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Engine Specific Info and Questions => IDI Engine => Topic started by: paolomarks on August 11, 2011, 12:13:54 pm
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Hello, I've converted my 82 diesel vanagon to AAZ. The AAZ fuel filter has 4 ports- fuel in, fuel out, then 2 more with a one way valve in the middle. Where do these last 2 connect to? and what is there purpose? Thanks, Paolo
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The return line to the tank
The large lines are the main feed from the tank to the pump.
The fuel returns from the pump to the white plastic fitting on the filter, this valve either circulates fuel back into the filter (if cold) or send the fuel out through the other half of the white plastic fitting and through a hose back to the tank.
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Ok, see if I got this right. Fuel exits the pump and goes straight to the fuel filter plastic fitting/valve where it's either recirculated back to the pump or directed out the outer side of the plastic fitting/valve and sent back to the tank. Is the valve temperature activated? Is the idea to warm up the fuel faster? Does it serve to purge air out of the top of the fuel filter as well? What would happen if you plugged both hoses coming out of the plastic fitting? thanks, Paolo.
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Fuel comes from the tank to the 'IN' steel barb of the filter, out the 'OUT' steel barb of the filter, goes to the injection pump, returns from the injection pump to the plastic valve, leaves the plastic valve and returns to the tank.
Yes, it is temperature controlled, its purpose is to circulate "warm" fuel through the filter at startup to help prevent formation of wax crystals in the filter in extremely cold climates. With today's diesel it is much less necessary than it used to be.
It is a complete PAIN in the butt. It actually doesn't do anything useful in terms of purging air out, in fact quite the opposite. It makes it very difficult to get air out of the fuel system until it has warmed up enough to close and direct fuel back to the tank as it circulates any air in the system right back in to the filter. Even worse they typically do not seal all that well to the filter so they are often a source of air getting in to your fuel lines.
You can safely block off the ports on it, but a better alternative is to find a filter from a different year that did not have that feature. I believe about 1985 is perfect if you are looking up the filter in a parts catalog.
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Sorry for tread jack, but would a old fuel filter cause bad starting?
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Sorry for tread jack, but would a old fuel filter cause bad starting?
oh yea..