Injection pressure on startup
Thread Starter
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Senior User
Joined: Jul 2005
Posts: 348
Likes: 1
From: Memphis, TN
Injection pressure on startup
Had my truck scanned today for this cold start / cold running performance issue since I had 4 injectors replaced. Diags showed the injection pressure (controlled by ICP sensor and IPR?) to be at 900psi (or trying to be 900psi) theoritically to compensate for something. After a good warm-up drive and a back to normal condition...(ie..idle was normal and perf was normal) the injection pressure read 460psi and 10% duty cycle. Tech said shoudl be 14% duty cycle at idle and around 500psi.
Anyway...the CCT then shows #8 so they suspect #8 o-ring causing IPR to try and compensate. Also...CCT was taken with completely warm engine after IPR pressure was normal.
Thoughts on the above?
Anyway...the CCT then shows #8 so they suspect #8 o-ring causing IPR to try and compensate. Also...CCT was taken with completely warm engine after IPR pressure was normal.
Thoughts on the above?
Post Fiend
Joined: Jun 2004
Posts: 9,293
Likes: 10
From: Parker, CO
Every truck I've ever scanned showed injection control pressure rising during cranking, anywhere from 500 psi and up (400 is bare minimum to start, but most trucks don't "catch" until at least 500 or more). Also at idle, I've seen 450-600 psi and usually 10-13% duty cycle. Yours doesn't sound like it's off the norm. I would be concerned if yours was showing low ICP pressure, but much higher duty cycle. Is it taking longer than usual to crank? If so, that might be why ICP pressure is rising to 900.
My chip settings change ICP pressure and duty cycle at idle. Stock will hover around 480-520 psi, and in say the econo tune, it's over 550 psi.
My chip settings change ICP pressure and duty cycle at idle. Stock will hover around 480-520 psi, and in say the econo tune, it's over 550 psi.
Thread Starter
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Senior User
Joined: Jul 2005
Posts: 348
Likes: 1
From: Memphis, TN
Never had a starting problem at all. Just have a rough idle and very, very poor performance until completely warm. When I mentioned the 900psi...that was at idle, not during cranking. After fully warm (poor idle and poor performance gone)...that number was about 460. Hopefully yanking #8 and replacing will actually be the fix instead of just another chase. I'm tired of the chase. All of this is preventing my DP-tuner.
Post Fiend
Joined: Jul 2005
Posts: 14,582
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From: 21791
The truck will build pressure until 500 when it fires off (keep in mind the cranking rpm is about 250), and then once it fires off, the pressure may spike upwards of 2000 or 2500 and settle off very quickly. When the engine is cold, the ICP will be higher, but warm in a stock setting it should be around 500 +/- 50psi.
Post Fiend
Joined: Jun 2004
Posts: 9,293
Likes: 10
From: Parker, CO
When I mentioned the 900psi...that was at idle, not during cranking. After fully warm (poor idle and poor performance gone)...that number was about 460.
Go into more detail about the cold idle problem so we can help you fix it instead of throwing parts at it.
