240zJon Posted May 15, 2009 Share Posted May 15, 2009 Okay well my 72 z is a major gas guzzler. i put 5 gallons in and it only gets me 35 or so miles, which is ridiculous. My setup is a l28 thats running duals su's the good ones. i don't have the charcoal canisiter or fuel return lines on it. I was wondering if anybody has some insight on how i can get more than 6 miles or so to the gallon? Quote Link to comment Share on other sites More sharing options...
Pharaohabq Posted May 15, 2009 Share Posted May 15, 2009 maybe you have a leak? Perhaps you're running super rich. You should measure our a Gallon of fuel and get a full gas can and see what your actual mileage is. It's gotta be better than 6MPG but if your Su's are way off you could be burning a lot of extra. do you smell fuel around your car? Quote Link to comment Share on other sites More sharing options...
MikeBZ Posted May 16, 2009 Share Posted May 16, 2009 I 2nd that, fuel leak or super rich. But unless your pushing serious horsepower with a cam and lots of compression, 6 mpg could also be a sign a serious problem. Check your spark plugs, and if you can do a compression test and cylinder leak down test. Quote Link to comment Share on other sites More sharing options...
essdeezee Posted May 16, 2009 Share Posted May 16, 2009 Wow, I thought me getting 15 mpg was bad! My condolences! I know I'm running a bit rich (SM needles on nearly stock l24) but you have a fairly serious issue. Unless all your mileage is at full throttle Quote Link to comment Share on other sites More sharing options...
ckolander Posted May 16, 2009 Share Posted May 16, 2009 I think that there's a loose nut behind the wheel. Quote Link to comment Share on other sites More sharing options...
240zJon Posted May 16, 2009 Author Share Posted May 16, 2009 Okay okay so i have a lead foot. i did a quick compression test and they were all around 75-85 so is that good? Also when i drive around it smells like gas for sure, i think the floats are not quite adjusted rigth so the carbs are running rich. also my spark plug get a lot of carbon build up on them it looks like, what could cause this?..oil?? next time i run low i'll try what Pharaoh said and see what i actually get. Thanks for the insight Quote Link to comment Share on other sites More sharing options...
srbigbutt Posted May 16, 2009 Share Posted May 16, 2009 I get bad gas mileage also and I found I had a fuel leak at one of the hoses at the fuel pump. Replaced it, but haven't noticed much of a difference. Then again i love the sound of my engine when I race through the gears!! so that doesn't help much! Quote Link to comment Share on other sites More sharing options...
extreme_accordion Posted May 17, 2009 Share Posted May 17, 2009 Okay okay so i have a lead foot. i did a quick compression test and they were all around 75-85 so is that good? Also when i drive around it smells like gas for sure, i think the floats are not quite adjusted rigth so the carbs are running rich. also my spark plug get a lot of carbon build up on them it looks like, what could cause this?..oil?? next time i run low i'll try what Pharaoh said and see what i actually get. Thanks for the insight You smell gas from the front or rear of the car? From the exhaust with a lot of black at the edge of the pipe - too rich. Black plugs - again too rich (that carbon you mentioned). I don't have a Z myself but learned long ago that on any car: White plugs = too lean/hot and Black plugs = too rich/cold. You in fact don't want any fouling on the plugs at all - you'll always get a little color but they should be 'clean' looking when they come out. And that's all I remember from 2nd hand osmosis automotive 101. Quote Link to comment Share on other sites More sharing options...
240zJon Posted May 18, 2009 Author Share Posted May 18, 2009 Yeah and the end of my tailpipe there is a lot of black build up.Okay so i should probably get my carbs adjusted to run leaner. And i was thingking about seafoaming it through the tank and the brake booster sound safe enough? Quote Link to comment Share on other sites More sharing options...
JMortensen Posted May 18, 2009 Share Posted May 18, 2009 Just a wild guess here, but try reaching under the carbs and push up on the nozzles. I'm thinking maybe they're stuck down. Quote Link to comment Share on other sites More sharing options...
Challenger Posted May 18, 2009 Share Posted May 18, 2009 Okay okay so i have a lead foot. i did a quick compression test and they were all around 75-85 so is that good? Also when i drive around it smells like gas for sure, i think the floats are not quite adjusted rigth so the carbs are running rich. also my spark plug get a lot of carbon build up on them it looks like, what could cause this?..oil?? next time i run low i'll try what Pharaoh said and see what i actually get. Thanks for the insight Looks like you got other problems too... 75-85 isnt very good. Does the tank have open vent lines? Where it can just evaporate fuel all day long. Quote Link to comment Share on other sites More sharing options...
Pharaohabq Posted May 18, 2009 Share Posted May 18, 2009 yeah, 75/85 isn't very good. on my L28 I'm getting 125-145 and that I think is low. You might need to look at your oil. you could be draining gas into your crankcase. though with carbs you'd think it would just flood. You might try a much heavier weight of oil, just to see what it'll do with your engine. Maybe try that STP oil treatment and see if it'll help your compression a little. (Tho you'll need to change your oil more often. ) Another thing to check is to pull your plugs and see if they are oily/wet when you pull them, if they are then that could tell you you're running too rich and/or getting a lot of contamination from blowby. If your plugs are dry, w/ maybe a little brownish ash on them then I would think your compression readings are off, since that would say your engine is running more correctly. White ash is like he said too hot. The Gas smell, if it's strong, would definitely make me think leak. tho carbs always smell a little. (thats one big + of switching to EFI. ) Check, and maybe replace your rubber fuel lines. Go ahead and replace using hi pressure EFI hose since it's not that much more expensive and will last longer. If you have Gas smell at the back of your car, esp after you've parked for 5 min or so, then you probably need to check the lines at the tank, (which means dropping it ) good time to replace old fuel hose here too. not to mention maybe draining and cleaning the crap out of the fuel tank too. be real careful around sparks and flame while doing that. don't need anyone getting blowed up... it DOES happen. My guess at this point is probably carbs way out of whack, maybe not even sync'd. Phar Quote Link to comment Share on other sites More sharing options...
240zJon Posted May 18, 2009 Author Share Posted May 18, 2009 I pulled the plugs and they had carbon and a little bit of oil around the number 3 cylinder. also looking at the oil dipstick it looks really runny. If gas is leaking down into the crank how could i test and what does that mean repair wise? Quote Link to comment Share on other sites More sharing options...
Challenger Posted May 19, 2009 Share Posted May 19, 2009 Hold a torch to the oil. Lights it has gas, doesnt your fine... As I asked before, can you check for open lines from the fuel tank? Quote Link to comment Share on other sites More sharing options...
dschock Posted May 19, 2009 Share Posted May 19, 2009 Check the gaskets on your float bowls. I had the same problem and it ended up being a shot gasket. Now i usually get 20-25mpg Quote Link to comment Share on other sites More sharing options...
Pharaohabq Posted May 19, 2009 Share Posted May 19, 2009 I would be real careful lighting anything... I'm sure he's talking about lighting the oil on your dipstick. no the metal one silly... Anyway yeah the gasket idea sounds plausible. Quote Link to comment Share on other sites More sharing options...
240zJon Posted May 20, 2009 Author Share Posted May 20, 2009 wow 20-25 mpg i wish i got that. I Going to buy the tune up video from z therapy since it has the su rebuild part included. and its only $15. I checked the new spark plugs and they seem oil free but covered in carbon bulid up. and they've only seen 120 miles so far. its dark out now so i'll try the oil trick in the morning. Quote Link to comment Share on other sites More sharing options...
Pharaohabq Posted May 20, 2009 Share Posted May 20, 2009 Carbon buildup is likely because of it running rich. I think your compression #'s were off or at least it's not the rings because if it were you'd be getting oily plugs. A good Haynes manual will also tell you how to rebuild those carbs. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted May 20, 2009 Share Posted May 20, 2009 Did you try pushing the nozzles up? Only takes a second, you do it with your hand, and it's free. Quote Link to comment Share on other sites More sharing options...
dschock Posted May 20, 2009 Share Posted May 20, 2009 I pulled the plugs and they had carbon and a little bit of oil around the number 3 cylinder. also looking at the oil dipstick it looks really runny. If gas is leaking down into the crank how could i test and what does that mean repair wise? Do a regular compression test, then repeat it with a spoonful of oil in each cylinder. If the compression is higher, rings are bad. Quote Link to comment Share on other sites More sharing options...
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