Compression test results and what they mean

[dsmmaniac12787]

Ok, not sure if this is where I should post this but I dont know much about compression numbers. This is the first compression test I have done. First numbers were

140,150,150,150 (from #1-4)

Then I realized I didnt keep the throttle open while turning over. After redo...

144,152,161,155 (#1-4)

Numbers arent exactly consistent, and Im not sure what it means. I know it looks like I have an oil leak coming from the passenger side corner of the head gasket by thermostat housing. Had one blow in this spot before. Fuel in oil, but no milky color as if a coolant passage was blown. Also sounds like a knock from cylinder #1. The car sputters when cold especially and takes 10-20 seconds to crank. It sat for over 2 years before I got it. Prob fuel filter or FPR.

Any input would be greatly appreciated!!!!!!

 

[dsmmaniac12787]

And yes the car was at running temp when test was performed

 

[CruisinGSX]

This post has a link which gives information about a compression test. Just scroll down a little , and you'll see where I had posted the link.

http://www.dsmtuners.com/forums/newbie-forum/303213-compression-s-good-bad.html

Have you noticed if you're burning oil? First thing I thought of when you mentioned fuel in oil is some of your compression leaking past the rings. Also, You could try putting a small amount of oil in your cylinders through the spark plug holes and doing your compression test again. IIRC, it's called a wet compression test. Basically, the oil will help seal the rings during the compression test, and if you have a good jump in your readings, it would be safe to say your rings aren't sealing as they should be.

Also on the link I provided, I posted another link to explain a leakdown test. Might prove useful.

 

[dsmmaniac12787]

Ok, I will try a wet test and post the results.

As far as oil burning, I have not noticed anything other than a leak. It was also leaking out of the cas. Thought I needed a new o'ring for it. Then all of a sudden the leak stopped and the knock got louder.

 

[dsmmaniac12787]

wet test results...

155,160,180,150

They were all higher except for #4 and the battery died while doing 4 so its probably not accurate.

 

[BoredDSM]

From the looks of it the ring in cylinder 3 is going. Usually when it is lower than 120psi is when they are serviced. But I bet if you ran seafoam through it your compression would be 120 or lower so yea from what I see your rings are toast or are on there way.

 

[dsmmaniac12787]

Yeah im running a walbro 255 with no afpr. Big no no. I guess my cylinders are washed and losing compression.

So do you think if I were to either; A-get an afpr and change the oil then put some RESTORE or something else in it. or B-put the stock pump or a 190 pump in it, then change oil and use some RESTORE. Think it would straighten out? Or is it just time for a rebuild?

 

[pj91gsx]

Yeah im running a walbro 255 with no afpr. Big no no. I guess my cylinders are washed and losing compression.

So do you think if I were to either; A-get an afpr and change the oil then put some RESTORE or something else in it. or B-put the stock pump or a 190 pump in it, then change oil and use some RESTORE. Think it would straighten out? Or is it just time for a rebuild?

The 255 will ruin the hone. Ive seen a motor with 167k that was ran hard until it spun a rod bearing and still had a perfect hone. And another motor with 157k that lost compression from a 255 in one year. I would try the restore thing to see if it would work, it maybe a waste of time. Definately put the stock fuel pump in or something.

 

[1992awdlaser]

I don't kow how many times I have to say this:

Putting oil in the cylinders will ALWAYS make the compression go up. The oil will sit in the dish of the piston which causes less space for the air to occupy when the piston moves upward. That of course means the compression will go up.

The only easy way to know what is wrong is to do a leakdown test.

 

[iluvmy4g63]

the can of restore says not intended for turbo cars. your choice though.

 

[dsmmaniac12787]

1992awdlaser, that makes sense to me...the numbers all went up relatively the same. Why is this method used so much if it doesnt even work?

As far as the restore, I probably will not use it. Is there any thing I can do to safely restore compression?

 

[SpiralOut]

1992awdlaser, that makes sense to me...the numbers all went up relatively the same. Why is this method used so much if it doesnt even work?

As far as the restore, I probably will not use it. Is there any thing I can do to safely restore compression?

Maybe try running thicker oil, 20W50. Also maybe you can get a junk 14b or something for $50. Then run the restore, It cant mess up the turbo if it is already shot. After you run the restore for a while flush the oil and put in some thick oil with lucas. Then put your good turbo back on.

 

[Freerevving]

the dry numbers are fine for a used engine... not perfect but fine. If #1 gets any lower than that then I would begin to worry.

As stated before, you'll need to do a leakdown test to find out anything more.

 

[SpiralOut]

The 255 will ruin the hone. Ive seen a motor with 167k that was ran hard until it spun a rod bearing and still had a perfect hone. And another motor with 157k that lost compression from a 255 in one year. .

So a fuel pump can ruin your cylinders? Damn

 

[Fast-Orange]

yes they can, your soaking the rings in gas not to mention you would probobly go through spark plugs like crazy

 

[chris9149]

So a fuel pump can ruin your cylinders? Damn

Its not just getting a fuel pump... it's the 255 without an AFPR. Not a good plan. If you don't want / will never need the AFPR / 255 combo, just go with a Walbro 190 fuel pump. But if you step up to the 255 you need to get the fuel pressure regulator as well.
I think that is what pj91gsx is trying to say.

 

[1992awdlaser]

With the 255, the fpr can't bypass enough fuel back to the tank to keep the fuel pressure where it needs to be. This causes the pressure in the fuel rail to go up which means the injectors will be spraying more fuel than they are supposed to. This extra fuel will wash down the cylinder walls and eventually contaminate the piston rings. There is where the fuel pump does its damage.

 

[SpiralOut]

Ok, Thanks for the clarification guys.

To the OP, You said you have a knock in cylinder 1? Sounds like your bearings are on the way out?

 

[dsmmaniac12787]

Well my 16g is already shot anyway. Oil is everywhere in the intercooler piping. When it was venting, oil would blow out the bov and put a nice spot of dripping oil on the undersided of my hood.

I bought the car not running and put another 1,500 into it easily just to get it running. The guy I got it from had a lot of other supporting mods, but sold them before he sold me the car. I didnt realize the effects of the 255 without the afpr.

 

[dsmmaniac12787]

Yeah, at first it sounded like the valves. Then it got louder and louder. Thought it was the crank pulley or something else. But you can hear it when you first crank the car and the rpms go up. somebody told me it was the main bearing.

 

[iluvmy4g63]

Yeah, at first it sounded like the valves. Then it got louder and louder. Thought it was the crank pulley or something else. But you can hear it when you first crank the car and the rpms go up. somebody told me it was the main bearing.

could be any bearing in there. my 90 gsx started sounding like a buzzsaw one day. so i pulled the oil pan. (and wow look at that a balance shaft bearing. )WTF. any way installed a balance shaft kit cleaned the oil pan as best i could and pretty much drove there car 10,000 more miles til it got fullly built bottom end.

 

[dsmmaniac12787]

Yeah, I have never even pulled the oil pan off. Thats one of the areas I havent messed with yet so Im not looking forward to it. Looks like a messy PITA.