Compression Test and Leakdown Test - 1999 4.0 SOHC

[albator]

The engine works great, but I'm in lockdown so I want to keep myself occupied...

I have bought a compression tester and a leakdown tester, and I'd like to use them.
This is my first time.

For the compression test it seems the hardest part is to access and remove some of the spark plugs.
I will remove the relay #5 to disable the fuel pump.
What about cranking the engine? Remote starter device, or just turn the key?
What about the ignition? Disable the coils? How?

For the leak down, I need to find the TDC.
How do I turn the crankshaft?

 

[ExploringOptions2004]

The engine works great, but I'm in lockdown so I want to keep myself occupied...

I have bought a compression tester and a leakdown tester, and I'd like to use them.
This is my first time.

For the compression test it seems the hardest part is to access and remove some of the spark plugs.
I will remove the relay #5 to disable the fuel pump.
What about cranking the engine? Remote starter device, or just turn the key?
What about the ignition? Disable the coils? How?

For the leak down, I need to find the TDC.
How do I turn the crankshaft?

Compression test How to Do a Compression Test

and for the leakdown test, if your tester gauge unscrews from the gauge than put the tube into the plug hole, stick a balloon on the end and spin the crankshaft with a rachet and socket, when the balloon starts to fill its in compression stroke. Stop there. Remove hose from head and stick a long screw driver in it. When the screw driver stops going up and starts going down try to stop there. May help to put a reference mark on the screw driver for the rest of the cylinders also. Cuz the stroke will be the same on all of the remaining cylinders. This should help. If not check youtube.

 

[masospaghetti]

I just use the key, no remote starter required. Disable the ignition by pulling the plug on the coil pack and disable fuel by pulling the fuel pump relay.

A 19mm deep socket with a short extension (like a 1-2" extension) is about the right size to fit onto the crank pulley with a ratchet. You can either lay under the front of the truck and spin it, or reach down from the top of the engine bay. Either way, if you are putting your hands and arms around the pulleys and fans, I would certainly pull the battery negative cable - you wouldn't want the engine to turn over for any reason while your arms in there!

The way I think of it: all it takes is a bad switch or solenoid to complete the connection and you potentially losing your hands or arms. These switches and solenoids have been under the hood for over 20 years. Not worth the chance...but I digress.

This might also be a good excuse to get an endoscope - you can use this to visually confirm the piston position by poking the scope down the spark plug hole. It's also an extremely useful diagnostic tool in general to have around the shop. This is similar to the one I have.

Industrial Endoscope, SKYBASIC 1080P HD Digital Borescope Camera Waterproof 4.3 Inch LCD Screen Snake Camera Video Inspection Camera with 6 LED Lights, Semi-Rigid Cable, 16GB TF Card and Tool (16.5FT): Amazon.com: Home Improvement

Industrial Endoscope, SKYBASIC 1080P HD Digital Borescope Camera Waterproof 4.3 Inch LCD Screen Snake Camera Video Inspection Camera with 6 LED Lights, Semi-Rigid Cable, 16GB TF Card and Tool (16.5FT): Amazon.com: Home Improvement

smile.amazon.com

 

[albator]

Thanks for the advice.
I had bought an endoscope a few years ago and I was disappointed. But it was 5 or 6 years ago and the quality has certainly improved since then, so maybe it's time for me to give it another try.

Also, on a side note, I appreciate you're using the "smile" amazon website.
Personally, I gift to "code.org"

Agreed about the 20 year thing. Furthermore the extreme temperature variations hasten wear.

I just use the key, no remote starter required. Disable the ignition by pulling the plug on the coil pack and disable fuel by pulling the fuel pump relay.

A 19mm deep socket with a short extension (like a 1-2" extension) is about the right size to fit onto the crank pulley with a ratchet. You can either lay under the front of the truck and spin it, or reach down from the top of the engine bay. Either way, if you are putting your hands and arms around the pulleys and fans, I would certainly pull the battery negative cable - you wouldn't want the engine to turn over for any reason while your arms in there!

The way I think of it: all it takes is a bad switch or solenoid to complete the connection and you potentially losing your hands or arms. These switches and solenoids have been under the hood for over 20 years. Not worth the chance...but I digress.

This might also be a good excuse to get an endoscope - you can use this to visually confirm the piston position by poking the scope down the spark plug hole. It's also an extremely useful diagnostic tool in general to have around the shop. This is similar to the one I have.

Industrial Endoscope, SKYBASIC 1080P HD Digital Borescope Camera Waterproof 4.3 Inch LCD Screen Snake Camera Video Inspection Camera with 6 LED Lights, Semi-Rigid Cable, 16GB TF Card and Tool (16.5FT): Amazon.com: Home Improvement

Industrial Endoscope, SKYBASIC 1080P HD Digital Borescope Camera Waterproof 4.3 Inch LCD Screen Snake Camera Video Inspection Camera with 6 LED Lights, Semi-Rigid Cable, 16GB TF Card and Tool (16.5FT): Amazon.com: Home Improvement

smile.amazon.com

View attachment 179797

 

[Gary Crist]

Would not flooring the gas petal when cranking,
shut off fuel flow to the injectors,thus negating the
need to mess w/ the fuel system?

 

[donalds]

Or just unplug the crank sensor

 

[masospaghetti]

Would not flooring the gas petal when cranking,
shut off fuel flow to the injectors,thus negating the
need to mess w/ the fuel system?

It probably would, but unplugging the fuel pump relay is literally a 5 second task once you know where it is. It's in the underhood fuse box.

 

[Deleted member 352605]

quick question, what is a healthy compression for the sohc? it's from 98 and has 330k on it... thanks!

 

[albator]

Good news, I did the compression test.
Cold engine, not hot.
I got about 185 psi, very little variations between cylinders.

I removed both wheels, and the big plastic wheel arches, to access the spark plugs.
Removed relay #5 for fuel pump, disconnected the coil, and kept the throttle wide open.
And connected a battery charger.