10 miles to the Gallon?

[RWD415]

Im kinda new to the forums so just work with me.

I own a 76 280z (auto)or about 3-4 years now and have done alot to fix it up, from the engine to the body work. and i have a huge fuel problem, ANY TIPS?

Heres an example of my problem:

I filled up the tank which is about 13-14 gallons and filled it up with premium fuel. then drove it for a couple days, with some speeding here and there, and not even by the end of the week my tank is empty and i only got 140-150 miles for a full tank.

I got 200 miles from a full tank once and that was like a year or two ago.

could the injectors be old or is something wrong with my engine.

i figured the original transmission is holding it back alittle but it cant be doing that much damage.

Any suggestions would really help me out thanks.

[Hrududu]

dang. Last time i did that bad was when i got 97 miles on a full tank. I had just gotten the car and didnt know anything about them, then I discovered the P/O had bypassed the fuel filter. Put in a filter and the problem was solved. could be an issue with your fuel pressure regulator? AFM? Cold start valve? maybe even a leak somewhere.

[c david]

i believe you have a fuel leak under load/cornering.

good luck

cdavid

[RWD415]

im still new to all the engine coimponents.but i haven't replaced the fuel filter in a while but could that really be the problem?

but thanks for the tips

[RWD415]

For all the automatic Z's out there whats an average full tank for you?

[beandip]

I have a ZX engine in my 240 with auto . better than double your mileage . I am running SUs though. Have you run any injector cleaner through the engine ? I would try some in the next tank full and see if this helps. You have something major going on . I will send you a PM with some info . Gary

[daddiodanger]

sounds about right. i get the same kind of mileage. figured it is because it has a big engine

[EScanlon]

What kind of RPM's are you experiencing while on the road? You mention that it's an automatic, could your transmission fluid be low? How about dirty and needing changing?

To me that may help isolate the problem from a poorly running engine to a transmission that's needing more rpm's for the mile.

I also have an automatic and I find that at 2,000 rpm I'm running @ 30 mph or thereabouts. It takes 3,500 rpm to go 60-70 (been a couple of weeks, I'll have to drive her tomorrow and re-post), but if you're consistently running over 3,500 @ those speeds, then I would bet you have a transmission problem.

Not being the mechanic some of these other guys are, you might wait to see what they think about this possibility.

E

[sblake01]

Well, since he's talking about an EFI engine, there are so many variables here. You need to troubleshoot the entire system. Go here and download and read through this: http://www.atlanticz.ca/zclub/techtips/efisystem/280zfuelinjectionbook.pdf Quotes like the following always leave me scratching my head.:stupid:

sounds about right. i get the same kind of mileage. figured it is because it has a big engine

[beezee]

I have a 74 260 automatic fuel range around 200 -220 miles .Its running rich at idle with round tops,needing minor tune up

[sblake01]

A minor tune up should do it for you as the carbed cars aren't quite as complex as the EFI cars. I don't know what the range should be for a 240/260 but for a 280Z with an automatic trans., the mileage as stated by Nissan in the brochure is 17 city-23 highway. That translates to about 290 to 390 miles with the 17.125 gallon 280Z gas tank.

[RWD415]

hey guys thatnks for all the advice,

"I also have an automatic and I find that at 2,000 rpm I'm running @ 30 mph or thereabouts. It takes 3,500 rpm to go 60-70 "

That sounds right to me, my car's RPM is about the same so i dont know what goin on. I tried the fuel injector cleaners many times and it doesnt help at all.

Since i got the car i never did any maintinance with the trans.,

I really think its an issue with my transmission fluid, to change my transmission fluid, would that be hard or just as easy as changing my oil?

Thanks agian all the help