"Fuel Filter" warning light

[Michael Fowler]

I do not have the "Die4sel Supplement" for my truck, so I am asking here.
What triggers the " Fuel Filter" warning lamp? ( '94 IDI turbo)
Here is the full story:
I added 2 gallons WMO to the rear tank, then filled the tank. I drove, using the rear tank, towing my 5th wheel, to Hershey, PA. No problems.
On the return trip today, while pulling a long hill on I 83 South, the " Fuel Filer" warning lamp illuminated. The gauge showed about 1/4 tank of the mixed fuel remaining. I switched to the other )pure diesel) tank, and the light went out in 15 to 20 seconds. I switched tanks to "rear" again, and the light re-lit in about 1 minute. I repeated this switching several times and at various loads--The warning light always came on when pulling fuel from the rear tank. The time varied from 30 to 120 seconds, more or less. The light always went out after switching to the front tank--the time varied 15 to 45 seconds.

I have an aux filter near the fuel selector switch that all fuel flows thru.

What is the most likely cause of the warning light" my aux filter, my main filter or the filter sock?
( There will be no more mixing of WMO on this truck).

Thanks for the help.

 

[EMD_DRIVER]

Mine came on too, when I started running WMO through the system. It is caused by a vacuum, in the line between the filter and the IP. Once I changed the filter, it stopped giving me the fuel filter light.

If you have a new(ish) filter on it, it's recommended that you do a fuel pressure check at the bleed valve on the filter head.

Hope this helps..

Gary

 

[Michael Fowler]

Replacing the fuel filter is one of those things on the "to do" list that I haven't gotten done (yet).
I guess it just moved up the list.

 

[Ironman03R]

I have that problem too, for some reason my 94 dont like WMO. The 86 would run anything, even started ok on it.

 

[Exekiel69]

The filter may be ready to go and the wmo accelerated the process. There is nothing wrong with burning some filtered wmo on every tank.
The fuel filter light means there is a vacuum between the filter and IP = not enough fuel.

 

[HammerDown]

Could running 1/2 qt of two-stroke oil in the front tank ( several tanks) clog up the filter??? Because ever since I started running the 2S oil I didn't get many miles out of the last filter >before the "filter light" flickered on.

 

[h2odrx]

I get something like this on my storke but it is water in fuel light when I shut down too early on the rear tank (mix) but as soon as I start up and run it on that tank it goes out? I still have never seen the filter light on my IDI?

 

[MIDNIGHT RIDER]

Two-stroke oil should have no bearing on filter performance whatsoever.

We have been running a 1-ounce/gallon mix of two-stroke in four seperate trucks for a LONG time with nothing but POSITIVE results.

CLEAN FILTERED used engine oil should run through the filters as easily as diesel-fuel, so long as the outside temperatures are above 40*; below that, the oil does just like it does in the crank-case and begins to thicken; a weak mix such as one-gallon/ten shouldn't even be noticable.


Before any fuel system diagnosis can be made, good fuel-pressure gauges need be installed at key points in the fuel supply stream.

At a minimum, there should be a gauge after the last filter in line and before the injection-pump.

The next gauge should be on the outlet side of the lift-pump, before any filters that are down-stream of the lift-pump.


Injector-pumps depend on the movement of a HIGH volume of fuel, cycling through the return-line system, to cool and lubricate the pump.

When this fuel stream becomes restricted, there may be enough fuel volume that the engine runs as well as ever, but the pump is suffering from lack of high volume cooling/lubing fuel.


Without fuel-pressure gauges, this might not be caught before irreversible damage has been done to the pump.


Also, gauges will show you where any restrictions are, whether it be clogged filter, weak lift-pump, or air intrusion.