Tuning big injectors

quinton

quinton

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Nov 28, 2011
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Granbury Tx.
Okay so I've got the truck running good only thing is after sitting awhile its hard to start. I have to pump the gas pedal a bit and then it fires up with a cloud of whitish grey smoke. It has stock rail pressure and pulse width for cranking and idle. Rail pressure is around 5500-6000 psi. Should I raise it to 8500 psi or so? What about pulse width? Do I need to lower anything for cranking or raise?
 
quinton

quinton

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Granbury Tx.
No, I leave the ignition on for about 45 seconds with lift pump running. But it does start up after 5 minutes or so of being plugged in? Yet still has the white/grey smoke.
 
SSchmi5519

SSchmi5519

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Oct 19, 2008
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I would say temp has A LOT to do with it. I was in ABQ, NM one time when the temp was high 30s/low 40s and the built motor truck took 15mins of cranking to start. Once started it chugged white smoke until it warmed up.
 
quinton

quinton

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Nov 28, 2011
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Granbury Tx.
No gelling, I asked a buddy with 15.5.1 if he has ever had that problem and he said he has started it up in 10 degree weather just fine. A little white smoke but cranked up fine. It will crank with out plugging it in but I have to feather the throttle a little to get it to start and takes a few times.
 
chevyburnout1

chevyburnout1

Fixing it till it breaks
Aug 25, 2008
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Berthoud, CO
What about the cranking injection quantity? Does it need to be lowered? I know way back in the DP days I remember the "Cummins Poof" at start up mod, where you increase the cranking injection quantity. Made my truck very hard starting when warmed up, and this was when it was stock.
 
Chevy1925

Chevy1925

don't know sh!t about IFS
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Oct 21, 2009
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Phoenix Az
SSchmi5519 said:
I would say temp has A LOT to do with it. I was in ABQ, NM one time when the temp was high 30s/low 40s and the built motor truck took 15mins of cranking to start. Once started it chugged white smoke until it warmed up.
Click to expand...

mine cranks right up in high 20s and doesnt chug white smoke even if not plugged in and im at the same compression as quinton.

sounds more like a glow plug issue to me
 
SSchmi5519

SSchmi5519

LLY Cult Leader
Oct 19, 2008
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catman3126 said:
Is 16.5 low enought to have issues? i thought thats whats LBZ runs stock?
Click to expand...

LBZ/LMM run 16.8, but they also have a grid heater to assist in cold weather. This LB7 came with an intake heater also, but usually these are removed when the truck is built. A good point however.

My concern here moreso is whether this truck is truly at a 16.5 compression.
 
quinton

quinton

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Nov 28, 2011
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Granbury Tx.
chevyburnout1 said:
What about the cranking injection quantity? Does it need to be lowered? I know way back in the DP days I remember the "Cummins Poof" at start up mod, where you increase the cranking injection quantity. Made my truck very hard starting when warmed up, and this was when it was stock.
Click to expand...

This is what I was wondering, but then I was thinking wouldn't it be the opposite if I'm having to give it some throttle to start?
 
SSchmi5519

SSchmi5519

LLY Cult Leader
Oct 19, 2008
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Chevy1925 said:
mine cranks right up in high 20s and doesnt chug white smoke even if not plugged in and im at the same compression as quinton.

sounds more like a glow plug issue to me
Click to expand...

Also a good point, but I had ruled out GP's since a code will appear if there is a GP issue.
 
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