Early 03 Fuel Rail Pressure??????

Foster#17

Foster#17

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Apr 1, 2015
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Ive been looking at my buddies early 03. It turns over for about 3 seconds before it starts (Mine fires right up) and then when it starts it idles rough kind of like a lope Which im guessing is the injectors because Ive checked about everything else. Now heres my question. I was playing around with my gauge (edge CTS) and checked the fuel rail pressure on the truck. I unplugged the injectors so it wouldnt start while I was cranking it. It would take about 3 or 4 seconds for it to get to 5000 psi which is what it needs to start! Do you think this is why its taking so long for it to start? Because the rail pressure isnt high enough to start until cranking a while? Also I did the same thing with my truck and it hits over 5000psi pretty much immediately Any input would be great!
 
03-04 5K- +- 200 at idle , generally rough idle is cause by FCA, long cranks cause by LV/Injectors......
 
I went through something similar on a buddy's truck.
Crank hard and long, would finally fire. Even cold it was a crap shoot.

He had it to a shop NUMEROUS times for injectors and changed the RPS, PRV, lift pump, once and it would never stay running right.

I was over there a couple weeks ago, after a whole new, fresh set of re-man injectors, then my buddy stuck in another lift pump, still the same deal, no start or hard starting.
Finally got it fired up and we both get to listening and it sounded like the engine was lightly surging, can't see it on the tach needle, but we can hear it.

Changed out the CP3 and voila, no more hard starting, power was back, fuel mileage, the works, acts like a whole new truck.

The troubling thing is, he had it to a local shop who was doing all of this work and they couldn't diagnose a weak CP3, though they claimed they'd checked rail pressures in all states of operation, yet when we changed the CP3, the problems all disappeared.

The ECM also never tripped any codes related to fuel pressure.

Mark.
 
Yeah he had it to a shop and he explained what was going on and they immediately told him it was the injectors without even looking at it. Then all they did was hook it up to a computer and tell him the injectors were all working some not 100%. I was like what the heck, they didnt even look into any other problems. I am fairly certain it does need injectors but I dont think the Cp3 is building pressure fast enough to start it right away. I checked his lift pump and its putting out a steady 9-10 psi so I dont think thats the cause
 
Weak CP3...Hmmmm its extremely rare ,More likely Bad COV , checking a COV takes less then 3 minutes. yes at idle or cranking is the weakest PSI for a CP3, but even if ..lets say only 30% at cranking, it only needs to produce 1800PSI to be pickup by the Pressure sensor 5volt to input the ECM to fire the hot hole. if the injectors low pressure side are leaking it will produce long crank or no start W/O ether.
 
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