03 Cummins 6 speed very hard start

[painekiller]

A freind of mine has an 03 2500 with a 5. 9 and a six speed manual. It has recently developed a problem where it is very hard to start, hot or cold, imediatly after shutting engine off or after sitting, the problem remains the same. The truck must be cranked intermittently for 1 to 2 minutes before it will start, then once it finaly does fire, it does so in a comepletely normmal manner, giving no signs of air in the fuel system. The truck has 137,000 miles on it, the original owner had the cp3 pump replaced under warranty at around 50,000 miles for reasons we do not know. the truck also has a new lift pump and filter on it, this however did not affect the problem. There is no evidence of any fuel in the oil, and when I had him crank the engine, and cracked a couple injector return lines loose, fuel did spurt out while cranking. I hooked my scanner up to it, I am getting throttle position , intake air temp , coolant temp, and RPM. readings while running and while cranking the engine that seem to be normal. Once the truck starts, it runs great, idles smooth, has plenty of power, and does not stall. While cranking, if I give it a small shot of either, it will fire right up and run fine. There are no leaks in the fuel fittings or lines that I have been able to find. Truck did have a quadzilla programmer installed for a short time, however it has been removed and is stock now. Please Help.

 

[rbattelle]

Where is the lift pump? In the tank, or on the back of the filter canister?

Ryan

 

[MPletchetero]

It's sounds like a symptom of a worn out injectors. Ball seat inside injector gets worn out allowing excessive fuel return and not able to build up enough pressure at cranking speed (150 RPM). Once you get it started and running, CP3 is able to build up and maintain enough pressure to fire the injectors because the are turning at a higher RPM

The CP3 was probably replaced because of a leak-very common on HCPR engine during cold season.

 

[betterthanstock]

Try changing to synthetic 5W-40 oil. It may crank faster and start without problems for a little while longer.



On second thought, if it does the same while hot, this will not work.

 

[JZona]

I had the exact same issues. Ended up being 3 bad injectors.

 

[painekiller]

The lift pump is not inside the fuel tank on this truck, it is on the left side of the engine by the fuel filter. JZona, did you diagnose the faulty injectors yourself, if so how do you diagnose them.

 

[MPletchetero]

Do an injector fuel return flow. Internal leak from either the high pressure connector or injector will result in increased fuel return flow from the cylinder head. Single cylinder cut out test will not be able to isolate this leak because it occurs before it reaches the control needle inside the injector. Because all injectors share the same pressurized fuel supply from the rail,all cylinder will share the loss of fuel equally.



Flow Spec at idle: 120 ml per minute max.



If the engine will not start,crank the engine and measure return flow.



Flow spec: engine cranking - 90ml per minute max.

Make sure not to overheat your starter.

 

[JZona]

After researching and finding that the usual cause to the hard start issue is the injectors bypassing fuel internally, I sent my injectors to Formula One Diesel to upgrade to Flux 1 nozzles. When you upgrade your injectors through them, they will rebuild them for you for $100ea if needed. They determined that there were 3 that needed rebuilt. Its been 6,000 miles and 4 months since installing them, and the truck hasn't had a single starting issue.