Help please

[mj!4200]

I've got a 04 Ford ranger 3.0v6 gas 144000 miles on it every thing is pretty much stock but I don't much about vehicle's so I'm wondering what is the tester called that check an see if I got a bad cylinder is it a compression tester or leck down tester and where is a good place to find one cheap but that works good

 

[alwaysFlOoReD]

A compression tester will tell you the PSI that the engine produces. Its more important to have fairly even pressures across cylinders.
A leakdown tester is more comprehensive and also needs a compressor to work. It will tell you how much air is leaking from a cylinder and where that air is leaking from.
The compression tester is the one you should get first until you build up more knowledge of mechanics. Any cheap one will do.

 

[mj!4200]

A compression tester will tell you the PSI that the engine produces. Its more important to have fairly even pressures across cylinders.
A leakdown tester is more comprehensive and also needs a compressor to work. It will tell you how much air is leaking from a cylinder and where that air is leaking from.
The compression tester is the one you should get first until you build up more knowledge of mechanics. Any cheap one will do.

Ok thanks alot

 

[RonD]

Welcome to TRS

You want a Compression tester gauge with spark plug threaded hose

Harbor Freight has a test kit for $30, seen here: https://www.harborfreight.com/compression-test-kit-8-pc-62638.html

You remove ALL spark plugs first
Then you screw in the hose fitting to 1 cylinders spark plug hole, and hook up the gauge
You then use the starter motor to turn the engine over, count to 5, then stop cranking engine
Write down the pressure shown on the gauge along with cylinder number, 1 to 6
Then release the pressure in the gauge
Move hose to next cylinder

Once you have tested all 6 cylinders you can then COMPARE the 6 pressures to see if any are 10-15% lower than the average

A compression number like 140psi means nothing on its own, could mean low battery voltage, incorrect pressure gauge(even new), poor testing method, leaking hose, ect.....................
By testing ALL 6 cylinders at the same time you will have taken all other things off the table so you can make a diagnoses

If you have 1 or 2 cylinders that are below the average then you would add a teaspoon of engine oil via spark plug hole, and then re-test compression, pressure WILL go up, but unless it goes up fully to the average you have diagnosed a Valve Issue

Just a heads up, there was a TSB for 2004 to 2006 Rangers with 3.0l engines
These years could have defective exhaust valve seats causing low compression in some cylinders
Only fix was replacing the heads or having a valve job done, replacing seats and exhaust valves
Even though the seats were "defective" its way out of any recall or warranty


If you want to avoid all this you can just do the "dollar bill test"
Google: dollar bill exhaust pipe test

It will tell you if your misfires are burnt/damaged exhaust valves
And so heads need to be changed

You can also use a Lighter next to tail pipe, if flame gets SUCKED IN that means burnt exhaust valve, seen here: https://mechanics.stackexchange.com/questions/61284/why-would-a-lighter-flame-go-into-an-exhaust-pipe

When an exhaust valve is not sealing, compression drops which causes the misfires, but what also happens is that on the INTAKE stroke when cylinder has 18" of vacuum applied that unsealed exhaust valve SUCKS IN exhaust, you can see that at the tail pipe by the Bill being SUCKED towards the tail pipe or the Flame being SUCKED IN
Working engine should have a constant OUT flow at the exhaust tail pipe

A cylinder that is misfiring from a bad spark or injector issue wouldn't cause the SUCKING, backwards flow, at tail pipe

 

[alwaysFlOoReD]

Your dollar bill test reminded me;
Back before i knew much about motors i watched a friends dad work on a carburated car. Air filter off and held at high revs could see puffs coming out of carb (iirc.... it was 40 years ago). I guess that would be intake valve...

 

[RonD]

Yes, too much valve overlap on cam or intake valve mis-adjustment, vacuum gauge is handy for that symptom

 

[19Walt93]

I'd unplug the injector harness before doing the compression test.

 

[pjtoledo]

hold throttle open during cranking.

 

[mj!4200]

Thank u everyone for the help and I think I know what is wrong I did the lighter test as suggested an it was sucked in so I think it's the exhaust valves..I'm attempting to locate information on how to get it fixed

 

[RonD]

Replacing the heads or having heads serviced(valve job) at a machine shop is the only fix