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Old 02-21-2021, 09:38 PM   #1
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Fuel tank line leaking at the tank

I have had an issue with power for a while now and I've already done an overhaul but new AFC line check the diaphragm put a new turbo actuator a new turbo still no power it's a 93 5.9 12 valve Cummins so I chase the lines back to the fuel tank and I can see the big main line as a slight crack in it dry rotting I was wondering is it one line or multiple lines? It also looks like the breather line has a leak around it but if it was just a breather line that wouldn't cause power loss I don't believe.... So what are the three lines? and any idea how much it would cost or where to get a replacement line
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Old 02-21-2021, 10:10 PM   #2
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Location: Northern Virginia
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Year: 2001
Coachwork: Thomas x2
Chassis: HDX/MVP ER
Engine: CAT 3126 x2
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I have had an issue with power for a while now and I've already done an overhaul but new AFC line check the diaphragm put a new turbo actuator a new turbo still no power it's a 93 5.9 12 valve Cummins so I chase the lines back to the fuel tank and I can see the big main line as a slight crack in it dry rotting I was wondering is it one line or multiple lines? It also looks like the breather line has a leak around it but if it was just a breather line that wouldn't cause power loss I don't believe.... So what are the three lines? and any idea how much it would cost or where to get a replacement line
Diesel engines use a feed line to the fuel injection pump and a return line from the injection pump or cylinder head. The use of a return line helps keeps the injectors and pump cooled and lubricated. If your feed line has a crack, then it's more than likely sucking air into the pump which isn't good for cooling or lubrication and will cause hard starting and low power. As the feed line is usually under a slight suction, a feed line often doesn't leak fuel while the engine is running. Rigging up a clear piece of hose inline with the feed can prove the presence of air in the fuel.

I do not know what the third line would be unless your bus has hydraulic brakes.
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Old 02-21-2021, 10:26 PM   #3
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Any idea how much or where to find a replacement line? And I do have hydrologic brakes it is hard to start but once it starts it starts up fine and no power you can hear the turbo start to spool up .... but only a few seconds then nothing 65mph top speed petal to the floor when it's always been 75 if I try goin over a overpass I'll drop from 65 to 55-50.....
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Old 02-21-2021, 11:05 PM   #4
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Location: Northern Virginia
Posts: 439
Year: 2001
Coachwork: Thomas x2
Chassis: HDX/MVP ER
Engine: CAT 3126 x2
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Any idea how much or where to find a replacement line? And I do have hydrologic brakes it is hard to start but once it starts it starts up fine and no power you can hear the turbo start to spool up .... but only a few seconds then nothing 65mph top speed petal to the floor when it's always been 75 if I try goin over a overpass I'll drop from 65 to 55-50.....
Then the third line should be a brake line leading to the rear wheels, which should be easy to trace back to verify.

You could try going to the chassis manufacturer, but a lot of this tends to be custom made. Building or repairing your existing line is likely more practical and cheaper. Swapping to "Pushlock" hose is another possibility, it's a popular choice for those doing major fuel system upgrades to their pickups. I've used it to replace my feed line to my 97 F250 as part of an electric fuel pump conversion.

If you suspect a boost problem, you could rig up a boost gauge and go for a drive. You'll have barely any boost at idle, it'll only make significant amounts at high load and maybe only a few psi at cruise. The turbo's ability to make boost is going to be determined by how strong the exhaust gases are moving. If the engine is already running poorly from another condition it'll affect the boost as the exhaust gases won't be as strong. Exhaust manifold leaks will likewise reduce the pressure driving the turbo and a restricted or pinched exhaust can choke the engine.

Also make sure you have no air leaks in the intake piping, even a small leak will rob considerable power. Depending on the size of the leak it may be audible as a hiss. You could have an assistant rev the engine for you as you look for leaks. You may need to manually apply air pressure or smoke to the piping to find leaks.

You said you overhauled the engine, was this low power issue present before you did so?
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Old 02-22-2021, 12:34 AM   #5
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We're in a old ford Amtran ward bus with the stock 5.9 12v 6bt b700 and the engine I hope the picture uploaded ... Sorry the only pictures I could get are from screenshots at the moment the second picture is a sideways pick of the center line I believe is the out line and the third is the farthest back on the tank and that whole area looks damp and the bus has been parked for two weeks ..... But I'm pretty sure that's the breather line hanging off the side and not sure why it would be damp back there.....
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Old 02-22-2021, 06:28 AM   #6
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Year: 2001
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Chassis: HDX/MVP ER
Engine: CAT 3126 x2
The tank could've been overfilled at one point and it came out the breather, I've had this happen on my F250 a few times. If third line just hangs off the edge of the back of the tank and doesn't look like it was connected to anything at one point, then I don't believe that's an issue. Were you counting the apparent breather as your third line, I was under the impression you were counting lines on the frame rail beside the tank instead lines from the top of the tank.

The center line looks interesting, it's too dirty to be certain but it looks like hydraulic hose with a regular coupler on it. Do you have pictures of the crack in the hose or of the front line? Is this is a side mount tank with the filler on the edge of the tank?
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