V8 3.5 EFI expurt needed !

Arrrrgh, RR V8 3.5 EFI + LPG kit

Now, ran down to London in the RR, filled it up w LPG, after 40 miles started spluttering. Switched to Petrol, still spluttering. Got to Party in Finsbury. Decicided to put new plugs in, the next day.

Would start after a while but plugs black.Poppping and spluttering

Recovered home ( Northampton ) still will not start.
Replaced coil with new one.

Plugs wet with fuel.
Distributor cap new, good spark at plugs.
Not firing at alll.
Good spark at plugs

Apart from a good dose of whiskey cannot decide next step.

EFI stuff to blame or shall I just torch it ?

Q

( At a loss......)

flooding?

Have you got good spark at all the plugs?

If you have then at least you have spark and fuel. Our RR V8 would't start the other day, had to adjsut the timing a bit and then it was fine.

Been there and found lots of things that can upset your engine. If you can get hold of one, swap your alternator with a known good one. It sounds like you may have a fuel injection misfire.

What's that got to do with your alternator? - well there aint no crank sensor on 3.5's or 3.9's and the injection is triggered from yout alternator.

If that doesn't work, check your timing chain for slack. This can cause the ignition timing to wander all over the place, I made a "tool" for this out of an old distributor. You are unlikely to have one of these so try (not too forcefully) to rotate the rotor arm in the distributor. Allowing for the movement of the lob weights you may find additional movement which will be the slack in the timing chain.

Next to check is the ignition amplifier - look in haynes or check rave. Run standard resistance checks on coil, oh and don't forget to check the battery - make sure you've got healthy volts.

If none of that works I would go for the various sensors that control the fuel injection system - fuel temperature thermistor, engine coolant thermistor, throttle potentiometer, air flow meter, air bypass valve(stepper motor). Again, the usual manuals have details on how to test/check.

After that little lot my guess would be check the injectors - I never got into that so you'll have to seek the advice of somebody who knows about it.

If none of that works try a new ECU and if that doesn't work then torch it!! (or you could always break it and get some money back).

Hope that helps.

I think 08093k has some very good points. I would add to that though that it could be a lack of air - so either something blocked or a leak.

Thankyou all for that- I knew I would get some sense out of this forum. A few things I did not know-about this engine setup.Will try it today and report back. Unless someone makes me an offer for it -It does have 10months MOT and solid chassis........

Cheers, Qhriss

Its bound to be something simple, don't give up on it! Besides, even if you were thinking of selling it, you wont get much for a non-runner.

True True-better get mucky then.....................

Q

Qrhiss,

I forgot to mention one other thing. I know on the 3.9 hot wire systems the engine will run if you disconnect the air flow meter - it goes into limp mode. You could try this on yours and see if it will at least run but it will be very rich ( I was getting 6MPG!!). This will tell you if the system is fundamentally O.K.

Then it will just be a question of playing around with it. You can trick the ECU on some things, all you need is a paper clip or short piece of wire to make a jumper/bridge - this can be used on the thermistors but I can't remember if a bridge makes it think it is hot or cold. Again on 3.5's I'm not sure if there is a tune select resistor you can play with I know there is on the 3.9 but you will need some resistors to do that so probably as well to leave alone.

There is some useful info on the RPI Engineering website.

Good luck, you're going to find this a lesson in patience and believe me I know.

Hi,
Remove amplifier. Connect ohmmeter leads to two pick-up terminals in body of distributor. The ohmmeter should register between 2k and 5k ohm if pick-up is satisfactory. If ohmmeter reading is correct, check all connections between pick-up and amplifier, if satisfactory, fit new amplifier. Also disconnect cold start injector on side of plenum chamber, had these spray constant before, controlled by thermotime switch (one infront of coolant temp switch) Also check there is no blockage in air intake. If you can, unplug anyone injector from both banks, (all four on one side fire at the same time then opposite bank) and plug in a node light, cheap on ebay, crank engine it should flash as injector pulses, if it's on constant the ecu or wiring is at fault as ECU earths the injectors.

Regards,
Nige

PS The alternator does not control the injection (what would happen if the belt was slipping ?) The rev counter is however.

Ta for the PM,as stated the ECU has nout to do with the alternator,only that it provides sufficient voltage to the battery to run the ecu itself.The rpm signal is taken through a resistor from the LT side of the ignition coil.
Were the replaced ignition components genuine or cheap aftermarket ? Genuine or nothing for these - otherwise you may have fitted a duff new bit and be no further forward.
The old 3.5 flapper type ecu's are dying from old age,lots of them died ages ago,if you can just hook up another ecu before you try anything else,(As long as its a known good one.)as its very easy to do.
Also remember that flooded Rv8's are very difficult to fire up - even when the fault is removed.May even pay to leave all the plugs out overnight,before trying to fire it up.Unplugging the cold start injector is a good idea,in the UK they will start without it.

This is going to be a long job- thanks for all your input, I seem to remember the speedo needle flicking when it usually started- which it does not do now Hmmmmm

Q

classic kev said:

In effect as I understand the system the ECU sees the coil through the rpm input but the source of the trigger signal for both injection pulse and ignition spark start with the alternator - is this correct?

Click to expand...

Regret to inform the alternator does not provide any signal to the ECU, the tacho, or the cruise control overspeed relay.

that signal come from coil negative and goes to pin 1 of the ecu via a trgger resistor as per this typical diagram of the period.

Ramon
Vintage Model Airplane and Rover SD1 3500cc Twin Plenum Vitesse

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