Hi All:

Does anyone know how the Aneroid Switch and Altitude Compensator Solenoid, on the D24T Diesel, work? The Green Book is pretty sketchy. It just says "The solenoid is energized until an Altitude of 6000 feet is reached". Than it deenegises.

What does this do in terms of fuel delivery / Timing?

I have an 83 and 86 with these devices installed. The 86 seems to go slightly advanced when the solenoid is deenergised. On the 83, nothing happens.

I'm trying to determine which one is defective, if any. But then, these are different pumps. The 86 has EGR. The 83 doesn't.

Thanks for the help.

Aside from the excellent information in Badge988's post, the '83 and the '86 should have two different altitude compensation devices on them (if I recall correctly). The '83 might have a more simplified version which needs to be manually enabled/disabled depending on altitude. It would be worth picking up a copy of the '83-'86 Volvo 700 Emissions control service manuals for more information. They're pretty common on eBay.

God bless,
Fitz Fitzgerald.
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'87 Blue 240 Wagon, 255k miles.
'88 Black 780, PRV-6, 148k miles.

it switches power to the control solinoid located down on the injection pump. I forget what the actual degree change is however when the solinoid is energized the timing is allowed to advance properly. When off the timing is limited in advancing in order to reduce fuel at higher altitudes under load. Someone at the EPA was concerned that the car might smoke slightly in the mile high city...

I wired mine on fulltime with no ill effects however when the solinoid is off cold starting seems to be affected as well and the car smokes slightly when cold.

If you want a close parallel go look at the "Housing Pressure Altitude Advance" control used on the GM 5.7 and 6.2 diesel cars and trucks, its the exact same operation and give a bit more detail in operation.

988

have you checked swedishbricks.net mailing list?
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Stef (81 245 B21A SU M46 3.91) 325000km my volvo pages