manometer blowby test

[JOHNFAK]

So... before I go spending too much more time and money on the truck I wanted to get an idea of engine health. Didn't want to spend the $300 on compression adapter and guage ..... so manometer.

My results were 2" at 2200 and 3" at 2800 ....

 

Problem is this I s about NEW engine spec .... so I think some things astray. Most obvious would be too much venting somewhere .... but my front gear vent is blocked off .... 

And I run a dual billet side tappet.... 

1 was blocked.

Other was blocked with 15/64 hole.

Measured from dipstick with clear tubing .... pics to come. Any ideas of where I'm venting or ....?? 

 

 

[JOHNFAK]

Only other thing is engine was cold ..... the test isn't clear cold or warm ..... but I might retry warm sometime.

Edited October 17, 2015 by JOHNFAK

[Mopar1973Man]

Just remember that a cracked piston / ring can pass a blow by test.

[JOHNFAK]

More details mike .......

I need to run this again warm .... See what the results are.  I don't particularly have a blow by concern ..... Truck starts well, sounds great , and seems to have minimal blow by out of crank vent. Just make me feel better about dumping more $$ into it.

Cant drive it today .... Blew a sidewall out on a $350 trxus tire ..... No spare ..... So 2 new nittos G2 on there way. 

 

Reference link. 

 

http://www.cumminsforum.com/forum/94-98-engine/232657-checking-blowby.html

 

[JOHNFAK]

Where I'm really heading with all this is trying to find source of white smoke at idle ... Ppump. 

From what I've been told this is typically too much fuel .... And the p7100 has no regulation on idle fuel. So normally its injectors. 

 

However have aver replaced injects with no difference ...... So don't think that's cause here.

leaves me to check ...... Timing .... Adjust valves. 

 

Beyond that ....... Probably a valve issue itself ....cracked etc ...... But I don't think so based on no "ticking" sound from fuel/air leaking by ..... As well as head was off less than 2 years back from PO. Assume they checked head at the time..... But never know. 

[Mopar1973Man]

Not enough coolant temp maybe?

[TFaoro]

If you want to compression test it I have everything.... all I ask is you pay shipping and make a donation to the site 

[JOHNFAK]

Thx..... May end up taking you up on the offer ....... But will be down the track ...... Next time I pull injectors. Going to run with manometer test on warm engine for now .... Will update results once new tires get in ......

beyong that hat going to adjust timing and valves and possibly deal with a rear main seal .... 

[TFaoro]

Yup. Just drop me a PM when you're ready and I'll send it all your way. It's actually pretty quick and easy! Mine made around 410psi in each cylinder before the rebuild. When I switch injectors I might do it again for the heck of it. 

[Cowboy]

Hazing at idle could be caused by injectors or a larger DV.  Are you sure it's diesel and not oil?  Check for a slight amount of air in your fuel.  Sometimes it will go unnoticed, but results in a slight drop in power and MPG's, slower throttle responce, and a haze. 

[JOHNFAK]

Yup. Just drop me a PM when you're ready and I'll send it all your way. It's actually pretty quick and easy! Mine made around 410psi in each cylinder before the rebuild. When I switch injectors I might do it again for the heck of it. 

I remember reading something about compression test being

a) Careful not to do "wet" ..... think this was referring to someone adding oil and repeating test ........ for leak ring/seal

http://www.cumminsforum.com/forum/89-93-powertrain/3319-compression-5-9-6bt-engine.html

b) Can be misleading in results (inconsistent) due to some reason ........ hence reason cummins recommended manaometer as their standard

Still be useful to do/know - so thx.

Hazing at idle could be caused by injectors or a larger DV.  Are you sure it's diesel and not oil?  Check for a slight amount of air in your fuel.  Sometimes it will go unnoticed, but results in a slight drop in power and MPG's, slower throttle responce, and a haze. 

Don't think its injectors (I originally did) as I have changed them out with no difference.
DV look fairly close to stock based on shoulder height etc. I do have another set I guess I could throw them in.
Hard to notice a loss of power when at 600+ ...... that same reason makes its hard on MPG and haze as I expect both to be worse than normal on truck with that HP.

 

[Mopar1973Man]

Dry test compression is fine and will show low compression cylinders vs. blowby which is a summation of all cylinder blowby. Like JL Welding found out you can crack one piston and still pass a blowby test but fail a compression test because compression test will show lower on a damaged cylinder. It will show othere thing a blowby won't like blown head gasket between cylinders will show up as a low number on two cylinders. Also using the compression test hose and compressed air you can pressurize the cylinder and feel the air escape through the adjacent cylinder. So blowby test is a quickie test but no conclusive of what is going on. 

[JOHNFAK]

Well then might need to do compression test.

Weird that supposedly cunmmins don't do compression - they do blowby (per bill [illflem]) ........

No other real signs ....... engine has no ticks ..... starts easy ...... and like I said probably over 600hp ......so strong. But I guess until I find the cause ...... hard to be sure.

So ...... add that to list ......... rear seal, timing change, valve adjust, vibration issue and now compression test with next inj swap ...... lmao - I need bill (W&F) here .....

[Mopar1973Man]

The only reason the blowby test came out is most don't want to spend money on the special tool to do the compression test. So the blow by test was simple for the general public to do and did require the costly tool. Like I said the only way to test each cylinder is compression test though.

[TFaoro]

That's why you let a dummy like me buy one... Then I can pass it around and let everyone have some fun!

[Mopar1973Man]

I'm thinking about just buying the cheap Harbor freight compression test which gives me the gauge and hose and some adapters. Then pick up a Cummins test injector and I've got a compression tester I can use.

[TFaoro]

I can't remember where I got my slug. I think it was 40-50 bucks though.

[Cowboy]

Couldn't someone just modify a junk injector, get a gauge and be good to go?

 

Or does the displacement of the injector/gauge screw things up?

[TFaoro]

You'd also need an injector hold down that was some way sealed to the top of the injector and has a fitting on the top for the gauge to hook up to. Getting the seal would be the hard part.

Otherwise the injector would just blow out of the hole.

[Cowboy]

Ahhh OK, makes sense.  I was picturing a 12V, I guess the 24Vs would be a little more difficult.