Dead V8 - HELP!!!

[vitesse3947]

Hi all, great site, I've been on here a few times and if anyonr can help me it's got to be you guys.

Appologies if this post is a bit long but I'm trying to include as much info as possible.

I have a '85 Vitesse auto with a 3.9 block, standard flapper type EFi system (except for a rising rate fuel pressure regulator and K&N filter) and standard ignition. The problem began a few weeks ago with the engine sounding ever so slightly throatier, as if the exhaust had a slight blow. After a couple of weeks, when sat idling, the revs would suddenly drop and the engine would splutter and cough, but, after a few seconds they'd pick up again and she'd be fine. The last time the revs dropped, she coughed and spluttered and cut out and now refuses to start. I've run all the tests from the workshop manual (proper Rover one not Haynes) the results of which are below, but no joy. I've changed the dizzy cap, rotor arm, coil, ignition amp module and finaly the entire distributor without a hint of success.

Any insight you guys could give me would be very gratefully received.

Battery voltage = 12.66v
Voltage @ coil '+' terminal = 12.20v
Voltage @ dizzy end of LT lead = 12.20v
Resistance between coil '+' & '-' terminals = 0.8 ohms
Resistance between coil '+' & HT terminal = 6.72 kohms
Resistance of dizzy pick-up coil = 3.12 kohms

Thanks all.

Alex.

[annodomini2]

crank position sensor?? if it has one?

[Liszt]

Have you tried checking the AFM and cold start valve thing. Not too familliar with Flapper or vittesses more of a hotwire in Landrovers person.

[steve_d]

Very similar to how my Range Rover died.
Posted the ECU to a guy in Southampton and got it back 2 days later.
Now goes like a rocket.
Do you have access to another car you can swap ECUs with just to prove it out?

Steve

Edit. Sorry forgot the most important bit. Replace the water temp sender. It's the rearward of the 2 sensors at the front of the engine. It's a pig to get out and it's easier to remove the front one first.

Steve

Edited by steve_d on Monday 26th June 20:19

[vitesse3947]

Hi all,

Thanks for the suggestions, as far as I know it doesn't have a crank position sensor. I've fitted a new water temp sensor, tried a spare AFM and a different ECU with no luck. I've just had one of the plugs out and held it against the block and I don't seem to be getting any kind of spark, even tried it firing direct from the coil, instead of from the dizzy, using a plug lead from a running car just in case the coil lead was duff. Again with no joy.

After all this effort I know it's going to turn out to be something dead simple.

Thanks again.

[GreenV8S]

Sounds like you have shown it is an ignition fault then. That's good news because it means you can eliminate anything to do with the ECU, sensors, fuel supply etc. The ignition is very straightforward.

The first test is that you have 12v on the +ve side of the coil - I understand you've confirmed this.

The second test is to momentarily earth the -ve side of the coil and show that you get a spark on the king lead. If you don't get a spark then you probably have a duff coil, but just double check that the +ve side is still showing around 12v while the -ve side is earthed (don't hold it earthed for more than about a second while you do this or you risk overheating the coil).

If you do get a spark then you need to do a similar test for the ignition amp and if that checks out OK you may have a duff ignition pickup.

Bear in mind that it's easy to damage HT components while you're plugging and unplugging things so even if you find and fix the fault, don't assume that everything else is still good.

And since it's an ignition fault you've almost certainly flooded the plugs by now so once you've sorted the ignition, fit a new set of plugs before you make a serious attempt to start it. And make sure the battery is kept charged up. It's far harder to start an engine if the battery is starting to run down and you need everything on your side until the problem is sorted.

[vitesse3947]

Back again, thanks for the ideas GreenV8.

Tried earthing the coil '-' and amp module '-' as suggested but got no spark from either. Replaced the coil with a new one but still no spark, the distributor pick-up and module are both new so they should be fine. Could there be something wrong with the engine's earth connections, stopping the circuit being completed? I'll clean them all as soon as I get chance.

Thanks again for all your suggestions.

[R6RY D]

you didnt mention fuel. are you getting feul up, i had a 350, which i changed the fuel pump on and a fuel relay. is youre filter blocked ?

[vitesse3947]

Hi, Back again.

I'm definitely getting fuel, in fact I've had to disable the fuel pump because the engine was flooding.

I've cleaned up all the engine's earth connections and replaced the LT lead but still get no spark (resistance on the main braided earth lead measured between 0 and 0.4 ohms is this right?).

This makes no sense to me as I've pretty much replaced the entire ignition system.

Cheers again for any thoughts.

[R6RY D]

not sure about the ohms readings? why not try fitting a temp lead from there to a good ground?

[leorest]

R6RY D said:

not sure about the ohms readings? why not try fitting a temp lead from there to a good ground?

For a quick test use a heavy duty jump lead from the engine block (or wherever the suspect earth is) to the battery -ve terminal.

[vitesse3947]

Already tried that, guys.

Thanks though.

[GreenV8S]

You say you've got 12.20 on the coil +ve terminal, and no spark when you momentarily short coil -ve to earth. That suggests the problem is associated with the coil or the supply to it. What happens to the coil +ve voltage when you momentarily short the coil -ve to earth?

Note: don't keep the coil -ve shorted to earth for longer than a second or so or you risk overheating and damaging the coil.

[steve_d]

Using a meter check to see if you have a connection between +or- on the coil and earth. There should not be a connection but I have seen a coil corrode through it's casing and short to the bracket.

Steve