I've got a 2000 ford ranger automatic 2WD with a 3.0l FFV engine. Now I compression tested it because it had a knock or misfire at around 2000 rpm going up hill. It also only gets 13 mpg when I think I was getting like 17 Mpg before. After a dry compression test 4 cylinders read 145 to 150 psi. However 2 cylinders right next to each other read 125 psi. It was the cylinder in the front right of the engine and the one right behind it. I put shop air to the engine and they seemed to have good sealing valves. I'm wondering if this could be a head gasket leak between the cylinders. What does anyone think? Is this compression test normal? Thanks.

Here is the fueleconomy.gov for the car. I was expecting at least 15mpg as that's the city. 13pmg seems low.

https://www.fueleconomy.gov/feg/Find...n=sbs&id=16411

 

If you are running E85(ethanol) then yes MPG is lower, but with gasoline if should be more like 18mpg

2000 3.0l should be closer to 165psi, it runs 9.3:1 compression ratio(CR)
General rule of thumb is CR x 18 = expected PSI at sea level to 2,000ft elevation
9.3 x 18 = 167.4psi

Could be gauge just reads low or battery was low, or you didn't have ALL spark plugs out for the test, last two means slower cranking speed so lower PSI
But yes, 15% lower on 2 cylinders should raise an eyebrow
Point of compression test is not the "actual" PSI, its the difference in each cylinders PSI, 8% is tolerable, 10% is pushing it, 15% is too much

I would pull the heads based on that alone

 

I'm running regular gasoline. I had all the spark plugs out for the test. It's a harborfreight maddox compression tester so it might just read low. So Your thinking I should replace head gasket then? I was basically thinking of doing that. When I get the heads off is there a better way to check if the valves are sealing? Just want to make sure it's absolutely the head gasket. I'm gonna do a wet compression test in the morning to rule out piston rings. Thanks.

 

Yes, after heads are off put spark plugs back in, then flip the heads upside down and level them out
Fill each cylinder "dome" with gasoline(or water), cover the valves with fluid, and see if it starts to leak out at the exhaust or intake port

You should also have heads pressure tested(cracks) and surfaced

 

Ok thanks, Will do and ill let you know the results later.

 

Ok so I've opened the engines valve covers so far. I checked all the rocker arms and it's like 6 or 8 out of the 12 that have play. I guess i'd like to get an opinion on the wear because that seems like a lot of rockers to be bad at 250k miles. However it was tapping pretty loud uphill so could make sense. I've uploaded a photo of the worst rocker arm pushrod and rocker. I can upload the medium shaky ones i'm just calling it a day today. One question I had was could the rocker bolts just have come loose and maybe I could torque them down? Thanks





Lifter side of pushrod

 

Does anyone know what this silver stuff is on the head and exhaust gaskets. Its really hard to scrap off. Was wondering if anyone knows a better way to get this off. Like maybe a solvent or something thanks. Still wondering about the push rod wear also. Especially on the lifter side. Lifters themselves have ok wear it looks like.

 

So I got everything back together and the knocking seems to have gone away. Apparently the 2 cylinders with bad compression had leaking exhaust valves. It was do to the fact that ford only case hardens the exhaust seats. Mine were beat down like .2-.3 of an inch. Which is quite a bit. I sent the heads to a machine shop and got hardened exhaust seats installed for $100. After installing and lapping the valves which I bought a new set of 12 on ebay for $65 they all held water. The real test will be when I load my trailer with 2k pounds and drive up a hill though, because that's when it was really knocking. Thanks for all the help.

 

Good work

Yes, time will tell

 

Hey there Stoneplanet, I'm looking at a similar problem with my 2001 V6 Ranger. Would you mind passing me the contact info on that machine shop you used, sounds like a good shop and I might need em. Thanks

 

I'm sure there's a machine shop closer to you than Pennsylvania