Kubota V1702 engine - Is 200-250 PSI too low compression to run?

[moocowman]

Compression is 200, 230, 230, 250PSI. I know this is lower than ideal (350PSI?), but shouldn't it still run at this compression? This engine died several years ago. Owner never had time to find out why, but suspects a fuel issue. Now I'm trying to get it running. Even with a constant spray of starting fluid, one of the cylinders might fire just once after 10-15 seconds of cranking. I'll deal with fuel system problems later, but I know it's getting some fuel. When I crack open injector lines, small amounts of fuel pulse out of each line. After a few seconds cranking, white diesel smoke starts coming out of the exhaust. But again, I'm using starting fluid just to make sure the engine has the right conditions to run at all.

 

[Shawn T. W.]

Starting fluid is probably the cause of the low compression, it should be more than double that ..

 

[Tinhack]

It might run on 250psi but will have no power. That could be the single fire you're getting. Check the valve clearance/adjustment before digging in too deep. After that, you could be looking at major disassembly to fix.

 

[moocowman]

It might run on 250psi but will have no power. That could be the single fire you're getting. Check the valve clearance/adjustment before digging in too deep. After that, you could be looking at major disassembly to fix.

Thanks for the answer. I guess next step is checking valve clearances. If they're ok, remove the head and check for valve leakage, check cylinder walls.

 

[rScotty]

Compression is 200, 230, 230, 250PSI. I know this is lower than ideal (350PSI?), but shouldn't it still run at this compression? This engine died several years ago. Owner never had time to find out why, but suspects a fuel issue. Now I'm trying to get it running. Even with a constant spray of starting fluid, one of the cylinders might fire just once after 10-15 seconds of cranking. I'll deal with fuel system problems later, but I know it's getting some fuel. When I crack open injector lines, small amounts of fuel pulse out of each line. After a few seconds cranking, white diesel smoke starts coming out of the exhaust. But again, I'm using starting fluid just to make sure the engine has the right conditions to run at all.

For any diesel compression test, be sure to use a Diesel Compression Gauge - it sounds like you have one. A diesel gauge normally goes to 1000 psi - much more than you can hold by hand. A gauge for a gas engine will not go high enough. In any compression test, test each cylinder by cranking the engine as close as you can to the same number of times, and with the throttle shut.

This is a general compression test procedure good for all diesels, but procedure 2,4,& 5 are specific to diesel motors that have pre-combustion chambers for indirect injection, and in which these pre-combustion chambers are held in place by the injector body. Not all diesels have indirect injection, but a lot of late model medium and small modern diesels do use indirect injection. In these there is a possibility that the pre-combustion chamber can come loose during a compression test if the right adapter isn't used.

This is the best desciption of compression test that I've ever found. It was originally given to mechanics at their factory school way back, but still good today.
Note that the graph shows the different pressures that can be expected with differing cranking rpm.
Luck,
rScotty

 

[Shawn T. W.]

Also when you got it apart ... Check for out of round cylinders and bent rods ...