Idle to boost ?

[Drillman]

Hey guys, new to this site and these trucks so if I come up with something dumb don't be surprised.
I've recently purchased a '97 6.5ltr Sierra 2500 to pull my gooseneck horse trailer (10,000lbs). The problem is that idle (750 rpm approx ) to boost (2000 rpm ) seems to have no grunt, is this normal? After reading posts I've done fuel filter, oil pressure switch, checked earths and power to circuit and added a second lift pump just in case.
Any ideas as to what else I should be looking at or is this as good as it gets. Definitely hoping for more.

In Australia so most of your suppliers aren't available other than online.

[Kennedy]

Are you saying that there is no boost until 2,000 rpm or no power until 2000 RPM?

Do you have a boost gauge on this truck?

They typically pull OK stock, then wake up nicely with exhaust and ECM programming. Shipping exhaust to Australia can be tricky, but the ECM is not an issue.

[Drillman]

No boost until about 2000 rpm and very little power. Trying to take off with the trailer in any kind of hurry just doesn't happen until yhe boost kicks in. Possible that the injection pump isn't doing its job?
About to change exhaust to 4" from downpipe back.
What does the different ECM do?

[a5150nut]

First you need to check the boost control circuit. Is it stock or a manual spring set up?

If stock what condition are the vacuum lines in?

Do you have vacuum at waste gate? On turbo

If so check waste gate actuator

If actuator is good then,

Do you have vacuum at waste gate controller? On left valve cover towards rear.

check for vacuum in and out of controller and check electrical connections. If all good then,


Do you have vacuum at pump.

[Drillman]

Manual spring type wastegate, no vacuum actuator, no vac pump. Plenty of pull once boost hits 5lb but pretty limp before hitting boost range. No black smoke, ever. Would this show that IP not putting out enough juice?
Is there anything else that controls output of pump? Faulty sensor?

Also has remote PMD behind bumper.

[Kennedy]

With a mechanical wastegate the boost should be there from the beginning as it is held shut physically.

If you need a lot of RPM drive pressure to get the boost rolling you may have a leak somewhere be it drive pressure or boost. Plugged air filter, failed/failing turbo etc. but the turbos seldom fail and especially not like this.