Diagnose V-Boost problems

smangelsen · Sep 19, 2016

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 · Sep 19, 2016

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 · Sep 19, 2016

This pic should help you out.

Mark

smangelsen · Sep 19, 2016

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

maleko89 · Sep 19, 2016

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

Sent from my SM-G920P using Tapatalk

smangelsen · Sep 19, 2016

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

maleko89 · Sep 19, 2016

There are several that can come loose

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smangelsen · Sep 19, 2016

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

maleko89 · Sep 19, 2016

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

Mark

smangelsen · Sep 19, 2016

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 · Sep 19, 2016

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

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smangelsen · Sep 19, 2016

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

maleko89 · Sep 19, 2016

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

Sent from my SM-G920P using Tapatalk

urso · Apr 10, 2023

smangelsen said:
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.

Diagnose V-Boost problems

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