78 1800 still purring but guzzling

John Fox · Post by **John Fox** » Mon Jun 19, 2006 5:29 pm

This website is a welcome discovery! I've had my spyder since the mid 1980s and kept it in solid shape. Heaven knows how many miles it's gone (its previous owner tinkered with the odometer) but more than 120K anyway. I'm not a mechanic so I've had to rely on experts, which weren't hard to find around LA, but seem as scarce as hens teeth since I moved to north New Jersey.

Two years ago a nipple broke in my carburetor and my new mechanic dropped in a replacement carb. Ever since then the little car drinks like a Hummer. It seems happy, but it's mileage range is probably 11mpg around town and 15mpg on highways. My mechanic seems unconcerned and waves me off every time I complain. I haven't a clue what could be the reason. I can check the carbs for details since I kept the old one, but I wouldn't know where to begin. And then again... it could be because of something else altogether. I'm mystified.

mbouse · Post by **mbouse** » Mon Jun 19, 2006 10:00 pm

Welcome to the forum. Just bought a '78 myself, and have not had it long enough to even begin to know the mpg yet.

Know of your love affair with the cars. Have had an '80 since I first discovered it 12 years ago. Not as long as you, but just the same.

Sorry I can't help with the thirst issue. Just dropped a line to say hello.

John Fox · Post by **John Fox** » Tue Jun 27, 2006 4:54 pm

My history with spider's goes back at least to 1972 when I had a crush on a girl who was driving around in one. I remember borrowing it a couple of times and tooling through the summer countryside with the top down. A few years later I worked with a film director who drove around LA in his little spider. Both of those two cars were dark blue. It was a few years after the cars ceased being manufactured that I finally bought mine - it happened, quite by chance, to be the same dark blue.

So Cal Mark · Post by **So Cal Mark** » Tue Jun 27, 2006 9:29 pm

Welcome. For the mileage to be that low it has to be carb related, and to the detriment of the engine. The fuel mixture has to be way too rich, and that will lead to accelerated engine wear, diluted oil, etc. It could be that the carb is jetted too rich, or there may be a problem as simple as the float set improperly. Hard to believe your mechanic would be unconcerned with mileage that poor, it should be double what your getting

Jim DeShon · Post by **Jim DeShon** » Wed Jun 28, 2006 5:52 pm

I would think the catalitic converter would be fried by now

...J.D.

mbouse · Post by **mbouse** » Thu Jun 29, 2006 7:56 am

Quite possibly true, but if original with all the shrouds on it, may not have been VISIBLY heated up.....just the insides cooked.

John Fox · Post by **John Fox** » Tue Jul 11, 2006 3:02 pm

How long would it take to fry the converter?

I went in with a screwdriver to adjust the fuel mixture (doing a little blind guesswork). I'm not sure which way is rich and which is lean, but I guessed lean was clockwise. (Weber carb)

The manual I have speaks of setting the fast idle. I could not find the set screw for the adjustment although I did get the engine to 2500 pushed the little button and backed off on the throttle. The rpms did not decrease at all. Is this something I should care about?

So Cal Mark · Post by **So Cal Mark** » Tue Jul 11, 2006 3:23 pm

merely adjusting the idle mixture won't make much of a difference in gas mileage. You'll need to determine if the low speed jet and primary jet are incorrect

John Fox · Post by **John Fox** » Thu Jul 13, 2006 10:30 am

>>You'll need to determine if the low speed jet and primary jet are incorrect.<<

How would I determine that?

Also - what's the deal with fast idle? Is it signficant if the engine does not lose RPM from 2500 when the button is pushed and the throttle is dropped?

78 1800 still purring but guzzling

78 1800 still purring but guzzling

Spider history