air in fuel line problemI

[Paraglider]

I mentioned the (unlikely) case of having a vacuum in the tank. An easy test for that is to leave the fuel cap off so air can get in easily.

Ive had my own drama yesterday of air in the lines from a faulty hand primer/filter head. At the moment I have by passed the primary filter and I am using only the pre filter.
I diagnosed it with clear PVC hose
When I can get a video uploaded I will show you just how much air it can take before it stalls.
When the air is entering in the fuel lines it moves around a fair bit,it doesn't stay still like you described.

I looked at it today and the fuel goes from the tank to the manual switch to go between tanks to the sedimenter to the primer pump to the main filter to the injection pump. Don't know if that's problematic that it goes that way. Today the line that goes from the manual switch to the sedimenter was visibly damp from fuel and I saw tiny air bubbles coming from it. The line was being stressed from the angle to go down to the sedimenter from the switch and I assume over time and with the nipple putting pressure and the clamp there, it created a tiny hole. I replaced that line, figuring it was a no-brainer. That apparently wasn't the only problem, though, because I'm still getting A LOT of air in the line when I bleed it. When I went to pour fuel back into the tank, the tank definitely had built up air pressure that was released when I opened the cap. I'm including pics of the line from the tank to the manual switch just because (in reverse order of that).

The switch is in the center top. There are three lines off of it. The one on the right goes to the auxiliary tank. The one closest goes to the main tank that the rest of the pictures are about. The farthest that is glistening is the one that I replaced and goes from the switch to the sedimenter.

Where the line disappears, it soon changes to what is in the next photo.

 

[Paraglider]

I just

I looked at it today and the fuel goes from the tank to the manual switch to go between tanks to the sedimenter to the primer pump to the main filter to the injection pump. Don't know if that's problematic that it goes that way. Today the line that goes from the manual switch to the sedimenter was visibly damp from fuel and I saw tiny air bubbles coming from it. The line was being stressed from the angle to go down to the sedimenter from the switch and I assume over time and with the nipple putting pressure and the clamp there, it created a tiny hole. I replaced that line, figuring it was a no-brainer. That apparently wasn't the only problem, though, because I'm still getting A LOT of air in the line when I bleed it. When I went to pour fuel back into the tank, the tank definitely had built up air pressure that was released when I opened the cap. I'm including pics of the line from the tank to the manual switch just because (in reverse order of that).

View attachment 1362709 The switch is in the center top. There are three lines off of it. The one on the right goes to the auxiliary tank. The one closest goes to the main tank that the rest of the pictures are about. The farthest that is glistening is the one that I replaced and goes from the switch to the sedimenter.

View attachment 1362710

View attachment 1362711

View attachment 1362712 Where the line disappears, it soon changes to what is in the next photo.

View attachment 1362714

I just realized that replacing the line with a normal fuel hose probably wasn't the brightest thing to do since the air could be getting in from the manual switch and a clear hose could show that.

 

[mudgudgeon]

Air is compressible, diesel is not. Air in the pump means you dont get the right amount of fuel to the cylinders when needed. In a rotary pump, air compresses affecting the timing advance mechanism, so timing is all screwed up. So you are not only getting an incorrect amount of fuel, your not getting it at the right time.

the video above is from my truck. it ran OK until it was under high load, mid rev range, and it would just bog down, stumble, and blow white smoke out the back. Not great when passing, or pulling up a hill etc.

 

[mudgudgeon]

I wouldn't be too worried about the air in the line when priming, so long as you can prime it and feel it pressurise the line to the IP. excess fuel passes through the IP and back to the tank. If the hose to the IP is higher than the return line, and the tank, I think it will possibly bleed back a little

 

[Paraglider]

Air is compressible, diesel is not. Air in the pump means you dont get the right amount of fuel to the cylinders when needed. In a rotary pump, air compresses affecting the timing advance mechanism, so timing is all screwed up. So you are not only getting an incorrect amount of fuel, your not getting it at the right time.

the video above is from my truck. it ran OK until it was under high load, mid rev range, and it would just bog down, stumble, and blow white smoke out the back. Not great when passing, or pulling up a hill etc.

Boy, you can sure see the air flowing through. Did you have that line going under your hood or something and in through a window?? Was the fuel source on your seat or floor in the front?

 

[mudgudgeon]

the clear line was looped up outside the hood, connected to the outlet of the fuel filter uynder the hood, and straight to the IP, the hood was only half latched down so the hose wasn't kinked. hose was outside.

after seeing the air, I used the clear line to bypass the fuel filter to confirm it was the filter/primer assembly that was leaking

 

[John Galt]

Does your fuel system return excess fuel to the tank or loop it back to the fuel feed pump? If it doesn't return to the tank then there is no way to purge air from the system.

I would suspect that manual fuel switching valve for air leaks.

 

[roscoFJ73]

Does your fuel system return excess fuel to the tank or loop it back to the fuel feed pump? If it doesn't return to the tank then there is no way to purge air from the system.

I would suspect that manual fuel switching valve for air leaks.

The 2H has a bleeder plug on the fuel primer pump.
Paraglider ,have you tried this yet?

 

[roscoFJ73]

I looked at it today and the fuel goes from the tank to the manual switch to go between tanks to the sedimenter to the primer pump to the main filter to the injection pump. Don't know if that's problematic that it goes that way. ]

Ok , I just thought it was logical to put the sedimenter before the fuel switches to stop any nasties getting into the switches. I wouldn't worry about it. Just put it away for another day

 

[Paraglider]

Ok , I just thought it was logical to put the sedimenter before the fuel switches to stop any nasties getting into the switches. I wouldn't worry about it. Just put it away for another day

Success!! It's running! I mentioned yesterday that I went direct from the fuel canister to the lift pump and it ran fine. This morning in the wee hours as my mind was churning, it came to me that I could go from the canister to the sedimenter and see what happens, and then if that got good results, from the switch valve to the lift pump direct. This is basically what you were telling me before. It's just that between the tank and the lift pump I had the switch valve and the sedimenter and so wasn't really thinking about the principle (of isolation). Sure enough, the switch valve direct to the lift pump revealed the problem--air and more air. So then I thought to test it from the tank, I'd by-pass the switch valve to make sure that was it and the only problem. I then started to prime it and it just kept bringing air in and I thought "This shouldn't be happening." So I checked the connection at the sedimenter and it was fine and then I remembered--I never connected the tank side. Once connected and primed, it ran just fine and so I took it for a short spin (got to find my wife to take her back to the shop). You see, my HJ47 has been at a commercial diesel shop for 3 weeks and I finally got tired of their not doing anything because they were always busy with their "bread and butter" commercial trucks, so I turned to you guys to help me out. You guys were the brains and I was the hands. This is a great day! Thanks.

Oh, I did have one other question, though. So I ran the fuel line directly from the sedimenter to the main tank. I had to do this on my back, so I just passed it over the transmission, trying to keep it from touching anything sharp or hot. It's not a permanent fix, but I was wondering is there anything I should be worried about as far as what the fuel line might be touching that I can't see?

 

[Paraglider]

Does your fuel system return excess fuel to the tank or loop it back to the fuel feed pump? If it doesn't return to the tank then there is no way to purge air from the system.

I would suspect that manual fuel switching valve for air leaks.

Yep, it was the switching valve alright. Good logic. I don't know where excess fuel goes yet, but I'll find out.

 

[roscoFJ73]

It's not a permanent fix, but I was wondering is there anything I should be worried about as far as what the fuel line might be touching that I can't see?

Good news. Fuel lines shouldn't be touching anything that vibrates as they wear a hole eventually. If you cant avoid it ,you can put the fuel line inside a larger diameter hose or sheath.
What's this "canister" you mention?

 

[Paraglider]

Good news. Fuel lines shouldn't be touching anything that vibrates as they wear a hole eventually. If you cant avoid it ,you can put the fuel line inside a larger diameter hose or sheath.
What's this "canister" you mention?

ok on the vibration. When I take it in to have some other work that I definitely cannot do, I'll have them look at it more closely and see about clamping it to the underside or otherwise controlling its whereabouts. The "canister" is just a 5 gallon vinyl type fuel container.

 

[John Galt]

Glad to hear you found the problem. Those fuel tank switching valves are notorious for that. It's a common problem with UVO conversions.

 

[Paraglider]

ok on the vibration. When I take it in to have some other work that I definitely can do, I'll have them look at it more closely and see about clamping it to the underside or otherwise controlling its whereabouts. The "canister" is just a 5 gallon vinyl type fuel container.

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Glad to hear you found the problem. Those fuel tank switching valves are notorious for that. It's a common problem with UVO conversions.

UVO? This looked like a really old valve. Hopefully, the new ones are more reliable. I'd like to have both tanks useable.

 

[John Galt]

Used Vegetable Oil in one tank, diesel in the other. It's a common alt-fuel conversion.

 

[mudgudgeon]

Good result