Cat c7 pto problems

rthomas · Dec 8, 2014

My big sweeper, 06 freightliner m2 w/cat c7/Allison 3500 has developed a very annoying problem that freightliner cant find, after the pto has been on for a bit (sweeping) the motor will start surging, as I know it the computer wants to give the motor 150 rpm when the pto is on, not specific to idle but any rpm up to governer limits, and this is what seems to be acting up. Does anyone have any insight on what the problem or fix could be?

towcat · Dec 8, 2014

you need to be more deseciptive. trans or engine PTO? brand of PTO? is there a rpm it auto disengages? is the rest of your powertrain on the truck stock?

FordGuy100 · Dec 8, 2014

Any codes? These CATS are hard to diagnose, I'll tell you that much (after solving a surging problem on a 3126, the C7's older version).

This only happens after the PTO has been on, not when just driving around?

rthomas · Dec 8, 2014

Its a tranny mounted pto, i want to think its a muncie but that might not be it, the pto is set to disengage at 25mph, it will hickup a few times after shutting down the pto but other than that it runs perfect when the pto is off, it used to take a.few hours of sweeping before it would start doing it but now its within 10 to 15 minutes, also the light on the pto switch will flash in time with the surging, and I have changed the switch. If its run long enough it will quit trying to run at the higher rpm and at that time the pto switch will flash a constant 1 second cycle. And no codes from the bulkhead module. Thanks for the help, this is going to drive me nuts if I can't find the problem

towcat · Dec 8, 2014

you checked your grounds already right? sounds like a loose electrical connection on the PTO to me. I'm still oldskool, i intentionally hoard and install mechanical PTO's in my trucks. If yours is a dana/chelsa PTO....."lotzagoodstuff" works for the company and can put you in the right direction, but it sounds like you need to do some homework first. you know it's not the kittykat since the CEL is not triggering. follow all the aftermarket wiring off the PTO and see where it leads.

Cat c7 pto problems

rthomas

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towcat

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FordGuy100

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rthomas

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towcat

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