Fuel Filter Standpipe Observation/Question
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FTE Fan
Joined: Jun 2007
Posts: 344
Likes: 1
From: Winder, Georgia
Fuel Filter Standpipe Observation/Question
I have been tracking down several issues with my crank no start problem. While recording data from the ScanGauge, I noticed that at low idle, my mass fuel desired (MFD) numbers were too high. I have been getting values anywhere from 17 - 22. From information gathered here, I know this number should be 7.5. I removed the fuel filter today and noticed that filter standpipe inside the bowl appeared to be broken and missing an oring. The outer plastic piece is hangs on a lip when I push it down. Can I assume that this is allowing the incoming fuel to partially bypass and return to the tank, which would affect the ability to maintain consistent fuel pressure?
A new assembly was ordered and will arrive tomorrow. Has the standpipe design been up updated?
Thanks.
A new assembly was ordered and will arrive tomorrow. Has the standpipe design been up updated?
Thanks.
Hotshot
Joined: Dec 2003
Posts: 15,368
Likes: 121
From: Stuttgart, Ar
Actually I'm surprised you're getting any fuel at all. With a broken standpipe in the secondary fuel filter it should actually be getting NO fuel. The high MFD number is the PCM asking for more fuel because it's fuel starved (in my way of thinking). I bet replacing the standpipe will help you out a lot.
Fleet Mechanic
Joined: Jun 2006
Posts: 1,589
Likes: 20
Actually I'm surprised you're getting any fuel at all. With a broken standpipe in the secondary fuel filter it should actually be getting NO fuel. The high MFD number is the PCM asking for more fuel because it's fuel starved (in my way of thinking). I bet replacing the standpipe will help you out a lot.
The standpipe is just a shutoff valve when the filter is removed for replacement. Not sure why a shutoff valve is needed but I'm sure Navistar has a reason. It has nothing to do with fuel regulation or fuel return. That is done prior to fuel entering the filter.
When I replaced my OEM fuel pump with an AD2, I removed the filter and standpipe from the filter bowl since it was serving no useful purpose and just another point in the fuel system that produces a fuel pressure drop.
DSMMH
Hotshot
Joined: Dec 2003
Posts: 15,368
Likes: 121
From: Stuttgart, Ar
Exactly as I did.......
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