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Mack Midliner- Hard Starting- White Smoke (Fuel) at startup - Thoughts??


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New to the forum!  I just bought a 98 Mack Midliner 24' box truck last week and am trying to work the bugs out. We use it for hauling floor tile-it works great with the 5,500# Maxon liftgate!  It's a great driving/running truck with 140k on it-still getting used to the turning radius with the rear tandem down but otherwise great.  This of course has the Renault engine.

  • The main issue is a startup.  It will crank but not start unless you tap the accelerator a few times while cranking.  Once started it will stumble and buck  for 5-10  seconds then cleans up.  It blows white smoke (fuel) while cranking until it reaches standard idle.  Power is fine, or as good as 210 hp with a 6 speed can be!  No coolant loss or oil consumption.  I'm anticipating the answer is in the fuel rack or a sensor.   I can live with it for now but anticipate as the temps drop, I won't be able to get it to light in the winter months.

Any insight is greatly appreciated.  Thanks all!

 

Edited by Midwest Farms
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I remember that on some of the midliner truck around that year model they had a timming advance that worked off of oil pressure that advance the timming and they would be hard to start and smoke white smoke, I can't remember for sure, I will check on it when I get to work tomorrow.

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If it has  timing control try unplugging it the orings sometimes give grief if it stays smoky with the timing unplugged you either got to repair the solenoid or unplug it totally and set the timing to 16 or so deg btdc its quite an involved process  drain the coolant remove the cover pop the gear lose from the pump and reset the motor to 16 and put the gear back on the pump

Edited by fjh
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Thanks BR549 and FJH, you appear to both be spot on.  It appears to be the solenoid or an oil antidrain back valve (check value) at minimum.  The truck will run rough until the oil pressure picks up.  On a cold motor, it takes about 4-5 seconds for the oil pressure gauge to move and it smooths out right as the oil pressure gauge begins to move.  I'm speculating this 4-5 seconds is how long it takes the sump to pump oil to the injection pump.  Oil pressure is good otherwise.  Also, if trying to restart the truck after sitting for 30 minutes, it fires right up.

So if I understand this correctly, the issue may be the solenoid failing to shuttle due to no oil pressure at startup to actuate it.  Is there an oil anti-drain valve or check value that could be causing this issue?  If I'm headed in the wrong direction on this one, feel free to call me out.

Thanks again for the help.  We are a new small business and this forum is  a huge help in keeping things moving!

 

Also, are there any online manuals for these motors or do I need to contact Mack to buy a manual?  Thanks again

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Solenoid Valve won't be cheap  if you can live with it do so you could trynew orings on the valve  if you can find some .these are dandy little engines and worth keeping running.

Edited by fjh
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  • 7 months later...
  • 4 years later...

White smoke can mean you have air getting in your fuel system 

If this is the case it usually disappears in a few minutes 

If so the air leak is in your return side

Also could be as simple as worn parts letting oil settle when not running and getting burnt off in the first few minutes

I doubt it's a restriction in the motor or there would be oil everywhere when running

 

Paul 

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