Excessive fuel consumption

[Ross S]

My RB30 is using way too much fuel. I have checked the oxygen sensor and the coolant temp sensor and both are working. It's been on a dyno and the mixtures were set at the air flow metre and the throttle body butterfly was set. Still using too much fuel. And no, the right foot is not too heavy, I've been trying to drive to maximise fuel economy but no luck.

Could it be that the oxygen sensor is too old even though it works???

Any suggestions?

[mag]

My RB30 is using way too much fuel. I have checked the oxygen sensor and the coolant temp sensor and both are working. It's been on a dyno and the mixtures were set at the air flow metre and the throttle body butterfly was set. Still using too much fuel. And no, the right foot is not too heavy, I've been trying to drive to maximise fuel economy but no luck.

Could it be that the oxygen sensor is too old even though it works???

Any suggestions?

Look here: Everything to know about VLs (open.. post your links here)

look for engine troubleshooting/maintenance step by step on the page

[Berlina wagon]

Check engine timing if advanced past 15 degree'd will cause it to use mor fuel, The other thing that will cause excessive fuel consumption is fuel regulator which is located on the inlet manifold, i have seen this before a few times.

[Ross S]

How do I check the fuel regulator on the inlet manifold? What is it doing wrong to make it use more fuel, allowing the pressure to be too high?

[jatsvl]

leaks in fuel supply- check all fuel line connections (turn ignition on leave pump to prime injectors turn off then repeat then check line connections)

to test fuel pressure regulator solenoid valve
1. dissconnect wire connector and vacum hoses from solenoid valve
2.using ohmeter, check resistance between solenoid valve terminals, resistance should be 35.2 ohms
3. apply a flow of air to the inlet manifold port of the solenoid valve, the air should be able to flow through the valve.
4.apply battery voltage to the solenoid valve terminals. with battery voltage applied, air should not be able to flow through the valve from the in let manifold port.

Note, to prevent damage to the diode in solenoid valve wiring connector, ensure that positive lead from battery is connected to the white wire terminal and negative lead to black wire

quoted as written in gregory's workshop manual

[harry3]

BTW, black inside the exhaust pipe is normal from unleaded and doesnt mean the engine is running rich

Ive had several fuel leaks on mine, and agree re checking for these

[Sabby]

how many K's are u getting per tank?
i think im in the same area as u ,coz im gettin 200 per tank, not good

edit: 200 per 3/4 tank, i dont fill up when its 99% empty

[qwertsta]

200km's per tank!!! I get around 200km's out of around 25 litre's.

[unrool_VL]

I get between 450k's and 600k's per tank, depending on the heavyness of the right foot.

[rb26dett]

I get around 400 from a tank also.

[Ross S]

I'm definitely not leaking fuel. I've got reco'd injectors with new seals and pintals and all rubber supply hoses new and tight. I'm using about 17 or 18 litres per 100k's.

[jatsvl]

fuel leaks happen at the rear of the car to in front of your tank near the high pressure fuel pump I had one, and other places if you haven't all ready check all the lines from the tank under the car! just a suggestion.

[Shane1989]

Even with a heavy right foot like I have. I am getting about 250K's per 3/4 tank of fuel. I never let it go below 1/4 tank. Cause then you get that jumping from the internal fuel pump needing to be fully submerged... That is a very bad design idea for holden... Especially with how small the bloody fuel tank is! Also got a question. There is a little black can thing that has three hoses going to it. It sits in a tilt tray and is held in by a spring on the drivers side of the engine bay. Say the top most hose was not connected. Would that cause a boost in fuel consumption??? It looks like a catch can.

[Shane1989]

Besides the heavy right foot other things that would have a noticable effect on consumption would be: Dizzy, Cap, Rotor, Plugs, Leads, Fuel Pressure Sensor, Oxy Sensor... All of those things arent excessivly expensive to change, they also have a major effect on how your car runs overall. I think your AFM could cause a change in fuel consumption as well. It seems possible because it measures the amount of oxygen going through your intake. The oxy sensor measures how much oxygen is leaving through your exhaust so it could be....

[mag]

Even with a heavy right foot like I have. I am getting about 250K's per 3/4 tank of fuel. I never let it go below 1/4 tank. Cause then you get that jumping from the internal fuel pump needing to be fully submerged... That is a very bad design idea for holden... Especially with how small the bloody fuel tank is! Also got a question. There is a little black can thing that has three hoses going to it. It sits in a tilt tray and is held in by a spring on the drivers side of the engine bay. Say the top most hose was not connected. Would that cause a boost in fuel consumption??? It looks like a catch can.

Doubt it, and it is a catch can but only for fumes/vapors..

[Shane1989]

On the Vl's, Which fuel line is which? I took a look and am sure in my choice but which lines are return and which is injection? I think I may have a fuel leak. The jumble of hoses at the very back just off the external fuel pump I can see a small crack in the rubber and its a little wet. Not dripping but just wet. What is that hose called so I can replace it. Or is there a name for it. Will a piece of high pressure fuel injection hose be sufficient???

[mag]

On the Vl's, Which fuel line is which? I took a look and am sure in my choice but which lines are return and which is injection? I think I may have a fuel leak. The jumble of hoses at the very back just off the external fuel pump I can see a small crack in the rubber and its a little wet. Not dripping but just wet. What is that hose called so I can replace it. Or is there a name for it. Will a piece of high pressure fuel injection hose be sufficient???

Not sure but the injection line should be bigger than the return line.

A piece of high pressure fuel injection hose would be good as then it won't matter if you put it on a low pressure side or high pressure..

[jatsvl]

more detail of which hose you are talking about?
under the car just in front of the fuel tank and behind the diff housing?
the injection hose runs from the round plate (sender unit/internal fuel pump) attached to the front of the fuel tank (with 6 screws in it) then goes to external pump to the damper then to the fuel filter then to the steel fuel line that goes under the car to the engine bay.
the return line is closet to the back wheel on the tank.

[ucwepn]

If you pinch the the fuel line with pliers the car will stall (i'm pretty sure anyway).

[Shane1989]

more detail of which hose you are talking about?
under the car just in front of the fuel tank and behind the diff housing?
the injection hose runs from the round plate (sender unit/internal fuel pump) attached to the front of the fuel tank (with 6 screws in it) then goes to external pump to the damper then to the fuel filter then to the steel fuel line that goes under the car to the engine bay.
the return line is closet to the back wheel on the tank.

Its directly off the external pump. Its accually metal with a rubber coating I think. Its behind the fuel tank on the drivers side I think. Its dark and i dont have a jack other wise I would go look.

[jatsvl]

metal fuel line running off the external pump???? I haven't seen that! usually its all rubber from the tank to the metal line that runs under the car to the engine as previously described.

[Shane1989]

Now that I had a chance to look. You are right jatsvl. Its front of the tank behind the diff housing. Its the thick rubber hose on the outlet side of the pump. Its cracked really badly and its wet again. So I just turned the car on and gave it a light squeeze and fuel came out... Whats that hose called??? So I can blind myself trying to replace it...

[jatsvl]

high pressure hose! you can buy it in the length you need any parts store. don't blind yourself depressurise the fuel lines before you start
1. start the car
2. open fuse box and remove the fuse for the fuel pump (fuse no.3) wait for the engine to stop running (it may take a minute or two) then activate the ignition again and wait again.
3. then change the damaged line (there may be still a little fuel in the line but it won't be under pressure and shouldn't spray out all over the place) wear some saftey glasses/don't lay directly under the line reach in from the side.
4. PUT THE FUSE BACK!

[Shane1989]

Could you show me a pic of the fuse box with the right fuse circled??? I know were the box is and stuff but the layout of the fuse panel is scrached off..... Please ?

[jatsvl]

the fuses have moulded numbers next to them. I'll try and post the layout make note of the spare fuse holders to work out which end is which!