Diagnose V-Boost problems

[smangelsen]

Hey all... I am relatively new to this forum and thanks for having
me.. This may have been discussed in here already but here goes..

I have an '86 max with virtually no top end after 6000rpm. I have gone
through the manual and when testing the servo it moves when I add power at the plug but only one way. I have to open it by hand first then it closes when power is applied... is this normal? Nothing g about this in the service manual.. Please help... pulling the last of my hair out...

 

[maleko89]

Do you hear the vboost cycling open and then closed when you turn the key on? Applying power to one set of pins opens the valve. If you apply power to another combination then it will close.

Mark

 

[maleko89]

This pic should help you out.

Mark

 

[smangelsen]

Negative, it does not cycle with the key switch..

 

[maleko89]

Try compressing or squeezing the vboost controller. If you hear cycling then that will need to be repaired or replaced.

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[smangelsen]

John Harris was telling me that too... is there a solder joint on that circuit board that comes loose?

 

[maleko89]

There are several that can come loose

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[smangelsen]

That would be nice, cheaper than a new servo I guess

 

[maleko89]

Yeah. Morley has a few spares laying around I'm sure. Kyle too.

Mark

 

[smangelsen]

Well, i squeezed the life out of that little black box.. nothing..
Even had the multimeter on to check voltage while squeezing
and nothing... does the controller reverse polarity to get servo to
turn the other way? Would feel better testing that before I
commit to the controller...

 

[maleko89]

Try applying voltage to the pins in the picture. That will eliminate the actual servo motor as the issue

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[smangelsen]

thanks Mark, servo checks out ... moves open and closed..
your help was greatly appreciated

 

[maleko89]

If your fuel pump and tach are working then the rpm sensing circuit is also ok.

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[urso]

Hey all... I am relatively new to this forum and thanks for having
me.. This may have been discussed in here already but here goes..

I have an '86 max with virtually no top end after 6000rpm. I have gone
through the manual and when testing the servo it moves when I add power at the plug but only one way. I have to open it by hand first then it closes when power is applied... is this normal? Nothing g about this in the service manual.. Please help... pulling the last of my hair out...

Hi,

I've just joined in this forum looking for help and saw you have had the same issue I am having naw.
The polarity is reversing when I turn on the key, did you find the problem? thanks.