Volvo D16 low compression

Hi walker09, If you have already set/ inspected the valve clearance (ruling out the valve being held open by incorrect adjustment) the most likely cause is a burnt out, chipped not sealing properly valve. The quickest test is removing the injector blowing air into the cylinder with a rubber tipped air blow gun via the injector hole. (rockers will be removed because injector is out, therefore both valves will be closed.) listen to see if air is escaping to the exhaust or inlet manifold. Be careful blowing air into the cylinder because when you release the blow gun any fuel or oil sitting on top of the piston will come spraying out the hole

In answer to your question. Do you also have either of these symptoms? Hard starting (extended crank time) or coolant being pushed into the overflow tank, out the cap? If the low compression is due to bad injector or cup the lost compression gases will cause these problems. If its escaping past the injector o-rings it will airate the fuel (this can be seen in the fuel tank at the return line at idle). If its escaping past the cup it will airate the coolant system.

That being said, if it is a bad valve, the head is removed and injectors removed in the process. On inspection of the injectors you could still find bad injectors that need replacing

 

That's why N14 Cummins was my favorite motor. They pull hard and every two cylinders can be torn down, and injectors can be changed out just by removing the Jake brake for that cylinder. Can even leave rocker boxes on.

 

Having the same issue. Thanks to Nasriza who told me how to conduct this test and I did the blow gun air compression test number 5 cylinder is not holding air as the other 5 cylinders, problem is trying to figure out where is leaking through past all the noise around me and I barely can hear a leak, kinder want to make me think my mind is deceiving me, but the # 5 cylinder is not shooting the air out with force like the remaining 5 so I know something is wrong with it.

 

Hey walker09, it’s possible, but not super likely, that a bad injector or cup alone is causing such low compression. A leak-down test would help pinpoint the issue - listen for air escaping through the intake, exhaust, or into the coolant system. If it’s a valve, as Volvo suggested, it’ll probably show up right away. If it’s the injector cup, you’d likely notice aeration in the coolant or fuel system as Fast Track Mechanic mentioned. Have you checked for other symptoms like coolant overflow or hard starts?

 

Walker09 said he got it fixed last week. It was a timing issue, kinda like the post I quoted.....

 

My fault, missed it