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OK, where are all the Cummins experts?

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CJLennon

Well-Known Member
Joined
Jul 24, 2009
Messages
62
Location
Chapel Hill, NC
I've got a 1975 Autocar dump truck with a PT-370 (smokin') engine. At the begining of the year, it was smoking so bad that we tore the heads off, found a burnt valve, ground all the valves, and put it back together. Now we had the opposite problem, no smoke but would not pull. Purs like a kitten at idle so I know we are hitting on all 6 cylinders. We sent the pump out and had it rebuilt but it made no difference. So we rechecked the valve clearance and the injector travel (using the dial-indicator method) and it made no difference. So, out of desperation, I increases the adjustment on the injectors from .170 to .200 in an effort to get more fuel into the engine but this made no difference. The fuel feed line to the cylinder head is not crimped. So, as hard as it is to believe that I have a Cummins that fails to smoke (except when cold), I am really lost.

To summarize, it smoked and pulled really well except for a rough idle and a popping noise in the exhaust pipe at idle. After grinding the valves, the smoke stopped and the power was lost. The injector adjustment was done 3 times by myself, the pump was rebuilt, we went from a number "12" pump shim to a "7" and it still made no difference. So, any thoughts? Let me know if you need any other details.

As always, thanks to all that take the time to educate me.

Chris
 
A

Autocar

Senior Member
Joined
Dec 20, 2009
Messages
261
Location
ohio
Good question, not sure where everyone went. A few months back I came on here and got a virus it took me two weeks before I got my computer back. Then for some reson the computer wouldn't let me into the site. So we did in time figured it out and I made a post about a add on govenor on my 89 Autocar with a cummins in it but not a word from anyone. Maybe we are the only one let :)
 
2stickbill

2stickbill

Senior Member
Joined
Nov 1, 2009
Messages
677
Location
Romayor Texas
Occupation
Sniffin diesel fumes.
CJLennon said:
I've got a 1975 Autocar dump truck with a PT-370 (smokin') engine. At the begining of the year, it was smoking so bad that we tore the heads off, found a burnt valve, ground all the valves, and put it back together. Now we had the opposite problem, no smoke but would not pull. Purs like a kitten at idle so I know we are hitting on all 6 cylinders. We sent the pump out and had it rebuilt but it made no difference. So we rechecked the valve clearance and the injector travel (using the dial-indicator method) and it made no difference. So, out of desperation, I increases the adjustment on the injectors from .170 to .200 in an effort to get more fuel into the engine but this made no difference. The fuel feed line to the cylinder head is not crimped. So, as hard as it is to believe that I have a Cummins that fails to smoke (except when cold), I am really lost.

To summarize, it smoked and pulled really well except for a rough idle and a popping noise in the exhaust pipe at idle. After grinding the valves, the smoke stopped and the power was lost. The injector adjustment was done 3 times by myself, the pump was rebuilt, we went from a number "12" pump shim to a "7" and it still made no difference. So, any thoughts? Let me know if you need any other details.

As always, thanks to all that take the time to educate me.

Chris
Click to expand...

Not an exspert but have you checked the injectors?I hope you didn't leave them in the heads while removeing and installing them.I knew a guy did that and set the head down on something and the injector tips were messed up.But this was on a Cat.
 
willie59

willie59

Administrator
Joined
Dec 21, 2008
Messages
13,396
Location
Knoxville TN
Occupation
Service Manager
Yep double stick, I'm not a Cummins expert either. Not much I can add. I hope someone does have suggestions though, as I am curious. :)
 
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BillG

Senior Member
Joined
Mar 26, 2009
Messages
510
Location
S. Wisconsin
Just a thought, is the manual stop (on the pump) seated all the way? May be a chance that you are bypassing fuel.
 
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oarwhat

Senior Member
Joined
Dec 14, 2009
Messages
840
Location
buffalo,n.y.
We had a couple PT 270's, I know they had an external aneroid which would hold back fuel until the turbo pressure was up. Maybe it's bad?? We never had a problem with them but the were seperate from the pump. Good luck Randy
 
MKTEF

MKTEF

Senior Member
Joined
Apr 5, 2007
Messages
1,013
Location
Norway
Occupation
Production manager
I'am not familiar with that engine, but is your turbo ok?
No turbo, no guts, no nothing...
 
B

busdrivernine

Well-Known Member
Joined
Sep 17, 2007
Messages
163
Location
TEXAS
re run over head if you went from.170 to .200of travel then you are running them too loose you set injectors what did you set valves on If I remember right it was .014 for intake and .027 for exhaust and you have mark on the accesory drive pulley that will have like a A ,B,or C or maybe 1-6, 2-5, 3-4, The firing order is 153624 If you rotate and the marker is on 1-6 if both valves are closed on say 1 then you adjust valve on cylinder 1 and the injector on #4 you then rotate engine to next mark 2-5 or B then you adjust valves on #5 and injector on # 1 and keep on till you get back to the setting of either 1-6 or A Here is a example
mark VALVE INJ
A-1-6 1 4
B 2 -5 5 1
C 3 - 4 3 5
A 1 - 6 6 3
B 2 -5 2 6
C 3 -4 4 2
IF ALL ELSE FAILS FIND A OLD MAN THAT IS GOOD ON OLD SCHOOL CUMMINS They are getting hard to find Hope this helps if not let me know and I will get somebody else to sign on and see if he can help you (NOTE ) you might wnat to try to find a good mechic tocheck out what UI have told you as it has been a long time since I worked on any Cummins PT engines Good luck Tony
 
truckdoctor

truckdoctor

Well-Known Member
Joined
Nov 14, 2010
Messages
152
Location
reno nevada
Occupation
mechanic
I don't want to sound like a jerk but did you change your fuel filters? I know this is a dumb question but I have found that this has been the start of many problems in the past that were unexplainable. Also did you check and see if there is a plugged fuel line back towards the tank. The last thing I would maybe consider is the cam timing. With the heads being pulled off maybe it changed the cam timing with the height of the new head gaskets. That one is a long shot but it is one to consider. Good luck
 
O

Oldiron

Well-Known Member
Joined
Dec 18, 2009
Messages
52
Location
Alberta Canada
Have you put a fuel pressure guage in the test port on the PT ?, there should be a pressure number on the data plate, is the throttle shaft openning all the way IE is the break over cracking ??? if all of the above check out try a regulated air source set to 15 psi in the aneroid port.(if you are getting 200 + psi at throttle crack at test port it is prolly not aneroid)

if the above test don't pan out bring this over to theDieselgarage HD forum (not trying to steal members just trying to help (i'am 379Longhood there) :cool2
 
S

surfer-joe

Senior Member
Joined
Mar 25, 2007
Messages
1,403
Location
Arizona
Most old Cummins, and some new ones, are being used with great
sucess as boat anchors and flower pots.
 
S

stinkycat

Well-Known Member
Joined
Oct 19, 2009
Messages
224
Location
Ohio
Occupation
retired, disabled vet
It's been along time but I remember that we torqued the unit injectors on Cummins At 180 inch pounds like Isay that was along time ago
 
Q

QUANIE

Member
Joined
Jan 18, 2008
Messages
17
Location
NASSAU
You did not respond to ,was the injectors removed during repair.if not, the injectors screen can also get cloged..,now smoke and low power is a sign of low fuel being deposited in cylinders.
 
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