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Fuel Filter Question?
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74M35A2
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I have not checked the TM, but the only way this canister will drain from the bottom valve on my truck is if I depress this top mounted Schrader valve to actually allow air into the system.
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The valve on the bottom of the filter can is for draining the water out of the filter.
74M35A2
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This we know. What is the top one for? I have only found one use for it so far...
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LOL, I guess I miss read it. I use the top one when you open the bottom one, helps it drain. Some of the A0 and A1's do not have the top one.
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Anyone have pictures of this valve stem? I don't see one on mine, or a place where one could be installed. I don't see how it could be used for priming, unless there's a check valve between the filter and the tank and you pumped diesel into the stem.
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Thinking about it, I guess if you pressurized the tank, you could bleed the air off the filter with it. I've never found it necessary though...
gimpyrobb
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Is it truly a Schrader valve? I guess you could un-screw the valve and use a vacuum gun to prime it with.
74M35A2
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It is.
I never understood how people pressurize the fuel tank. Isn't it vented? Also with it's large surface areas, even a few PSI would blow a wall of it out.
The more I think about the potential leak areas of this filter, the more I don't like it and want to remove or replace it with a spinner.
I never understood how people pressurize the fuel tank. Isn't it vented? Also with it's large surface areas, even a few PSI would blow a wall of it out.
The more I think about the potential leak areas of this filter, the more I don't like it and want to remove or replace it with a spinner.
red
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It's a proven method for priming the fuel system. Even on brand new class 8 trucks and equipment.
74M35A2
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I'm not against it, just don't understand how it is done. How is the tank vent handled? Easy to say block it, but do people really do it? Just blow more air in than what the vent can relieve? Makes sense if so.
OTR (Over The Road) trucks typically have cylindrical tanks. M939 tanks are rectangular with large flat surfaces. Even 2psi is huge pressure against a wall and may cause it to bow or "oil can".
Cummins ISX engines have an electric lift pump on the engine mounted fuel distribution manifold. A lot of other engines or filters have a mechanical priming pump, including the 6CTA8.3. Every diesel engine we are testing here at work has a pump of one sort or another. Not sure why people are blowing air into fuel tanks if this hardware is present and operational.
I think the Schrader valve is to vent the canister during water drain.
OTR (Over The Road) trucks typically have cylindrical tanks. M939 tanks are rectangular with large flat surfaces. Even 2psi is huge pressure against a wall and may cause it to bow or "oil can".
Cummins ISX engines have an electric lift pump on the engine mounted fuel distribution manifold. A lot of other engines or filters have a mechanical priming pump, including the 6CTA8.3. Every diesel engine we are testing here at work has a pump of one sort or another. Not sure why people are blowing air into fuel tanks if this hardware is present and operational.
I think the Schrader valve is to vent the canister during water drain.
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If the truck has the vent on the intake stack, just use that. I have used it a number of times.
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The top air vent. Can use used by letting air out for the bottom plug or to pressurize the fuel system from the tank or to put a vacuum pump to suck Air from the system they all work
red
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Those electric lift pumps from the manufacturer only have enough suction if the fuel filters are full and the fuel lines have absolutely no air leaks. Once the lines are about 6-12 months old they can't prime a empty system anymore. Alot of my roadside calls as a mechanic was for that.
Personally with priming the system I remove the return line fitting and pressurize the tank from there. Then take my finger and use it to cover the vent line. Does 2 things this way. 1. I can visually see when the system is primed because fuel will be coming out of the return line. 2. Easy to quickly reduce the pressure on the tank.
You're not cranking the fuel tank up to 120 psi. 5 psi is enough and the tank won't split or deform from that.