Three years ago I had a new fuel pin and governor spring installed in my 90' 1st gen 12v Cummins 5.9L engine. Having taken a long trip in my truck, I wanted the extra 40hp and the new spring extended the power band to 3,200rpm. While the performance benefits have been tremendous, ever since the installation the engine has developed a tendency to die when I least expect it. It's not sudden but more like a slow starving of fuel to the engine until it comes to a full stop. Once parked I can't get the truck started again until I let it sit for anywhere between 2-8 hours and then it starts up again. I can drive the truck for hours, weeks or even months before it dies again like this.

Again, this never happened for the years I've had the truck prior to the installation of the new pin and spring. Can installing one or either of these upgrades create a systemic fuel starve problem? If so, how do installs like this go wrong, where in the pump could there be a blockage of fuel, and why would be do remarkably intermittent?

Appreciate again feedback.

 

I;m guessing, certainly not an expert. Did the new fuel pin increase fuel consumption? If so, When was your last fuel filter and fuel water separator change?
Also, how old is the fuel lift pump? It should put out 15 psi.

 

It did as I went from a high of 26mpg on the highway to around 22mpg. But since this post I've solved the issue by disconnecting the fuel solenoid valve and building a manual shut off cable for the truck. Several problems were solved simultaneously: no more stranhge voltage fluxuation at startup, idle is consistent again, and accelleration has no hesitattion, being much smoother through the power bands.

Unless I completely re-build leads, diagnosing electrical issues on a 53 year old truck with a 30 Dodge wiring harness is a complete pain.

 

Great. I like your work around. Sounds like the solenoid or the wiring were at fault. Simple is always better.
So, if the upgraded pin cost some fuel economy, what did you gain? Better performance? Black smoke? I;m asking because I;m looking for ways to improve performance in my motorhome.I have to pass emissions here in Phoenix every year so not looking for smoke. Also need to focus on exhaust gas temps. I like what I've read so far of this web site. but haven't been able to start a thread. Tried twice but they don't post. Any suggestions would be appreciated. Thanks

 

It gave me 40hp more for a total of 200hp and I had a 3,200 rpm govenor spring installed that extends my power band a bit. Both for highway use since it helps to be able to pass people with the extra power and comfortably stay at 80mph when need be. Not much difference in smoke. I used to run B50 which really helps with performance, low smoke, MPG and engine noise.

 

Hmmm. My motor is a 94. Think it was rated at 235 hp outta the box. Also think the governor trips at 3500 rpm but I never reach that level. Major problem is hill climbing. A 6% grade puts me in 2nd gear and 25 mph, blinkers on and far right lane. Egt at 1100. Not sure B50 is available most places I go. Do add Clean Diesel most every fillup. I'm happy to cruise at 65. Rig weighs 22,500, plus we flat tow a small car (2,500#). Mpg seldom better than 10. Rebuilt the motor in 2013, @ 60,000 miles since then. Didn't mess with the injector pump, just removed and reinstalled using the timing pins in the motor and pump to "calibrate". Runs better with a clean air filter... Don't know if previous owner did anything to the pump. He did modify the turbo...
So, where to start? Clean the intercooler, test the lift pump, calibrate the waste gate controller, Dutch the exhaust brake or just shut up and walk the dog as we creep up hill. Any suggestions would be appreciated. Thanks

 

I'd start with cleaning and inspecting the charge air system.
If your EGT is pre-turbo then it's not high, post means you risk meltdown.
Pump timing with the pin is dubious at best- do timing with the plunger lift method, get the correct chart for your pump. (RV pumps are different from Dodge and marine application pumps)

Check the exhaust brake- needs to be completely open until commanded shut.
How much boost do you run on a 6% grade?

 

The fix was building a manual fuel shut off cable and bypassing the fuel solenoid entirely. For some reason that also fixed an ongoing voltage regulation issue I was having as well. Now idle is constant, and accelleration smooth and consistent. The truck hasn't failed since then.

 

Thanks, Alpine. I appreciate your suggestions
IHC, I didn't intend on hijacking your thread but have not been successful in starting a new one. Tried several times but my message just disappears when I hit "submit". Is there a site administrator I can talk to? Any help on correct posting procedure would be appreciated. Thanks!
Alpine, my EGT sensor is in the exhaust manifold, before the turbo.
The exhaust brake opens completely. Did have some sticking problems until I replaced both the "pull" and "hold" relays. Some genius had installed 30 amp horn relays and the contacts fried...
The turbo outlet, the connector to the exhaust brake and the brake are all 3" dia. The exhaust pipe expands to 4" after the brake. When climbing, I limit boost to 15 psi to keep EGT at 1100 or less. On long grades that puts us in 2nd gear and 25 mph, RPMs around 2300. The original spec sheet for the motor shows 235 hp, Governor set at 2500 rpm. The turbo has been modified. Will put out 30-35psi. I suspect the governor (and maybe the fuel plate) have been "adjusted" because the motor pulls strongly, at least up to 3200 rpm. Just can't take advantage of that potential due to rapidly climbing EGT.
I'll start with the intercooler and lift pump pressure check. Timing procedures for the injector pump sound pretty complicated...Not sure I can pull that off.
Thanks again for your help.

 

There is a funny relationship between boost and EGT.
The turbine in the turbo is a thermal machine, needing the EGTs to work. The Cummins feels fine up to 1200F pre-turbo even for prolonged periods. (If your cooling system is up for it)
Sometimes giving it a good bit more fuel results in more boost and that lowers EGT then.
If you have the same charger as the pickup trucks, it would be an HX35, and the stock wastegate setting limits it to 21psi. It runs quite nicely up to about 30 psi, but falls off the efficiency map if going over 35.
Only 15psi of boost @2300 rpm does not produce a lot of power.