As I sit and ponder all the possibilities that could be tied to my hard start problem, I find myself drifting off towards loosely related topics. The CP3 injection pump is a whole world different from the VP44 found on earlier CTD's. I look at an exploded view of the CP3 from a few pages in the DIPACO (www.dipaco.com) Common Rail Fuel System parts brochure and it makes me wonder just what the most common mechanisms of failure are. The CP3 is a 3-plunger (piston) pump. The shaft has lobes like a camshaft that operate the plungers. There are about a dozen seals and o-rings, the FCA, the Cascade Overflow Valve, and a few other robust little devices. What really fails? I could understand if the pump were leaking fuel, then output pressure to the rail would fall, thus the ECM throws a low rail pressure code. If the FCA were trashed, I'd understand. The Cascade Overflow Valve looks to be very stoutly made. If a bearing/bushing went bad, you'd hear it. Aside from getting clogged up with trash, could there be internal leakage? Anybody ever replace a CP3 that wasn't leaking or one that didn't throw a code, and it fixed the problem?????

 

I have read a couple threads where they just have low output... but I dont know why or what causes it?????

 

"Low Output" would dictate that fuel is not getting to the pump, or it's leaking out of the pump, or it's losing (or never gaining) the energy (pressure) that the pump is supposed to add to the system. So there's an escape path somewhere. But where? The Cascade Overflow Valve, if I am correct, is the only path for fuel to be returned back to the return system. Maybe a weak spring that allows more return than is required depending on demand? See, it's kind of a weird deal. I wonder how many CP3's have been replaced un-necessarily.....?????????? - curtis

 

Does it have start-up problems if you try a restart shortly after you kill it?

 

Well, here's my truck's start schedule:

Morning: Starts in about 5-6 seconds.
11 Lunch: Starts in about 20-30 seconds maybe, maybe needs ether
4 Go Home: Starts in about 20-30 seconds, may need ether again
Get Home and Shut Off
Go To Start Right Back Up: maybe 7-8 seconds......

Strange......CR Pressure Relief Valve is good, FCA is brand new, FASS pump is good, filter is good, had a Quad Fuel/Rail Pressure monitor....pressures good once started. Haven't changed camshaft position sensor, crank position sensor, fuel pressure sensor, injectors. I do have a camshaft position in the console....tomorrow. Still, trying to play out the logic.......need beer, yes, more beer.................-curtis

 

If there are no DTC's, it almost certainly has to be fuel - or cranking speed - sure the starter is up to the task? Batteries? Corroded cable ends?

Could be the IP is leaking internally, not building enough rail pressure, which could also be the COV - at crank there should be no overflow from the rail, the FCA or the COV, easy enuff to check with clear vinyl tubing from yer local emporium

 

No return flow from rail pressure relief. Brand new FCA. I haven't pulled the return off the CP3 to check that...yet, but I have a banjo fitting for doing that. I'd almost really love for it to be the CP3 or COV. I can get the seal/o-ring kit for the CP3.........the COV is about $350........still better than injectors. I have 1 brand new Bosch injector sitting on my kitchen counter right now.......don't wanna go there if not necessary. Otherwise runs great.

 

most of the ones I read about come from trucks with lift pump pressure gauges...anybody who throws a $1500 CP3 on with out checking lift pump pressure is crazy

 

I have been reading alot of our fellow 03 model year members having similiar simptoms to what you are describing. Along with a no start sitiuation or complete engine failure. It is my understanding most are replacing injectors to correct this problem. Although, I agree with you. I think there is some under lying problem that we are missing.

I thought I read a week ago about a guy that disassembled the CP3's Fuel Control Acutaor (FCA) and was looking at checking the pressure relief valve. From what I read after checking one or the other there was some residue build up in one piece or the other and after knocking it loose and reassembling the parts the truck ran fine and started fine too. However, long term test results were not posted yet and I think the post is now buried on these forums and I have not checked to see if any new results were reported.

From reading the service manual step on removing an injector, it talks about how bad fuel that passed the filter can still clog the fine metering orfices that connect the fuel rail to the injectors. So, the complaint about bad fuel is a legitimate concern.

Shawn

 

CatDiesel, that post you referred to is from Moparman ("Bad FCA.........."). It seems he's back to hard start probs again, but looks like his lift pump crapped out. Man I tell ya what, I'd almost lay out the cash to obtain all the equipment that is necessary to do a complete and thorough diagnostic and rebuild/repair routine on fuel injectors and injection pumps. There's obviously a market out there. I have come to terms with the reality that I'm probably looking at injectors or CP3, BUT, I mean BUT, I just have a small struggle with a few issues that I don't understand......and it's eating me up alive.

#1 - Why, when cold, it starts way better than when it's hot ?

#2 - Why, when I replaced the FCA, it cranked right up (hot or cold) for about a week, then went back to the same old thing ?

#3 - When running, it runs fine. What's actually making difficult during the "crank" cycle ?

The way I understand it, the "crank cycle" involves this:

a. The ECM looks for a signal from the Fuel Pressure Sensor that it should get when the rail pressure is within spec.

b. The ECM also looks for a signal from the camshaft position sensor so it knows when and where the #1 cylinder is on top dead center.

c. The ECM outputs to the PCM which in turn outputs a "fire or pulse" command to the injector.

I know there's more signals and so forth that have to align and all, but that was just a simplified understanding. What if the ECM is getting bad or confusing signals? Hmmmmmmmm......

I shall kep pondering for a bit longer as I am able to get back and forth to work everyday so far.....-curtis

 

If you have a laptop, Autoenginuitydotcom has a pc-ware OBD2 scantool that talks to all the DCX vehicles, emulates the DRB - fairly easy to use, allows you to observe all the parameters the ECM sees, with all the testing functions of the DRB - ~250-600bucks depending on the options, such as all the GM, all the Ford, other brand vehicle functions

 

gmctd - thanks, I may just check into that. I have a lot of friends and family with CTD's, many of them newer than mine, so their woes lay ahead. Heck, $600 is just a few weeks bar bill..........easy to earn back !

 

what was the end result of your problem?