Thread: 87 drinking vast quantites of fuel!

Originally Posted by Knightmayre

Hi guys

I have just manually advanced the ignition timing by ear as I have no light (but I prefer dialing it in by ear, I advance it and listen for the revs to increase then decrease so I back it off a bit, lock her down and go for a drive to see if she pings under load).

For 10% of your huge fuel bill you could have bought a cheap timing light and saved 10% of your huge fuel bill, making it essentially free...

NEW Timing Light Inductive Pickup Ignition With Bright Xenon Strobe Auto Tool | eBay

Do remember to check that base timing, mechanical advance AND vacuum advance are all adjusted and working correctly.

I don't know a hell of a lot about these but maybe disconnect the cold start injector which is located on the RH side of the plenum chamber.
Sometimes the time temperature sensor/motor or whatever it is called buggers up and the cold start injector keeps on injecting.

It could be a simple as the temperature sensor has failed or has a bad connection and the injection thinks it is cold the whole time. It should read 300 ohms or thereabouts when hot.
Regards Philip A
If you use the google box at the bottom of the page and enter 3.5 V8 running rich or similar there should be some threads come up.

Around town mine used to use 20l/100km. Advice others have provided are good starting point ; remove cold start injector (one on plenum), check temperature sender readings, check flapper is working ok, check throttle position is correct (voltage equal to or a bit lower than required), you can add a resistor to temperature sender to change ecu fuel injection length, use a good quality fuel injection cleaner. Engine does bank injection (all 4 on one side then the other) not sequential (the injector for that cyclinder) so fuel economy will never be flash.

Not really helping here .....but if I drive to work return it's 110km in a p38 that's approx 13l of fuel .
So to drive an hr to home star would be approx 80 to 100 kms for you ( I'm guessing ) at a minimum of 15l/100 ish .

Or a qtr of a tank . A rangie is a fat girl shaped like a block of home units - economy is a foreign concept , but very comfy , like a couch .

Now I'll do my fathers impression " slow down a little bit " even 10k will make a difference - oh and try it on 98 over a few longer runs . It seems to make a difference .

Keep in mind my other cars are either a 5l Holden (old n carby ) , a 1960's Valiant . So economy is relative .

Just think , you could buy a really economical new car - it would cost approx $400 a month , it would make you unhappy when you drove it !

At least the RR gives back some involvement - can you see yourself outside in the rain swearing at your "new economical car ? "

Just for reference, the trip was only 54km in total so assuming I have the 79 litre tank (as per the owners manual) that would give me a range of 216Km from full to empty and at $1.35/l that's just over $290!

Most of it was a 100km/h limit and I was puttering along at 70, barely touching the throttle.

Oh yeah, and that's using 98 octane too.

Bah. LOL

I used to have a timing light (well, several) but they either got broken or never came back to me.

Never trust or rely on your fuel gauge... It's only a"gauge" Remember, it's English, NOT 'Japanese'.

That timing light looks similar to the one I've got, worth their weight in Unobtanium. Buy it.

Ears are OK, but a vacuum gauge is much better, and when both used with a timing light...

Amen to getting every detail about the 'timing' to 101% accurate and correct. Remember, they will take a lot more advance than the book sez...
- Also, when you want to waste/spend more money, check IGN leads, spark-plug heat range, Distributor Cap and Rotor. And IGN module/coil, if your wallet is too heavy.

My 3.9 used to guzzle 16 to 21 litres per 100km. That's around $30 per 100km, which is the best way to decide/calculate just what BRAND and 'octane' number gives you the best value.


"Brand" of fuel ??? - Yep, depending on where they all source theirs from, different brands can respond differently in different cars... Keep OCD-standard records and you'll soon see...
#1 son's Statesman-International is fussy, and goes well on Shell... Father-In-Law is convinced that a country run in his Merc. costs less on BP 'Ultimate/98' - despite the higher price per litre.

Tyre pressures ? Tyre size? - Road-Rollers use more fuel than normal width wheels. Checked the alignment recently ? Handbrake dragging? Transmission slippppping a bit ?

Remember the Swiss Cheese model also applies here... a little bit 'out' on several details has a synergistic effect on your bank/mental 'balance'

Lastly, get used to it. I don't keep fuel records anymore... too depressing

If all else fails, only drive it when the moon is in the 7th House and Jupiter aligns with Mars...

EDIT:- Do your fuel mileage checks by filling the tank to the same (click-off) "FULL" from the same bowser, they can and DO vary, which makes it difficult to be accurate especially when dealing with shrt distances like your 54km.
My money's on the Cold Start system...

Why 98 octane? Even the high compression model has low compression ratio IIRC. Run 91 octane as no advantage on 98. Won't help your fuel economy though. Engine is too primitive. (Eg no O2 sensor in the exhaust). What's a compression reading of the cylinders give you?
I recall that I also adjusted the flapper to see if I could get better economy.

As suggested by others I'd check the fuel guage. Fill up and run about 100 to 150km and fill up again.

Btw: there's a reason l drove a cheap economy car to work when I had my 87 RR and now have a TD5 Disco.....

IMHO, the only reason to use '98' in a bog-standard 3.5 or 3.9 V8 is IF you've put in lots and lots of advance...

The 3.9 is supposed to run on '92' octane according to my handbook, and alternating between 91 and 95 will do that nicely.

There's lots of info here about advancing the 'standard' timing.