Mpg again...Sorry!

bro973x

bro973x

Well-Known Forum User
Just another little question on the 12mpg front...My fuel tank has a lot of pressure after the engine is started. Its like a rocket blast when you unscrew it! So could the fuel pressure valve thing between the injectors and return be a potential culprit??? I got her back on thursday and went for a drive....admittedly a heavy-footed one but £20 has gone in 30 miles. She starts perfect at 1400rpm and then idles at 750 after a minute or two. There is no smell of petrol and the temp guage never goes above normal... Please help again!!! Thankyou!!! :bow::cheers::driving:
 
Hiya,
Did you download the 280z manual from http://bjlvdesign.tripod.com/PDF/280zfuelinjectionbook.pdf
If so, by following the troubleshooting guide using a multi-meter then you should find which part or parts of the injection system is playing up. Note this is for a 280Z and not a ZX but there is only one test that is different. Where it suggests putting the meter across pins X & Y, you'll find one pin is missing but the next on is missing on the Z and is there on the ZX so use that one. This has worked for me on quite a few occaisions and got me out of a whole. Conducting all the tests takes under an hour.

The manual should be in the articles section but follow the link above if you have not got it.

Please let me know how you get on.
 
Hi,

I too suffer from poor MPG but as most of my mileage is short distance, I'm not sure whether to expect better than 16-17mpg. So I thought I'd run the tests and downloaded the excellent guide in Andy's post. However, the layout of pins in my connector is very different from the one shown, even allowing for the difference you mention. Eg mine has 12 occupied slots on the 'top' row compared with 17 for the 280z, and 14 on the bottom compared with 10! It's an '83 or '84 - any ideas gratefully received!
 
You could do a plug chop ( Thrash it through the gears & switch the ignition off while in 5th on a quiet road while booting it but don't turn it too far or else the steering lock will come on then coast to a stand still & take all the spark plugs out, they should be a light brown in colour)
 
bro973x said:
Just another little question on the 12mpg front...My fuel tank has a lot of pressure after the engine is started. Its like a rocket blast when you unscrew it! So could the fuel pressure valve thing between the injectors and return be a potential culprit??? I got her back on thursday and went for a drive....admittedly a heavy-footed one but £20 has gone in 30 miles. She starts perfect at 1400rpm and then idles at 750 after a minute or two. There is no smell of petrol and the temp guage never goes above normal... Please help again!!! Thankyou!!! :bow::cheers::driving:
Click to expand...

The petrol tank IS pressurised when taking the cap off a fuel injectered car, it depends what you call "a lot". Check the plugs as above post & take it from there.
 
bro,

Are you still struggling with low mpg? I ask I have just filled up today and made 20 mpg, a defintie improvement. I wonder whether the warmer weather means the choke is off ealier on my daily commute.

The other variable is a freer right front brake pad. I changed the tyres and noticed that that wheel didn't spin easily so spent some time on making sure the pads were free in the caliper.:thumbs:

Couldn't find tyres for the metric rims though, had to replace the wheels too. :unsure:
 
good point rick,check that all the brakes are free,and spark plugs or smell your exhaust fumes after the car has warmed up the check for unburnt fuel.
 
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