Milage goes from 10mpg to 17mpg with a little adjustment!

[abe280SL]

I noticed decreased milage in the car while the car ran well with a few put put sounds.  At first I thought it was rich setting on FI pump or somehow something got affect after using ?44 FI cleaner.  To my surprise after using the Gunston analyzer the C0 was 1.5%!  Surprised car ran as well as it did. Adjusted to 3.5-4% and milage increased to usual 17+mpg.  I thought that since the setting was lean it would have had higher mpg...instead it was down to 10mpg! 
Well, thats my story for the day.
abe

[al_lieffring]

Fuel mileage is an indicator of efficiency, either too rich or too lean will make the combustion inefficient, and lower the MPG (increase L/100Km)

[RickM]

You probably extended the life of your pistons and cylinders as well. Good catch.

[bpossel]

Hi Abe,

That's great!  How did you measure your co?  Engine at op temp, idle at ~800, in park?

Very interested in your method of measure.

Thanks!
Bob

[abe280SL]

Bob,
I usually take the car out for drive 10-15 minutes...run the rpms up a little (mini Italian tune up).  Then after following the instructions on the analyzer I keep the car at idle...my idle is actualy lis more like 900. I check it with car in park/neutral. Now, I remember years ago a mechanic used to  put it in drive when he had to adjust the fuel injection pump in the days that it had to pass smog testing.  He used to lean her out..pass the test...then enrich her back to  a "happier"  condition.  My haynes book does not mention to put it in drive...so I test in park/neutral.  I also had the car tested by  a mechanic friend of mine with his expensive analyzer and the Gunson was off .25-.5%...good enough for me when your goal is 3.5-4.5%.  For fun I run the rpms to 2000 to see what happens and the C0 goes up to 7-9%.  I don't know if thats too rich but not worth it for me to fiddle around with the other adjustment screws on the pump.  I was just really surprised how a lean ratio could make combustion so inefficient...expected this from rich more not lean.  BTW, I went through 3 full gas tanks thinking it was a miscalculation or not filling the tanks correctly ...so I know this was not a calculation error.
The part I do not understand is why the fuel injection cleaner messed this up...unless it was already messed up.
abe

[J. Huber]

Hi Abe, for those of us unlucky enough to have a Gunson on hand -- what is the actual procedure like? Does it get hooked to exhaust? and what do you do to change the numbers? air and FI screws? Pretty novice guy here...

[jeffc280sl]

Abe,

Glad you improved mileage on your car.  The fip has three rpm range adjustments.  The idle thumb screw we all know about is for idle.  There are two other internal adjustments under the idle thumb screw cover.  These adjustments are used for co or air fuel ratio in mid and high rpm ranges.  I've been using a portable wide band afr meter to tune my fip.  I can record data and I can tell you that even with a perfectly tuned injection pump the co/afr mixture is constantly changing when you're driving.  Sometimes it's rich and other times it's lean.  MB provides us with the attached performance specs for co/afr.  If you are within these specs you are good to go.

[abe280SL]

James,
I was talking more about instructions about using the instrument.  The instrument has 2 small and 1 long clear rubber hose you have to assemble  easy to do.  The long hose has a 12" metal tube that is placed in the exaust just like the big boys do.
At first you connect the instrument to the car's +/- battery for a few minutes to let it adjust.  Start the engine so the correct voltage is going to the instrument.  There is a rotary knob in front of the intrument that you calibrate  2.0 on the instruments digital readout.  All this is done before placing the metal tube into the exhaust pipe. Once there is no flactuation just stick in  exhaust pipe and wait a few minute for a reading.  If its too rich, turn the knob on the FI pump clockwise to lean it out....too lean, turn counterclockwise to enrich  (engine must be off or you will shread your fingertips).
Keep doing that till you get 3.5-4.5% CO.  Its a fun instrument to play with.
Other thing you can do is if you disconnect the linkage rod that comes up from the FI pump and you open up the throttle on the FI pump...if it stalls it means it is too rich if it picks up rpms it means it was too lean and adding the xtra fuel helped.
The other way would be to open the throttle on air intake while the pump is left alone....rpms go up it means that it needed more air and thus it was too rich.  Rpms go down means you added more air on an already lean mixture.
After you get the linkages properly adjusted (their is a tour here), timing, dwell...then you can do all the above.
The air screw is used to set idle speed not fuel/air adjustment.
I learned all that on this site.
abe

[abe280SL]

Jeff,
So I assume when I rev up the engine to 2-3000 rpm for fun and see the CO go up that its probably meaningless since those specs are for car under load?
abe

[jeffc280sl]

you're right Abe. no load cos tend to be rich

[jameshoward]

For those owners with a 230 or a 230-type FI pump arrangement (ie, one that has an isolated oil supply rather than the later pump that has a line which provides the pump with oil - the older ones have a dipstick) I found I got a significant MPG difference by draining the old oil from my pump (when I opened the distick the oil flooded out) and replacing with the correct amout (I think around 180ml, but can't quite recall). If you have a pump with the dipstick and haven't checked the oil level, give it a go.

JH