steveo

Well-Known Member

• Apr 26, 2017

• #1

So, I noticed tonight that at idle on my 300tdi defender, the boost gauge needle vibrates (for want of a better word) from just under zero to just over.

I'm sure it hasn't done this before. The gauge measures both boost and vacuum (hence it reading under zero) but obviously as its plumbed into the boost pipe, it only measures boost.

How could it be measuring under zero? If I rev at standstill, it then measures boost, which I'm also sure it hasn't done before. Any thoughts, wise ones?

 

N

notenoughtime

Active Member

• Apr 26, 2017

• #2

It should show vacuum at idle as turbo isn't producing boost and the Pistons are sucking the air from the intake hence the vacuum

 

steveo

Well-Known Member

• Apr 26, 2017

• #3

notenoughtime said:

It should show vacuum at idle as turbo isn't producing boost and the Pistons are sucking the air from the intake hence the vacuum

Click to expand...

But its connected via a t piece in the boost pipe to the injection pump - surely this would never have a vacuum?

 

N

notenoughtime

Active Member

• Apr 26, 2017

• #4

Inlet will have vacuum when there is no throttle/boost

 

Kwakerman

Well-Known Member

• Apr 26, 2017

• #5

steveo said:

So, I noticed tonight that at idle on my 300tdi defender, the boost gauge needle vibrates (for want of a better word) from just under zero to just over.

I'm sure it hasn't done this before. The gauge measures both boost and vacuum (hence it reading under zero) but obviously as its plumbed into the boost pipe, it only measures boost.

How could it be measuring under zero? If I rev at standstill, it then measures boost, which I'm also sure it hasn't done before. Any thoughts, wise ones?

Click to expand...

Descent gauges will often use some form of dampening system (it could be fluid damped). If its vibrating (when it wasn't previously) then it could be a physical fault with the gauge or the whole gauge is being vibrated. Try disconnecting the pipe at the pump end, if the gauge still vibrates then you know it isn't being caused by actual pressure/vacuum variations in the pipe.

 

Last edited: Apr 27, 2017

bankz5152

Well-Known Member

• Apr 26, 2017

• #6

Ive got a Stack gauge plumbed into the inlet it has never read below zero but it does vibrate a tiny bit at idle, i wouldnt be too concerned tbh.

 

steveo

Well-Known Member

• Apr 27, 2017

• #7

Cheers guys - my concern is that this is new, and there is no vibration of the gauge housing (its not fixed in the dash).

Can someone rev theirs up at idle and see if the gauge moves? I'm sure one didn't before.....

 

bankz5152

Well-Known Member

• Apr 27, 2017

• #8

If I rev it hard and rev up and down eventually the boost gauge will move up a little

 

Kwakerman

Well-Known Member

• Apr 27, 2017

• #9

bankz5152 said:

If I rev it hard and rev up and down eventually the boost gauge will move up a little

Click to expand...

Snap mines the same, I've got a VDO gauge and it doesn't flicker (in a mud pod on top of dash)