Lots of air bubbles

[prancer00]

I'm hoping to get a little advice on my 82 VW truck, running Biodiesel (B100) for about 5000 miles (since a new 1.9L engine was put into it).

It started running rough this week, like it was starved for fuel, and I noticed air bubbles in the line before the injector pump. I checked all fuel line fittings, and replaced a couple that were clips with the stainless threaded ones. I let some fuel drain from the tank to make sure there were no blockages. I changed the fuel filter and refilled the new one with ATF before installing it (I read somewhere that ATF is good for cleaning the injectors). I removed the metal fuel lines that go from the injector pumps to the injectors to make sure they weren't blocked, then removed the injectors. When I did that, I noticed that one of my return line hoses on the injectors was frayed, so I replaced all the return hoses, put in new heat shields, replaces the injectors, put the fuel lines back on.

That is about the extent of my diagnostic ability. I can't find a physical leak where air could be getting in. When the engine lurches to a stop, I can see air bubbles (lots of them, big ones) travelling back up the hose from the injector pump to the fuel filter. I can even hear air coming in somewhere, this faint sucking sound, but it really sounds like it is somewhere in the injector pump, and I can't see it at all.

Is my injector pump bad? Is there another test I can do? Also, is it bad for the engine if I nurse it to the mechanic in this shape--I can get there, but it is a bumpy ride--should I tow it instead? Any help or advice would be very much appreciated.

thanks!

[95gltd]

have you tried running it out of a can to bypass all the lines and filter? mine the check valve was faulty.

[prancer00]

I haven't; I have always been too worried about non-filtered fuel to just throw the line into a bucket.

[ssray]

i had this it was a bad seal on the return lines into the fuel filter, it seems that unless you use a orig filter the little rubber `o` ring dont fit(fram worst) you could see if you can get a bigger `o` ring or use a sealant carefully,hope this helps
Ray

[prancer00]

I'm using Bosch fuel filters, and have never had a problem with the filter sealing with these.

Someone else suggested maybe a bad injector pump. I opted to try running it out of a can, and put the fuel-in line directly into a new bottle of ATF. Once primed, it ran fine, like nothing had happened. I think that tells me that the injector pump is good, and that there is a blockage. the question is, where?

I need to remove the tank to fix my fuel sender, so I'm thinking that I might as well go for it all at once, and check out the in-tank screen while I'm at it.

Any tips on fuel tank removal methods?

[Darkness_is_spreading]

The fuel sender is right behind the rear seats under a panel,  as for your rabbit truck, it may be under the bed of your truck......

[shwartzbewithyou]

Air bubbles from the pump towards the filter?  That's backwards.  You're sure you have the send and return lines on the right way?

[prancer00]

today I removed all of the fuel lines to check for blockages, and found none. I ran it directly out of a can of ATF again, and I noticed a fuel leak at the base of the injector pump; this would explain the air coming in on the pump side.