Outer Limits 4x4 Board

hi ive got a patrol 4.2 carby/gas. My problem is i only get bout 2 to 3 klm per litre.its had countles tuneups and still no better. the head is new and i have replaced everything from coil to plugs.it still has points ignition.
any help would b great...

bad economy on gas or petrol, or both?

Jes

You've done the tuning, so assume that's all good. Fuel / Air filters? Also check that you haven't squashed your exhaust sufficiently to seriously restrict exhaust flow.

Tyre pressures are another area than can cause significant fuel issues - what pressure are you using?

Here's a left field one for you.

I recently went through 3 months of fuel economy issues with my 4.2 diesel.

Eventually found the problem to be a seized front brake caliper that would constantly hold one pad (the outside one) onto the disc. There was no pulling, shuddering, loss of braking performance or any other sign - just poor power and economy.

2-3 km per litre is abyssmal.

4-5 is standard though :(

It sounds like something is seriously wrong there somewhere - you're using way more fuel than you should be.

Other than "leaving the handbrake on" here's soem other questions.



Hubs locked?

What tyre size?

Is this the same on Petrol and LPG?

Any other symptoms than massive fuel use?

jessie928 wrote:bad economy on gas or petrol, or both?

Jes

petrol is a steady 3 klm per litre

i am getting about 3.3km per litre of gas on mine, with pertronix, remapped dizzy for gas, extended rotor button, extractors and 2 1/4 exhaust with an impco 300a mixer. My compression over all 6 cyclinders ranges from 127psi to 135 psi.

I have been told that gas likes higher compression, and that my low(ish) compression could be one of the reasons that i am getting bad ecconomy. It also lacks power.

marin

Beastmavster wrote:2-3 km per litre is abyssmal.

4-5 is standard though :(

It sounds like something is seriously wrong there somewhere - you're using way more fuel than you should be.

Other than "leaving the handbrake on" here's soem other questions.



Hubs locked?

What tyre size?

Is this the same on Petrol and LPG?

Any other symptoms than massive fuel use?

hubs not locked 31in tyresand petrol is not much better only other symptoms r a slight miss every now and then

jessie928 wrote:bad economy on gas or petrol, or both?

Jes

both but petrol is a bit better

Hmmm... sounds like an ignition problem if it misses on lpg as well as petrol.


How long ago was it serviced and are you sure they used new points, plugs and rotor (rather than just cleaning up the existing ones)?

When I had an LPG Nissan I used to go through plugs heaps.

Ohhh yeah, one other question? Automatic?

i'm told the best you will get on petrol with 31's is 5k per litre. I never worked it out properly, i was getting about 28/100 out of mine with 35's on it. Thats about 3.5 k per litre. I'm currently getting 5 per litre with the V8 in it. Is your auto or manual?

marin wrote:i am getting about 3.3km per litre of gas on mine, with pertronix, remapped dizzy for gas, extended rotor button, extractors and 2 1/4 exhaust with an impco 300a mixer. My compression over all 6 cyclinders ranges from 127psi to 135 psi.

I have been told that gas likes higher compression, and that my low(ish) compression could be one of the reasons that i am getting bad ecconomy. It also lacks power.

My mechanic happens to be a bit of a GQ fan, used to have one and his brother has one, and he has told me a few time that valve adjustment is a persistent problem with the TB42. Getting the valves done could help your compression and economy a bit.

Having said that, I am not sure what the compression is meant to be on the TB42 anyway... what's the spec?

chimpboy wrote:

marin wrote:i am getting about 3.3km per litre of gas on mine, with pertronix, remapped dizzy for gas, extended rotor button, extractors and 2 1/4 exhaust with an impco 300a mixer. My compression over all 6 cyclinders ranges from 127psi to 135 psi.

I have been told that gas likes higher compression, and that my low(ish) compression could be one of the reasons that i am getting bad ecconomy. It also lacks power.

My mechanic happens to be a bit of a GQ fan, used to have one and his brother has one, and he has told me a few time that valve adjustment is a persistent problem with the TB42. Getting the valves done could help your compression and economy a bit.

Having said that, I am not sure what the compression is meant to be on the TB42 anyway... what's the spec?

just reading out of my nissan manual

pressure standard - 171 psi@200rpm
pressure minimum - 128 psi@200rpm
differential limit between cylinders - 14 psi@200rpm

marin

p.s. i did my tappets about 6 months ago to spec., not saying they couldn't have moved though. My engine is just very tired, but keeps on going.