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Rough Start This Morning

Hawkez
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Hawkez

Hawkez

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I recently had the high idle enabled on my truck, as a matter of fact, I haven't driven the truck since I did that.  I went out this morning to start it and it had a heck of a time firing.  It would try to start, catch for just a second and then die.  I cycled the grid heaters a couple of times, not sure if that helped.  It finally did start and it ran like a pig. I've never seen, first hand, a truck run on 3 cyl, but I imagine this was it.  It seemed like there was a miss, sounded awful.  You should have seen my wife's face when I went back in the house.  After about 10 seconds the idle changed in an instant and ran smooth; the RPMs ran up to around 1200ish (High idle?) 

Before flashing the ECM, I have never had any rough starts like this in the cold, the temp this morning was only about 25*, never any issues starting in colder temps.  Maybe cold fuel??

I am questioning why it was such a tough start.  It shouldn't have started in 3 cyl because it was cold enough, right?  It wasn't plugged in, I'm sure that would have helped.  Any thoughts, or is this normal High Idle software activity?

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Mopar1973Man

Mopar1973Man

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I'm going to say to check to see if your getting power to the grid heaters. It might have lit the WAIT TO START light but the relay might be having issues. (P0380 and/or P0382). Fusible links corroded off battery terminal or burned out. Contact in the relays good? All this can be checked by looking for power at the grid heater terminals.

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Me78569

Me78569

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ok,

 

Just trying to make sure nothing funky is going on with the sensors before we start digging into the issue at hand.

 

Was this the first cold morning you have started the truck recently?    Sounds like there an air leak in the fuel system that presented itself due to the cold weather.

 

The high idle function won't go into effect until after the truck has idled normally for a minute or two.  The truck will not jump right to 3 cylinder mode either.  I think your rough running was another issue. 

 

Maybe one of the grids isnt working?  I had similar issues when my relay busted causing only one grid to work.

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Hawkez

Hawkez

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This is the coldest I've started it recently, yes.  It didn't seem like a normal hard start due to fuel.  It was trying to ignite, just couldn't.  I'll look into that.  It will be easy enough to hit it with a DVM and check for power.

Thanks for the ideas.

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Mopar1973Man

Mopar1973Man

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10 minutes ago, Me78569 said:

If it is colder than 15*f I think it will kick in after the truck goes into 6 cyl.

So maybe 3 minutes?

Ok... Here is the down low.

For 6 cylinder high idle its IAT temp of 32*F or lower WITH grid heaters firing.

For 3 cylinder high idle its IAT temp of 15*F or lower WITH grid heaters firing.

So in other words its got to be a lot colder that 32*F or 15*F out to trigger these modes normally. I would typically see 6 cylinder without a switch with a outside temperature of 25*F or colder and 3 cylinder at 5*F or so.

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Hawkez

Hawkez

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No, it has only sat for a few day, nothing out of the normal.  I haven't been having any hard start issues prior to this.  Maybe it is a loss of prime issue, but that seems the least likely to me.  I'm off tomorrow so I should have time to look at it, I'll let you know what I find.

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IBMobile

IBMobile

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10 hours ago, Me78569 said:

Was this the first cold morning you have started the truck recently?    Sounds like there an air leak in the fuel system that presented itself due to the cold weather.

The high idle function won't go into effect until after the truck has idled normally for a minute or two.  The truck will not jump right to 3 cylinder mode either.  I think your rough running was another issue. 

 

Bad starter motor contacts can cause a hard start problem also but with it starting and running badly for 10 seconds then smoothing out sounds like it's loosing prime, Air leak in fuel system.

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Hawkez

Hawkez

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The batteries are good, it was turning over just fine and strong.  I'm assuming that there should be 12 vdc at each post on the intake heater, correct?  I still leaning away from it being a fuel issues, but I've been wrong before.  I looked over the motor this evening and I can't see any obvious sign of a fuel leak.  The motor was still warm and the grids weren't kicking on, I guess I'll wait until the morning, supposed to be cold again. 

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dripley

dripley

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If it is pulling air in you may not see it until it gets bigger. Mine was the return line and it was leaking at the back of the head and the T the return from the VP ties into. Pretty easy to check the T but you need a mirror for the banjo bolt on back of the head.

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Buzzinhalfdozen

Buzzinhalfdozen

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I'm chasing a mysterious loss of prime issue on my truck right now that has me stumped. I've been bumping the starter and letting the lift pump run for its 20 seconds. Do that twice if it's been sitting for a few days. If I do this it'll fire up in a few cranks, if i don't it'll crank for a long time.

If this helps then it pretty much rules out the grid heaters being bad, at 25* it should pop right off without the grids anyways. You could also try plugging in the block heater overnight and if it still does it then you know the grids aren't the problem.

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