Air in fuel line from filter to injection pump

[Trucky McTruckface]

I seem to be getting a significant amount of air in the line from the filter to the IP. I recently installed a clear line. This is causing the truck to lose power at heavy loads. Is there a method on how to look for the air leak? Apparently there are a million things that can cause this.

[TylerDurden]

I'd feed the filter from a clean bottle, and send the return from the IP back to the bottle. If there are still bubbles between the filter and the IP, it's likely the filter is plugged.

[Fatmobile]

Air in the fuel is usually caused by a fuel line restriction.
Could be the screen in your tank but it's usually a clogged filter.
A dash mounted vacuum gauge attached to the fuel line will let you know of a fuel line restriction way before you are stuck beside the road.

[Trucky McTruckface]

Thank you for the tips. Where in the fuel circuit should I place the gauge? Anywhere? What are normal readings?

[Fatmobile]

My favorite way is to find a double stacked banjo off a gasser rabbit distributor and use it to replace the input banjo bolt.
Then cut one of the banjos off the injector lines because they have a 1/8" barb and will bolt to the top banjo.
Otherwise I drill and tap an input banjo bolt for a 1/8" NPT to 1/8" barb.
You could just "T" it into the fuel line before the pump.
But the double stacked banjo looks great.
vacuumbanjo by vwfatmobile, on Flickr

[Trucky McTruckface]

That would look pretty good. It will be on my list. Here is some more information. At startup I get no bubbles and the engine runs great. When I drive it down the block it runs rough and I see tons of of air. As soon as I shut down the engine I see all the bubbles get pushed back to the filter. Also I noticed that the daisy chain lines to the fuel injectors barely have any fuel in them. I still don't have a clear return line but I will get one soon. I tried to find a good place to remove the lines to place then in a fuel can and bypass the tank but there doesn't seem to be an easy place to do this. Where do you usually do this? At the soft lines between the tank and the hard lines?

[Trucky McTruckface]

Also just a note I replaced the fuel filter this year so it's not very old. My fuel gauge doesn't work so I've considered replacing it. Might have to convince myself to drop the tank.

[TylerDurden]

There is probably air coming in from the IP's main seal. Very common. Fairly easy DIY job to replace.

[Fatmobile]

With air coming down the line when you accelerate it could be anything from a bad mainshaft seal sending air back to the tank and getting pulled back to the engine,.. or a clogged intank screen.
A clear return line will help understand what's going back to the tank.
But fuel getting pulled back to the tank quickly after shutoff usually means a fuel line restriction, fuel is getting pulled back to the tank.
Air coming slowly from the pump right after shutdown usually means a mainshaft seal.

[Trucky McTruckface]

I dropped the tank since I needed to fix my fuel sending unit anyway and true to form I broke a bunch of god damn hoses that were so hard the literally had to be cut to get them off. One runs to the safety valve by the filler neck that shuts off I guess if the car flips upside down which then goes to the vent line in the engine bay. Now I don't advocate eliminating safety features but it would make my life easier if I bypassed this and just had the vent line from the fuel sending unit go straight to the vent tube that goes to the engine bay. Does that safety valve do anything else? Can it just be bypassed? I also broke the vent that goes to the filler neck itself which I have to replace. The old lines are just so brittle Also looks like a lot of sludge in the tank so I'm going to clean it up and I think it may have been the issue. This bottom feeder tank design looks like a bad engineering idea.

[Trucky McTruckface]

Well that damn valve thing broke too. And it's a discontinued part. Either I bypass it or figure out some kind of replacement. Is there any valve that can take it's place?

[Trucky McTruckface]

I've been doing some more research into this and that part has essentially disappeared from the face of the earth. Now in my ponderings over this I don't see a reason why I can just plug this vent and use a vented gas cap instead. Any reason why this wouldn't work?

[Fatmobile]

So the ones in my drawer are becoming more valuable? or less? ha.
Sounds like it would work.
I once carved a V in the gas cap gasket for a vent but it would probably be better to run the vent line somewhere dry. Well the pickup has a fuel door so it might be dry enough.
Maybe like you suggested; just bypass it and splice into the line going to the engine bay.
Sounds like those old brittle lines needed changed anyway.

I cut a hole in the bed of my pickup.
Just above the fuel sender so I'd never have to pull the tank again.

[Fatmobile]

You and chuck should get together and talk about your trucks, ha.
http://forums.vwvortex.com/showthread.p ... bit-Diesel

Maybe that's you who already responded to his ad.

[Trucky McTruckface]

Haha not me but it's nice to know I'm not the only one. I guess those valves are still kicking around. Yeah I've talked to some people that just bypassed it and it seems to be ok. I've considered your hole in the bed mod several times over the last few weeks lol. In other news I got my fuel sending unit working kinda. Just have to get it to read a full tank. Going to get some new lines and clean the tank maybe this weekend and hopefully get this thing back on the road again.