Timing advanced to far?

[cutlas]

What are the signs indicating your timing is advanced to far on a DB2 pump?
What can be damaged by this?

[moondoggie]

Good Day!

If it sounds like a 7.3PS, it might be too advanced. You might have trouble cold-starting, too.

Blessings!

[cutlas]

Thats what I wanted to know. Thank you. I think I have it set ok then. A bit of clatter when cold advance is activated and engine is cold buy no clatter when cold advance is activated and engine is hot just an increase in idle.

[DmaxMaverick]

Probably too retarded. It should clatter hot with the HPCA engaged. The engine should clatter when cold under just about all conditions, w/ or w/o HPCA.

[cutlas]

Before advancing the timing the truck was a dog with no power. With the 1-2mm of advancement I have given it it is nice to drive now. I will bump it a bit more and see what happens. How much advancement does the cold advance give?

[moondoggie]

Good Day!

Sorry, can't remember the cold advance; I think it's around 10°. If so, the above makes sense: activating it when idling warm oughta make it noticeably noisier.

At the scribed timing marks, rotating the IP 1/16” ≈ 2.9° of crankshaft rotation; 1° crank rotation ≈ .022" at the scribed marks. Your 1-2mm gave you 1.8 - 3.6° of advance.

Also, if you go too far retarded, you'll start to get white smoke on a cold-start.




Blessings!
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[9365turbo]

Cutlas what kind of MPG do you get? I have a 93 k3500 intercooled. new injectors, home made cold air filter kit. Whats the point in moving the injector pump timing?

[cutlas]

I am getting about 20 mpg imperial with a mix of city & highway driving. I have 4.11 gears.
When advancing the pump on a diesel you are putting fuel in the combustion chamber earlier in the compression stroke allowing the fuel to burn earlier in the power stroke and creating more power at higher engine speeds.

Fuel is injected into the combustion chamber a few degrees before the piston reaches TDC (top dead center) giving the fuel time to burn and create maximum pressure in the combustion chamber at TDC forcing the piston down on the power stroke. As engine speed is increased the amount of time the fuel has to burn at TDC is reduced so the pump based on engine speed advances injection timing automatically to compensate for this. By advancing static timing further than factory settings more power can be gained assuming the factory settings are conservative.

These are my thoughts on what is happening if I have it wrong help me out.

Joe.

[DmaxMaverick]

That's the basics. The DB pumps are manually advanced in relation to throttle input. There is a cam/plunger on the input shaft that advances timing as throttle input is increased. Problem is, it is not load dependent, so it is a little sloppy with varying loads, but on a millisecond level. The very nature of the 6.2/6.5 fuel injection system, and all diesels for that matter, makes fuel timing very critical. Older systems, like yours, operate at a relatively low pressure. This means it takes more time to inject X amount of fuel than a higher pressure system. Ideally, all the fuel for a specific combustion event should be injected into the cylinder instantaneously. Unfortunately, not possible. Later HPCR systems, like on the Duramax gets us closer to this fuel injection nirvana with significantly higher pressures to shorten the injection event. The best we can do with any system is optimization. If you have the time, all the adjustable parameters of the pump and injectors can be optimized for greater economy and/or power, with some trial and error.