|
It's sometimes called a chopper valve; it bypasses the control pressure past the fuel distributor, under the control of the lambda box. The lower the control pressure, the richer the mixture; if the valve isn't operating(it buzzes, you should be able to hear it with the hood open), the mixture will be lean. The valve is a small cylinder(~1"dia. X 2 1/2" long) clamped behind the fuel distributor with a fuel line on each end and a 2-pin electrical connector in the middle. +12 volts is fed to one pin and it's grounded by the lambda box through the other. If it isn't working, the O2 sensor voltage will be fixed and low, ~.1-.2 volts. See http://www.swedishbricks.net/faq/fio2.html
My '78 245 would intermittantly lose power to the FI relay(on the fender); sometimes I'd be idling in traffic and the idle would go from normal to lumpy and wierd and back randomly. Once on a long trip(just before I fixed the problem) the relay continuously lost power; the engine ran hotter than usual, idled strangely, had even less power than usual, but got ~30 mpg. The culprit turned out to be the fuel pump relay, where one set of contacts(not the fuel pump ones, obviously) wasn't closing, so the FI relay wasn't pulling in.
There are obviously other possibilities, but your problem sounded familiar.
|
