What is the purpose of the bleeder valve on top of the CDI fuel filter?
 

On top of the fuel filter in the CDI (and later) there is a valve that can be loosened and tightened. I've read/watched a few tutorials on how to change the fuel filer, but have seen no mention made of using that valve. PO of my car changed the filter many times and never touched that valve.

Is it for bleeding air from the fuel system and under what circumstances might that be needed?

Nothing said about it in the service manual CDROM either.

John :confused:

picture??

It will let you drain off the water collected in the bottom of the filter. Not that I've ever seen water in the fuel be a problem, at least where I am. The electrical connector on the filter is for contacts that can sense water in the filter and set a fault code. FWIW bleeding of the CDI fuel system isn't necessary as they all have low pressure electric pumps.

So let's say that the fault code went off. What would I do to drain the water?

Open the valve a bit, put a hose on the nipple in the center, and turn the key on. Fuel pump will run for a couple of seconds which should be enough to push out any water. Catch it in a clear container and if necessary cycle the key a few more times until straight fuel comes out.

so its a sediment trap for water.

I recall them on old japanese diesel engines, they had a screw type job on the bottom - just unscrew it, catch all the drain in a pan - prime the filter again and start it up.

some even had a basic switch on the tap. once shorted with water a lamp lit up on the dashboard.

Yes they do have the alarm. Under the black cap is an electrical probe assembly. It dips down into the well at the center of the filter. Water shorts the probes and triggers an alarm on the console.

if you turn the key with the valve open and without a hose hooked up, fuel will hit the ceiling......

I can personally atest to this!

:laughing:

:laughing:

A few decades ago I owned an Isuzu I6 5.9 liter diesel, that had an aftermarket Racor brand fuel filter / water separator installed at the fuel tank. Worked great!

I've got a water separator as standard equipment on my 2002 Ford Power stroke diesel 7.3 liter V8. I've never had any residue come out of the manual release valve, nor, water-in-fuel instrument cluster indicator light come in 14-years now.

The warning system is great. most times if you have water it was pumped in when you brought fuel. Typically you might drive away from a station and some miles later the warning goes on.

I really try to stay away from low volume diesel fuel sellers. I even had to change a frozen fuel filter and thaw a frozen blockage in a low spot on the fuel line one winter.

Never ever buy fuel at a place that has a heater running at their pump in the winter. In most cases it is summer fuel that has gelled in their pump.