Ping Badger Re: Rover V-8

What you have mentioned below how does the AFM adjust on a 94 Disco Mk1.

Inside there is a solid circuit with a pot adjustment on the board which is accessed through the side.

I;m playing with it now but need some guidance - its running too rich / using too much fuel. They want an arm and a leg just to calibrate the AFM when there is only one adjustment.

Any advice

Thanks.

Std 3.5 pump is ok, no probs there. You need to use a decent CO meter though. Set fuel pressure to 42psi with engine not running and fuel pump relay shorted to allow it to run, prise cover off AFM and you'll see a plastic toothed wheel and a spring-steel locking catch. ease the catch back and tension the spring by turning the wheel roughly 6 notches, start engine and get to normal temp. Adjust idle mixture screw to 1 turn out from fully home then re-adjust spring tension to get a CO of approx. 1.8%, then fine-trim mixture with CO adjusting screw. Finally, re-seal cover onto AFM. That's what I did when going from a 10.5:1 3.5 with a Piper 270/110 cam to a

9.35:1 3.9 with a std cam, it worked perfectly for me. Badger.
Reply to
Rob
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The std disco 3.5 efi's were all "hotwire" type systems, same as the 3.9 versions. The meter I referred to for recalibration procedure is the SD1 and rangerover 3.5 "flapper" type, I assumed that was what was being used on the

3.9. You cannot re-calibrate the hotwire meters easily at home, only the flapper type. If it's a hotwire system, simply fit a 3.9 ecu (early 3.5 ecu's didn't have the 3.9 fuel map in them, later ones have maps for 3.5, 3.9 and 4.2), leaving the fuel pressure standard (36psi) and all should be ok, remembering to fit the correct 3.9 tune resistor to the harness near the ecu end. (white or green resistor, one is for lambda the other is for open-loop systems, can't remember off the top of my head which is which).

Sounds like a hotwire.

Try dropping the fuel pressure back down, assuming you've raised it, it might be ok just with that. Calibrating the afm is not the same thing as adjusting the CO trimmer pot. Badger.

Reply to
Badger

A bit more history.

This vehicle was on the diagnostic computer about 3 years ago apparently, and one of the items mentioned was that it needed a recalibrated AFM - by the dealer (very expensive) - hence was not done.

Its gradually been consuming more fuel over that time and I could no see why the AFM should affect the consumption. Plugs need replacing, so it will start, at about 5000KM intervals, but they don't look too bad, even colour on all eight.

The vehicle is worth nothing now although the parts still remain at an all time high and the owner doesn't want to spend any money on it. I'm no expert on fuel injection stuff nor have access to the resources to diagnose problems but can try simple adjustments along the way. (dealers just throw parts at any problem, which is not understanding or necessarily the answer). The dealer only came up with the AFM anyway.

So Ill look at reducing the pressure which may reduce the fuel consumption. Thinking now it may also be worn injector problem!

Thanks

Reply to
Rob

Can I ask another question? What compression ratio do 3.9 Range Rovers have? Or was there a choice? And how can you tell?

Reply to
Dave Plowman (News)

I think that I read about 8:1

The 3.6 carby engine is 8.5 :1

They haven't varied off the 8 to 8.5 what ever size.

There are high compression piston available - Hepolite from memory.

Reply to
Rob

UK market, 9.35:1.

From about 1978 on, all 3.5 carb rangerover/landrover were 8.13:1 until the intro of EFI, when they went to 9.35:1, same as the SD1 always was.

9.75:1, std rover vitesse 3.5. 10.5:1 (ideal for LPG), P6 rover but a slightly weaker piston design.

For the current rich running fault, it'd be worth pulling the injectors and looking for any signs of corrosion around the fuel inlets - I'm seeing more and more of this in the workshop these days. Fit a pressure gauge to the schrader connection on the fuel rail, check pressure at idle (it won't be

36psi, as the vacuum in the manifold will cause the prv to open at a lower fuel pressure) switch engine off and see if the pressure drops off. If it does, it's almost certainly leaking past the injectors if you have rich running as well. Badger.
Reply to
Badger

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