Lower the CO on a Volvo 264 B27E -78

Hi everyone!

I want to lower the CO on my 264 -78. I have received a few tips and the best one came with a picture from a 264 -79. Unfortunately it does not look the same as mine does. Here follows some pictures and descriptions:

Here is the picture of the PRV6 in the 264 -79. Top is the screw for the CO and bottom the screw for the idle.



This is how my car looks under the hood with the air drum on.



This is how my car looks with the air drum taken off.



And this is a close up.
Number one is the screw that holds the air drum in place and also lowers the idle heavily when it is taken away. It sucks air. The car stops automatically after a while if the screw is not in place.
Number two is a plastic thing that can be pulled up and pulled down. I notice no change whether it is up or down. I have not tried to take it away.



Could someone please help me?

Thanks in advance!
Jesper

I've never seen anything like that... my '76 264 looked just like the one in your first photo.

I'm guessing that somehow your car was retrofitted with a fuel system and intake from a non-volvo PRV car of some sort?

casioqv said:

I've never seen anything like that... my '76 264 looked just like the one in your first photo.

I'm guessing that somehow your car was retrofitted with a fuel system and intake from a non-volvo PRV car of some sort?

Click to expand...

Hi!

It has never been modified in any way, as far as I know from the car's complete documentation from 1978 til now, and I have seen other 264:s from -78 that look exactly like mine under the hood. Modified or not, does anyone know how to adjust the CO?

Kindly
Jesper

Jesper your car is equipped with an 'E' version of the PRV six that never made it's way to the States!

The number one screw that when pulled makes for poor idle that turns into a stalled engine.... This one is clearly going into the airbox and when not there it makes for a 'false air' leak such that K-Jet measures less air. I'll wager that #2 is accessed with a very long 3mm allen to adjust CO.

Do be sure to look for vacuum leaks anywhere and everywhere.... K-Jet really wants the air getting into the engine to be measured.... IE passing the airflow sensor plate.

Somewhere on your intake there will be an idle air bypass that will be for setting idle speed. This guy lets measured air past the throttle plate

JohnLane said:

Jesper your car is equipped with an 'E' version of the PRV six that never made it's way to the States!

The number one screw that when pulled makes for poor idle that turns into a stalled engine.... This one is clearly going into the airbox and when not there it makes for a 'false air' leak such that K-Jet measures less air. I'll wager that #2 is accessed with a very long 3mm allen to adjust CO.

Do be sure to look for vacuum leaks anywhere and everywhere.... K-Jet really wants the air getting into the engine to be measured.... IE passing the airflow sensor plate.

Somewhere on your intake there will be an idle air bypass that will be for setting idle speed. This guy lets measured air past the throttle plate

Click to expand...

Thank you very much John for your explication! Interesting that the E version never reached the US.

I will really search for that idle bypass for setting the idle speed. It needs to be lowered. If you come up with any suggestions about where it may be situated, please let me know.

A long allen key 3mm to adjust the CO. Clockwise to highten the CO and the other way around to lower it, right? Should I take away the plastic thing that can be pulled up and down and see what is underneath?

Thankful regards from Sweden!
Jesper

JohnLane said:

Jesper your car is equipped with an 'E' version of the PRV six that never made it's way to the States!

Click to expand...

Cool, I knew their had to be some reasonable explanation... the idea of someone swapping an entire intake and fuel system from a weird french car or something and making it look clean and stock didn't seem very plausible.

What's different about the E if it's still k-jet? It looks like you have to get the intake manifold off to get to the fuel dist?

allen screw

hello
if you do turn that screw with allen head just go a very small amount at a time.
im betting thats not your problem. check all other things first.
you really need to read up on this before you get all messed up.
it can be done with a couple digital multi meters and some knowledge and its been a while since i messed with k-ket. the bentleys should have some type of info that may help you.
good luck
Mike

244ti said:

hello
if you do turn that screw with allen head just go a very small amount at a time.
im betting thats not your problem. check all other things first.
you really need to read up on this before you get all messed up.
it can be done with a couple digital multi meters and some knowledge and its been a while since i messed with k-ket. the bentleys should have some type of info that may help you.
good luck
Mike

Click to expand...

Thanks Mike!
I will go very slowly with the allen and I will investigate whether there is leakage in other places.

Regards
Jesper

244ti said:

you really need to read up on this before you get all messed up.
it can be done with a couple digital multi meters and some knowledge and its been a while since i messed with k-ket. the bentleys should have some type of info that may help you.
good luck
Mike

Click to expand...

Quite true. The A/F mixture set by the Allen hex key on the fuel distributor is very easy to get far off the proper A/F curve that tth A/F plate provides, especially if there's an air leak or other malfunction that causes the A/F ratio to shift. Even the setting of that screw when the engine has old oil versus fresh oil can shift the A/F curve. It is the last thing you want to attempt to adjust, after you've verified everything else is in good working order, like ignition parts, valve lash, compression, injector spray, fresh oil, air filter, etc.

I would not set the mixture unless you have access to an exhaust gas analizer. The total range from lean to rich is only about 10-15 degrees of turning the screw. Once you put it out of the proper range after the car isn't running properly due to other reasons, it is very difficult to get it back to where it should be.

Also, AFIK, the B27E of the pre- 1980 vintage didn't use a frequency valve, so tuning by O2 sensor feedback may not be possible by using a DVM on the dwell reading off the frequency valve.

Thanks for all the answers and all the advice!

Kindly
Jesper

#2 is the access hole for the mixture adjustment via a allen key

Yours is a B27E with the early 'octopus' manifold that came on >78 cars, 79 got the twin rectangle manifolds and 80> went to the B28.