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Engine Discussion of preventative/corrective maintenance and other technical issues regarding your coach's engine.

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  #21  
Old 10-10-2014
revolution revolution is offline
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Quote:
Originally Posted by cemjam View Post
If I undestand it seems that the 4 injectors are pushing air out when the piston is moving in the upwards motion. Does the injector have a check valve to prevent this from happening?
I'll admit it's been 30 years since I was a diesel mechanic but yes, that's my recollection. If not, then combustion pressures would surely push into the pump and create what I seem to have.
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  #22  
Old 10-10-2014
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iamflagman iamflagman is offline
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Daryl,

Please check the "Show your signature" box below the "Additional Options" section when you type in a reply or start a thread, this helps our members know what type of coach you are dealing with it can sometimes make a difference. I've already done that for you a couple of times.
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  #23  
Old 10-10-2014
revolution revolution is offline
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Quote:
Originally Posted by Bill Pape View Post
Folks are only trying to help you out, if you are convinced all 4 injectors failed at the same time have them checked or replace them & let us know the outcome.
I realize that, thanks. I'm just looking for an argument that makes more sense than mine. And maybe I should rephrase that, I'm not looking for an argument, I'm looking for better logic than what I'm pushing. I agree it's ludicrous 4 injectors should decide to quit while the vehicle was parked for a week..

Anyway, swapping injectors about should prove it one way or the other.
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  #24  
Old 10-10-2014
revolution revolution is offline
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Originally Posted by iamflagman View Post
Daryl,

Please check the "Show your signature" box below the "Additional Options" section when you type in a reply or start a thread, this helps our members know what type of coach you are dealing with it can sometimes make a difference. I've already done that for you a couple of times.
Oops, sorry. I'll keep an eye on that in future. Thanks.
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  #25  
Old 10-10-2014
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giderich giderich is offline
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It is past time to be talking to the folks who did the rebuild on the Inj Pump.

Quote:
Originally Posted by revolution View Post
I realize that, thanks. I'm just looking for an argument that makes more sense than mine. And maybe I should rephrase that, I'm not looking for an argument, I'm looking for better logic than what I'm pushing. I agree it's ludicrous 4 injectors should decide to quit while the vehicle was parked for a week..

Anyway, swapping injectors about should prove it one way or the other.
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  #26  
Old 10-10-2014
wtom24 wtom24 is offline
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There should be no air blowback from any injector. The injectors work by having the pintle seal against the nozzle until the spring pressure is overcome by fuel pressure from the injection pump stroke. Caterpillar uses a closed injector that does not have a return line, so any air that leaks past a closed injector nozzle will move toward the injection pump during the fill cycle of the injection pump plunger. On my coach, one injector stuck open left us by the side of the road. It was #1, the only one I could not get my finger in to feel the air coming out. I finally installed a pressure gauge in the plug on the top cover of the injection pump and could clearly see the pulse of air while cranking. Then it was a matter of loosening one injector nut at a time until the pulse went away, proving which injector was the culprit. I wish I had done that first-I could have left the nut loose and limped home rather than having it towed. In any event if there is air in the return line it is more than likely coming from an injector. The injection pump internal cavity is kept under about a 35# pressure by the transfer pump on the front of the injection pump during normal running conditions. I ,like you, don't understand how 4 injectors failed at the same time.
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  #27  
Old 10-10-2014
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Leaving the nut loose would have bathed the engine in fuel, not a good plan. If the tip a nozzle falls out of the nozzle compression will back feed. 4 nozzles feeding back air aren't good working pieces.
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  #28  
Old 10-10-2014
revolution revolution is offline
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Quote:
Originally Posted by wtom24 View Post
There should be no air blowback from any injector. The injectors work by having the pintle seal against the nozzle until the spring pressure is overcome by fuel pressure from the injection pump stroke. Caterpillar uses a closed injector that does not have a return line, so any air that leaks past a closed injector nozzle will move toward the injection pump during the fill cycle of the injection pump plunger. On my coach, one injector stuck open left us by the side of the road. It was #1, the only one I could not get my finger in to feel the air coming out. I finally installed a pressure gauge in the plug on the top cover of the injection pump and could clearly see the pulse of air while cranking. Then it was a matter of loosening one injector nut at a time until the pulse went away, proving which injector was the culprit. I wish I had done that first-I could have left the nut loose and limped home rather than having it towed. In any event if there is air in the return line it is more than likely coming from an injector. The injection pump internal cavity is kept under about a 35# pressure by the transfer pump on the front of the injection pump during normal running conditions. I ,like you, don't understand how 4 injectors failed at the same time.
Yep, I suppose you could have rigged something to catch the fuel and driven on one less cylinder. Hind sight....

I find breakdowns don't always put me in a mind to be creative unless I am totally stuck. If not, I like the tow truck and then work on the problem in my own garage, if that's feasible.

Well, I'm glad someone aside from me has experienced this with at least one injector. Thanks for posting your experience. I was definitely getting plenty of air out of the bad injectors. Because its Friday and I'd like to use the vehicle Sunday I opted for purchasing 8 reman CAT injectors. I turned the old units in as cores but asked that CAT check them on Monday to see their condition just out of curiosity. I guess if the test is too expensive I will just let it go. By then I'll know if my diagnosis was good, by tomorrow morning I'll know that..

Weird that FOUR would die in this manner. My wife suggested that seeing the bus sat idle for 4 months with a quarter tank of fuel, maybe the varnish on the sides of the tank hardened, then when I filled it, the hardened particles were washed off and went into the fuel system and could have caused this. I knda think any solids would have been caught in the filters but I can't come up with a better explanation.

Thanks for your input.
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  #29  
Old 10-11-2014
revolution revolution is offline
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Quote:
Originally Posted by Mike Hohnstein View Post
Leaving the nut loose would have bathed the engine in fuel, not a good plan. If the tip a nozzle falls out of the nozzle compression will back feed. 4 nozzles feeding back air aren't good working pieces.
Agreed.
Physically, the nozzles all looked normal, ie. no parts missing..
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