I am the worst driver....I get 9 mpg...help!

AUSMHLY

Obi Wan

Offline

• Aug 29, 2009

• #1

My Mechanic and I are trying to figure why my MPG is so bad.
Exclusive in town I'll get 9-12 mpg.
Exclusive highway I'll get about 21 mpg.
Combination is between 10-14?

New plugs, wires, pertronic and carbs and timing are adjusted. My British Mechanic doesn't think it's the tune up.
He's sat next to me while I drive the car and says my driving is fine. I don't push the car. I don't jack rabbit start. Freeway speed is about 70 in overdrive.
He doesn't understand why the in town is so low if I get 21 on the highway.

Can my in town shifting, driving be so bad that it really is my fault?

Funny that Greg offered to take my car for a while, for I actually told my mechanic that I'm going to fill the tank and let him drive it and see what he gets.

I'm happy my car drives like a dream and I've worked out all the bugs....except the mpg one. When push comes to shove, I'll take bad mpg over constant running problems and being stranded on the side of the road.

9 miles per gallon!

Any ideas at all guys?

Cheers,
Roger

 

1

100DashSix

Jedi Trainee

Offline

• Aug 29, 2009

• #2

I'd be worried about the mixture, since it sounds like you've checked the points. Have you tried warming it up then quickly turning it off and checking a plug? I bet timing can affect it, too.

 

Keoke

Great Pumpkin

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• Aug 30, 2009

• #3

Yep I tried to tell you so.--Keoke-- :laugh:

 

OP

AUSMHLY

Obi Wan

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• Aug 30, 2009

• #4

100DashSix said:

I'd be worried about the mixture, since it sounds like you've checked the points. Have you tried warming it up then quickly turning it off and checking a plug? I bet timing can affect it, too.

Click to expand...

I'm willing to check anything again.
I do not have points, I have a Pertronic set up.

I will warm it up, turn it off, then check...a plug? Which plug and what am I looking for?

I'm looking for something to offer my mechanic to check out.

As previously said, he has set the timing, new plugs, wires, cap, roter, pertronics, and tuned both carbs. He also did a drop test with the carb bell housing. He rebuilt both carbs, so they have new parts. Starts and shuts off with no run on. Car runs great.

 

OP

AUSMHLY

Obi Wan

Offline

• Aug 30, 2009

• #5

Keoke said:

Yep I tried to tell you so.--Keoke-- :laugh:

Click to expand...

What is it you tried to tell me Keoke?
Roger

 

GregW

Yoda

Platinum

Offline

• Aug 30, 2009

• #6

How long has this problem been going on? I recall you had an issue with the carbs a while ago, wasn't it a sticking piston? Are you sure the floats are closing properly? A small vacuum leak? I'm using a shotgun here.

 

OP

AUSMHLY

Obi Wan

Offline

• Aug 30, 2009

• #7

Hi Greg,

Thanks for shotgunning this.
My poor mpg thing has been going on for about a year now.
The carbs were totally rebuilt and the drop test done. The only time I have encountered the float bowls sticking (twice only)is when I could not start the car. I gave it a tap and then it unstuck. We've checked for a vacuum leak too, no leak.

Here's what my mechanic throws out. I don't know where the problem is. You car idles between 7-10. You're getting 21 on the highway.

The tranny has been rebuilt within the year and the more I drive, it's getting quieter and shifting smoother. He threw out to check what the rear end ratio was, which was my previous post question.

I'd like to find out what is going on. Maybe my driving style really is the source.
Roger

 

A

anthony7777

Yoda

Offline

• Aug 30, 2009

• #8

roger, do you know if your fuel gauge is reading correctly?, are you using the "stick" check against what your fuel gauge is reading?, im asking just how are you checking your fuel level?

 

tahoe healey

Yoda

Offline

• Aug 30, 2009

• #9

Pull a plug from the first three cylinders and one form the last three. They should look alike in color. They should be a light tan. YOU should check the gap on the plugs (which ones are you using?) There is something wrong with that millage. How long are you warming up for? How fast are you idling? Who's gas are you using and which grade? You could also try putting the points back in and check the millage again. I get 15 to 18 in town and 21+ on the highway.

 

OP

AUSMHLY

Obi Wan

Offline

• Aug 30, 2009

• #10

anthony7777 said:

roger, do you know if your fuel gauge is reading correctly?, are you using the "stick" check against what your fuel gauge is reading?, im asking just how are you checking your fuel level?

Click to expand...

Hi Anthony,
I am not using the stick method. I fill the tank, clear the odometer, refill the tank and divide the miles into the gallons.

I will go buy a stick and mark it. So next time I will make sure the gas level is the same on the stick when I do the gallons vs odometer.

Thank you,
Roger

 

A

anthony7777

Yoda

Offline

• Aug 30, 2009

• #11

tahoe healey, im in total agreement with what you and others are suggesting, we all know how accurate our healey fuel gauges fungtion, im just wondering how he judged the amount of fuel he says hes burning, i.e did he just drive the car until it ran out of gas, or did he just fill the tank and think his gauge reading of 1/8 tank remaining was correct, does he have excessive smoke exiting the exhaust at idle?, i think id check the easy stuff first then go on to changing back to points etc, etc.

 

OP

AUSMHLY

Obi Wan

Offline

• Aug 30, 2009

• #12

Guys I don't think the fuel gauge is the issue. I don't use it for MPG.

I fill the petrol tank, set the odometer to 000000
I refill the tank and divide the number of miles driven into the number of gallons of gas used.

No excessive smoke at idle.

Why do you think using points would provide better mileage?
I was under the impression, electronic was better and more reliable.

Roger

 

Bob_Spidell

Yoda

Offline

• Aug 30, 2009

• #13

A thought: can you hear the fuel pump at idle? If so, it should be clicking no more than every 2-3 seconds. Faster than that and you might have a fuel leak somewhere. If you have a stock radio, tune between stations and you might be able to hear the pump firing on your radio.

 

Keoke

Great Pumpkin

Offline

• Aug 31, 2009

• #14

AUSMHLY said:

Keoke said:

Yep I tried to tell you so.--Keoke-- :laugh:

Click to expand...

What is it you tried to tell me Keoke?

Roger

Click to expand...

Your engine when it is idling is operating in its most inefficient mode.
Yous for some reason is operating considerably below the norm.

This is to say it consumes too much fuel when you are driving in town and the engine idles at stops.
I am not sure how this is happening if your at speed freeway mileage is about correct.
If you have a yard stick you can check the fuel consumption in both modes. Keoke

 

S

shorn

Jedi Knight

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• Aug 31, 2009

• #15

This is just a theory. One of your carb floats might be sticking or perhaps even has a small leak and is partially submerged. When driving at higher speed (highway driving) the demaand for fuel is greater and the fuel is going into the carbs as needed. However, when you are driving slower or idleing and the demand would normally be less from the engine, the sticking or submerged float just dumps the excess gas out the overflow, causing the miles per gallon to decrease more than normal. OK, just a theory. I only suggest this as I have had experience from brand new floats that are not always reliable.

 

OP

AUSMHLY

Obi Wan

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• Aug 31, 2009

• #16

Shorn, thanks! I will look into that.
Really guys, I'm open to all theories. Keep them coming. I'd love to find the problem.
Cheers,
Roger

 

J

johnea

Jedi Hopeful

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• Aug 31, 2009

• #17

Could be a sticking carb piston that won't rise properly. Check the centering of the jets, make sure the suction chambers are clean on the inside. Also check if a needle is not bent and if it's fitted flush with the piston.

 

G

gblawson

Guest

Guest

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• Sep 1, 2009

• #18

I used to drive my brother's MGA (I was 17), and would drive way too far, so turned back the odometer and drove a whole lot more to get it just above where it was....he caught me with MPG....think he was getting 3mpg during my drives???

 

HEALEYJAG

Jedi Warrior

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• Sep 1, 2009

• #19

Is the odometer working correctly???? Take it on the freeway and use the miliage markers to check the accuracy.

Pete

 

OP

AUSMHLY

Obi Wan

Offline

• Sep 1, 2009

• #20

I'm wondering what impact the spark plug gap may have.
I have a pertronics, Lucas sports coil and my plugs are Champion RN12YC.
I don't know if David Nock set the gap to .025 which I think is correct for the standard coil. My other Mechanic told me today they should be set at .035 for the Lucas coil.

I just bought some new plugs and gaped them .035

Any thoughts on this?
Roger