Fixing the Truck to Death – time to cut my losses?

[GoToGuy]

By manual, do you have the OE service manual? The GM oe service manual is here in the forum it a free download.
You can do a lot of guessing, and random parts changing, that will eventually fix it but at what cost?
Not doing or checking on regular service items leads you down a path to self destruction. This isn't a 64 pickup. It's more complex, meaning some basic test equipment, and correct reference material. The other choice is take it to shop.

 

[PlatonicSolid]

By manual, do you have the OE service manual? The GM oe service manual is here in the forum it a free download.
You can do a lot of guessing, and random parts changing, that will eventually fix it but at what cost?
Not doing or checking on regular service items leads you down a path to self destruction. This isn't a 64 pickup. It's more complex, meaning some basic test equipment, and correct reference material. The other choice is take it to shop.

Yes, I have downloaded the manuals from this forum. Based on the manual I purchased a fuel pressure tester that lead me down the path of replacing the fuel pump only to end up with the same 3lb priming pressure I had before the pump change. Maybe the meter sucks or both pumps suck or there's nothing actually wrong with either pump. I can also drown in the expenses of purchasing various testers that may also be difficult to use for the inexperienced.

Having the vehicle towed to the shop is certainly an option, but once it's there I guarantee I'm not getting it back for less than $1K - running or not. Last time I took it to a mechanic to resolve the always ON brake warning light cost me $750 for him not to fix it.

At this point I'm tempted to get out the sawzall and cut the catalytic converter out to see if that solves the idle issue. If it doesn't, I'm no worse off than I am now.

 

[Komet]

3psi of fuel pressure is absolutely your problem.

 

[GoToGuy]

I would recheck the test gauge. Did you check with the system in normal configuration with just the test gauge in a "T" fitting? Then I would also checked with pressure line capped and what is pressure indicating? Did you read the part about TBI pressure is regulated by a diaphram, if it fails to regulate then fuel just returns to tank ?
Did you check for excessive exhaust back pressure? Yet your gonna whip out the sawzall cause that will fix your problem.
You ever have that time you give someone good advice.

 

[PlatonicSolid]

I would recheck the test gauge. Did you check with the system in normal configuration with just the test gauge in a "T" fitting? Then I would also checked with pressure line capped and what is pressure indicating? Did you read the part about TBI pressure is regulated by a diaphram, if it fails to regulate then fuel just returns to tank ?
Did you check for excessive exhaust back pressure? Yet your gonna whip out the sawzall cause that will fix your problem.
You ever have that time you give someone good advice.

3psi of fuel pressure is absolutely your problem.

My sawzall rant is just me getting frustrated - sorry about that. Even if the exhaust was semi-clogged, it's not running long enough to build up any real pressure. At this point it's turn the key - sounds like a normal start and then almost instantly dies.

Fuel pressure tested with "T" fitting between feed line and filter (before filter) filter is new. WRT TBI pressure regulated by diaphragm, TB was replaced with rebuild, which had no positive effect on the issue.

Diving back into the manual I see it states: "If the vehicle is equipped with a fuel module, the module must be disconnected before performing the fuel system pressure test." That would mean the pump is only ON for 2 seconds at prime. I didn't do that, thus pump was on for 20 seconds at prime. Not sure that makes a difference, but worth noting.

WRT pressure line capped - dead head pressure - It says to gradually pinch the gauge outlet hose (I have no outlet hose to pinch). I suppose I could attach a hose to pinch if it's really necessary. How does one gradually pinch a hose when the pump is only running for 2 seconds? Is there risk of pump damage by just connecting the gauge directly to the pump with no outlet?
If I do that, do I let fuel run through the meter so I'm measuring fuel pressure vs compressed air pressure - or doesn't it matter?

Procedure also states to "disconnect the injector". I don't understand the purpose of that.

 

[Scooterwrench]

You can keep the pump running by jumping the orange and gray wire terminals at pump relay. If you still only get 3psi then the guy that rebuilt the TB screwed up. May want to check the numbers on the injectors to be sure they're 80lbs per hour. Good rebuilders are a crap shoot these days.

 

[PlatonicSolid]

Just checked the dead head pressure and it measures 16psi with air in the line and 19psi when I purge the air out. This made me say WTF, so I put the GM adapter that comes with the tester back in the line to see if it still read 3psi and it turns out the adapter is leaking. So I replaced the fuel pump based on a crappy HF tester (link) and I have no idea what the actual pressure is. Fantastic...not. I guess I can do it the hard way with standard rubber fuel line.

 

[Schurkey]

I replaced the fuel pump based on a crappy HF tester (link) and I have no idea what the actual pressure is.

One of several reasons I won't set foot in a Hazzard Fraught store.

The sale of Tool-Shaped Objects should be a crime.

 

[PlatonicSolid]

The sale of Tool-Shaped Objects should be a crime.

Nicely put. I'm going to use that: HF - Seller of Tool-Shaped Objects. Made the mistake of buying drill bits and calipers from them in the past. I can't complain about their angle grinder or rolling tool storage cabinet though.

I can't put a rubber test line in place of the filter as the filter output line is an old flex line that doesn't have enough solid line to fit a rubber hose over. I'll have to get a different adapter.

When I siphoned the gas out of the old tank, it went into a 5 gallon clear water jug. The gas looked fine and I put it into the cars and tractor until I ran out of places to put it. Then I picked up two 5 gallon gas cans and siphoned the rest into them - this is the gas I put back into the truck after tank replacement. While cleaning up from today's pressure testing it was notable that the gas that I captured while messing with the fuel lines looks separated. I may need to siphon the tank again - get as much out as possible - to see if this is really the case. Yes, I'm now wondering if this whole problem is due to separated gas.

 

[GoToGuy]

Separated fuel is a condition indicator of fuel contamination. If you could get sample into a glass bottle and swirl , whirlpool in the middle. The contaminates will come together and sink to bottom, if it's water type. Then let it slow down , if it's their you'll see it. That's why you use glass.
19 psi is 19 psi whether it's fuel, air, jello, poop. So it compressed, just means it took a second longer, and reduced volume till it became equal to applied force( pump output ).