I swear I have a high altitude injection pump

[85-m1028]

my 6.2 usualy run kind of rough "shakes the truck pretty bad" I went up to Big Bear yesterday where the elevation is about 7000 feet. The engine runs silky smooth and still has the same power. I wish it ran like this all the time! Do I need to restrict the intake, change the timing or tweak the pump?

I am running the single plane intake that came with the hmmwv engine. The fuel lines are new and no air leaks in the system. The tank cap is good and creates a good seal.

I'm not crazy my friend riding with me noticed it with me not having said anything.

[john8662]

Good question!

It probably does need some adjustment. I've been kind disgruntled with rebuilt DB2 pump due to the reason you just decribed. Have to dig up the differences between high and low altitude settings.

J

[ccatlett1984]

just retard the timing a little, it will do wonders for you.

[HammerWerf]

My 82-85 Injector system manual has a page that talks about altitude adjustment. Altitude is >4000 ft. If the truck is to be used above that altitude permanently or a majority of the time, having the IP adjusted is recomended. This is an internal recalibration, and cannot be performed on the truck.

It appears that a High Altitude Engine option (RPO NA6 ) was available at that time.

HammerWerf

[85-m1028]

Well bummer, time for a new pump!!

[More Power]

my 6.2 usualy run kind of rough "shakes the truck pretty bad" I went up to Big Bear yesterday where the elevation is about 7000 feet. The engine runs silky smooth and still has the same power. I wish it ran like this all the time! Do I need to restrict the intake, change the timing or tweak the pump?

I am running the single plane intake that came with the hmmwv engine. The fuel lines are new and no air leaks in the system. The tank cap is good and creates a good seal.

I'm not crazy my friend riding with me noticed it with me not having said anything.

A "high altitude" DB2 is simply calibrated to deliver slight less fuel (smoke less). It's an adjustment that owners can do, such as after installing a turbocharger.

I suspect your engine ran smoother because of the drive. The 6.2 I owned always ran smoother after using it to tow for 100-200 miles. I suspect that running the engine harder and at a higher EGT help to clean the injector nozzles of carbon.

Jim

[82gmc]

I bought my truck in California and brought to my home (Montana) at 3800 ft .

So this means my ip needs to be adjusted????? If so, any documentation on how????

[85-m1028]

I did reatard the timing a bit and that helped quite a bit.. I really didn't notice any change in mine until I got over 5000 ft, sounds like if it's an issue you need to turn the fuel down a bit for higher elevation.