solenoid vacuum line - charge air pressure control system - 85 240 GLT

I have a problem two mechanics and a Volvo dealer couldn't figure out. I
have an '85 240 GLT that has a hole in the air intake line. On the passenger
side of the engine compartment is a solenoid with a vacuum line that's not
connected. This vacuum line is just the right length to fit into the hole in
the air intake line. Just found out for the first time (tonight) that it's a
solenoid valve - Bentley in the "Turbocharger" chapter. Bentley manual
describes it as having an inlet and outlet vacuum line, with the inlet
coming in from the wastegate actuator and the outlet returning to the air
intake hose. The manual says,. "...when the solenoid is open, boost pressure
acting on the wastegate actuator is reduced". Cool, never knew that! Problem
is, when one mechanic "plugged" the hose into the hole, the engine tanked -
very rough idle under 500rpm, repeated stalling, hard-starting and no power.
Removing the hose resulted in the car "running well". This mechanic called a
dealer in Long Island who didn't have a clue what the mechanic was talking
about (suggested I get a newer car). Second mechanic also didn't know what
the setup should be (suprising as he was very knowledgable regarding
Volvo's). The car's been running in this state for quite some time and I
just happened to look at it today and wonder what it was all about. Some
questions that come to mind: Does any of this make sense? Shouldn't there be
a simple vacuum line connector entering the air intake line hole? Does it
make sense that connecting this line could cause the engine to idle poorly?
Is it possible that this is in some way connected to potential problems with
the wiring harness and/or maybe the solenoid is always open or the engine
rpm relay is bad? I'm thinking (it's late, so the brain's a little slow
right now) that checking vacuum lines and testing the components in the
charge air system might shed some light on the situation? Appreciate any
help anybody can offer as I'm pretty confused about this problem and want to
eliminate what is essentially a debris-intake hole leading directly into the
turbo.

Thanks,
Mike

 

They used that system for just a couple years to give a boost increase
in the high RPM range. The hose from the solenoid valve should just poke
into the hole in the intake pipe with a tight friction fit. You'll
probably wanna clean the compressor wheel of the turbo with some carb
cleaner or something after having that hole open, yes that will make the
engine run poorly too, I'm surprised it ran at all with such a large
vacuum leak after the airflow meter.

Personally I just bypassed that system, after several years it doesn't
seem to have hurt anything and it improves low end torque.

 

The rpm relay and solenoid came standard on 85YM cars. It was previously
sold as an accessory called the "turbo +" boost kit. The idea is to
restrict pressure going to the wastegate actuator in order to hold more
boost on the motor for a longer period before allowing the wastegate to
dump pressure on the system thus yielding an increse in hp at whatever
rpm the rpm relay is programmed for. Once the specified rpm has been
reached the solenoid opens and allows full manifold presure to the
wastegate to keep the overboost relay from shutting off the fuel pump.

You'll proably want to go to:

http://www.turbobricks.com/mods.php

and muck around. There are several modifications that allow the tube to
be open and the hose disconnected that simply let the boost overpressure
relay control overboost. There are also tweaks to the boost overpressure
relay that allow a higher maximum boost pressure. You can also tweak the
length of the actuating rod for the waste gate actuator to raise the
maximum boost pressure. Read, learn, be very precise in your changes and
use accurate instrumentation. The dynamic pressure of a detonating flame
front is very impressive.

If the hose has been removed from the intake pipe then someone has
adjusted the fuel distributor screw way rich to compensate for the
vacuum leak. If you return the hose to its correct place you will have
to lean the mixture way back to allow the motor to idle correctly.

If you go to:

http://www.swedishbricks.com/faq/turbo.html#thoughts

and read about the turbo plus kit it seems to say that it couldn't be
retrofit on -86YM cars. However if memory serves, and lately it doesn't
seem to have as much accurate info as it once had twenty years ago,
there was a boost kit available in '85. Someone I knew had installed the
rpm relay and solenoid on a factory employee car that grounded the
#11 pin on the fuel control unit to drive the mixture full rich whenever
the boost control solenoid was energized.

Bob

 

IIRC the Turbo + kit was for the LH-Jet 700 series cars. The one on the
240, or at least the setup that was on my 240 Turbo is a solenoid which
remains closed until the engine reaches around 4000 RPM at which point
it opens, dumping some of the air pressure from the wastegate hose into
the intake which causes the boost to increase. When it was hooked up,
the boost would sit in the middle of the yellow, and then spike up
almost to the red at high RPMs. After I bypassed it, it would go up to
the base of the red right away. The same circuit cuts out the A/C
compressor and IIRC turns on the aux fan in front of the radiator.

 

That's so cool! I've been wanting to know this for years. How does one go
about cleaning the compressor wheel? Just disconnect the hoses and spray? Or
should the turbo be pulled?

The car's been running poorly for a very long time. Last 2-3 years have cost
a bunch just trying to pass inspections. Now I know why. Kind of bummed as
we really thought highly of the mechanic we'd been seeing. Guess I'll hook
it back up, clean the turbo, adjust the fuel distributor and see how the car
runs. Have always wanted more low-end, so will consider bypassing the
solenoid.

Mike

 

Man, I'm so stoked! I was just hoping to find out what the hose was supposed
to plug into. Now I know why my car runs so poorly and the exhaust always
smells so rich. Thanks for the info and links. Skimmed some of the
brickboard turbo mods and will print them out and study them for a while.
Lots of detail to consider, but since I'm still in restoration mode,
performance improvements will have to wait until a little ways out in the
future. Read the article on swedishbricks and found this admonition pretty
sobering:

"For increased specific power output, the wastegate can be adjusted so that
the high/low boost settings are higher. The caveats of this are plentiful, I
have known MANY turbo Volvo's with altered boost levels that while
awe-inspiringly fast, tend to eat u-joints, transmissions, motor mounts,
etc."

Between that and your sentence about, "The dynamic pressure of a detonating
flame front is very impressive" (that's a great quote!), figure I'll just
take your advice and start slow and take my time. Heck, the car's been
running so poorly for so long that just getting back and running well should
be gratifying - for a little while.

Mike