Compression Test Results

[FordTruckinRanger]

I started looking for help with diagnostics in my "intro" post but maybe this a better place to continue. Long story short: truck came with misfire codes, did some tune-up maintenence and got more misfire and also lean codes. I was going to chase exhaust and small vacuum leaks but was advised to do a compression test. I did that and don't think the results are too good. Now I'm looking for some guidance on my next move. Thought I was starting to learn some diagnostics but now I'm in over my head a bit.

Results: 1- 150psi, 2- 82psi, 3- 148psi, 4- 142psi, 5- 116psi, and 6- 138psi. Cylinders 1,2,&5 had their first jump at 30 while the others had their first jump around 90 before getting to their final value in 2 or 3 jumps.

 

[pjtoledo]

definitely bad numbers.
did you do it with the throttle held wide open? the answer should be yes.

if you want to refine the results a bit, squirt some wd40 into # 2 and repeat.
a big change means rings, small or no change is a valve issue. or cracked piston.

I'd pull the pass valve cover, check all the stem heights, make sure the lifter & rocker is ok.

what's your skill level?
3.0s are easy to work on. rusty exhaust bolts are the biggest headache.

 

[alwaysFlOoReD]

Edit, PJ beat me...
You can further refine your results by adding a teaspoon of oil in the low cylinders. If the reading comes up then it indicates rings.
If you have a compressor you may be able to "rent" a leak down tester from local auto parts place. Good tool to find exactly where the problem is.

 

[FordTruckinRanger]

I did not have the throttle wide open. I will test again in the morning with that change and then try with the wd40 and see who has a leak down tester to rent. Not sure where to put my skill level; I can wrench and have always done my own work but I'm not great with diagnostics and don't want to install new heads only to find there's problems deeper in the engine. This is certainly a helpful place tho, thank you all.

 

[FordTruckinRanger]

I did compression test with wide open throttle and all the numbers were within a couple pounds of the first test. The change was at the first jump in pressure. Cylinder 1 was now around 90 like the others while 2 and 5 were now up to around 60 on the first jump. I also sprayed some oil in 2, 5, and 6.
1- dry 150
2- dry 80, oiled 93
3- dry 150
4- dry 148
5- dry 113, oiled 114
6- dry 135, oiled 148
Are things going from bad to worse here? Give it to me straight doc

Edit: There's a leak down tester available about 25 minutes away I'm going to go rent in a few.

 

[bobbywalter]

i would get a good running used engine. do a cold test to said engine before taking it if you can not hot test it...i can usually floor start and run engines but time is sometimes a factor....as long as the numbers are 10 percent cold and it has good cranking oil psi it will be the most cost effective way to go.

you could buy a good running 4.0 engine cheaper than replacing head gaskets just to look. ...that is a quality felpro kit per se...

the 3.0 otoh is usually really cheap to do gaskets...and bolts...like sub 140 bux. this is where a camera is gold....look in the cylinders to see if there is any obvious disaster....if its not terrible then digging further can be warranted.


time and money....just swapping the critter. unless its just a broken/bent rocker or something.


but prices on the 3.0 have rose more than 100 percent since 2020. what was 150-300 is now 300-800.

remans range 1500-2400.

so there is that.

 

[rusty ol ranger]

i would get a good running used engine. do a cold test to said engine before taking it if you can not hot test it...i can usually floor start and run engines but time is sometimes a factor....as long as the numbers are 10 percent cold and it has good cranking oil psi it will be the most cost effective way to go.

you could buy a good running 4.0 engine cheaper than replacing head gaskets just to look. ...that is a quality felpro kit per se...

the 3.0 otoh is usually really cheap to do gaskets...and bolts...like sub 140 bux. this is where a camera is gold....look in the cylinders to see if there is any obvious disaster....if its not terrible then digging further can be warranted.


time and money....just swapping the critter. unless its just a broken/bent rocker or something.


but prices on the 3.0 have rose more than 100 percent since 2020. what was 150-300 is now 300-800.

remans range 1500-2400.

so there is that.

If he buys a 4.0 he'll need a trans too...

 

[FordTruckinRanger]

Is the leak down tester still worthwhile for more data at this point? If I'm getting leakby in 2 places would that tell me?

 

[Blmpkn]

Is the leak down tester still worthwhile for more data at this point? If I'm getting leakby in 2 places would that tell me?

With your 2nd cylinder coming up near 10% with oil in it id wager that it's just a piston ring issue.

That being said, a leak down tester is a good piece of equipment to have.. and they don't cost too terribly much if you wanted to buy one rather than just rent one. 80$ on jegs last time I checked..

 

[FordTruckinRanger]

Do you think its safe to say the engine needs to be rebuilt whether or not there's also issues in the heads based on this data?

 

[Blmpkn]

Do you think its safe to say the engine needs to be rebuilt whether or not there's also issues in the heads based on this data?

Well, it's kinda tough to say at this point without further disassembly. As pjtoledo suggested, taking the valve cover off and checking the valve train bits associated with #2 might tell you more about what's going on.. getting a borescope and slipping it in the plug hole might tell you something as well (also a good piece of equipment to own)

Mabey you just need new rings, mabey you need a head.. but definitely be worthwhile to do more diag before spending money though.

 

[alwaysFlOoReD]

A leak down tester will pinpoint the leaks. Basically you put 100psi into each cylinder at TDC and then listen at the following;
crankcase breather: rings,
intake: intake valves,
exhaust: exhaust valves,
bubbles in radiator: head gasket,
other cylinders: head gasket.
There are 2 gauges. Input pressure 100psi. Cylinder pressure. Usually expressed as a % loss. I don't remember what % equates to how good the cylinder is, but goggle can tell you that.

 

[Blmpkn]

A leak down tester will pinpoint the leaks. Basically you put 100psi into each cylinder at TDC and then listen at the following;
crankcase breather: rings,
intake: intake valves,
exhaust: exhaust valves,
bubbles in radiator: head gasket,
other cylinders: head gasket.
There are 2 gauges. Input pressure 100psi. Cylinder pressure. Usually expressed as a % loss.

Aah learnt something new. Is this usually audible to 'the naked ear'? Or would a guy need a stethoscope or something to really hear the leak

 

[alwaysFlOoReD]

Naked ear

 

[FordTruckinRanger]

Thanks for that info. The parts store did NOT have the leak down tester they said they did. Guess I'll either order one or get the harbor freight one this afternoon. In the meantime guess I'll be looking to see whats around for parts trucks and engines.