Quote:
Originally Posted by 300TDT 1987
Now I'm just getting more confused 
I blew compressed air back into the tank from the hard fuel line.
Changed out all fuel lines again from hard fuel line from tank- primary plastic filter - lift pump.
Still had half fuel volume in primary plastic filter when I let it idle.
Then I got the bright idea that maybe because the car is just idling I'm not engaging the lift pump enough.
Drove around the block once and parked it again.
Before I make my order at Fastlane, I think I may try and drain the tank and check out the tank filter and see if it's gummed up. |
It is perfectly normal for a bubble of air to be trapped in the Pre-filter – in reality it is not trapped there. Air is entering the Spin-on filter continuously as it is flushed out of the Pre-filter. The Spin-on filter is designed to cope with it. The source of the air is fuel foaming in the tank as it sloshes around - ever filled your tank right to the top and had to wait for all the lather to settle?
Once the fuel system has been fully bled it is impossible for air entering the main Spin-on filter to reach the Fuel Pump L/P chamber unless:
a) The filters, tank strainer or fuel lines are blocked
b) You run it out of fuel.
Quote:
Originally Posted by 300TDT 1987
The results where strange, the plastic fuel filter had fuel half way up the internal screen (which has been the case) but there was fuel at the very top of the filter where it connects to the tank line. Not sure why that fuel didn't fall into the filter. (I've been keeping that filter as vertical as possible so it won't suck in as much air.)
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That is quite right what you describe. When you fill a new filter from the “In” end a bubble is trapped inside the screen – air can’t permeate through the fine screen, unless under pressure, once it is wet
Quote:
Originally Posted by 300TDT 1987
Do I need to burb the fuel system or fill the plastic fuel filter with diesel before I connect it.
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Right! Fill it from both ends before you connect.
Quote:
Originally Posted by 300TDT 1987
Not sure if the problem is before or after the lift pump, or the lift pump itself.
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The functionality of the lift pump can be thoroughly checked in less than 1 minute by removing the hose from the steel return line and checking for a steady flow into a can at idle that increases with RPM. Remember well over 90% of fuel by-passes the IP and returns to the tank for cooling. This is also a good check on the state of your filters - a dribble means its time to change them.
Don’t worry about the bubble its best to mount the filter horizontally.