[Gadzooks]

thanks now sorted

[Ben_Sierra]

First things first, I wouldn't be putting 91RON fuel in my Sierra... 95 minimum...

[Gadzooks]

We are paying $1.70 per litre for 91 octane, here. 95 is strictly for the rich in these parts.

[SierraDan]

Try flushing your fuel system. Could be crap in the tank.

[banga]

i used to find that different servos used to affect my old liberty i used to run 98 in it.If i put caltex vortex i used to get a big serge when i put my foot down. but bp and shell 98 were sweet never uesd to get a serge was just clean acceleration. it wasnt just a one off so i just stopped buying caltex fuel.

[Ben_Sierra]

Gadzooks wrote:

We are paying $1.70 per litre for 91 octane, here. 95 is strictly for the rich in these parts.

Its up to you but I know my Sierra runs like a dog on any 91RON fuel... for 4c a litre extra 95 is worthwile... And for 10c so is 98 really...

[SierraDan]

I get 98 no matter what. The fuel consumption of a Sierra isn't crazy enough to warrant going cheaper in my eyes.

[christover1]

Check tank breather and carbon cannister,
if after taking cap off, it runs good,
and runs bad after a fair amount of driving,
fuel tank can vapour lock could be issue.

If it goes woosh when you take cap off, breathing could be the issue.

Also filling up can disturb the crap in bottom of tank.

Sometimes rough roads can disturb crap in the tank, too.

[SierraDan]

So that whoosh sound isn't meant to happen!?

[shep]

Gadzooks wrote:

We are paying $1.70 per litre for 91 octane, here. 95 is strictly for the rich in these parts.

you lucky bastard, i wish that i could get it that cheap.

[christover1]

SierraDan wrote:

So that whoosh sound isn't meant to happen!?

No it isn't under normal conditions.
Drive with cap loose, see if it improves.
Some Sierras had a vented cap, some didn't, that could be an issue.

If it appears to suck inwards,
then air can't get back in tank when fuel sucked out.

If it blows outwards,
then heat build up/pressure in tank is not being released.

My old Sierra had a blocked breather,
when parked in sun, it would force fuel out thru carby.
My problem was in the carbon cannister.

[SierraDan]

Right. I thought it had something to do with the fuel system being under pressure.(just assumed it was because of the whoosh noise)

I may suss my breather and carbon canister out then. So is the breather the smaller tube that runs with the filler pipe?

[christover1]

SierraDan wrote:

Right. I thought it had something to do with the fuel system being under pressure.(just assumed it was because of the whoosh noise)

I may suss my breather and carbon canister out then. So is the breather the smaller tube that runs with the filler pipe?

That is most likely fuel return line, unused fuel is pumped back in tank.
the breather breathes thru the carbon cannister, idea being it collects fuel vapour to be re used.

But different models go about it different ways.
If no breather pipes, then put a vented cap on

[SierraDan]

I'll look in my service manual.

[Gadzooks]

I am having the whoosh but I would prefer the surge.
If it was the BP fuel then it would have mixed with the other stuff pretty quickly meaning the whole tank would have given the same performance which it didnt.

Do carby's and fuel pumps lose efficiency over time as they wear or do they just work or not work?

[SierraDan]

Why?

[JrZook]

Does it normally run sweet at <1/2 a tank?

[Gadzooks]

JrZook wrote:

Does it normally run sweet at <1/2 a tank?

No, it has never done that before (if anything she was running sweet at more than half a tank not less). I would like it to do that all the time; never thought she had it in her.

[JrZook]

Gadzooks wrote:

JrZook wrote:

Does it normally run sweet at <1/2 a tank?

No, it has never done that before (if anything she was running sweet at more than half a tank not less). I would like it to do that all the time; never thought she had it in her.

Well imma thinking you may have something floating around your tank/carby or even a fuel pick up issue. Sounds like a bit more than just a bad batch of fuel to me