Need help on diesel powered compressor

robpeever · 07-03-2012, 10:30 PM

Hoping someone has insight into this problem. I recently found an old diesel air compressor in a farmers field and was able to purchase it very cheap. Brought it home, cleaned it up, changed fuel, oil, filters and installed a battery... fired right up! Impressive, but I still need help. The motor is a Cummins V378 6 cylinder. One side of the motor runs, the other side compresses air. It's called a "monoblock" compressor and was made by "Grimmer schmidt" (no longer around). The motor starts like a charm, runs like a dream, makes no funny noises, and does not viberate, sputter, or bog. However, when I push the lever to build air pressure it revs up and sounds good...then slowly the motor starts to stall and finally does (at around 80psi). I need to get 110 psi for sandblasting headstones. My initial thought was the motor is in need of a rebuild and does not have the power to build the pressure I need, but it starts and runs so good I have a hard time believing it's that.
It does blow black smoke when its running so I'm thinking it's running quite rich, but I cant find a manual for this machine anywhere. Any insight would be great!
Thanks,
Rob
Ontario, Canada

379Longhood · 07-04-2012, 12:34 AM

Have you checked the air filter, diesels do not run rich like a gas engine, black smoke is a sign of lack of air, Also check the diesel sides intake system for blockages.

Backslap · 07-04-2012, 12:42 AM

I would also run the overhead for correct clearance when you find the information for the engine.

bmoeller · 07-04-2012, 01:41 AM

Replace the air filters and check the fuel pressure.

Is there a Murphy switch on it? (Safety switch to prevent full RPMs til the oil pressure comes up).

robpeever · 07-04-2012, 01:50 AM

I have replaced the air filter and checked the intake... Not sure if its a "murphy's" switch, but it does have a fuel shut off valve with an electric selinoid. I have only a basic understanding of diesel motors. Am I correct to assume that because of the easy start it has decent compression? It starts with 2-3 seconds of cranking.
I have also pulled the injectors and cleaned them up.
Thanks everyone

Dodgefarmer · 07-04-2012, 04:00 AM

Does the motor have a governor control to maintain rpms under varing loads? If it does maybe its not adding fuel as load increases, although that wouldn't explain the black smoke.

Being an older engine the injectors would be all mechanical and you should have the injectors bench tested to see what its pop off pressure is (then you also need to to know the specs) and also check spray pattern. if the pressure is low or pattern fouled that can cause thye black smoke.

robpeever · 07-04-2012, 08:11 PM

It does have a governor and it seems to work. When I demand air the throttle opens, the motor revs up, then as the pressure builds it starts to stall out (the throttle still stays fully open).

Red Diesel · 07-06-2012, 01:44 PM

I bet it's so old it doesn't even have a turbo. It's always gonna smoke in that case.

Check cylinder compression ??

robpeever · 07-06-2012, 06:48 PM

It is that old and does not have a turbo

At the risk of sounding like a complete idiot and exposing my lack of diesel knowledge... How do I test the cylinder compression without a spark plug hole?

dbennett48 · 07-06-2012, 08:25 PM

Glow plug holes, if you have glow plugs...

07-03-2012, 10:30 PM	#1
robpeever Junior Member Join Date: Jun 2012 Posts: 7 Points: 378 Thanks: 0 Thanked 0 Times in 0 Posts	Need help on diesel powered compressor Hoping someone has insight into this problem. I recently found an old diesel air compressor in a farmers field and was able to purchase it very cheap. Brought it home, cleaned it up, changed fuel, oil, filters and installed a battery... fired right up! Impressive, but I still need help. The motor is a Cummins V378 6 cylinder. One side of the motor runs, the other side compresses air. It's called a "monoblock" compressor and was made by "Grimmer schmidt" (no longer around). The motor starts like a charm, runs like a dream, makes no funny noises, and does not viberate, sputter, or bog. However, when I push the lever to build air pressure it revs up and sounds good...then slowly the motor starts to stall and finally does (at around 80psi). I need to get 110 psi for sandblasting headstones. My initial thought was the motor is in need of a rebuild and does not have the power to build the pressure I need, but it starts and runs so good I have a hard time believing it's that. It does blow black smoke when its running so I'm thinking it's running quite rich, but I cant find a manual for this machine anywhere. Any insight would be great! Thanks, Rob Ontario, Canada

07-04-2012, 12:34 AM	#2
379Longhood Senior Member Join Date: Oct 2009 Location: Alberta t0m0r0 Posts: 2,014 Points: 36,633 Thanks: 146 Thanked 387 Times in 311 Posts	Have you checked the air filter, diesels do not run rich like a gas engine, black smoke is a sign of lack of air, Also check the diesel sides intake system for blockages. __________________ Canadian Club member 27 '88 379 exhd 3406C 15 40s 10 pete unimounts '93 K3500 6.5 4L80 4" exh '62 gmc shortbox 454 super t10 big brakes JD 820 black dash 12V92 waitin' for a truck (mega ratrod) pettibone s20 3306 pc

07-04-2012, 01:41 AM	#4
bmoeller Senior Member Join Date: Dec 2008 Location: NW IL Posts: 4,545 Points: 33,392 Thanks: 132 Thanked 310 Times in 264 Posts	Replace the air filters and check the fuel pressure. Is there a Murphy switch on it? (Safety switch to prevent full RPMs til the oil pressure comes up). __________________ "Some people are educated beyond their intelligence." '93 W350 CC, LE, 5spd, HTT modded H1C, 4" DE Sold- '99 3500 Q/C, SO CTD, 4x4, 5spd. Traded off- '97 3500 C/C, 4x4, CTD '92 W250, LE, CC, CTD w/ tweaked pump (SOLD) "Obama = Hoax and Chains" If Obama is the answer, it must have been a stupid question.

07-04-2012, 04:00 AM	#6
Dodgefarmer Senior Member Join Date: Dec 2008 Location: Northern California Posts: 964 Points: 33,646 Thanks: 130 Thanked 170 Times in 118 Posts	Does the motor have a governor control to maintain rpms under varing loads? If it does maybe its not adding fuel as load increases, although that wouldn't explain the black smoke. Being an older engine the injectors would be all mechanical and you should have the injectors bench tested to see what its pop off pressure is (then you also need to to know the specs) and also check spray pattern. if the pressure is low or pattern fouled that can cause thye black smoke. __________________ Remember not to talk bad about farmers with your mouth full! --07 6.7CTD 2500 4x4, Quad Cab, Big Horn Pkg. 3.73, airbags, 6sp auto, with Mag-Hytec deep pan. --08 36' Jazz 5th wheel,triple slide, 12,000lbs --28' 22,400# PJ goosneck beaver tail trailer --95 & 96 5.9CTD 4x4 5sp. ext. cab. 33x12.50x16 front, 33x15.50x16 rear tires. R-1 tread, wheelbase shortened 30". Used as tugs on farm --81 IH 1800, DT466 210hp, 10 speed, --95 FL70, 8.3 cummins 275hp, 10speed --79 GMC 7000, DD 6V53 210 hp, 6sp ally -- A whole bunch farm equipment, all colors singles club # 198 WALNUT MEMBER #11(workers aganist lazy non-producers united together)

07-06-2012, 01:44 PM	#8
Red Diesel O'Skool Member Join Date: Dec 2008 Location: The greenest state in the land of the free Posts: 497 Points: 25,527 Thanks: 55 Thanked 88 Times in 76 Posts	I bet it's so old it doesn't even have a turbo. It's always gonna smoke in that case. Check cylinder compression ?? __________________ My Ride Album

07-04-2012, 12:42 AM	#3
Backslap Aimless Wanderer Join Date: Jul 2011 Posts: 356 Points: 16,928 Thanks: 13 Thanked 102 Times in 78 Posts	I would also run the overhead for correct clearance when you find the information for the engine.

07-04-2012, 01:50 AM	#5
robpeever Junior Member Threadstarter Join Date: Jun 2012 Posts: 7 Points: 378 Thanks: 0 Thanked 0 Times in 0 Posts	I have replaced the air filter and checked the intake... Not sure if its a "murphy's" switch, but it does have a fuel shut off valve with an electric selinoid. I have only a basic understanding of diesel motors. Am I correct to assume that because of the easy start it has decent compression? It starts with 2-3 seconds of cranking. I have also pulled the injectors and cleaned them up. Thanks everyone

07-04-2012, 08:11 PM	#7
robpeever Junior Member Threadstarter Join Date: Jun 2012 Posts: 7 Points: 378 Thanks: 0 Thanked 0 Times in 0 Posts	It does have a governor and it seems to work. When I demand air the throttle opens, the motor revs up, then as the pressure builds it starts to stall out (the throttle still stays fully open).

07-06-2012, 06:48 PM	#9
robpeever Junior Member Threadstarter Join Date: Jun 2012 Posts: 7 Points: 378 Thanks: 0 Thanked 0 Times in 0 Posts	It is that old and does not have a turbo At the risk of sounding like a complete idiot and exposing my lack of diesel knowledge... How do I test the cylinder compression without a spark plug hole?

07-06-2012, 08:25 PM	#10
dbennett48 Junior Member Join Date: Nov 2009 Location: Ukiah, Ca Posts: 361 Points: 22,250 Thanks: 52 Thanked 54 Times in 48 Posts	Glow plug holes, if you have glow plugs... __________________ Dave 2004 F-350 Regular cab with 6.0, Torqshift, 4X4, and just about all of the rest of the options. I added Guages, XM Satellite Radio, Air Horns, and a coolant filter. Bilstein shocks. Battery Desulphater that really works. Installed Jimmi Jammers. Pictures here: http://community.webshots.com/user/dbennett48 Completely Stock. I had a Detroit Diesel 8V92TA in a KW dump truck in 1980. That sucker would put out 425 hp but would never out pull a CAT.

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