Fuel economy - Charcoal box / Vacuum lines

[Alex]

Evening all, I've got a 77 M110.

The car has pretty shit fuel economy, I think I average several months of city and occasional freeway to 26l/100km.

Currently my research has led me to replacing or servicing the charcoal box.

(The vacuum system on the car does not work properly, it pulls the door handles but doesn't properly lock nor shift nicely) (perhaps inefficient shifting is causing poor fuel economy?)

I took out my charcoal box to take a look at it. And I found a white tube and a vacuum line.

The white tube seems to go to the tank, but the vacuum tube goes to somewhere above the distributor. What does it do?

The charcoal box itself, what does it inherently do to the gases? And how can I optimise it or service the charcoal?

The Y piece for the vacuum line exiting the charcoal box is cracked, where can I replace this? (Do I order, or can I manufacture out of existing straight tubing).

I have another vacuum line that goes to nowhere on the fusebox side of the engine. It's blue and purple.. any ideas where it goes?

Cheers.

[ramiro]

The Euro cars don't even have a charcoal box , the vent line just ends openly in front of the rear axle, i doubt that would make any difference on fuel economy.
On you car the line goes to the charcoal  box , and the other should go into the trottle body so the gases get into the engine.

I think the blue and purple line is for the vacum front light heigt regulation.
Also the vacum for the shifting is a seperate system there should be a steel line that brings vacum to the transmission directly from the intake manifold.

I would check the basics like fuel pressures ,ignition timing, also on the m110 you have to regulary adjust the valves

[daantjie]

You can open the canister and refill with new charcoal, but as stated there is no benefit to fuel economy so really the benefits are negligible, if any.  Remember this was the first very rudimentary attempts at smog/emission reduction so it's very old tech at best and very much bullshit to be honest.  Unless you live in California or some other nanny - state where emissions are verboten I would not sweat it.

[Randys01]

Yep...std on Aus cars in pursuit of ADR27a.
The idea was to purge the fuel tank of fumes...draw them thru the charcoal and into the engine via a one way valve.
You can ensure that it is all still hitched up if you like. This will enhance a smooth idle.  You can refill the cannister as suggested if you like.
It will make no difference to your fuel economy.

The fuel economy you are getting is another story and unrelated to these idiot ancillaries.
The nub of the problem will lie with the fuel injection. If yours is an early car it will have Bosch Djet.post 77 it will have Bosch K jetronic.

Either way, unless you are at least mechanically adept or have hundreds of hours to spare, this problem is one for the pros.

[Randys01]

Footnote.,. I see yours is a K jetronic...1977?
In all  probability the excessive fuel consumption can be sheeted home to fuel pressure issues. There's plenty of potential culprits that can contribute to this problem.
But in order to make a start you must have a CIS fuel injection test pressure gauge.

I have found after many years of frigging around with this system  that the only way to get them sorted out after 40 years of neglect is to start at square one.

Plenty has been written about diagnosis/techniques etc but I reckon there's only 4  basic tests.

- what is the fuel volume delivery?
- what is the cold control pressure?
- what is the hot control pressure?   
- is the aux air valve working properly?

Taking in the broader picture......
Does the car start readily and assume a fast idle for the first 3-4 minutes?
Does it revert to a smooth idle around 750 rpm when warm?
Does it have plenty of power?
Does it blow black smoke under power?

Something in those few litmus tests will not present as correct. .home in on that.




 

[Alex]

Footnote.,. I see yours is a K jetronic...1977?
In all  probability the excessive fuel consumption can be sheeted home to fuel pressure issues. There's plenty of potential culprits that can contribute to this problem.
But in order to make a start you must have a CIS fuel injection test pressure gauge.

I have found after many years of frigging around with this system  that the only way to get them sorted out after 40 years of neglect is to start at square one.

Plenty has been written about diagnosis/techniques etc but I reckon there's only 4  basic tests.

- what is the fuel volume delivery?
- what is the cold control pressure?
- what is the hot control pressure?   
- is the aux air valve working properly?

Taking in the broader picture......
Does the car start readily and assume a fast idle for the first 3-4 minutes?
Does it revert to a smooth idle around 750 rpm when warm?
Does it have plenty of power?
Does it blow black smoke under power?

Something in those few litmus tests will not present as correct. .home in on that.




 

77, K jetronic I believe.

I don't know how to test half these things haha. I think I'm gonna have to do some research on my end.

The car does take a fair bit of convincing to start, a good 3 or so seconds to get her going. The idle smoothers out after about 15 seconds I'd say.