Actually sticking open is an interesting possibility. I was trying to grasp the possibility. A totally dead cylinder seems to be the suspected result.


Over the years non soluble particles in the fuel might get compressed and stick to the seat or valve face. Providing enough of a compromised surface to leak. It would not take much leakage to disable the function in a hydrostatic situation like this. Volume of fuel flow is probably also low so a washing type action may not be strong enough to erode the compressed and sticking contaminates.

I was more concerned with a finding a testing method to find out if leaky delivery valves are present in place. Especially since this threads originator proved we could address the delivery valves at home.


Perhaps taking an old hard line cutting it and brazing or silver soldering a usable attachment on the cut end.

Apply perhaps 25 pounds of air pressure with a gauge in the rubber line that feeds it. . With a shutoff at the end and an air input at the extreme end. A good delivery valve should hold the pressure for days I expect. For testing a more sane period could be established. I think we could quickly develop what a problem delivery valve acts like. Or establish the leakage factor that is acceptable.

You might have to run the injection pump out of fuel and rotate the engine to expose the port in the injection pump element. Giving a route for the air to easily escape if the valve was leaky. May require a few magnets and a degree wheel stuck on the harmonic balancer. As an indicator when a specific fill port was exposed on each element.

All four of my diesel 616 and 617 engines run very well. Although the 616 engine that has rebuilt or all new parts including the basic engine runs just a little better. That engine still has only a very few thousand accumulated miles since it was installed by a dealer.

It is possible in my mind because these cars are so old that there are a lot of sub standard delivery valves out there in service. Not causing any signifigant problem but degrading the engine just enough to notice a difference like I observe. There is no fairly quick test to see what shape they are in that I can think of quickly.

Other than the sitting under a head of air for a period yet to be established. Or taking an old hard line and teeing in a high pressure gauge with an injector on the other end. Building pressure by rotating the engine and seeing if it holds.

Once the delivery valves are removed I think my vacuum pump and one of my better vacuum gauges that reads down to low microns could be used.

If a hose could be clamped on the delivery valve casing. It could quickly pull down to 100 microns and sit there when the vacuum pump is isolated from the circuit with a valve. The test could be done very fast and be very conclusive.

I also think with any leakage it would be obvious with my stronger pump in only a very few seconds. You could evaluate each delivery valve this way establishing if it needs attention. Plus testing after you repair it to verify it is now good to reuse. This to me is a very fast way to deal with them.

What is a little scary is the majority of injection pumps on these cars are still the originals. Very old now with high miles on many of them. I suspect even a little leakage will have consequences. Nothing you might be able to put your finger on but still something. Could be for example fuel milage. A slightly leaky delivery valve might delay the injection for example. Or under fuel a cylinder. Or both.

The much maligned milli volt system should indicate it as one of many possibilities if a cylinder is running cooler. At the same time if an engine is producing no more than .1 milli volts difference between all the cylinders in a power balance test the overall delivery valves are probably very good.

We did experience on this site and in private messages and emails. That some engines settled to a perfect milli volt test after what was wrong was repaired. All the cylinders were exactly the same after in the milli volt power balance testing. Not that many but there were a few of them.

Years ago now when I joined this site there was little known about these pumps by most members in comparison to what now is. Pumps got changed out very frequently when they were either not the issue or we could have addressed the issues.

There are much fewer injection pumps changed out today in comparison. Certain things are and will still remain beyond what we can do. These cars like myself have continued to age over those same years. Delivery valve issues seem to be increasing.


These are just a few quick thoughts. Others can come up with better and easier hopefully. Or perhaps I can with some thought.