Rabbit 1.5 diesel fuel feed trouble

[Gnarlodious]

My '78 Rabbit with original 1.5 diesel has developed a problem with missing at low speed. I rev it up and it runs great. Lower RPMs it misfires. So I yanked off a return tube from an injector and no fuel fell out but it suction gurgled. For a while, it musta had a lot of suction in there and had been sitting for several days so the suction was not relieved by sitting. What do you think?

Should mention the first thing I did was replace the filter. Also the tank is definitely vented, no vacuum there.

I took out the original (extremely rusty) tank a few thousand miles ago and put in a cleaned out tank from a newer Rabbit. Do you think the uptake port(s) are clogged? Is there any access without dropping the tank again? Through the fuel gauge opening maybe?

Any knowledge can help keep the work to a minimum.
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Vanagon ’83 diesel AAZ w/Giles injection, 5spd 4.57R&P+TBD and a '78 diesel Rabbit

[TDCTDI]

Get a quart of ATF, remove the feed line from the filter housing & the return line from the body, drop both lines into the bottle of ATF & start the car (if you don’t put the return line into the bottle, the pump will suck all of the fluid out of the bottle & send it back to the tank in 15-20 seconds).
If your car runs normally afterwards, then there is a blockage somewhere in the delivery system.


Check the bottom of the injection pump to see if it’s wet with fuel, if so, your pump seals are bad & this will introduce air into the pump & it will have hard start/self priming issues. It will also allow the fuel to return to the tank due to gravity.
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Everybody born before 1975 has a story, good, bad, or indifferent, about a VW.


GOFUNDYOURSELF, quit asking everyone to do it for you!


An air cooled VW will make you a hoarder.


Do something, anything, to your project every day, and you will eventually complete it.

[Gnarlodious]

I think I figured this out. Some years ago I put in a new used fuel filler tube, at that time I painted it inside the best I could with Rustoleum or Krylon. Then sometime last year I used some Diesel Kleen which contains cetane. Upon inspecting the filler tube, it appears the chemical caused the paint to loosen and peel off. I fear there is a screen inside the tank that resides upstream of both the fuel supply tube AND the return tube. My Vanagon has the same plumbing, I know this from experience. So if I am right, the peeled goopy paint has effectively clogged my fuel feed screen. If anyone knows for sure what is inside that tank please let me know. I put a used tank in from an '82 so it is not the original
'78.
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Vanagon ’83 diesel AAZ w/Giles injection, 5spd 4.57R&P+TBD and a '78 diesel Rabbit

[TDCTDI]

Yes, there should be a screen in there. Remove the fuel sender access door, then the fuel sender & you should be able to see a plastic circle with a loop on the top, find something to feed through, or grab the top of the loop & pull it up.


https://www.heritagepartscentre.com/us/431201511a-in-tank-fuel-filter.html
_________________
Everybody born before 1975 has a story, good, bad, or indifferent, about a VW.


GOFUNDYOURSELF, quit asking everyone to do it for you!


An air cooled VW will make you a hoarder.


Do something, anything, to your project every day, and you will eventually complete it.

[Gnarlodious]

Thanks! I was finally able to pull out the screen and it was clogged. Test drove the Rabbit and it is back to running good!
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Vanagon ’83 diesel AAZ w/Giles injection, 5spd 4.57R&P+TBD and a '78 diesel Rabbit