Truck cranks longer than usual if the humidity is very high, colder and with rain or fog. Two or more trys to get it started. Any thoughts? Electrical?
2006 5.9L Auto 130,000 miles. No HP mods, just Baldwin fuel filters 5um.

 

It seems that long crank times in cold weather is often the first symptom of failing injectors.

As the injectors wear, the volume of fuel return flow increases, and the CP3 takes longer to reach the rail pressure needed to fire the injectors.

There are a couple of special fittings needed to seperate the injector return flow from the CP3 return flow, so that measurements can be taken. As I understand it, a leaking pressure relief valve can cause the same symptoms.

 

Only experience longer cranking when its high humidity, colder, rain or fog. Otherwise starts fine.

 

So it starts fine in low temps when it is not humid?

 

Yes, starts fine cold low humidity 10 degrees this AM. Started fine this AM, no block heater just one grid heater cycle. Fired off on 1st try and went to high idle. Just did the fuel, air and oil filter (and oil) changes last weekend.

 

You got me, then.

Long crank times generally seem to be high return flow, or partly discharged or old batteries not cranking the engine as fast as you think.

I have no idea what would cause long crank/hard start with humidity. Does it set any codes?