1989 CF Mack Tower Ladder Back Firing

[TowerLadder5]

My fire department has 1989 CF Mack Tower Ladder that back fires when it is not completely warmed up. The truck originally would top out at 52mph so we had the fuel turned up. Top speed is now 62mph which is plenty fast enough however, it back fires when the engine is not completely warmed up. When we take off out of the station, the engine is fine but as we go through town, the second that we let off the accelerator to slow down and then depress the accelrator again, it back fires. Does anybody have a clue as to why it would be doing this? Any help is appreciated!

[gearhead204]

a back fire in a diesel is almost impossible , does this truck smoke heavily when accelerating? my best guess is that you have a bad injector and it is pushing unburnt fuel into a cool exhaust manifold then when back under power, the fuel ignites and causes a back fire. once the manifold is hot the next time you let off the fuel the raw fuel is partly atomized and would create white smoke but probably wouldn't back fire. does the engine oil dilute or smell of diesel?

[General Ike]

Any chance it's backfiring through the turbo? Just a stab in the dark.

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