Hi guys! I hope y'all are having a nice weekend.
I'm getting ready to run my first compression test in the next hours, but wanted to run a check list first, just in case I may be missing something:

1. How warm does the engine need to be? I ask since I need to move the Disco less than half a mile from where I'm parked in order to work on it.
2. If I pull the fuel pump fuse and let it run 'til it runs out of gas, do I still need to unplug the coils?
3. After disabling fuel pump and coils as necessary, should I crank it up for a while before removing any of the plugs?
4. To run the test, must I remove ALL plugs at once, or one by one?
5. I've read and heard people suggesting to maintain Throttle Body opened while running the test; should I? If yes, what is the best way to achieve it?
6. Do I need to record first puff reading PLUS highest after 5 puffs aprox, or just the highest reading?
7. Am I missing anything?

I'll wait for any final input, thanks in advance.

 

1. Start with a cold compression test, if possible.
2. Don't run it out of gas. That can lead to difficulties getting the air out of the fuel system. Just pull the fuel pump fuse and the coil connectors, as you have already been told.
3. No. That would not achieve anything.
4. People do it either way. With all the plugs out, the engine will spin more easily.
5. Throttle should be open as far as possible. Perhaps put the handle of a wooden screwdriver into the throttle bore to hold the plate without damaging it.
6. Record the highest reading, which normally comes after a couple of upstrokes.

 

Thanks for confirming MOLLUSC, but ended up aborting while trying to disconnect the coils; didn't want to risk losing the metal retainer of the coil's plug in the attempt; also it's troublesome to work in there without removing some things that are in the way, besides not being in the mood to remove parts today; but I will be pulling the trigger on Extinct's coil relocation mod, and once I get it, hopefully disassemble the upper intake for the last time to relocate the coils, replace the upper intake gasket, and resume troubleshooting. Thanks again for your response.

 

Adolfo, what you refer to as the metal retainers on the coil plugs do not need to be removed. They function more like the plastic tabs on most other connectors.

Just press on them in the middle of the long, exposed side to release the coil plugs from the coils.

FWIW, I removed them when I first changed ignition wires on my truck in Nov. 2009. Removed them and replaced them while lying face down on top of the engine. It wasn't until much later that I figured out or read how they work. Duh!

 

If you don't want to remove the signal wires from the coil packs, you could pull the spark plugs and leave them connected to the HT leads with the plugs sitting on the engine. The ignition system will function as normal so there's little chance of damaging anything, but the sparks will be outside of the cylinders.

 

...damn, I gotta try that out! ...and I thought that exposed side was to insert the screwdriver tip to pry them opened; ...gotta luv this Forum, so much things to learn, thanks! ;-]#

 

..:: UPDATE ::..

Hello Roverers! ...just wanted to let y'all know that I've been unable to troubleshoot further these past days due to work and holidays get-togethers. Issues still present, nothing has changed; same codes, same rough idling and shakiness, but Disco still moving forward. As soon as next troubleshooting steps gets done, I'll report back! Happy Holidays to all! ;-]#

 

Is it possible for injectors/injector to work just poorly enough to make the engine run a bit rough at idle, but not poorly enough to throw a code? (I’m asking for the sake of my P38).

 

That has not been my experience, the misfire/lean detection is very sensitive in these, maddeningly so.

 

Thanks Extinct.