is the biggest give away. Junk in the tank could be doing it to but usually it won't just happen on a hill. On my friends 3000gt a shop towel had got in the tank and was being picked up every now and again. Only knew something was up at the high-end of the power range because of the wideband. Any damage to the needle/seat or float level would be seen across all situations. Major running issues like after fires and stumble will be your big clues. While you should get a regulator I don't think it's the problem in this case. Also on the gauge install. After you get it running right and have confirmed everything eliminate the gauge if it's a truck you drive a lot.

 

I didn't run mine off the original tank and an inline pump long enough to run into problems. Though mine would of originally have mechanical. Definitely could be that. Maybe after cleaning get a full tank and go to a hill and test.

 

Also how do you have you pump mounted? Is it close to the tank or in the engine bay? Really those need to be gravity feed but if you keep it close it can suck a sort distance.

 

I’m guessing your original pump was mechanical. Try switching back to that and see if the problem goes away.
The 42s is really small for what you’re asking it to do. Especially if mounted in the engine bay. Those small inline pumps need to be close to the tank and mounted level.
I use a 42s to power my Onan generator. Would never try to run my truck with it.

 

A shop towel in the tank?!?! geesh that is nuts to leave in there. Well Fred and Pearce now you have me wondering about the pump location as well. Its smack up against the carb. Also Fred I had my doubts from the beginning with the 42s so they are getting stronger to want to swap it out with a better one. Especially since this issue did not exist before I replaced the pump.... All good ideas! Pearce why do you say to pull the gauge once its running smooth? Would that recommendation also exist on one mounted on the regulator?

 

I've got my electric pump located right on the fender well next to the carb. Not sure what model it is but looks like generic 12v.

 

I see you have the larger particulate filter before and the smaller after there. What engine version is that? Your oil dipstick is on the passenger side. Mine is on the driver.

 

That is weird. As far as I know its got the original 20r.

 

The gauges are pretty fragile and can leak. Big time fire starter. Also @Ivey glass fuel filters are another fire starter.

 

I would do it inline close to the carb. When your done with it throw on a clear fuel filter.

 

hmm I only have one year newer. I know there has been work done on this in the past so I wonder now... how can I tell if this is a 20/22 hybrid?

 

To tell if it's a hybrid look for a 22r stamp on the block with round intake ports on the head.

 

Funny thing about the 3000. Went through a very well know shop for a motor and tune. Was on a dyno and what not. No one knows when it got in there. Might of been the thing to take out 3 engines. And it still had the blue color.

 

So from what I see the 20r block has the oil dipstick on the passenger side and the 22r block has it on the drivers.... Maybe that is why someone scratched off the 20r sticker... i'll look on the block for the 22r over lunch and see if I can find it. Pearce do you know where it would be stamped?

 

https://lcengineering.com/engine-22r-block-head-identification/ this gives you most of it but the stamp I spoke of are blank in this example. I can go look at mine again to be sure.

 

That's it. oh and the 77 did have intank pumps. It wouldn't have a boss on the head for the mechanical if it didn't. Intank pumps do better for dead head systems because they have the fuel keeping them cool. Good thing to do when you clean out the tank.

 

Excellent! its break time

 

Sad, its not a hybrid, it has 20r on the block but it does have a different serial than the vin so its been replaced if I understand it correctly.

 

Just doubled checked mine and its also a 20r lower.