Detroit 8V92 hic-up

[k2diesel]

Hey guys,I usually hang out at the 1st gen forum, but I have a question about a detroit. I'm an LA city fireman at fs70. Our ladder truck is a 1990 Seagrave, 100' aerial, with an 8V92 & allison trans. Recently the engine has developed a miss at around 1900-2000 rpm. Above and below that it runs fine. Anybody out there with detroit experience with some ideas? TIA K2

 

[chuckwilson]

Let me ask you this? Is the miss wile its under load or free reving.

 

[k2diesel]

Chuck,thanks for the reply. The miss is only under load. When going downhill, you hardly notice it if at all. K2

 

[chuckwilson]

Ok its probably an injector going bad, Does the engine have electronic controls (DDEC) or is it mechanicel do you know!!!

 

[k2diesel]

Chuck, I believe its mechanical injection with an air actuated throttle. Also problem is more pronounced when warm, and under heavy throttle.

 

[dieselshu]

Detroit engine troubleshooting

K2, An easy check for bad injectors is remove valve cover and take a large flat tip screwdriver and push down on the injector spring while the engine is idling, do this on each injector, if you have a bad injector you wont notice a difference in the sound of the engine idling, if the injector is working properly you will hear a difference. Also since you have a mechanical rack check the control arm, pin and cotter key to make sure there is no binding or rubbing, do this check after the engine has run and is up to temp over 140deg.

Hope this helps



Dave

 

[chuckwilson]

K2 it is most likely an injector or the rack has come loose on one injector and backed off on fueling one cyl. Try wetting the exaust manifolds with some engine oil and run it around the block and check the oil will burn off the good cyl. but still show on the weak one. You will see some smoke but it wont catch on fire just stink a little!!!/ That will find your miss under load> Chuck