| Author | Message | ||
| Brandon M (Brandon314159)
Registered Member Username: Brandon314159 Post Number: 67 Registered: 3-2011 Posted From: 173.8.221.225  Rating: N/A |
Quick question to hopefully pool the brain-power of some of the board here. I have a 6-71 in my TDH-4512. Upon acquisition, it had a 2-valve head on it. I have since then installed a fully rebuilt 4-valve w/ jakes, and rebuilt injectors. The power output from the 4-valve has never been up to snuff compared to the 2-valve. My dad (a 30+ year diesel mechanic) and I set the rack again, adjusted all governor settings (air gap, high idle, low idle, and buffer) however the after doing so the power got WORSE. I had to fully turn in the governor air-gap setting just to get the coach to move uphill. It doesn't blow a single bit of smoke on accel or under load, which has me thinking it's being limited somehow. Checking the obvious (rack binding/touching valve cover, fuel filters changed while doing tune-up). Going to re-check fuel pressure as well. I know a 10ton coach being pushed around by a 6-71 shouldn't be fast, but I'd expect it to blow a little coal when working hard. Thanks for any words of wisdom! | ||
| JC Alacoque (Jc_alacoque)
Registered Member Username: Jc_alacoque Post Number: 120 Registered: 7-2006 Posted From: 207.34.166.7 Rating: N/A |
There is possibly a shut-off rod at the back of the head, under the valve cover, that is operated by an air cylinder. It is adjustable, and pushes the fuel rod to the no fuel position to shut the engine off when you turn the ignition off. It might have gone loose and is not allowing you full fuel. It happened to me on my 4-71, with the same symptoms you describe. Worth a look anyway. JC | ||
| Brandon M (Brandon314159)
Registered Member Username: Brandon314159 Post Number: 68 Registered: 3-2011 Posted From: 173.8.221.225 Rating: N/A |
Hey JC, I actually converted the air-shutdown over to standard electric solenoid w/ the lever on the governor box. I swapped out the sprung rack-to-governor rod w/ a solid one since it no longer needed to change length for the air cylinder operation. Thanks! | ||
| Tim Brandt (Timb)
Registered Member Username: Timb Post Number: 644 Registered: 10-2003 Posted From: 74.251.162.133  Rating: N/A |
Might try a post over on the Yahoo Detroit group http://autos.groups.yahoo.com/group/DetroitDiesel/ | ||
| Brandon M (Brandon314159)
Registered Member Username: Brandon314159 Post Number: 69 Registered: 3-2011 Posted From: 173.8.221.225 Rating: N/A |
Thanks Tim, I posted over there too see if anyone had any thoughts. I'm almost to the point of installing a seat on the back of the coach so I can tinker with the engine while running under load. I need someone w/ a truck dyno! | ||
| Steven Foster (57_gmc)
Registered Member Username: 57_gmc Post Number: 73 Registered: 12-2010 Posted From: 24.151.174.38  Rating: N/A |
Brandon what kind or type of electric solenoid did to go to for the shut down. I still have the air but sometime I get little water in line and valve and when you come back from eating supper it will not start due to water that is holding the lever in shut off. Like to change my 6-71 over to electric. Thanks | ||
| Brandon M (Brandon314159)
Registered Member Username: Brandon314159 Post Number: 70 Registered: 3-2011 Posted From: 173.8.221.225 Rating: N/A |
Steven, here is a picture of my setup:  The trick is to get the solenoid to fully seat when in the 'on' position. This disconnects the pull-in coil and activates the 'hold' coil. Not having this seat will burn the solenoid up in short order. These are readily available all over ebay/etc. | ||
| john w. roan (Chessie4905)
Registered Member Username: Chessie4905 Post Number: 2245 Registered: 10-2003 Posted From: 71.58.71.157  Rating: N/A |
Did your two valve head use HV injectors? What injectors did you install in 4 valve head. What were the numbers and tag color on injectors? Is the governor a limiting speed version or a fuel modulating version? | ||
| john w. roan (Chessie4905)
Registered Member Username: Chessie4905 Post Number: 2246 Registered: 10-2003 Posted From: 71.58.71.157 Rating: N/A |
make sure you don't need fuel filters...just sayin.. | ||
| Mel La Plante (Mel_4104)
Registered Member Username: Mel_4104 Post Number: 182 Registered: 7-2006 Posted From: 173.180.112.173 Rating: |
Steve, where are you parking your bus when you go for supper, in the lake? there is no good reason to have water in the air line going to the air shut down. are you draining ALL the air tanks to get all the water out of the system.i have seen buses and trucks with the air tanks nearly full of water.if you are getting water in this shut off just think how much water you are getting in your brake system. check that front tank under the drivers seat compartment and let all the air out drain the tank so no air is left in it, the go drain the other tanks, how much water did you get out of each??? now go to a truck shop and get some air line anti freeze to flush the lines and tanks. undo the fitting going to your shut off sel. and let that stuff clean the line out' then hold a piece of paper towel over the end of that air line to see how much junk comes out of the line, when it is clean put it back on the sel starting the engine and shut it down, and try to see how it operates. good luck Mel 4104 | ||
| Brandon M (Brandon314159)
Registered Member Username: Brandon314159 Post Number: 71 Registered: 3-2011 Posted From: 173.8.221.225 Rating: N/A |
John, I will find out what injectors were installed in the 4-valve. They were the injectors that came out of the 4-valve head before I sent it in for new valves/springs and inspection. I changed the both of the fuel filters before doing the rack adjustment (Spin-on style). Checked for air in the fuel return, didn't see any. | ||
| FAST FRED (Fast_fred)
Registered Member Username: Fast_fred Post Number: 1664 Registered: 10-2006 Posted From: 67.238.59.158  Rating: N/A |
How old is the engine? IF built for H series injectors , the more modern N series can not be used with out changing pistons. FF | ||
| Luvrbus (Luvrbus)
Registered Member Username: Luvrbus Post Number: 1393 Registered: 8-2006 Posted From: 184.10.190.159 Rating: N/A |
Disconnect your shutdown they need a air gap,check the fuel pressure you should have at least 50 + lbs,could be the filters on the injector body it self stopped up people forget those little guys and you could have a injector rack on one injector seizing when the engine gets hot. I presume you have the old style 2 screw fuel rod ? good luck | ||
| Brandon M (Brandon314159)
Registered Member Username: Brandon314159 Post Number: 72 Registered: 3-2011 Posted From: 173.8.221.225 Rating: |
Update: I tinkered w/ the engine a bunch last night (much to the unhappiness of my neighbors). I changed out the spring pack on the governor, changed a few other suspect components and tuned it up enough to idle and gain RPM. Fuel pressure looked solid at 60PSI+ in-gear revving to about 1500-1600RPM (automatic transmission...so under load) I shut it down, and listened for the tell-tale 'injectors full fuel' noise that I could hear with the gov cover off. No dice! Except every time I pulled the cover off I could go full rack... So I yanked the breather tube off the side and peered in and cycled the rack back and forth a few times with the throttle lever. TURNS OUT that the )*&#$*^%#$ shutdown arm had been modified by someone and was such a thick piece of metal it was holding the rack about 1/3 travel away from full rack. So no matter what the governor did, it could never push that out of the way and get the rack up to full. To remedy (until I find a proper cover) I just drove the stop pin out of the way so the shutdown lever inside would swing an extra 1/2" away from the rack pin setup and not interfere. It locks back since I have a spring, so no worries there. Amazing that I drove 1300+ miles with about 2/3 rack available to me from Portland, OR to Reno, NV and back! Haven't test driven it yet, but looking forward to it. Thanks for the help guys. This one really got me good. | ||
| Brandon M (Brandon314159)
Registered Member Username: Brandon314159 Post Number: 73 Registered: 3-2011 Posted From: 173.8.221.225 Rating: N/A |
BTW it has N65 Brown Tag injectors installed. Rebuilt ~9mo ago. | ||
| marvin pack (Gomer)
Registered Member Username: Gomer Post Number: 1629 Registered: 3-2007 Posted From: 76.4.123.74  Rating: N/A |
Isn't it amazing what we nuts find that cause us big time headaches? glad ya foung it and now LOOK OUT LOL gomer | ||
| JC Alacoque (Jc_alacoque)
Registered Member Username: Jc_alacoque Post Number: 121 Registered: 7-2006 Posted From: 207.34.166.7 Rating: N/A |
Great you found it! I had the feeling it had to be something keeping it from going to full fuel. Onward! JC | ||
| Luvrbus (Luvrbus)
Registered Member Username: Luvrbus Post Number: 1396 Registered: 8-2006 Posted From: 184.10.190.159 Rating: N/A |
That was common practice on industrial engines back in the day before tamper proof governors you see that on older generators and pumps good luck | ||
| john w. roan (Chessie4905)
Registered Member Username: Chessie4905 Post Number: 2250 Registered: 10-2003 Posted From: 71.58.71.157 Rating: N/A |
with the number of previous owners, age, maintenance, etc. you never know what you may find |
