i put my isspro boost, fuel pressure, and pryrometer gauges in today. got everything hookup up and put in. my boost gauge isn't reading anything above 20 psi. the highest it goes is around 15-18. shouldn't it be higher? where would i hook the vacuum line up too? the line between the fitting on the housing and the actuator? i hooked a t-fitting right there and thats where i tapped it off of. my fuel pressure is a mechanical one and it stays at 15 when i first crank it at idel but when i drive it, it fluctuates from 5-10-15-5-10psi, etc. whats going on with it? i hooked it up straight to my fuel canister because i couldn't find a needle valve to work. i am going to order one if i need it. is this why it is fluctuating? do i have air in my line? what should i do? my EGT work great, no complaints! thanks

 

Boost readings sound pretty normal for a stock truck.

Is the fuel pressure needle vibrating or does the pressure just change depending on how hard you're mashing the gas? If it's not vibrating, the fluctuations you are seeing are because your lift pump is weak. If it's bouncing all over the place to the point it's hard to read you need a needle valve to calm it down. Air in the pressure gauge line won't affect the pressure reading, the air gets pressurized same as the fuel so the gauge reads just fine.

 

The FP gage will fluctuate depending on what your doing. If you are accelerating, the pressure will drop, if you let off the pedal, it will rise back to idle.

On my '99, it goes to about 15 with key on and idles at about 12.5. When I accelerate, it goes down to about 9 or 10. before I change my lift pump, it would go down to about 2 at full pedal.

CR

 

the needle sits still. no vibrating or anything. it will just drop down to 5 psi and go back up to 10 psi or higher. it will keep doing this. down then up, down then up. i replaced the lift pump 3 or 4 months back.

 

did tap the vacuum line in the right place?

 

Most people tap into the intake elbow on the driver's side of the engine, but where you are is OK too.

So the FP changes are not connected to engine RPM and load? That's wierd... I'm not real well versed on the 24 valves so I won't even hazard a guess as to what's up with that.

 

the fluctuation is for no reason. not by me pressing the throttle or anything. where is the intake elbow? the compressor housing is the only place i could think of.

 

The intake elbow is the piece on the driver's side of the engine that the air duct from the intercooler connects to. Most folks take it off, drill and tap for the gauge fitting, and reinstall. The only difference is you're not seeing the pressure drop across the intercooler.

 

so my boost gauge is ok tapped into the actuator/housing hose? my fuel pressure gauges holds 7 psi idle after it had beed driven for awhile and when i drive it i held the rpms to 1500 and stayed slightly on the gas. not massing it down or anything, holding it steady. and the gauges goes to 12 psi for a few seconds and then to 5 psi for a few seconds. it flutters like that. does that needle vlave that i didn't put it affect pressure readings? or is it my lift pump?

 

Nothing wrong with how you ran it.

A needle valve is needed only to cure a vibrating gauge needle. If you can read it easily, it's not vibrating, the pressure is going up and down. Somebody else will have to tell you why, I don't know enough about the 24 valve fuel system to be able to say why you're seeing what you're seeing.

 

How's your fuel filter?

Check my gallery for pics of my installation.

CR

 

could my fuel filter be causing the fluctuation? how often do i need to change my fuel filter? i heard something like every other oil change. i haven't changed it since i bought it about 4 or 5 months ago. i've changed the oil 3 times since then.

 

That would be my next step. After that, I would check for leaks in the fp gage lines.

I change mine fuel filter every 15k miles or so. Don't buy the filter at the Dodge dealer, too much money. Get it from a Cummins dealer or off the internet.

 

the fp gauge isn't leaking any fuel. i don't know what the deal with it is. maybe it is my lift pump or the fuel filter.

 

If you tap in to the accuator line it is inaccurate because at the set pressure the waste gate functions and your only reading how much it takes to open your waste gate. The elbow with its own port for reading boost is much more accurate.
Trust me I spent the time with trial and error when I tryed to make my own boost controler . Then I grew up and got a real turbo with no waste gate.