Hey folks! My girlfriend friend recently got a 1981 Volvo 244 with "low miles" - odo stoped at 66000... Well she's very happy with it and it was taken care of but unfortunately for her free mechanic it seems like a never ending process of replacing parts as they go.

What I'm on here looking for advice on is it's having trouble idling on cold starts. The engine will surge then drop to about 500 rpm over and over for a few minutes until warmed up a bit. I read this could be caused by the in-tank pump not working. I recently replaced both fuel pumps when the main went out. Still has the same issue.

For what it's worth, I was talking to an old timer the other day. He has a few old old volvos and saabs. He said "Oh no that's not a fule issue. You have a bad temp sensor."

Any input from you guys would be great. My research into the matter isn't being very fruitful.

Thanks!

 

Your US 1981 244 will have CIS fuel injection. The cold start issue - is probably caused by the mixture being off, too rich or too lean when cold. - What operates as the "choke" (providing additional fuel when the engine is cold) is the control pressure regulator. Your first step in checking to make sure that system is working properly - is to check fuel pressures. Line, rest and hot/cold control pressures. Simply takes a fuel pressure gauge designed for that system and the knowledge of how that system works. One possibility is the "frequency valve" is not working and someone adjusted the mixture for the car to run when warm - but without that valve working properly - the cold mixture is way off.

The frequency valve was added to the CIS system when Oxygen sensors were installed. (1977?) There needed to be a way to control the mixture according to what the O2 sensor was commanding and that was done with a valve that would modulate the control pressure. Control pressure is the pressure trying to resist the air metering plate from coming up with air flow. The control pressure regulator puts less pressure on the plate when cold, therefore allowing the plate to rise higher with a given volume of air and with a higher plate more fuel is injected - a richer mixture when cold.

If you are unfamiliar with how CIS works with the frequency valve - it might be hard to find anyone with that knowledge (that still works on cars!)

I can tell you one basic thing to look for related to the frequency valve - it makes a buzzing noise whenever the engine is running. It's located next to the air bellows, (that's the rubber part between the throttle plate and the air metering plate, slightly in front of the fuel distributor) The frequency of buzzing changes with inputs from the Lambda control unit to change the fuel mixture very slightly so the cat converter works best.(using signals from the O2 sensor)

If it does not buzz - the car will not run right. Power to it is controlled by a relay, square originally silver relay under the hood. Sample picture of frequency valve below (that's not from a volvo, but a googled image) 2 prong wiring connector and pressures hose on both end.


BTW - the only temp sensor you have on a CIS car is for the dash gauge. It is possible however on an electronic injection car (1971-1973 and late 1982 to present for Volvo) for a temp sensor to cause problems

 

Check eBay to see if you can find an old Bosch CIS service manual.