Bubble test for compression gases
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Bubble test for compression gases
How about a little discussion on a common test we use to determine combustion gas getting in the fuel rails.
Now I have done this myself countless times but something has always bugged me.
It actually should not work. Not on a stock fuel system. Both fuel banjo fittings have check valves in them.
My question is how does the exhaust gases get in the filter houseing?
Any ideas?
Now I have done this myself countless times but something has always bugged me.
It actually should not work. Not on a stock fuel system. Both fuel banjo fittings have check valves in them.
My question is how does the exhaust gases get in the filter houseing?
Any ideas?
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Joined: Dec 2004
Posts: 4,138
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From: South Weber, Utah
How about a little discussion on a common test we use to determine combustion gas getting in the fuel rails.
Now I have done this myself countless times but something has always bugged me.
It actually should not work. Not on a stock fuel system. Both fuel banjo fittings have check valves in them.
My question is how does the exhaust gases get in the filter houseing?
Any ideas?
Now I have done this myself countless times but something has always bugged me.
It actually should not work. Not on a stock fuel system. Both fuel banjo fittings have check valves in them.
My question is how does the exhaust gases get in the filter houseing?
Any ideas?
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That was my rational at first. However does not a check valve allow flow of anything in one direction only. If gas pressure was greater would it not only force the valve closed tighter?
Thinking out loud.
Thinking out loud.
Logistics Pro
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From: South Weber, Utah
I agree if it were designed to be a 100% shut off but it may just be designed as a snubber/pulsation dampner of sorts where it is not meant to completely stop flow but to stop pressure spikes from the injectors opening and closing.
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I think I found the answer to my own question.
When we test the fuel pump is disabled no fuel flowing in, the check valve is open to allow fuel to come in. Compression gas d ilutes the fuel in the rail doesn't have to starve the filter just the rail.
The check valve is probably spring loaded so it stays open and allows combustion gas to flow into the filter since it is not under full combustion pressure.
Maybe??
When we test the fuel pump is disabled no fuel flowing in, the check valve is open to allow fuel to come in. Compression gas d ilutes the fuel in the rail doesn't have to starve the filter just the rail.
The check valve is probably spring loaded so it stays open and allows combustion gas to flow into the filter since it is not under full combustion pressure.
Maybe??
Senior User
Joined: Apr 2015
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From: Florida
check valves are normally spring loaded closed. the fuel pressure unseats them and fuel can go by.
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Then that would put us back to square one and the bubbles in the filter test shoud not be able to work. But it does so how does it work? If nothing can flow backwards out of the fuel passages how does it get to the filter.
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