Compression Numbers, The Good Bad and Ugly (Ford Ranger)

[xintersecty]

Yes, I know it's off topic, off forum, but I love you guys and you seem to really help. Please Please don't throw me off the forum for posting Non-Aveo.

I had an new manufacture engine put into my truck. I have a 96 Ranger Extended Cab 2WD with the 3.0 Liter Engine.

From the beginning, it has SUCKED. I have been going round and round with the mechanic who installed the engine. I am on my third oil change since the replacement. It's using about 3 quarts in between oil changes. Can anybody tell me if my numbers are good or not. I honestly don't have a feel for it. I used the procedure out the Haynes Manuel. I did each cylinder twice.

Cyln. | 1 | 2 Measurements
1 | 135 | 135 (all numbers are in PSI)
2 | 125 | 130
3 | 130 | 130
4* | 130 | 140
5 | 130 | 130
6 | 110 | 120

Picture of the testing tool

*Cylinder No. 4 has issues. When I pulled the plugs no 4 had oil stains around the threads.
Picture of 456


And 123


Any suggestions?

[thehunterooo]

we dont mind other cars at all, we welcome them all, Z34 didnt get banned for his love of luminas but other things lol

[Daox]

Those numbers look low to me. Pour some oil into a cylinder and retest it to see if the compression improves much.

[xintersecty]

I read about adding oil on retest in the manual. I had a difficult day when I took the measurements, it was cold as hell with snow flurries. I have my truck in Raleigh and I may not have enough time to take a second measurement. I made sure the engine was at temperature and I had changed the oil. It was not fun reaching around the HOT HOT exhaust headers to get the spark plugs out. This may be enough to start bitching and get that engine replaced.

[AveoJunk]

From what i have read about compression numbers, they should all be within 10 % of each other. So your first test 135 was highest and 110 is lowest. There should be a 11-13 psi difference. this is 25 psi. problem with a cyl. second test highest 140 lowest 120, should be 12-14 psi, this is 20. I think there is a thing called a leakdown test that is more definitive in finding the problem, but if it is a "new" engine, it should have a warranty and I would not be doing this myself.

[petrified.rabbit]

i agree with aveo junk to a point.. in that you need to use a cylinder leak down tester to track down the leak.. if it is the cylinder causing the leak.

but the compression as mentioned, should be done both dry and wet. You say the engine was new, the rings probably have not "seated" yet, which means you will possibly have unreliable compression test numbers. as if you started with 1 and went to 6. you had a lot of dry cranking by the time you go to 6, but depending on your speed, and how you tested and a lot of other factors i am not surprised by the possible drop.(i tend to break the rules and pull only the plug AND fuel injector wires on the cylinder i am testing, not ALL the cylinders).

how many miles do you have on the engine? i think you need to worry less (at this point) about the compression, and more about the oil loss.

now i am guessing this is a traditional head, with the spark plug going beside the header? not down past through the valve cover?

the electrode on the plug looks clean in the picture? is it? that means the oil might be on the top side of the plug not in the cylinder (a cylinder full of oil would have more compression i believe, just like a wet test). Does the exhaust smoke? any sign of a leak under the vehicle?

3 quarts between changes is a lot of loss, you would have signs of it. being a new engine, it could be anywhere because of a miss handled seal, etc. I would look for leaks on the block, check the coolant, if they are both clean everywhere, there is no oil in there, pull the inspection plate for the clutch/torque converter check for leaks there..

if our burning that much oil you would have smoke and a clogged cat by now.

why did you need to replace the engine anyhow?

[xintersecty]

why did you need to replace the engine anyhow?

My original engine lasted 220K miles when I blew it. I mushroomed a crank bearing. I replaced with a really junky junk yard engine. Well I had a new job and wanted to get my truck up to speed because junk yard engine had no power. I paid a shop to do the replacement. 6 grand later I am still not happy.

how many miles do you have on the engine? i think you need to worry less (at this point) about the compression, and more about the oil loss. ?

I estimating about 8K on the engine. It was replaced in July and I have driven it sporadically as it spent a lot of time in the shop and I was moving. They wanted at least 4K on the engine for the rings to seat.

if our burning that much oil you would have smoke and a clogged cat by now.

DARN DARN DARN. He replaced the CAT in August when he said it was clogged at a tune of 600 bucks. DARN DARN DARN :0(

OK, I am writing my letter and I might have to get a lawyer to "fix" my engine.

I have a leak down tester but I ran out of time for doing numbers that day. The leak down test will take considerable more time.

Thanks Everybody for their answers!

[petrified.rabbit]

but do you have smoke coming out the exhaust? oil doesnt burn clean, you could pull the o2 and check for residue.

that must oil, you woull almost be smoking like a 2 stroke engine 50:1 mix..