Fuel filter half empty after sitting all night

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Dec 4, 2012 | 12:01 PM

mozzles

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From: Bend, Oregon

Fuel filter half empty after sitting all night

Well I finally did the test today to see whether I have any air leaks in my fuel system. The filter was only maybe half full, does this mean that I have air leaking into the system or fuel leaking out, or both? Where would be some spots I should check and how?

Thinking this could be part of my problem with hard starts in the morning.

Dec 4, 2012 | 12:37 PM

'94IDITurbo7.3

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yes that will cause hard starts in the morning. it has to prime the air out before fuel can get to the injectors.

fuel out=air in.

check return line caps and lines, check the fittings on the filter head, check the fittings at the lift pump. there will be fuel at any spots that are leaking.

Dec 4, 2012 | 02:48 PM

Phy

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From: 8600 ft in Colo

There won't necessarily be fuel leaking out where the air is leaking in; fuel could be draining back to the tank.

Dec 4, 2012 | 06:24 PM

joshofalltrades

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in most cases, the leaks are too small for fuel to come out of most of the time. only a more major leak will allow fuel to leak out. you can either play guessing games like most of us do, or pressurize the return lines to like 5PSI to see if you can find a place that leaks

Dec 4, 2012 | 06:40 PM

akamacgyver

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From: Denver, CO

Quote:

there will be fuel at any spots that are leaking.

As previously stated, this is not always the case. Fuel is approximately six times more dense than air, so it won't fit through all of the places where air can get in. gravity acts on the weight of the fuel in your system and can suck air in which allows fuel to drain back to the tank. Think of it as a straw in a glass. If you keep your finger over the end of the straw, no air can get in, so the liquid is held in the straw. If you allow air to pass by your finger the liquid will drain from the straw. The same concept applies here. A pressure test will cause either fuel or air to escape from any small leaks, but be careful, too much pressure can make a whole bunch more leaks than you started with!

Good luck,

Mac.