So I did a boost leak test on my 99 cummins found a t clamp that needed to be tighted. Took the tester to 25 psi. The gauge is slowly going down like .5psi every couple second. Did the soapy water test can't find anything. Can't hear anything. Is this normal to loose psi with it pressured up or should it stay at 25psi. 

Normal.  It would be very rare for all valves to be %100 closed.

Ok sweet I just did it again. And I can kinda hear something next to the turbo. All boots are tight. I think it's just the air moving at 25 psi. 

Boost elbows tend to have a bleed hole in them. Normally we test using a regulated air pressure and leave it hooked up and spray soapy water around all the fittings, intercooler, MAP and IAT sensors looking for leaks, don't forget the intake cover plate and grid heaters too.

Ha ok wish I would saw this before I've put everything away lol

Ok so I still think I have boost leak hate to say it. Maybe it's just me, my boost guage ticks or vibrates however you wanna put it the needle is not steady. Might just be me I took a video hopefully you can see it. It's a pretty bad video. 

 

IMG_0690.MOV

Edited March 8, 20178 yr by abner99

I see more movement from the camera than anything lol

Yeah it's pretty bad the roads around here are pretty rough. It's like your at 16psi of boost but it wiggles back inforth between 16.5 and 15.5 not a lot I'm  exaggerating like its vibrating.  I changed sending unit that didn't help. 

Do you have a snubber? 

For the boost? I knew you used it on your fuel pressure, but for the boost? 

I just switched from a 1/4" line to a 1/8" (both id) and my boost gauge bounces around at lot now.  Gonna figure out a little oversized expansion chamber to see if that fixes it.  If not a snubber valve.

8 hours ago, SilverMoose said:

I just switched from a 1/4" line to a 1/8" (both id) and my boost gauge bounces around at lot now.  Gonna figure out a little oversized expansion chamber to see if that fixes it.  If not a snubber valve.

So you went smaller and it still bounces that weird. My fuel pressure bounces a lot with a needle valve and about a 4 foot 1/8 line plus a isspro snubber. So I don't know I'm gonna try another snubber in there plus a restictor. 

My bad for not being specific.  Boost didn't bounce around with 1/4" line. 

 

L8tr

D

Weird I have an 1/8" line to both my fuel pressure and boost guage and it's been fine for years. I have a needle valve on fuel pressure that is barely cracked open. Could there be a kink in line somewhere or maybe just a faulty gauge.

21 hours ago, SilverMoose said:

I just switched from a 1/4" line to a 1/8" (both id) and my boost gauge bounces around at lot now.  Gonna figure out a little oversized expansion chamber to see if that fixes it.  If not a snubber valve.

How far do you open the needle valve for your fuel pressure gauge.  Like was said above, it doesn't need to be opened much.  Mine is also just barely cracked open, if I open it too much more it will bounce around.

I have the valve opened all the way on my fp gauge  with 1/8" line and steady as can be.  I would have figured both gauges would be the opposite.  My fp gauge is teed of a 1/2" line from filter to IP so that probably helps.

 

L8tr

D

That seems weird to me. That's basically zero dampening from the vp's water hammer. What pressure is the gauge reading? Does it fluctuate at all?

Steady as can be.  19 idle just shy of 15 wot.  Weird to me also.  Maybe it's the 1/2" line that buffers.  There's a lot of volume difference between that tiny stock 1/4" line and new 1/2".

 

L8tr

D

 

I would still run needle valve barely cracked on fuel guage, it may be steady now but with time it may go waky. 

2 hours ago, SilverMoose said:

volume difference between that tiny stock 1/4" line and new 1/2".

Actually stock is 6mm ID which is actually smaller than 1/4".

On 3/21/2017 at 0:41 AM, abner99 said:

For the boost? I knew you used it on your fuel pressure, but for the boost? 

Yes I use one, otherwise needle jumps around.