Duff injector pump?

[moTthediesel]

No, I'm not talking about what Homer Simpson uses on Friday nights --

My #2 Son and I are trying to resucitate a '85 Golf diesel that's been parked since '96. We've primed the injectors using a small temporary tank and a new fuel filter. We're getting it to fire, but it won't quite start.
 
Cylinders 2, 3, & 4 all spurt nice with the injector lines cracked open. Something with #1 one seems amiss though. At first all we could get from it was foam when cranked, now it pumps solid fuel, but very weakly. Do you guys think the pump is knackered? Is there something else we could try to bleed that one injector line?

Previous owner says that he parked it when it began to get hard to start in the winter. Want to get an idea how sound the engine is in this baby before we add anything to our original $50 investment.  :lol:

moT

[QuickTD]

There are very few parts in the injection pump that can affect only one cylinder. The only component that it unique to any one cylinder is the delivery valve. Delivery valves are just high pressure check valves. They don't often fail and a failed one would certainly not be noticed when the injection line was loosened and the pressure was relieved.

 Given what the previous owner said, I would think that the starting problem is more likely related to glow plug, compression or timing issues.

[veeman]

>>No, I'm not talking about what Homer Simpson uses on Friday nights --

Ha-ha!  Oddly enough, that was the first thing I thought of.  I can just see Duffman now, starring in a VW commercial in the early 80's...

[moTthediesel]

The only component that it unique to any one cylinder is the delivery valve. Delivery valves are just high pressure check valves. They don't often fail and a failed one would certainly not be noticed when the injection line was loosened and the pressure was relieved.

Wouldn't a bad or stuck check valve allow air to be drawn into the pump chamber on the suction stroke?

moT

[Dr. Diesel]

i doubt it. the pump's internal vane-style pressure pump keeps the case pressure at somewhere around 100psi!

[chrissev]

Is there something else we could try to bleed that one injector line?

why don't you try bleeding it from the pump instead of from the injector?  The line could have holes in it or could be plugged with wax or congealed fuel.  Or somebody could have run it as a bio diesel and there could be vegetable oil in there.  

Previous owner says that he parked it when it began to get hard to start in the winter.

sounds like low compression.  That's why they usually don't start when they're cold.  Solution to this of course, other than replacing the rings, is to crank them FASTER (ie, bigger, or multiple batteries).

[QuickTD]

Wouldn't a bad or stuck check valve allow air to be drawn into the pump chamber on the suction stroke?

Not really, the pump plunger outlet and intake ports are closed by the rotation of the plunger in the head, fuel cannot back up the injection lines even if a delivery valve fails open. The delivery valves are used to dampen pressure reflections at the end of the injection cycle and hold a stable pressure in the line for the next injection. They would have minimal effect when there isn't thousands of psi of pressure in the line.

[Patrick]

You could try trading two of thevalves on the end of the pump. If the problem moves to a different cylinder, you know where the problem is! Be careful doing this though. There's a spring/ball check valve in there. Never had one apart on the engine, but I imagine it could be done. Just trade the offending one for another one.  You might even find some dirt/rust/crap in there when you get it apart.