Recently, I noticed a bunch of air in my pre-filter on my duralift e-pump. It was usually about 10-15% air. It never seemed to affect performance, so I left it as is.

In the last week, I dropped my front tank to replace the fuel sender. Woohoo, now I have working front and rear tank gauges. Freaking FINALLY.

However, I checked the e-pump pre-filter housing and now it's 50% air. Still doesn't have any affect on performance, but seeing that much air is disconcerting. The really weird thing is, it only has air when it's idling. When I kill the engine, the prefilter refills with diesel.

I thought maybe I had an air leak on my new fuel sender and the e-pump was sucking air. However, it behaves the same on the Rear Tank when I switch the fuel selector. My e-pump is directly in front of the fuel selector on the rail, so there is almost no place for the air infiltration to occur. Perhaps the selector valve itself has a air infiltration issue, but IDK. Something tells me that I don't have an air infiltration issue.

Just to inform you, I have a custom schrader valve at the highest point right before the IP inlet. I purge the fuel system and there are no bubbles or air spirting out. I'm really confounded.

Another side comment, I bought the R&D IPI Performance Stage 1 filter setup. I was thinking that maybe there was a decent sized air bubble in one of those filters, that was maybe working its way back to e-pump filter housing. However, my stage 1 filter head is AFTER the e-pump, so I doubt it would let air bleed back from the filter heads against the flow.

Another idea I thought of was maybe the e-pump was creating a vacuum from my new fuel senders, thus the air gap (reduced pressure might make the fluid a gas) but I doubt the duralift is pulling that hard.

The thing that really bothers me is when I purge the air out of the schrader valve, it never spirts air and the pre-filter has no air when the engine is off. If it was sucking air into the pre-filter from somewhere, you'd expect the purge to show some air somewhere in the fuel lines. Any ideas?

 

Could it pressure not just air?

 

It could be pressure. I doubt it is air cuz I bled it a half dozen times now. As long as it's not affecting performance or getting worse, I'll keep driving it and keep an eye on it.

 

The more I fiddle with this pump, the more I think I have a hole in my fuel line somewhere. It must be pulling air trying to suck fuel from the tank. But since it behaves exactly the same on the front or rear tank, that leaves the 12" fuel hose from the selector valve to the e-pump OR the selector valve itself.

But when I look at the fuel hose, the connections, and the selector valve, I don't see any seepage or any indication that my fuel lines are problematic. IDK. I can't figure out this crap.

 

Did you change the orings that sit inside the fuel line where it connects to the sending unit?

Electric pumps are horrible about masking air intrusion problems, if you went back to mechanical I bet it would run like poo

 

I changed the o-rings.

Maybe I'll run the e-pump from a diesel can and see if that clears up the air prob.

 

Now the weirdness continues....

I checked the hose that goes from the selector valve to the e-pump. It is clear blue, so I can see the fuel in it. When I idle the engine, there is air in the e-pump housing, HOWEVER, when I shine a flashlight thru the blue clear line, there are NO bubbles.

Very very strange. I'd expect if there was air intrusion before the e-pump, then it would be sucking air thru the fuel hose, likely from a hole or leak somewhere in the line or connections. However there was NO air bubbles at all. That means if there was air intrusion, it probably is in the e-pump or the e-pump fittings or the e-pump seal pre-filter housing.

The fittings are tight and don't have any seepage at all, so I doubt that has a hole. maybe the pump has an air leak somewhere. IDK.

Still working on it.

 

Should I be running a check-valve somewhere in my system after the e-pump but before the Stage 1 filter assy?

 

There is no need for a check valve if your system is leak free, it's used more as a bandaid than anything.

Most e-pumps contain check valves even the janky Mr. Gasket 12D does...

Can you apply some pipe dope to the pump fittings? Would be easier than thread tape anyways..

 

Good ideas.

After tinkering with this for a while, I think there is an air bubble that cannot get out, because the e-pump is about the same level as the tank. I recently dropped my tanks to do some sender maintenance, and i'm thinking that since my tanks are near empty (only about 3-5 gallons in each), then maybe the fuel level is just matching what it is in the tank. So, I plan to fill them up tomorrow, then see if the air bubble rises.

 

I notice anytime I put aftermarket inline fuel filters on say lawnmowers or a carbureted truck, it always holds an air bubble in the top of it.

 

Even with two full diesel tanks, the air is still in the pre-filter. Can't purge it out. Doesn't affect performance. I guess I'll just leave it as is.