My buddies having some problems with his truck. It's been hard to keep running. The truck will fire up and then die. He has to fire it up about five times in a row and then hold the throttle to about 2500 each time til she stays running. Other symptom is a horrible idle. It misses real bad. It also has a miss around 2500 rpm. We replaced the fuel system from the tank to the pump 6 months ago and it's been running fine til about 2 weeks ago. Fuel system has noe leaks, no air, and good fuel pressure. We were thinking that it is about time to rebuild the p-pump. But when pulling the truck apart the injector nozzle looked real bad, full of carbon deposit. These are the original injectors. My question is, Could the injectors cause these symptoms?

 

Original injectors? Are you saying the 24V injectors are being used with a P-Pump?

 

yea original injectors with 306,000 on them!

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yea, it's original injectors, 306,000. We were going to have the injectors rebuilt if they didn"t work out with the p-pump, however it's been running fine for a couple years.

 

id go ahead and have them rebuilt and see if thats it, then go from there

 

i would start with the injectors because p pumps are a million mile pump

 

strt with the easiest stuff first

 

yeah what he said

 

The 24V VP injectors are not a great option for P-pump trucks, IIRC the pop pressures and hole size and design does not work very well at all with a P7100. Maybe Weston will drop in a give some information.
All the P-pump 24's I've seen need extensive injector work and tuning to get the truck to make decent power.

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Straight from Don M:
"A VP injector that has not been converted will only run worse behind a P pump with large lines. It is not just resetting pop pressure. For the best results on an unconverted VP injector you need to run a small ID line. .082-.084 MAX. And it will still run with less than optimum results.
The pulse from the pump travels at roughly the speed of sound through the line when the system is properly matched. The length of that pulse is what changes with diameter. No matter what you do, the pulse will get shorter AND the pressure curve of that pulse will shorten with increasing the diameter of the "road" or "tunnel" that pulse travels down. Pretty simple to understand why the line diameter is sized in accordance with of the fuel slug being pumped and the pressure curve needed.

Think of it like this: Imagine a line diameter with an ID of 1/2 inch between the pump and injector. How much pressure could that pump really build up with a diameter that large? It would not even be enough to open the injector, much less inject ANY fuel. The same thing applies in any line diameter change. Increasing diameter lowers the overall pressure, speed and time the fuel has to overcome the injectors spring.

A VP injector is designed with delivery curve much lower and a spring pressure much higher. Forget the fk'n opening pressure. Thats a trojan horse that 99% of vendors and purchases get hung up on. The pressure curve the VP injector spring operates at is mucho higher than a P pump injector spring. It requires a higher pressure to keep it open throughout the delivery pulse of fuel coming from the pump. Resetting the pressure to a lower point only lowers the pressure required to initially open the stupid thing, not the force/pressure required to KEEP it open. The P pump has a crap/low pressure curve compared to a VP and of course A CR. It needs a spring with a low pressure curve required to open it and a pressure from the line feeding it.

We have been coverting VP injectors since the early days. Not just resetting opening pressures. Thats a novice's game."

 

thanks for all your input. We'll order a set of fireballs set to the right popoff and go from there.

 

I would make sure the injector manufacturer has experience with the P-pumped 24V trucks, There's more to it than just pop pressures!
I would contact one of the following guys and make sure your getting what you need!

Don Morrison (F1 Diesel) or one of his vendors like Llyod Mills
Smokem (Weston) Also available from our very Own Southern Diesel Extreme here on DB
DDP
Industrial Injections Pump Shop
Scheid Diesel
Enterprise Engine
Columbus Diesel