PROPLEM WITH FUEL CONSUMPTION

[Hybrid_From_Hell]

Why ................. because there are a lot of Classic RR 3.9's that have had engine swaps to 3.5 flapper due to block & cam problems with the 3.9 engine.

Ian

^^^^^^^^^^^^^^

Spot on

Nige

[SIMON64]

Why ................. because there are a lot of Classic RR 3.9's that have had engine swaps to 3.5 flapper due to block & cam problems with the 3.9 engine.

Ian

is this something i should be aware off block & cam problems with the 3.9 engine. what are these problems and is there anything i should be doing to prevent them

regards simon

[DEANO3528]

is this something i should be aware off block & cam problems with the 3.9 engine. what are these problems and is there anything i should be doing to prevent them

regards simon

The forum search facility is a good tool for this type of enquiry.

Just type something like "V8 block problem" or "porous block V8".

[FridgeFreezer]

The forum search facility is a good tool for this type of enquiry.

Just type something like "V8 block problem" or "porous block V8".

Except you can't put "v8" in as it (still) doesn't allow two-letter search words

Seriously mods, can't we change it?

[geoffbeaumont]

Was just going to add that if the problem is on both petrol and LPG then it must be something common to both. My system does not pick up on engine temperature for the LPG, so I am fairly sure that it is a combination of aggressive tyres, viscous coupling, heavy right foot, and worn engine!

On the other hand, a mates RRC which has a hotwire AFM and is fitted with LPG, does sense engine temp, and will not change over to LPG until the engine is at normal operating temperature, so there could still be a common connection there.

As has been said, we need to see what type of system is fitted to be more specific with the fault finding.

There may well be LPG systems that share the OEM coolant temperature sensor, but I think the one I had used it's own in the vapouriser (which makes sense - that's the bit that needs to be warm enough). In that case at least there's still no common fail point.

is this something i should be aware off block & cam problems with the 3.9 engine. what are these problems and is there anything i should be doing to prevent them

regards simon

Far more people don't have problems than do, so I wouldn't stress about it. I wasn't aware there were cam problems unique to the 3.9? What are they? I know about heavy wear due to poor oil supply to the rearmost cam lobe, but I thought that was a problem across all rover V8s?

Except you can't put "v8" in as it (still) doesn't allow two-letter search words

Seriously mods, can't we change it?

Nope, 'fraid not - the underlying search system doesn't index groups of less than three letters. When we first set up the forum we used the alternative 'simple' search, which doesn't use an index and does allow shorter search strings - we had to change because the simple system was getting unusably slow as the forum grew. It probably wouldn't work at all now.

Simon - how many miles has your truck done, and what major work (if any) do you know of that's been done on the engine? For example, head gaskets, cam, full rebuild...

[SIMON64]

Simon - how many miles has your truck done, and what major work (if any) do you know of that's been done on the engine? For example, head gaskets, cam, full rebuild...

hi its done 140,000 miles dont now what it has done to engine i have not had anything done but not had it long. my millage should not be a problem being so big or will it i dont have a clue i drive um thats about the total of my knowlage of cars

regards simon

[geoffbeaumont]

Simon - how many miles has your truck done, and what major work (if any) do you know of that's been done on the engine? For example, head gaskets, cam, full rebuild...

hi its done 140,000 miles dont now what it has done to engine i have not had anything done but not had it long. my millage should not be a problem being so big or will it i dont have a clue i drive um thats about the total of my knowlage of cars

regards simon

Any signs of fairly significant oil leaks around the valley? Loss of coolant? Exhaust gasses or 'milk' in the coolant? I'm wondering if your head gasket(s) are on the way out. That's not a big deal, though it'll be expensive if you pay a garage to do it due to the amount of labour involved.

At that mileage the cam will be passed it's best, but I would have expected a more gradual deterioration?

The other obvious cause of lousy economy on both fuels would be ignition trouble, which you're already looking into.

As a couple of people have already said you need to download a copy of the very comprehensive hotwire engine diagnostics manual from the tech archive on this site and work through it. It'll take you a while but you'll learn a lot about your truck which is a very wise investment when you own a land rover, unless you like handing over most of your income to garages... I didn't know a great deal about the inner workings of engines before I bought a land rover either - it's a learning experience

[Dr W]

So took car in for LPG service and was told that there was some problem with the vaporiser membrane and this would cause me to have low mpg?

Anyway it's being replaced today along with adding a RPi Power Amp and the rest of the lpg service.

I've put on Magnecor 8mm HT leads, a new Lucas distributor and rotor arm.

I'm then going to fill her up and do a run up to Manchester trying to leave crusise control set on 70mph so get a steady result with which to compare to the 150 - 160 miles I was getting before hand from 64 litres. (2 x 36 litre tanks).

I'll post the results after the weekend.

For the record it's a 1991 3.9 on 96k miles.

[Dr W]

So did a couple of long runs this weekend

1. 230 miles from London to Manchester, mostly a steady 68 on cruise control, 50 litres of gas = about 21 mpg

2. 250 miles from North Wales to London, 125 on winding A roads to Telford, doing about 50 mph, lots of stop starting with lights, sharp turns etc, then the remainder on motorway, doing about 70 but quite a few bursts to over take stuff, used a full tank (2x 36 litre tanks so I guess around 65 - 68 litres) = 17 mpg.

Quite an increase from what I was getting before and quite chuffed as it's now more economical (comparing like for like gas and petrol costs) than the 1.8l golf I used to drive.

[disco_al]

with twin 36 litre tanks you have a theoretical capacity of about 56/57 litres. so with the distance you covered on that amount that is an impressive increase.

i managaed to get 20mpg out of my 3.5 the other week, on mostly back roads (Hereford/Pandy/Capel Y Fin/Hay and back to Hereford)

[Dr W]

with twin 36 litre tanks you have a theoretical capacity of about 56/57 litres. so with the distance you covered on that amount that is an impressive increase.

I've read that capacity etc can depend on heat of the day, pressure in the tank the gas is coming form etc.

Usually I can get in around 65 litres although yesterday I got just over 70 litres in according to the fuel pump reading.

Is this normal, I generally just hold down the button till it stops.

[disco_al]

when filling you will hear a "machine-gun" style rattle when the tank solenoids sense that the tanks are full. This is when you should stop filling, or so i have read anyway.

[Dr W]

Mmmmh haven't heard that noise when filling?

I reckon I'll just fill till it stops unless anyone thinks I'm going to cause problems doing this?

[disco_al]

Taken from the Go-Lpg website;

14. Long term effects of 'machine gunning' during filling

It is not uncommon for multi valves to make the 'machine gunning' sound during filling, normally when the tank is almost full.

It is not dangerous in itself as the moving parts are non spark generating, and I have observed many owners filling through (and past) the sound to get a few litres more gas in the tank.

Yesterday we saw a long term effect of this practice - The car was brought to us leaking gas from the undervent when filling was attempted. A short investigation showed that the filler pipe had snapped clean off right next to the tube nut on the multivalve. Closer inspection reveled the almost crystalline appearance of the ends of the copper tube, suggesting that the fracture and eventual complete failure was due to work hardening of the metal.

The only source of vibration sufficient to cause this problem is thought to be the owner's practice of allowing the valve to 'machine gun' to get as much in the LPG tank as possible. The pipe was replaced and normal filling resumed. We advised the owner to stop filling when the noise (vibration) begins, and not to fill through it.

An interesting footnote is that the latest OMVL multivalves do not 'machine gun' in this manner and the problem is completely eradicated.

Go LPG only install OMVL multivalves as a matter of course

.

that's where i read it anyway, www.go-lpg.co.uk in the LPG motoring hints section

[geoffbeaumont]

Mmmmh haven't heard that noise when filling?

I reckon I'll just fill till it stops unless anyone thinks I'm going to cause problems doing this?

Some vehicles do it much worse than others - some never at all. I think the argument for stopping was that the judder from the valve could over time fatigue the fuel pipes, rather than any issue with over-filling. On dual tank setups one tank often fills faster than the other (in theory they shouldn't, but in practice they do), so if you stop at the first shudder you'll have one near full and one tank that may have very little in it. My old Range Rover did this - one tank filled much faster than the other.

[Dr W]

I don't know if it is just multi valves that do this, mine is a Venturi single point system which is 5 years old and running fine (no back fires etc).

I guess if there is no noise and no vibration there shouldn't be a problem just filling it up till the pump stops.

[sheltie50]

Just seen a P38 with very poor MPG, turned out to be the Temperature Sensor which send info to the ECU, migh be worth checking/replacing but again might not be, side effect was very high exhaust temperature, have since found that the cat internals have been shot out through the tail pipe.

Good luck.