Low boost

hesutton · Feb 19, 2018

Macrobb said:
Not in my experience, depending on the restriction. If the fuel being starved is replaced with air, you get big changes(surging, bucking etc). If it's just drawing a vacuum... it tends to just be anemic because the plungers can't push fuel. It also becomes somewhat retarded due to less internal pressure.

That's what I'm saying. There are more symptoms than boost numbers. The truck will not run normally (doesn't have to be complete stalling/dying/surging), but you will notice more than a change in what the boost gauge reads.

This is why I've had a fuel pressure gauge in the cab of my IDI's for the last 12 years. If the truck isn't running right, I quick glace at the fuel pressure gauge and I know if I have a supply issue or not.

Fuel supply issue here could be easily diagnosed if he (we) knew what his fuel pressure was doing when driving the truck.

Heath

pelky350 · Feb 19, 2018

The other symptom would be running slightly off at idle sometimes like the other day it seems like it was gonna die at idle almost misfiring sounding and very quiet.

79jasper · Feb 19, 2018

Well if that doesn't sound like air intrusion, you can call me Santa.
Or its just a junk pump......

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pelky350 · Mar 6, 2018

So another symptom not yet thought about much is if I cruise around town in like 2nd or 3rd at 2000 rpms plus my truck sounds very clattery almost surging and finicky. Doesn't seem to like that much to keep a steady speed with no load on it. I'm not sure if that's normal or not but I don't know if I noticed that before really because I tend to just keep rpms down anyway

IDIBRONCO · Mar 6, 2018

With that information, I'd have to point you back to 79jasper's last post. I'll second it.

79jasper · Mar 6, 2018

And/or A restriction somewhere.

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plywood · Mar 7, 2018

I'm now going with a broken thrust washer in IP.

pelky350 · Mar 7, 2018

Hopefully nothing in the pump it's Not very old only like 1 year from r and d 90cc. I still haven't even had a chance to change my lift pump out been dealing with wayyy to much other life stuff right now unfortunately my truck will have to suffer some for now.

plywood · Mar 7, 2018

There's a wavy thrust washer in there that break sometimes. It wouldn't really be something a rebuilder could predict unless they could be measured for wear. Long shot probably but it happened to me about ten years ago when my engine was in a standard cab.

pelky350 · Mar 12, 2018

UPDATE! Changed out lift pump and line before pump, still now boost low power, but my fuel pressure guage reads very steady and at like 5.5 psi with almost no drop upon reving. I'm thinking something is wrong with my front tank. Or fuel valve. My rear tank is not in use due to leaking it is dry by now. Maybe I need new sending unit and shower head since guage doesn't work and possible clogged shower head maybe even broken i think it's runs out around 1/4 tank but not sure due to no guage. Maybe just run new line and use only front tank?

hesutton · Mar 12, 2018

I don't know man. If your fuel pressure isn't dropping and is pretty steady, but you are still having power/drivability issues...... I'd start looking elsewhere in the system. It sounds like supply is good now.

If you are sucking air, it will act like it. Hard starting, surging and the like. Yes, the tank issue you have need to be addressed, but I'm not sure that is causing your issues.

Heath

pelky350 · Mar 12, 2018

I'm lost on it, hopefully I figured it out soon I've just got a ton of stuff going on lately

pelky350 · Mar 16, 2018

Today took it for highway run and I've concluded it's fueling issues. I got 12 psi out of it this time and it still cleared up. I only had 10 before the change. Something is benign restricted before my lift pump I think. It's got to be front tank issues or fsv issues. My rear tank is out f service due to leaking. I'm considering just changing out front tank and shower head and sender since it doesn't work anyway and possibly replacing the fsv with one from salvage yard just to see if any change is possible from there. if I do that I will have literally changed out my entire fuel system from tank to injectors so why not at this point?

pelky350 · Apr 3, 2018

More recent update. I have "modified" my throttle cable. Removed the spring and removed all the plastic covering where the spring used to sit I can post pictures soon to make I think more clear. But now I have 100% throttle before I guess I only had like 70% estimated and now I have 14 psi wot. It clears up pretty well but I think my new limit isn't the factory exhaust housing and my intake filter set up couldnt be a little better. I think that will account for my 3-4 psi that I don't think I'm getting. Theroitically with my fueling and set up I should be at 17-19 psi. Intercooler, 90cc, stage 1's, and banks dp 4 inch exhaust. I'm thinking is my exhaust housing, and my 3 inch intake piping slowing me down now. It sure does get up and go with being able to hit full throttle now

pelky350 · Apr 3, 2018

Also after fuel pump change my pressure is now constant at 5.5 psi and needle doesn't bounce while idling or drop with throttle. And when I turn off the truck the pressure stays so I think my check valve was bad in my pump. It was only like a year old too.

Low boost

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