[Diy_efi] Motronic fuel cut on excess boost??

[Kenny W]

Quoting Chris Wilson <chris at formula3.freeserve.co.uk>:

> AFAIK it doesn't have a MAP sensor, works of AFM
> (swinging gate type)
> throttle pot and RPM, with normal temp trimming.
> If it HAS a MAP sensor
> I haven't found it! UK spec 1988 Volvo 740 turbo
> intercooler, on
> Motronic, the one with 2 flywheel sensors, one
> counting ring gear
> teeth, the other about 90 degrees BTDC ( a metal
> tab on the flex plate,
> it's an automatic). Cheers.


Oh! And I meant to repsond to this because being a 
Volvo guy I actually know what you have to do! lol I 
got talking about sensor scaling and missed the point. 
Wouldn't be the first time. 
Anyways, there is a pressure switch that is set to 
about 14psi usually that cuts the fuel (simply called 
an overboost switch), no map sensor, just a "hobbes" 
switch thta triggers if you lose the wastegate control 
line. It is near the center console, almost near your 
feet somewhere on the driver's side of the car (oh, in 
north america anyways, hmm, may be pass side for you). 
Anyhoo you can track it down by pulling your boost 
gauge out and following the vaccuum line attached to it 
to the firewall. The fuel cutout switch is "t"'d from 
this line. So basically hunt around for vaccuum lines 
coming in through the firewall, there's a switch 
around. There is an adjustment on the switch, but it's 
filled with glue. Melt out the glue and tweak it, or 
buy an adjustable pressure switch from a parts store 
and wire it up in place of the stock switch (normally 
closed.
Hope that helps. You can be glad to know it's not 
related to the ecm at least. 
-Kenny
AKA Captain Bondo

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