Very likely you will not get fuel gelling at 11* F while trying to start it cold. Your more likely to experience the gelling issue around 0*F or lower when your burning uncut fuel.
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6.2 on its way out?
- Thread starter erasedhammer
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erasedhammer
Active member
Doesnt diesel start to cloud at 32F, and gell between 10F and 15F? All I know was the truck stalled when pulling out of the driveway at 11F. Twice
At least thats what I found on the internet.
erasedhammer
Active member
Just tossin an idea around here, can't seem to find if it would even work.
Why are return fuel lines sent all the way back to the fuel tank? Wouldn't it make more sense to T the return line in to the suction side of the lift pump? Or is there a problem here I'm missing?
Why are return fuel lines sent all the way back to the fuel tank? Wouldn't it make more sense to T the return line in to the suction side of the lift pump? Or is there a problem here I'm missing?
Garagefull
Member
The fuel temps on the return side would be my guess. As far as gelling, I have operated vehicles as low as 20 below zero and have never had a fuel issue.
erasedhammer
Active member
I think I read something about the injection and lift pumps being cooled by the fuel? So I suppose the return line going to the tank is necessary to dump heat into the large volume of diesel.
erasedhammer
Active member
On another note, does anyone know how the fuel flows inside the injector? Just out of curiosity, How does the return portion of the injector work? Does it just blow off fuel at a certain pressure, or does it constantly let fuel flow out at a very low volume?
dependable
Well-known member
Any chance there was a percentage of bio-diesel in the tank? I had some 10-15% bio diesel gell up on me around 15F once.
erasedhammer
Active member
Might have been some 2 stroke oil that could do it
If your fuel gelled/waxed up when you pulled out of the driveway at 11* it would not have started a second time until that fuel was warmed back up or additives were mixed in. I think you most likely had air in the lines.
erasedhammer
Active member
Not surprising then, these old steel lines had been on their way out for a while. I guess only recently the problem started to worsen.
erasedhammer
Active member
Thought the air bubbles were gone as the truck has been running fine and starting easy for the last week, but when I revved the motor it immediately starting having trouble maintaining rpm and stalled twice while driving. RPMs definitely seem to exagerate the ingress of air from wherever the leak is.
I do plan on keeping this truck indefinitely, so I rather not replace the rubber and steel just to have it rot and rust 15 years from now. I will be switching all the lines to nylon/stainless steel braided teflon hydraulic hose with AN fittings in as many places as I can get them.
In combination will also be a bed mounted 50 gallon fuel tank from RDS and total elimination of the under body fuel tank.
I'm tired of seeing this cheap CPE rubber hoses used everything that don't last 5 seconds in practical use...
I do plan on keeping this truck indefinitely, so I rather not replace the rubber and steel just to have it rot and rust 15 years from now. I will be switching all the lines to nylon/stainless steel braided teflon hydraulic hose with AN fittings in as many places as I can get them.
In combination will also be a bed mounted 50 gallon fuel tank from RDS and total elimination of the under body fuel tank.
I'm tired of seeing this cheap CPE rubber hoses used everything that don't last 5 seconds in practical use...
erasedhammer
Active member
Normally I would just go OEM and call it a day, but seeing how annoying the problem is when these fuel lines leak, I'm shooting for as much "over-engineer" as possible.
Do you see white smoke when this happens? Had this happen once and it turned out to be a bad injector pump. It was a LOT of white smoke and wouldn't rev high.
erasedhammer
Active member
No smoke at all, revvs super easy. I've actually been trying to add resistance to the throttle because it's basically an on/off switch.
cucvrus
Well-known member
I am not sure where you are on this project. But if you vacuum tested the feed and return lines and they held vacuum I think the lift pump and hose needs to be looked at. I just completed a no start project that lead me down a rabbit hole that found multiple fuel related issues. Even when I thought it was repaired and resolved it came back and presented a new challenge. I left the customers truck sit for a week and last night I went out and glowed the truck and it fired right up. But if you know nothing of the condition of the lift pump may I suggest you visit that. I could not see this issue on the truck I was working on but I decided the lift pump because I did everything else and when I removed the lift pump and uncrimped the bowl this is what I found. It explained some of the issue. 
This is not something that you see and I learned a lesson now. That cracked diaphragm was only part of the issue. I replaced the injection pump with a rebuilt pump. The truck runs perfect now. I know a lot of dancing and songs are played to avoid getting the injection pump rebuilt but in the end it is the main heart of a good running CUCV. If you have a questionable injection pump the drivability and reliability is always in question. That added to the fact you begin to loath the truck and the amount of time you spend working on it. I know my punctuation and grammar are not always the best in my posts but you get the message. If you are in Maryland I am in Pennsylvania. If you loose the patience. I can offer some assistance. But that requires the truck to be here. Let me know. I have plenty of things to do so I am not looking for work. But I wanted to make the offer. I don't do home remodeling because I can't suit myself with the end results. So I hire someone to get it done. It costs more, but in the end I have a nice job that suits me. Take Care and Good Luck. Getting the CUCV running good requires research and discovery. Don't change everything. Only what needs to be changed and repair everything as you go.
This is not something that you see and I learned a lesson now. That cracked diaphragm was only part of the issue. I replaced the injection pump with a rebuilt pump. The truck runs perfect now. I know a lot of dancing and songs are played to avoid getting the injection pump rebuilt but in the end it is the main heart of a good running CUCV. If you have a questionable injection pump the drivability and reliability is always in question. That added to the fact you begin to loath the truck and the amount of time you spend working on it. I know my punctuation and grammar are not always the best in my posts but you get the message. If you are in Maryland I am in Pennsylvania. If you loose the patience. I can offer some assistance. But that requires the truck to be here. Let me know. I have plenty of things to do so I am not looking for work. But I wanted to make the offer. I don't do home remodeling because I can't suit myself with the end results. So I hire someone to get it done. It costs more, but in the end I have a nice job that suits me. Take Care and Good Luck. Getting the CUCV running good requires research and discovery. Don't change everything. Only what needs to be changed and repair everything as you go.
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dependable
Well-known member
Some related things;
If you want to run metal lines, but not worry about rust, try SUR&R copper nickel line. It is also easier to bend and flair than steel. Summit racing has it. Makes good brake line too.
I had a lift pump turn out to be the source of an air leak recently, which was a first for me. It was not leaking fuel into oil like usual failure, and still had good pressure, but was letting air in on crimp seam around pump.
Just did an IP this week, truck was running great, but leaking fuel out of weep hole at front bottom of pump (bad front seal) this truck had no running problems except for leak, but would have a little air in lines if not run for a few days. This was a very low miles pump that had been rebuilt by Tooele Army Depot in 1992. Goes to show those old seals can fail by age alone.
If you want to run metal lines, but not worry about rust, try SUR&R copper nickel line. It is also easier to bend and flair than steel. Summit racing has it. Makes good brake line too.
I had a lift pump turn out to be the source of an air leak recently, which was a first for me. It was not leaking fuel into oil like usual failure, and still had good pressure, but was letting air in on crimp seam around pump.
Just did an IP this week, truck was running great, but leaking fuel out of weep hole at front bottom of pump (bad front seal) this truck had no running problems except for leak, but would have a little air in lines if not run for a few days. This was a very low miles pump that had been rebuilt by Tooele Army Depot in 1992. Goes to show those old seals can fail by age alone.
erasedhammer
Active member
Lift pump is new. I'll probably end up pulling it to see if the push rod is broken. Bought the truck with a broken push rod and replaced it and the lift pump.