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jfperkins3
New Member
4 Posts |
 Posted - 04/25/2011 : 1:02:51 PM
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I have a 1990 Wayne school bus with a Detroit 8.2 that has been running well since I bought it 25k miles ago. I drove it for 90 minutes this weekend, moved it once or twice, and then it wouldn't start.
For the last few months it has been stalling out at stops. I suspect the low idle governor needs attention. But it has been running fine and delivering full power. Suddenly it won't start. Both fuel filters are new, and when I crank the engine I get fuel out of the return line, but no ignition.
Could this be related to the governor?
I'm baffled.
Thanks for reading this, I hope someone can help.
john
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ralph55
Active Member
USA
21 Posts |
Posted - 05/01/2011 : 12:33:30 PM
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i think that there is probably something wrong with the buses engine.
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78fordwayne
Top Member
USA
2868 Posts |
Posted - 05/01/2011 : 1:13:14 PM
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quote:
Originally posted by ralph55
i think that there is probably something wrong with the buses engine.
FYI
PROFESSIONAL garage |
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bwest
Administrator
United States
3820 Posts |
Posted - 05/01/2011 : 3:04:46 PM
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quote:
Originally posted by ralph55
i think that there is probably something wrong with the buses engine.
Here's your sign!
Seriously though, there are only a few people who will even attempt to work on an 8.2 fuel pincher. I knew enough to get rid of mine when I could so I personally can not help you. Good luck. |
Bryan |
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ralph55
Active Member
USA
21 Posts |
Posted - 05/01/2011 : 5:33:40 PM
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| well your bus is 21 years old |
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bluebirdvision
Top Member
USA
1081 Posts |
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Tatum
Top Member
United States
606 Posts |
Posted - 05/01/2011 : 7:01:25 PM
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Most of the time, ralph55, old buses tend to break less than new buses.
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Jake
Top Member
USA
3528 Posts |
Posted - 05/01/2011 : 7:05:09 PM
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quote:
Originally posted by ralph55
well your bus is 21 years old
That is completely irrelevant, plenty of older buses still on the road. This, again, is the professional garage. Please do not reply to these topics unless you can provide helpful information that might help the original poster diagnose what is wrong with their bus.
The people who post in this section are real life, employed (or retired), bus mechanics or diesel technicians and they know what they are doing. It is very hard for them to help somebody out if a topic is filled with rude or sarcastic comments.
Thanks! |
Edited by - Jake on 05/01/2011 7:11:17 PM |
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Thomas Ford 85-16
Top Member
USA
4177 Posts |
Posted - 05/02/2011 : 06:44:03 AM
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Alrighty, I'm the eighth reply and might be the first that's useful to you. That's sad.
What chassis is this in? And does it use the key to stop and start the engine, or is there an engine kill lever (for normal use, not emergency)? On my 1985 Thomas Ford with an 8.2L, I had problems with the connection to the fuel shut off solenoid. Same symptoms you describe... It would randomly not want to start back up again, and sometimes it would die out of the blue when we were underway. When I cranked the engine it would spin freely and very quickly. Later I found out this meant it was getting no fuel.
What the solenoid does is move the fuel rack between full-off and the idle position. Since the 8.2Ls used unit injection, there is a rack that runs along the length of each cylinder bank to each injector. The rack turns a gear on each injector to meter the amount of fuel. That shut off solenoid could be losing it's electrical connection and pushing the rack back to full-off. In my bus, it was just a matter of disconnecting and reconnecting that harness...never had an issue again.
On my Ford, this solenoid is located ahead of the air cleaner, behind the thermostats, right near the mechanism that connects to the accelerator linkage. (The accelerator and the shut off work using the same fuel rack.)
Now, if you have a mechanical engine stop lever, it would be a cable attachment replacing the function of the solenoid. I'm not positive about how this is attached, but I think there is a spline coming upwards from the same unit that the accelerator connects to, and the engine kill cable would be attached to a lever attached to that spline.
Until you investigate further, DO NOT TOUCH THE GOVERNOR! They are very finicky on Detroit Diesels, so I hear. If you touch it, you may get a lopsided idle for the rest of the engines life, best case. Worst case, the engine will run away and do lots of damage. Check for loose wiring connections, bad solenoid, loose cable connections, etc. and report back to us.
Clear as mud? With no pictures this can be tough.
I'm not a mechanic, but I'm pursuing an engineering degree so I can wrap my head around this stuff. I've owned my bus for nearly 12 years now and I am very happy with my 8.2L. It leaks oil like a sieve, but it's very reliable, it's great on fuel, and makes a beautiful sound. |
Mike's Bus Yard - http://buses.zwebpages.com - Since 1999
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slippert
Top Member
USA
630 Posts |
Posted - 05/02/2011 : 06:49:25 AM
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Not knowing exactly what the top of an 8.2 looks like, as i have never had the pleasure of working on one. Didn't the 4 cycle's have a rack to operate injectors? correct me if i'm wrong. if they have similar injection system to the 2cycle's 53,71 92 series you could pull valve covers and ck to see if the injector racks are moving properly. I have seen many of the 2cycles that won't run or stall out do to stuck or sticky injectors depending on the type of rack whether it's solid or spring and the position the injector sticks or is stuck at. hopefully this is helpful? the post above also has some useful info, apparently wasn't there when i started my post and didn't refresh before exit. it doesn't take a lot of moisture in fuel to raise havoc with DD's older injectors, use to replace them quite regularly with stuck or frozen racks. especially if vehicle sets a lot.
as stated above unless you know what your doing you're not going to want to get into governor and probably not under valve covers either hopefully its your shutdown solenoid. |
Edited by - slippert on 05/17/2011 07:01:09 AM |
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mastertech
Advanced Member
274 Posts |
Posted - 05/02/2011 : 1:51:42 PM
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I think I would first take a few minutes and pull the valve covers to be sure the rack is moving free to full fuel and back. That will tell if an injector is sticking.
Unless you have training or at least a service manual you should not mess with the governor or rack. They are not tricky or dangerous but if you dont know how they work and how to set the parts in order yes you will have problems.
I personally loved our 8.2's for their ease of repair,reliabilty and fuel mileage. As far as leaks the fuel supply pump ,oil pans rusting out and valve cover gaskets were the biggest offenders but all easy to fix and would go 100,000 miles easy between changes. |
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jfperkins3
New Member
4 Posts |
Posted - 05/17/2011 : 02:56:37 AM
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Thanks Thomas. I checked the solenoid, and it made a resounding clunk on and off. Also, I can get fuel out of the return line when I crank the engine with the battery. Just no ignition. Wouldn't a rack in the wrong position keep fuel from passing through at all, or would it just keep fuel from going into the cylinders?
Thanks for your help.
John
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jfperkins3
New Member
4 Posts |
Posted - 05/17/2011 : 03:01:56 AM
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| Thanks, Mastertech. I agree that that's a good place to start. But if the solenoid is moving, where might the rack be binding or missing a linkage? |
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slippert
Top Member
USA
630 Posts |
Posted - 05/17/2011 : 04:37:22 AM
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you should have a constant flow of fuel thru fuel rail in heads, sounds like you do. the fuel injectors are individual unit injectors that regulate the amount of fuel injected to each cylinder by the position of it's rack.
The shut down solenoid is suppose to push the injectors via the linkages, rails and racks from the governor to each head into the no fuel position when shut down and allow the injectors to move via the governor when started.
So no a rack in the wrong position will not keep fuel from passing thru the heads,and it could keep fuel from getting to the cyl's. it's not hard to ck racks with valve covers removed. all inj racks and linkages should move from no fuel to full fuel freely without binding, just remember that the shut down solenoid will hold racks in no fuel, and unless the engine is running the gov springs should move racks to full fuel with key on, engine off. their are steps to release gov springs by backing off certain adjustments to really get a good feel of inj's and rack's that come's back to the manual.
do you have access to a service manual? if not it would be a really good idea to find one, manual should explain cks and tune up procedures clearer than on here.
again if your are not familiar with steps and procedures you can cause yourself more problems.
basically the shut down solenoid should move inj rack to no fuel,when shut off. when you turn key on, it should release and allow gov springs to move rack to full fuel position for start up, then when engine cranks and starts gov weights should move rack back to idle position, and keep there until you throttle up with foot pedal. a good manual and being familiar with steps, adjustments and procedures on any GM diesel would still be in your best interest before attempting any repairs or adjustments.
as MT said their not difficult or dangerous, but something you do not want to do blindly or in their proper order.
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Edited by - slippert on 05/17/2011 09:55:52 AM |
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IBTMech
Top Member
USA
973 Posts |
Posted - 05/17/2011 : 8:00:34 PM
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I've only dealt with one 8.2 in our fleet and when it died I removed the fuel shutoff solenoid and drove it back to the shop. I had to stick my finger into the injector pump and depress the lever to shut it off. Pretty basic.
A sticking rack is not unusual and not limited to Detroits. ULSD may be a factor in sticking racks in older diesels.
If it was running fine before those issues I would not mess with the pump. Check the voltage to the solenoid and the ground. Remove the shutoff and see if it will fire up. You can shut it off with your finger. |
If it doesn't fit, FORCE it.
If it breaks, well, it needed replacing anyway.
Pullin' wrenches for 45 years. |
Edited by - IBTMech on 05/17/2011 8:06:33 PM |
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engine ran fine 1 minute, wouldn't start again
