can't make boost like I used to, please take a look

[srichard]

here are some data points:



new:

- stock: boost up to 34, stabilize around 32



5000mi:

- quad race (60, 100, 130hp setting): boost up to 40psi

- quad race (off): boost up to 32psi



8000mi:

- quad race (60, 100, 130hp setting): boost up to 36psi

- quad off: boost 32psi

- quad removed: boost up to 30, stabilize around 26psi



right there, there's a 4psi boost loss.





9000mi:

- quad removed: boost up to 30, stabilize around 26psi

- quad race (reflash - 100hp, 130hp): boost up to 26psi

- quad race (reflash - 60hp): boost up to 36psi

- quad race (reflash - off): boost up to 32psi



getting worse?





I have looked for boost leaks, no luck. I had the dealership check it out and say the turbo was functioning fine.



Could it be that my fuel pump is on its way out? I guess now would be a good time to finally install that FP gauge I've had sitting for 3 months?



any idea, comment or suggestions welcome. thanks.

 

[RankRam]

Does your 05 have the dreaded plastic ends on the intercooler?

 

[srichard]

yes it does. but what makes me think that it may not be a boost leak is that it will boost up to 32 psi and more with the quad on the lower and off setting. but as soon as I turn it up, the boost goes away. wouldn't that point to the pump just falling on its face and not supplying enough pressure to keep up any more?

it's not like it spikes the boost and then goes back down, in the higher settings, it just doesn't build the boost at all past 26psi.

 

[MLimpert]

Could it be temperature related at all? My stock truck will make anywhere from 26-35 depending on outside temperature conditions.

 

[Bertram65]

Does not sound like a gauge issue, but I have had two boost gauges act up making me think there was a fuel or air problem, both times turned out the gauge was the problem.

 

[Diesel Power]

put that gauge on asap. have the dealer check your rail pressure at idle and at wot, chances are its a fuel problem! idle sould be aroun 7-7500psi and wot should be 24,000psi

 

[mberry]

Sounds like a good time to change your air filter and see what you get after that. I notice when my air filter starts to plug up when my egt's go up while I'm cruising. New air filter egt @ 68mph is a little over 600. It's starting to climb up into the 700 degree range now and the air filter doesn't have that many miles on it but the air is rather dirty here this time of year.