Compression Test Question

[roostercogburn]

I have a 98 B2400, low compression on #2 (100 psi) have pulled head and measured cylinder bore, its within specs (3.074) rings look good and no scoring, no blown head gasket, no burnt valve. Can the injector be bad (allowing pressure to flow through it), as I went through glow plug for test? This is the only thing I can think of, I am wanting to find the root cause before I spend any major money.
Thanks

 

[North Idaho Wolfman]

Yes compression can escape via the injector base gasket.
Just use some heavy oil and look for bubbles.

 

[roostercogburn]

If not thru the base gasket, can it backflow thru the injector, seems to have been allot of overflow of fuel on the return, might that been indicative of cylinder pressure thru the injector, if that's also possible, then I may have the problem.
Thanks

 

[North Idaho Wolfman]

I've never seen that happen, but I guess it's possible, send the injectors to be tested.
Note:
If it was passing compressed air back through the bypass it should have air and not just fuel in the bypass.

 

[Diydave]

Or try swapping the bad injector to another hole. If the problem follows, its with the injector...

 

[rbargeron]

I'm not Chubby - more like plain fat - but I'd suggest turning the head upside down and pouring some gasoline in the valve recesses to see which ones hold it and which ones let leak out through the seat.

 

[roostercogburn]

I did leak down test on valves, injectors were last thing that I can't test myself without spending any money, that's why was curious if it was possible to backflow thru injector.

 

[roostercogburn]

Well finally getting some where, tested injectors and they are good, injector pump is shot (being rebuilt), and diesel tech suggested I pull a vacuum on valves and damn if they did not hold, so off to get the head rebuilt, hopefully will have all the parts in next week for assembly.
Just a side note, you can't get the oil pan off without pulling the front frame, weld nuts block access to a couple of pan bolts. It wasn't that bad because I pulled the front axle assy. first.