81 diesel rabbit with fuel issue

[astewart]

I hope someone out there has some opinion on my fuel issue with an 81 diesel rabbit.

It had several fuel issues, ie cracked fuel line, cracked return lines @ injectors, clogged fuel filter (in-line AND in-tank) PLUS, we drilled 2 holes in the 'cup' area in the tank, as there was still some issue that fuel would not exit the fuel tank easily. However, after all of that mess, we now have good fuel all the way...and the car runs great if you have it run off of a small jar of fuel right @ the engine....but when you re-hook the gas tank, it only runs until it's exhaused all of the fuel already past the filter...ie it still isn't getting fuel from the tank. if you wait a little (1 min or less), it will re-start quickly, but it won't stay running.

So, is my fuel pump beginning to fail? will a small in-line electrical fuel pump do the job? or do I need to buy a new injection pump?

we were planning on putting the 12v pump before the fuel filter to pull from the tank and push into the filter.

Also, it seems we will be purchasing a cheap "parts" Rabbit diesel that has the same problem....so I need to figure this out!
Any suggestions would be greatly appreciated!

[zagrot]

try blowing the lines with compressed air. an electric lift pump is not nessecary, just find and remove the obstruction.

[astewart]

I did blow through it...but via mouth not compressed air, and all flows just fine...flow from the tank is just fine, but there was a crimp in the metal fuel line that the diesel guy cut and spliced with rubber fuel line...if you put diesel in a cup and attach it to the fuel line there (ie bypassing the tank) the problem still exists...so I don't think it's the tank now (although i'm sure what we did to the tank helped the situation)

Also, we added the elec pump AFTER the fuel pump...and it's still not enough, so we are suspecting a problem between the splice and the filter

(the current set up is tank...metal...rubber splice...metal...fuel filter....elec pump...to stock stuff of engine...)

so....now she still starts, runs a little, and then is fuel starved...is replacing the entire fuel line my only option? I don't understand why I blow through by mouth, but there still may be a problem in that section of line????

should the elec pump have been placed BEFORE the fuel filter?

[zagrot]

check to make sure you don't have an air leak between the fuel tank and diesel pump. if you were to replace the tubnig between the pump and filter with clear hose you'll see some bubbles in there, but it should not go dry. if the fuel line between the tank and pump is free from obstructions and there is good fuel flow but the pump keeps running dry there is probably a bad air leak; if the engine shuts off with fuel in the line and there is good flow the problem may lie in the pump ( i have yet to see a case of the high volume pump failing, though i suppose the vanes could get stuck if the car sat for a long time).

[astewart]

the car started & ran fine...we jacked it up to check the alternator belt, took it off the ramps, and she wouldn't start and hasn't since (Feb)!

We'll check for air bubbles. I just bought all new rubber fuel line also....

by high volume pump, are you meaning the one I added in addition to the stock system? or the stock pump?

[zagrot]

the bosch diesel pump contains two different pumps, a vane type pump near the front of the aluminum housing that moves fuel in great volumes but at low pressure, and a piston type pump in the cast iron head at the rear of the pump. the piston pump is what makes the high pressure associated with diesel fuel injection.

http://www.cs.rochester.edu/u/jag/vw...i/injpump.html

what is the condition of your filter/ water seperator? by the way, just read your first post again, i don't think the diesel rabbits have an in tank filter, and if you replaced it did you get one that is compatible with diesel fuel? and yet another thought, is the tank vent obstructed? the tank vents through a metal line that runs along with the fuel suction and return lines into the engine compartment and then from somewhere near the passenger strut tower is should be connected to a black plastic tube that attaches to nothing. it should be hanging around the area of the crush structure in front of the passenger strut tower or maybe stuck in a 1/2"-ish hole in the top of that crush structure.