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280zx Fuel Economy


tonycharger72

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Hi Guys, was wondering if i could get some help with my 280zx,

 

I have a problem with the fuel consumption,

 

Im getting roughly 330km's (200miles approx) out of a tank, roughly 65Litres of fuel,

 

That seems kinda rough to me,

 

Ive had a bit of a look around and other folks have said they are getting (or its possible to get) out of an L28E atleast around about the 20mpg's mark, which would give me in-access of 500km's out of a tank by my calculations,

 

The car runs really well, starts first time, dosent seem to be miss-firing,

 

Anyone got any theories on what could be leading to this kind of fuel consumption???

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With a stock 280ZX (L28E) with no cat and a K&N filter I got about 22-25 mpg in regular driving. Thats an average of city and highway. I think if you are only getting 12mpg, you have a problem! Maybe the cat is plugged or the fuel pressure is out of wack. Check your timing. I bumped mine up to about 14 BTC and it helped some. Hope that helps!

 

Aaron

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No, pretty much stock as a rock 1982 280zx 2+2 with Auto,

 

Im about half-way through a tank now and its gone 220km's, so if it get's to 440km's (267 miles) i will be around the 15-16mpg mark, which is a tad better, but it kinda went like this last tank, last 1/3 went really quickly,

 

I will change the Oil & Filter, fuel filter, plugs, leads, coil and set the timing as i just bought the car and it has been sitting for about 3months so i thought i should probably do this anyways,

 

If that dosent work i guess its more serious investigation, how do i inspect the O2 sensor? How do i check if there is a vacum leak?

 

My car is an Auto, does it have over-driver, ie.........a 4th gear? Its just when driving it dosent ever seem to kick into over-drive, feels like there is only ever 2 gear changes, this might be related to the fuel consumption, but when i start the car i sometimes have to start it in Neutral, sometimes in park, the cut-out switch is a bit dodgy, so im thinking that maybe because the trans dosent get into 4th, because the cut-out switch is f#cked, this might effect other parts of the tranny,

The car revs at around 3500rpm when at 100km (60 mph) - Just a theory...............

 

I was thinking of getting a larger exhaust and extractors so at that point i will just piss the cat off, probably get the K&N filter aswell,

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A good possibility is your fuel pressure regulator has failed.

This is very common for age of car. When it does, the pressure at the injectors goes to about 75psi instead of about 32 psi. You have to install a pressure gage in the line to tell for sure, which is a pain in the *** !

But an indirect couple of clues will be you will often hear an extra irritating buzzing noise coming from the rear of car at idle--this is the fuel pump being overloaded and the pressure relief on the pump venting gas back into the tank--also the inside of the tail pipe will be sooty black-black due to running way too much fuel-- extra rich mixture. I've had three zx's do this so I think it is an inevitable failure. The fuel pressure regulator sits on top of the fuel rail and it costs about $80. although right on top in plain view, it can be a little booger to change because the hoses are all old and hard-- if so use use new hose--high pressure injector hose--very important--it costs about $5 a foot for the correct hose--- 5/16" as I recall works good as a replacement--anyway the regulator is something to suspect--I wouln't have brought it up but it took me quite a while to figure this out and a lot of extra gasoline.

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Well early 80's skylines with the L24's had over-drive 4spd auto's in them im pretty sure, so it would be a touch weird if the 280zx didnt have them aswell, just because im pretty sure they were flogged of as more of a luxury sports car, i mean it has electric everything, even lumbar support in the seats :-),

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Ok guys I got my license back yesterday and i put $40 of gas in the car. I used half of it so quickly!

 

Today i drilled a new hole in the exhaust and welded in a new fitting to put a brand new o2 sensor in. The car is performing alot better now! Still uses alot of gas on 1 bar but what doesnt!

 

The thing about the FPR. If you can hear the fuel pump loudly from outside the car (pumping hard) does that mean the FPR could be stuffed? I never even thought of replacing mine because of fuel consumption but I'm putting an Adjustable FPR in soon (what pressure should I run?)

 

Oh the auto in my car is 3Speed as far as i KNow. it has overdrive too.

Oh by the way...auto 280zx http://www.trademe.co.nz/Trade-Me-Motors/Cars/Nissan/auction-52363843.htm

auto 280zx http://www.trademe.co.nz/Trade-Me-Motors/Cars/Nissan/auction-52099814.htm

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My aftermarket pump always got louder when it was straining to pump enough fuel (ie. when there was a clogged filter in the line before it). This could be seen as well, in the form of a slight wobble in my fuel pressure needle. You might look into getting a fuel pressure guage.

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  • 10 years later...

This is very late but if anyone else sees this, perhaps these tips will help: I get around 11L/100km in my 4-speed 1975 280z 2+2 under mixed driving conditions (using regular fuel from shell). But when I first bought the car I was getting half that. After I adjusted the ignition timing the fuel economy improved greatly. Then I replaced a leaking injector hose, and it went up ever so slightly more.

So a zx, which has a 5-speed and a lower drag coefficient ought to manage better gas mileage than me (assuming you drive like I do, which is to say gently).

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