Compression Tester
 

I am parting out my 740 and would like to run a compression test before I pull the motor. Any suggestions for a tester or is there anyone wanting to rent theirs? Thanks for your help.

You can get a cheap tester that works at harbor freight.
Why are you pulling the motor?

Thanks. I'll check it out. The frame is rusted out on the passenger side, some body rust and the frame member below the motor is cracked almost thru. The motor runs great and I have a rust free 84 760 so I want to clean it up and put it in the 84.

Sounds like a good plan.

Your 84 probably has the same crack-prone front crossmember, so check that closely before you swap in the other engine. You may find it needs welding/reinforcement or replacement (the newer ones have reinforced boxed-in sections at the weak points).

I've looked at it closely and don't see any cracks. It's an automatic and the donor car has the 4 speed w/overdrive and is a year newer and 50 K more miles on it. Just a thought.

thanks

Picked up a tester at harbor freight on Saturday but was only able to get 1, 3,4 injectors out and unable to get the heat shield out of 3. One of the adapters fit in the injector holes so I tried number 1 and only got 110 psi. I tried 4 and got 350 psi. The engine ran very quiet and smooth. Planning on pulling the head anyways but would like to be able to do a compression test. Is there a socket that is made just for pulling these injectors?

thanks

Something is not right with your measurement technique based on those numbers. 350# is pretty low, and 110 would be a dead skip on that cylinder. If it ran well, and started decently, then these readings probably can't be correct.

Are you sure you're setting up the tester correctly and getting it all sealed up? Having a few injectors still in can also affect your results since it slows down cranking speed and could affect different cylinders irregularly.

The best tool I have found for pulling injectors is a Craftsman 1-1/16" socket, the US size gives a slightly looser fit on the injector than the correct 27mm size, and it has thin enough walls to not foul up on the side of the cylinder head, enabling it to get all the way down on the injector. You need one with deep enough hex reliefs to get around the injector spill nipples, which not all tools have.

For injectors that give you a struggle to get loose, remember to pull on the wrench from the passenger side or the front of the car, don't pull towards the outside of the head on the driver's side or you can break the head at the injector boss. If access is the issue on #5 and #6, sometimes you can slip the socket on by itself then get a wobble-end extension into it good enough to engage. Or you can temporarily or permanently move the pump out of the way, as you were discussing elsewhere.

Getting heatshields out, best way is to get all injectors removed then spin the engine on the starter and let compression blow them out. (Protect for fuel leakage from the IP injector unions while doing this.) You can give the shields a few gentle taps using a blunt drift or socket extension beforehand to shock them loose beforehand too, to ensure they fly out. Or, can put in a screw that's the right size for the opening and yank the shields out with a slide hammer, more work but usually does the job. Don't use a pick or anything else that can break off inside, because it will.

Curious, why are you planning to pull the head?

I have the craftsman socket and it's to thick and hits the head on three and no way I can get it on 5 & 6 without moving the pump. My 84 pump looks to be in the same position, very close to the head. The one heat shield should have blown out as many times as I tried to get a good reading from 1. I'm parting out this car because of the frame is rusted out so I want to practice on this one before I pull it for rebuild. The head has some exterior leakage by the third injector and looks to be original. I'll try the slide hammer this weekend on the heat shield. Guess I could bite the bullet and pull the pump. Going to have to someday, I just need to grow a pair. Thanks for your help.

Leaking what? Oil, coolant?