Fuel - how much should I be getting??

[Rhyso]

Hey guys

Got a 1.6 Mk2 Driver and it seems to be a bit heavy on the fuel consumption 

I fill it up between a quarter and the red zone but only getting around 250 miles by this point.  Just had the waxstat replaced as it was idling fast but this dont seem to have helped! Had a word with my local mechanic; he thinks it could be the butterfly flap on the choke being stuck open making it too rich. Does this sound about right? Gonna put it in for a full service soon anyway but would like some advice on what the cause may be!!

And before u ask I don't cane it that hard! Average between 60-80mph motorway cruising and dont rev it hard around town... its driving me mad especially as fuel prices keep fecking rising!!!

Rhys

[mikereynolds]

ive got something seirously wrong with my MK2 16v, put ?45 in and have been driving it sensibly and have got 220 miles out of it!!!
ahhhhh any ideas would also be appreciated!
mike

[Rain]

must me nice

my 8v wouldnt even take ?45 worth max i get in with optimax is ?38 from deep in the red. as for mpg i did london to newark and back with just under 1/4 tank left think it was about 330 round trip but thats one trip not daily

250 on 1 tank is about 19mpg i get on average about 25 on long journeys. but stop start on a daily basis i get about 10-15. the choke would be a likely fault get it checked out incase your constantly driving on choke.

[tinman]

to give you some idea of how bad things are, my valver gets about 26pmg when driven hard and i mean hard, and is doing about 24mpg at around 100mph (GPS). if i drop to 60 then the mpg goes to about 44-48.

i wouldn't say my engine is perfect, but it is rebuilt in the last 2k, and it has a virtually new injection and fuel system.

[VeeDubGTI16v]

i got up to 400 miles out of a tank in my old driver, but it had an ecotech valve so i got a bit more than usual, and that was mostly motorway too, im lucky if i get 275 out of a tank now

[davidhawkins_78]

In my 8v GTi a full tank of optimax does about 300 miles ... not great but I do have a pretty much 'digital' accelerator, either on or off?

I think i've got an 11 gallon tank (ish)

So that's still an average of 27mpg ... not too shabby?

[JMallows]

Dont know what the MPG  is, but i get 100 miles out of ?10 on normal driving. Bit more on a run...

Although, now fuel prices have gone up, its gone down a little bit

[rubjonny]

Your problem is almost definitely due to the coolant channel in the inlet manifold being blocked by a knackered o'ring, causes random overreving and sh!te running:

Before you start, MAKE SURE you can reach ALL 6 bolts on the inlet, the third one from the right is a right sl*g to get to!! Oh and you'll need a gasket and the o'ring, part 32 in the diagram below.

First take the carb off:
Remove the airbox
Remove the fuel line from the carb
unplug the 2 electrical bits on the left side at the back
remove the earth connection from the front
Unplug the vacuum connection to the green reservoir
Remove the coolant connection to the inlet manifold
Remove 3 securing bolts
Check the condition of all the vacuum pipes, do one at a time its a bit complex back there?

That should give you enough slack to move the carb over to the right out the way, next get the manifold off:
Undo all 6 bolts, remove manifold. Thats it?

Then lever out the knackered old oring and clean up the hole it came out of, mine was full of limescale and all kinds of crap! Check the inlet manifold preheater looks ok, and fit the new gasket & oring, then refitting is the reverse of removal

[rubjonny]

Checks on the Carb itself:
TTV & idle over run valve:
These should both get 12v when the ignition is on, and there should be an audiable 'click' from the engine bay when the key is turned.

"Expansion Element" (Waxstat)
When engine is up to temp the pin should be fully extended, can be tested by chucking it in a bowl of hot water.  This sometimes helps to fix knackered ones as it resets the wax inside it apparently, sounds iffy to me

3/4 Point Unit:
When engine is off, should be extended to 14.5mm. When engine is started should immediately retract to about 8.5mm.

Pull Down Unit:
When engine is running, the choke flap should be easy to push closed until the last 5mm or travel, then resistance should be felt. If not = buggered 

Inlet manifold preheater:
Located at the bottom of the inlet manifold, directly below where the carb mounts, looks like a hedgehog  The electrical connection is at the back of the engine bay behind the carb, should get 12v when engine is cold, should switch off when engine has warmed up. (controlled by grey temperature sender, see below)

Autochoke:
Should get 12v with the ignition on & engine is cold, should switch off when the engine is up to temp. (controlled by the red sender, see below)
The autochoke should pass current, test by placing 1 prong of multimeter on the plug, and the other on the autochoke housing.
You can check the autochoke visually by removing it and checking the condition of the spring around the outside of the unit, looks like the kind of spring you find in a ball point pen  When refitting, align the mark on the housing with the notch on the choke.

Temperature Senders:
At the front of the engine block there are 2 temperature senders, red & grey. The red sender controlls the autochoke, the grey controls the inlet manifold preheater. When the engine is cold these should pass current, when the engine has warmed up they should not pass current. You can test units from the scrap yard by putting them in a tray filled with boiling water (just immerse the metal bit at the bottom!) to make sure they switch off correctly.

[VeeDubGTI16v]

you can leave the carb on the manifold when you take it off