Rough Idleing?
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Joined: Oct 2009
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Rough Idleing?
05 QC, short bed 4.10 gears, 179,000 miles. Was wondering if a bad lift pump (tank) would cause a rough idle problem? If the lift pump was bad would the cp3 injector pump pull fuel without the tank pump helping? Was at the auto parts place and the counter guy came outside to hear my idle and said it was (lobeing)? Starving for fuel? Starts fine, runs good except for idleing and on the highway (50 or 60mph, if you hold the pedal still, she tends to buck)? Only code showing are p2609, but that would not effect my situation? Only mods are 5" exhaust, air cleaner, trans rebuild.
All Star
Joined: Dec 2008
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From: East Alabama
Sounds more like a rail pressure issue.
Most likely it's the FCA on the CP3 crapping out on ya.
I'm assuming you've done the common stuff, like change the fuel filter?
Also, that code for the abnormal voltage drop at the grid heater starts showing when the batteries are getting weak. Are they the original batteries?
That could be part of the problem.
Most likely it's the FCA on the CP3 crapping out on ya.
I'm assuming you've done the common stuff, like change the fuel filter?
Also, that code for the abnormal voltage drop at the grid heater starts showing when the batteries are getting weak. Are they the original batteries?
That could be part of the problem.
Last edited by Coal Train; Nov 30, 2009 at 04:57 PM.
All Star
Joined: Dec 2008
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From: East Alabama
Fuel pressure and rail pressure are 2 different animals.
You should be seeing 13 - 15 psi of fuel pressure at the CP3 inlet.
You can see any where from 6400 - 20000+ psi of rail pressure.
At idle you should be seeing between 6400 - 6800 psi of rail pressure in park or neutral.
Have those batteries tested, I bet that's part of the problem. If they're weak and th grid heater is kicking on, the rest of your truck is sucking for power.
If you need the FCA, the best place to get it is a Cummins dealer or a Bosch service center.
You should be seeing 13 - 15 psi of fuel pressure at the CP3 inlet.
You can see any where from 6400 - 20000+ psi of rail pressure.
At idle you should be seeing between 6400 - 6800 psi of rail pressure in park or neutral.
Have those batteries tested, I bet that's part of the problem. If they're weak and th grid heater is kicking on, the rest of your truck is sucking for power.
If you need the FCA, the best place to get it is a Cummins dealer or a Bosch service center.
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All Star
Joined: Dec 2008
Posts: 863
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From: East Alabama
Tap the bolt lightly with a SMALL hammer.
They have a bit of blue loc-tite on them.
Once you have the FCA out, shake it back and forth, you should hear it click.
If you don't hear it click, it's sticking and that will cause the erratic idle.
I'm still betting on the batteries.
They have a bit of blue loc-tite on them.
Once you have the FCA out, shake it back and forth, you should hear it click.
If you don't hear it click, it's sticking and that will cause the erratic idle.
I'm still betting on the batteries.