Blown turbo or hung jake?

Discussion in 'Trucks [ Eighteen Wheelers ]' started by zx150, Jul 7, 2012.

  1. zx150

    zx150 Medium Load Member

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    Just got my '94 KW W900 back on the road after an engine rebuild on the CAT 3406b. The truck was running great with minor hiccups after letting off the fuel after climbing a hill, that was with no load. I bobtailed about 175 miles to pick up my load and the truck ran great but awhile after picking up the load the truck started to fight me going up every single hill. At first the truck was acting like it had no power then the pyrometer spiked along with the coolant temp gauge then the engine started to knock, backfire then stall out. I limped the truck to the nearest truck stop and kept having it die out after a half mile or so each time, I came to a flat stretch of road and the truck was able to maintain the speed limit no problem but as soon as I hit a hill the problems started back up. A driver that was behind me let me know that I was blowing flames from the stacks.

    I initially thought I blew the turbo but I popped off the intercooler hose and found no oil, it was bone dry.

    I did notice that every time the engine went to stall out it almost sounded like the jake was on, while going downhill I couldn't get the jakes to do anything so I unplugged them but that didn't help at all.

    So did I blow the turbo or do I have a jake that's hung up? There's maybe 350 miles since the rebuild, the truck starts right up and runs great until it gets down the road with a load on it. If this is a jake issue could I remove the jakes and run without them? The truck is safely parked at the FJ and off the road but I've gotta get it to the shop and I'd like to avoid the wrecker if at all possible.

    Thanks for the help!
     
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  3. bender

    bender Road Train Member

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    Sounds like the timing is off. If you drive it that way you'll likely scorch pistons and liners. I would stay put until you talk to your service provider since it's actually their problem to correct at their cost.
     
  4. Les2

    Les2 Road Train Member

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    Do what bender said and if the timing is correct check the fuel pressure. Years ago we had a truck that did something like this, it would idle all night but as soon as you put any type of load on the engine it would start starving for fuel and do some of the things yours is doing. It ended up being the fuel transfer pump was bad, actually completely shot. The guys at Cat couldn't figure out how it even made it into the shop on its on will.
     
  5. bender

    bender Road Train Member

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    Sounds like he's getting plenty of fuel with shooting flames out the exhaust.
     
  6. Superhauler

    Superhauler TEACHER OF MEN

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    you said it sounded like the jake was on. when it (backfires) is it when you give it fuel? if so you have a bad jake switch. usally the one on the back of pump which if i remember also sets your low idle. turn the main jake switch off and see if it still does it. if not that switch has gone bad.
     
  7. Superhauler

    Superhauler TEACHER OF MEN

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    opp's sorry didnt see where you had them unpluged. did someone forget to adjust them and have them to tight. the reason i ask is i did that once. screwed the adjustment screws down and forgot to back them off to adjust them. ran ok empty but under load it sounded like it was backfiring.
     
  8. zx150

    zx150 Medium Load Member

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    I rebuilt the engine myself so I'm the service provider. I suspected the timing so I reset the timing(on the side of the interstate) and that didn't solve the problem. The timing is spot on. Only thing that could use adjusting might be the governor on the fuel pump but if that's off it ain't by much.

    It still acts up with the jake switched off on the dash, I also disconnected the wires that run to the jakes at the valve covers and it still acts up. As far as the backfiring goes it is backfiring under throttle, usually the engine is just about to quit when it gets to that point and the pyrometer is showing VERY hot.
     
  9. Superhauler

    Superhauler TEACHER OF MEN

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    beyond my knowledge. could you have a pluged return line or a broke rocker arm?
     
  10. zx150

    zx150 Medium Load Member

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    I'm not really sure to be honest, I think I set them up right but then again this rebuild was my first time into a diesel engine. I do know that the first few trips up the street and back the jakes were working normally so I didn't really give it much thought as to whether or not I set them up right. I'll take a look tomorrow and see if the adjusters are too tight.
     
  11. bender

    bender Road Train Member

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    It could be pre-ignition from incorrect pistons. Did you have any problems before the overhaul?
     
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