Hi All,

I have a 97 Ranger 4.0 OVH which I recently purchased and I was changing the plugs (which I've read are to be gapped to 0.054) so decided to do a compression test. I've read I should get 155-165PSI on each cylinder but I'm only getting 70PSI on every cylinder. The steps I took:

1. Removed cool pack plug
2. Removed plugs
3. Shut off fuel
4. Installed compression tester in cylinder 1
5. Held throttle open and cranked over a minimum of 7 times

on every cylinder the needle bounced up to 70PSI (a couple bounced to say 65 on the first crank then 70 on the second). So I'm a little confused as all cylinders were balanced and getting equal PSI but it's under half what I expected. Surely not all 6 could have failed to the same extent as each other? The car runs absolutely fine and idles great I was just doing some preventative maintenance.

Does anyone have any ideas suggestions?

Thanks
Scott

 

At only 70 to 65 psi, it shouldn't run.
I would say your tester is faulty or it's not screwed all the way in and it's leaking.

 

Engine wouldn't start with 70psi compression.

Since all are the same, within 10%, then engine is fine, compression gauge is incorrect

 

Thank you, all connections were tight so it has to be the gauge which is bad as it's brand new. I assumed all was well since there was no variance between them.

I appreciate the prompt responses!

 

What's the brand name and how much was it ?

 

it's an Innova, it wasn't hugely expensive at $18 but had a ton of good reviews on Amazon so I figured it would be good for occasional use.

INNOVA 3612 Compression Tester - 4 Piece Kit https://www.amazon.com/dp/B000EVU89I/

Thanks
Scott

 

Probably made in China _ no quality control...