Boost drops in higher gears, leak or fueling issue?

[Niki]

On an auto truck, the boost goes to about 24 psi when you first get on it, then slowly drops after a few seconds to about 12 psi when going 65-70. Boost leak or fueling issue? The EGT's stay around 1150, the truck blows a small black cloud when you first get on it then a light haze the rest of the way.

 

[DanaLittle]

what is your RPM? It is probably defueling.

my truck does the same thing at 2500 rpm.

 

[LEggers]

Sounds normal for them speeds. . Get a $15. 00 gov spring and that problem will go away fast. Make sure you have a set og gauges.

 

[Greenleaf]

Because the EGT is well with in specs, that means you have no blown boost hose. If you did the EGT would climb rapidly and possible heavy smoke too dependent upon the fuel rate you incorporated into the pump/nozzels.

 

[Niki]

So a governor spring would probably fix this? I just had my pump top off to fix the throttle shaft leak(o ring) and decided to put the stock spring back on because I'm probably selling it and was going to use the spring on my other truck. I have the high idle screw backed off, that helped a lot also.

 

[LEggers]

So a governor spring would probably fix this? I just had my pump top off to fix the throttle shaft leak(o ring) and decided to put the stock spring back on because I'm probably selling it and was going to use the spring on my other truck. I have the high idle screw backed off, that helped a lot also.

There is nothing wrong with your truck if your going to sell it use the spring on your next truck. .

 

[Niki]

There is nothing wrong with your truck if your going to sell it use the spring on your next truck. .

By "Fix" I meant make it faster and hold boost

 

[HRDROKN]

By "Fix" I meant make it faster and hold boost

It's normal for the boost to drop off if not under a load... the spring won't fix this.



If you pull a grade in high gear does the boost hold? For a while... . ?

 

[cerberusiam]

On an auto truck, the boost goes to about 24 psi when you first get on it, then slowly drops after a few seconds to about 12 psi when going 65-70. Boost leak or fueling issue? The EGT's stay around 1150, the truck blows a small black cloud when you first get on it then a light haze the rest of the way.

Thats quite a bit of boost for the speed and an unloaded truck, if it was. I see about half that with POD's and the fuel turned up. If anything it is too much boost.

 

[Niki]

there may have been 300# in the bed, max, and 1 passenger. The boost holds for a few seconds, then slowly drops off after you've been on it for a while. It probably holds better up a grade, I only went up one slight incline while on it, IL's pretty flat. I have to get guages on my 5 sp truck so I can compare the two, the auto has a boost and EGT guage but no tach, the 5 sp has a tach only. Don't worry, I take it easy in the 5 sp...