Cat D4G Air in Fuel System

[roostertn]

I have a 2005 Cat D4G with the Mitsubishi Engine. Have removed the Fuel Tank a few years ago to have it cleaned and lined because of rust problems. Use to have all kinds of problems keeping it running until I did that. The symptom before I had the tank cleaned was it seamed to get air starting in the fuel seperator in the rear and then air would get into the secondary filter. Figured it was sediment in the tank from being rusty. Anyways for two years after cleaning the tank no problems. Then recently it started again. Checked for the obviousl, changed filters and still happens. I have drained the tank and looked inside. Liner material is still intact. Cannot find anything in there that could be floating around inside the tank to block the intake line and possibly cutting off fuel flow. Like I said no problems for two years until recently.

What could possibly be the causes of air in the water seperator filter and the secondary. It is so bad when it happens that when you unscrew the blead screw on the secondary you can hear it the vacum lock.

 

[Bluox]

You have something in the fuel line between the tank and the water separator ,try blowing the line out.
Bob

 

[thepumpguysc]

Yup.. the pumps sucking or TRYING to suck the fuel & cant.. vacuum=blockage.

 

[d9gdon]

My D4G was bad about getting trash into those little elbows right before the water separator that you're talking about. It was a common problem on that series according to my dealer.

 

[roostertn]

When this happen I took a portable air tank out and blew the line and could hear the bubbles in the tank. What I did was took the Water Separator Off and blew air in the center hole. It ran better for a few weeks but then it acted up again. I blew it again.

The mechanic at the equipment place I take my dozer said that maybe the lift pump is weak. This dozer has about 5500 hours of which I have put 3000 of those hours.

 

[Bluox]

When this happen I took a portable air tank out and blew the line and could hear the bubbles in the tank. What I did was took the Water Separator Off and blew air in the center hole. It ran better for a few weeks but then it acted up again. I blew it again.

The mechanic at the equipment place I take my dozer said that maybe the lift pump is weak. This dozer has about 5500 hours of which I have put 3000 of those hours.

This tells us you have something in your tank.
Bob

 

[Delmer]

This tells us you have something in your tank.
Bob

Air can blow out the little stuff like fuzz and tiny bits of vegetation that find their way into fuel and into the tank. You might have a piece of something bigger stuck that won't block fuel until it builds up a dam of little trash that would ordinarily go right through the pump and get trapped in the separator or filter. You can either take the pieces apart and check them, take them apart in smaller segments and blow through them, or get a vacuum/pressure gauge (like $10) and tee it into the suction line to see what happens. Any rubber lines should be replaced.

 

[roostertn]

I will be taking it to the mechanic next week. He did mention rubber hoses breaking down inside. He was not sure where the rubber hoses were in the fuel system of my D4G. My prefix is CFN. It looks like the line coming from the tank to the water separator is steel. When the line leaves the separator and go goes forward it is steel for what I can see but I think I have seen a drawing where the steel morph's into a rubber line moving forward towards the engine compartment. Thanks all for listening and giving your answers.

My name is Ron

 

[Bluox]

If your transfer pump pulls that much vacuum I drought it's bad ,If they change it make sure they clean the tank.
Bob

 

[thepumpguysc]

Good call Bluox.. ya beat me to it.. [#9]

 

[d9gdon]

Those plastic priming pumps on top of the filter separator housings are bad about leaking air into the system too. Unscrew it and check to see if there's trash in the top of the filter housing. Air won't get rid of chunks that are lodged in there.

I agree that you have trash in your lines or tank.

 

[roostertn]

This is the water separator that is on my D4G. The housing this goes into has a hand pump on top of it. Is that the plastic priming pump.

 

[Wastepro]

Like d9g says, the primer plunger can leak air into fuel system if oring/gasket is bad. Easy thing to test and rule out

 

[d9gdon]

Yes it is.

 

[roostertn]

Sorry to ask this hear, but i would like to print this out to have with me when I visit my mechanic. Does anyone here know how I can do the printing?

 

[kshansen]

Sorry to ask this hear, but i would like to print this out to have with me when I visit my mechanic. Does anyone here know how I can do the printing?

I'm assuming you are asking if you can print out this whole discussion? That is a good question! I looked around some but did not see an obvious way to do it.

Maybe some one of the moderators will stop by and let us know if it is actually possible?

One crude way would be to start a text file on you computer and then highlight one post at a time and copy and past it to that file then print from there. If that does not sound easy for you I could do it and then email you the file so you could print it out.
If you want to do it that way click on my name over to the left and when the box opens up click on the "Start a Conversation" and send me an email address to sen it to.

 

[DPete]

Anytime I have had air in the fuel system it accumulated in the filters, there was a slight leak in the fuel line from tank, it would suck air but not leak fuel. Happened on 2 scrapers

 

[d9gdon]

Just hold down the Ctrl button and hit the P key. Then pick which printer that you want to send it to.

 

[thepumpguysc]

I like the ctrl button option!!! Didn't know it existed..
On mine, top left, where it says "file, edit, view, tool, ect.. if you hit "file" a print option will come down..

 

[roostertn]

Update on the problem:

Pressure at Lift Pump is about 1-5psi at best. When they took fuel cap off the tank it had a vacum on it. Tank is not full only got about 10 gallons of fuel in it.

Found one of the lines at the lift pump with a crack in it near the fitting. Going to look at Lift Pump more closely but it looks like a new lift pump might be in order. Does any of this sound right?