compression not!!!

[2Don2]

Ok I justhad my engine rebuilt 94/6.5 , cold starting is problem. I took it into my local gm guy and after a new IP and a bunch of other stuff the compression test has come back like this,
#1 after one crank 100 after 10 cranks 270
#3 50,220
#5 40,260
#7 220,340

#2 50,280
#4 0,200
#6 0,0
#8 did not do saw no point

So I have to go to the rebuilder and say What??

any ideas on what is wrong here?
and what should those numbers be?

a going broke fast ... :confused: Don

[Polar Diesel]

boy, that sucks! when you get it running check the blowby. maybe a valve or several valves. Put shop air in each cylinder thorugh the glow holes, check where it comes out, crankcase, intake, exhaust... at the worst a cracked piston.... 0 psi is major.

[Polar Diesel]

how many miles since rebuild?

[cruzer]

If you are going to supply air into the cylinder
(cyl leak down test)as Polar Diesel says be sure that cyl is at top dead center (compression stroke)so the valves are closed.

[2Don2]

Thanks for the comments

I had the engine rebuilt 3000km from here, Yellowknife NT Canada. The day I picked it up the rebuilder noticed the rough start but we attributed it to poor timming, as he had little experiance with the gear drive set. As I was going to drive trough Saskatoon where Diesel Services Group is located, They are the ones who I bought the geardrive set from, we thought DSG could check things over and that would be that.They did find the timming to be out and noticed my IP might me on its last legs. BUT as I was intransit and on my way back to Yellowknife with four kids in the Suburban they assumed as did I that once the timming was adjusted It would fix the cold start issue....
However as was descovered the very next morrning 300 miles away the cold start issue only shows up after a overnight rest. Once the engine is running, a restart is almost normal, that is what fooled us after setting the timming. We just had to let it get cold and then it would of been clear that it was more than just timming.

So to answer your question around 3500km on the rebuild, and there was no drivabuilty issues on that trip. Good millage 13-15mpg pulling a car hauler 5000lbs's at 100 kph, and know that we have a new IP it is blowing black smoke which it did not due with the old pump....???

I can not do the work my self but need to hear from others what I might discuss with my rebuilder?

Don

[ 04-16-2004, 01:45 PM: Message edited by: 2Don2 ]

[ucdavis]

Clearly there is nothing about a rebuild that should deliver the compression numbers you state, and clearly that is not something to which an installer contributed (compression chamber is closed w/valves, glow plug, head gasket & rings, none of which the installer handles). Therefore it is the rebuilder's fault all the way (unless he sold you a short block, no heads).
Valves seat against seats so one or the other could be snafu'd.
Glow plugs seat against their tapered hole; you can look there easily.
Head gasket seals by tension of the head bolts which is a mess to check at this point, but possibly the issue. Also, you might check for signs of water in the oil, use of coolant... indicating head gasket leak; sounds like enough miles on it to see something if that's it. I once got a rebuilt 283 w/improper head bolt torque that would barely run, some bolts were finger tight.
Rings are more or less dummy proof but there's some pretty creative dummies out there. No way to check this that I know of except the draw down test (how 'bout that guys- squirt oil in GP hole & rerun compr. test? I though I read somewhere not to do that on a diesel).
On a rebuilt you should be getting uniform compression all around within a 20psi band or so. Cruzer posted previously: " According to The Diesel Depot in the advertiser section, it states they sell used engines and the min compression on them is 350psi." And that squares w/a quick calculation based on gasser usable compression of 165 @ ~9:1 as follows:
165 x 21.5 / 9 = 394 psi. 350 used vs 400 new sounds about in the BP to me. And it should definitely be close to even between cylinders./

[tom.mcinerney]

Need to find out what service you agreed to purchase. Legally, in some areas there are definitions of 'rebuilt' and 'remanufactured' which differ, neither necessarily great.
For a diesel to run well, the heads need to seal well. New or reman heads should do, if quality reman. I bought 'used, low mile' heads which were crap.
For an engine to be rebuilt , it should have had resurfaced cylinder walls, and new rings, if not pistons.
In order to get comparable readings, it is good practice that a compression test be done by a shop in a manner that they use on other similar engines, at similar temps, etc.
Your comp test results indicate a used, not new engine. But your mileage {13mpg) indicates an engine that is not too bad. You might be seeing a combo of poor glowplugs(bad start), weak compression testing technique, and unseated/cracked ring(s).
The black smoke could be a combo of new pump delivery and no boost; or the smoke is from the cylinders too weak to fire. Were the injectors replaced? This is not included as part of a rebuild, but may be necessary.
On a new engine the compression is the clearest indication of the reassembly of parts whose dimensions have been restore to specifications in the rebuilding/remanufacturing process.
Good Luck.