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Original line lasts 20 years cause it’s made with quality, new stuff ... who knows ....
 

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Hi TundraWolf,

Sorry I did not read this any sooner.

A cheap and fast way to isolate your faulty injector(s):

Before going through the hassle of pulling all injectors and overhauling them, try this:
Remove all the rubber return lines on one end and plug the open end of the tube; start at the rear injectors and work to the front.
Now push a good length of clear tubing onto the injector fuel return pipe and do this with all 8 injectors; about 6Ft length of clear tube each, but remember to use exact same lengths of tubing for each injector!
Run each tube as high as possible, run them to the highest possible point under the open hood and hang them in a loop there, coming back down with the other open end hanging into a clear jar or measuring cup or alike; one for each of the eight clear tubes.

Start the engine and let idle.
Immediately you will see which clear tube is filling up unusually fast and eventually starts spitting out fuel into the jar. This is (these are) the ones needing your attention and overhaul!

A cheap and fast way to diagnose faulty injectors...

Hope this helps!?!
Best,
Jake
 

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Discussion Starter #23 (Edited)
Hi TundraWolf,

Sorry I did not read this any sooner.

A cheap and fast way to isolate your faulty injector(s):

Before going through the hassle of pulling all injectors and overhauling them, try this:
Remove all the rubber return lines on one end and plug the open end of the tube; start at the rear injectors and work to the front.
Now push a good length of clear tubing onto the injector fuel return pipe and do this with all 8 injectors; about 6Ft length of clear tube each, but remember to use exact same lengths of tubing for each injector!
Run each tube as high as possible, run them to the highest possible point under the open hood and hang them in a loop there, coming back down with the other open end hanging into a clear jar or measuring cup or alike; one for each of the eight clear tubes.

Start the engine and let idle.
Immediately you will see which clear tube is filling up unusually fast and eventually starts spitting out fuel into the jar. This is (these are) the ones needing your attention and overhaul!

A cheap and fast way to diagnose faulty injectors...

Hope this helps!?!
Best,
Jake
An interesting hypothesis, however I don't see how this takes into account pintle vs.seat leakage. Is it specifically for wave washer leakage?

I have removed my bed but the dual fuel tank connection's remain under the cab...the cab resting bolts are so incredibly tight I don't know if they can be removed? Can I replace those lines surgically under the cab?
 

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It can be done if you reach them. Why can’t you unbolt the tank switch valve and drop it down?
 

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Discussion Starter #25
It can be done if you reach them. Why can’t you unbolt the tank switch valve and drop it down?
I actually removed the bed,the lines are so far under the cab I don't know if I can reach them to replace the lines,it looks like someone already tried changing them out, cheap hose clamps, looks like there's fuel on them.

I tried taking the bolts out of the back of the cab, I even tried using my 650 ft lb impact driver to try and remove it, I haven't used a cheater bar yet but any idea what those bolts are torqued at? How to get them out so I can lift the cab and get to the lines?
 

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I actually removed the bed,the lines are so far under the cab I don't know if I can reach them to replace the lines,it looks like someone already tried changing them out, cheap hose clamps, looks like there's fuel on them.

I tried taking the bolts out of the back of the cab, I even tried using my 650 ft lb impact driver to try and remove it, I haven't used a cheater bar yet but any idea what those bolts are torqued at? How to get them out so I can lift the cab and get to the lines?

I'd be careful trying to loosen those cab bolts, GM didn't put much of a weld on the nut in the cab and they end up spinning. If that happens then you have to cut holes in the floor to get at the nuts.




You should be able to get at those lines without doing anything with the cab.

http://67-72chevytrucks.com/vboard/showthread.php?t=396114

 

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Discussion Starter #27
I'd be careful trying to loosen those cab bolts, GM didn't put much of a weld on the nut in the cab and they end up spinning. If that happens then you have to cut holes in the floor to get at the nuts.




You should be able to get at those lines without doing anything with the cab.

Dual fuel tank photos? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Any chance I can get in there and weld the nuts a bit better? The heat might help loosen the bolt, too. Theres quite a bit less room under my cab than in those pictures, even when I use a 6x6 and a jack to force it up a little...
 

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Yup gm engineering ... few more bong riiieeps .... let’s design a truck !!

Be very careful trying to undo those cab bolts or you’ll be cutting holes through the floor cause they go into blind pockets .... see above ...

Do you have access to an impact? Ratting them looser, then tighten....can pop em loose compared to breaker bar and cheater pipe which ripes things apart.

I personally would drill a 1/8in hole from the top or side and spray in lube. My personal nut buster recipe is 50/50 atf & acetone .... beats anything on the market. Dab of rtv to plug the hole after.

Ya if those lines are wet, you gata get in there and replace em, I know it sucks .... see above ...
 

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Discussion Starter #30
Okay, awesome, I was able to remove both lines and replace the 1\4 return line with fuel Injection hose clamps.

Do you know what size the main fuel line is? Napa said the biggest they had was 5\16 inch and it's definitely bigger than that. I couldn't get it on and don't want to stretch it that bad I don't want to have to do this again in the future... Also where could I buy larger line? The dealership?
 

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Discussion Starter #31
Turns out the guy was wrong they had 3\8 and 1\2 fuel lines my guess is 3\8 I bought 3 feet of their best stuff pretty sure this is the right size, I'm done for the night.
 

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I personally would drill a 1/8in hole from the top or side and spray in lube. My personal nut buster recipe is 50/50 atf & acetone .... beats anything on the market. Dab of rtv to plug the hole after.
..

This sounds like a good idea, can't hurt any and would actually help with rust prevention.
 

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Discussion Starter #33
I actually was able to secure the lines without removing the bolts, I replaced all suction and return lines on the suction side. The switching valve and several of the lines looked like they had an old leak and we're a bit wet, especially on the main output line. Pictures enclosed.

So I realized that modulating the cold advance solenoid would let bubbles escape the housing, whereas just leaving it on did not do this. I modulated it until no more bubbles were visible, but...

I decided to test the output from the electric pump before the filter, and a whole bunch of foam and bubbles came out before the fuel turned clear.

I replaced the fuel filter and opened one of the outlet ports, the pump ran for a while until fuel finally came out, but when I first removed the output plug, a bunch of foam and bubbles also flowed out.

I will have to Install a half inch ball valve (it's 1\2 npt) on that output for bleeding purposes.

So, apparently, I had a TON of trapped air in the aftermarket fuel filter (there is no bleed but I will install one) so maybe that was the problem all along. I still haven't rebuilt the injectors yet but will probably do that tomorrow.

If I were to install a manual bleed valve, should I tee it off from the actual output fuel line to the IP, or at the top of the fuel filter housing? What would be more efficient?
 

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Nice job, that electric pump should be back by the tanks though.
Electric pump like to push instead of pull.


I would put the bleed T on the line to the IP that way you would know all the air is out of the filter.
 
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Discussion Starter #35
Okay you had the same idea as me, let the air bleed out into the return line.

So I did that, rebuilt the injectors, cracked the lines and cranked it for a bit, tightened the lines, and she fired up pretty fast, had the studs removed for the air cleaner and a plastic tray in case of runaway.

Well, it's never sounded so smooth, but there is an issue of bubbles popping out of the cold advance valve on the top of the IP.... I bled the air out until I saw no more, thought it seemed some remained for a long time.

I hope this air I am seeing is just residual from the system being opened like I had it.

Engine is running very smoothly. Let's hope it starts tomorrow morning, I will turn the key for the fuel pump to run and crack the air bleed line to see if I'm still sucking in any air bubbles, but if I am I don't know where from.
 

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Discussion Starter #38
I haven't checked the system yet, I will after I wake up and get coffee of course.

I think I'll power the pump up with the bleed line open and see if I see air... Right? Because it shouldn't siphon back into the tank, right?

Yesterday while it was running, a time would go by when the outlet from the cold advance on the IP had no visible bubbles, then periodically a small bubble would pop up, and then more small bubbles, and then periodically a whole mass of bubbles would be expelled suddenly, then more periodic small bubbles. If I have a leak somewhere I literally don't know where.

I guess I can also try switching tanks and see what happens, there. Also, the filler nozzle where the gas caps screw, are both open and rags stuffed in them (not sealed) could this be having anything to do with it?
 

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Discussion Starter #39
Nice job, that electric pump should be back by the tanks though.
Electric pump like to push instead of pull.


I would put the bleed T on the line to the IP that way you would know all the air is out of the filter.
I have heard they like to push rather than pull, is there any issue with keeping it where I have it? Would I put it on the output from the tank switching valve instead? I could do that, but it seems to be working pretty well, unless cavitation is causing the air bubbles to form?

Also, is the cold start advance in play when the solenoid is powered on? Or off? Because the engine sounds "meaner" with it on? If that makes sense.
 

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Discussion Starter #40
I looked it up, the advance is active when. The solenoid is on.

Okay so I forgot to remove the jumper to the cold start advance solenoid, and it was on all night.

But, I powered the pump on, and opened the bleed, and I didn't notice any bubbles... I guess that's a good sign?

Well, hard starting again. It ran so well yesterday. I was so hopeful. I have no idea what to do, now.
 
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