1) if 1 or more glow plugs are bad will the GP relay still click on and off
2) how can tell if the vacuum pump ,injectors , ip pump are still working
3) how do you go about taking a compression test
4 ) THANKS

1. GP relay function - The GP schematic indicates that the relay will still function with all glow plugs and the idiot light not functioning.

2. a. Vacuum pump - Put a vacuum gauge or your thumb over the output vacuum hose to feel suction.

b. Injectors - Someone else may have a quick check for this.

c. injector pump - If the engine runs, it is working. with the engine stopped, loosen the nut on the injector line slightly and crank - fuel should come out -don't let the engine run. you must be getting fuel TO the IP for this test.

3. compression test - you need a high pressure diesel compression tester which will screw in the glow plug hole. Gasser testers WILL NOT WORK!

4. Thanks - Your Welcome.

Injectors can be tested with an injector tester. Afaik the tester allows you to see the opening pressure of the injector and the spray pattern.

Since there are so-called high-flow injectors, maybe the tester also provides a means of measuring how much fuel an injector can flow, but I would think that largely depends on what the IP is set up for.

Lee, I don't imagine injector testers come cheap. A mickey mouse tester might involve disconnecting one of the injector feed lines at the IP and replace it with another line which an injector could be connected. By placing the injector in a glass jar and starting up the engine, you would be able to see the injector spray pattern.

You must be very careful when doing this test as the pressure is 1500 LBS + and could easily penetrate your skin or eyes. It would be best to have an assistant to start and stop the engine and be ready to call the paramedics.

They sometimes show up relatively cheap on ebay :)

However, I won't mess with it, I'd take the injectors to a shop that has a tester and have them test them if I wanted them tested. I was only saying that they can be tested with a tester ...