rough running v8

I'm getting kind of peeved now.

Couple of weeks back had to tow the boss back, she was in the v8. On her way along the motorway it had been losing power, then as she got onto Bluebell hill she got 1/2 way up, and had to abandon the car in the middle of the garage entrance as it came to a stop. She said that it manifested as a loss of electrics - radio went off, wipers took forever to do one sweep, no headlights or indicators.

Got home, and just for the sake of it tried a jump start - fired up no problem. Took off the boost, still no problem. So I ran the v8 for a few days on local journeys, and last weekend, it was having trouble once it warmed up - aha - ECU temp sensor i thought. changed that. no changed :-(

So has begun the great game of trying to work out what the f*ck is going on.

She'd mentioned a burning smell, offside front, so had a check - cant find anything.

Changed the coil - better, but no change in running - in fact wednesday night, I almost had to get towed back!

Cleaned the stepper motor (sooted) - no change

Changed the AFM - bit better, but essentially no change.

Now today, i was looking at that big canister thing, behind the battery. I pulled the pipes off, and just pushed one into the other - man what a difference! Smooth running, tons of power - except there is now a pump of some description running near the back of the car all the time.

Sooo, whats the canister thingy? what does it do? and whats with the pump?

any other ideas?

Cheers

Si

Reply to
GrnOval
Loading thread data ...

Refit the petrol cap correctly.

Reply to
EMB

I've swapped caps with the others in the fleet and the pump thing is still going - so back the original questions - what is that canister? what does it do? why does a pump run when its bypassed?

Si

Reply to
GrnOval

OK, so replying to self isn't the best of form, but...

The pipes on the canister - one goes to the fuel tank, the other says "purge". It appears to be some kind of relay - and its going mental. =46rom what I can find out, the canister is a charcoal canister - whats its purpose?

Si

Reply to
GrnOval

Thought it might be that but wasn't sure...

Basically the canister absorbs petrol vapour from the tank and is "purged" by having fresh air sucked through it, on my old Esprit the vapour-laden air then goes into the engine manifold, not sure where it goes on your engine. Mine doesn't have a purge pump, the air is sucked out by the manifold vacuum, if I were you I'd start hunting for manuals that include details on the evaporative emission control system. It probably feeds back into the intake somehow and if it's letting air in then that might be your problem. See if you can trace the pipes, but in the meantime best set it all back up as it was before otherwise you risk fuel vapour escaping.

Hopefully someone who knows how it works on your specific engine will be along shortly ;-)

Reply to
Ian Rawlings

You have e-mail.

Reply to
Dougal

received - thanks Dougal

Si

Reply to
GrnOval

ok, so reading that which Dougal sent me, it sheds no more light on to why things would run better with the canister bypassed

Damn und blasten

back to square 1

Si

Reply to
GrnOval

I'm not familiar with this - just reading what you have read.

You mentioned 'boost' earlier - is this vehicle standard or has it a turbo conversion?

In a non-turbo installation I'd expect ....

By connecting together the two hoses at the charcoal canister you have not bypassed it. It seems that you've connected the plenum chamber (vacuum) to the 'air' space in the tank. This tank is not open to atmosphere so you are reducing the pressure at the pump inlet which may change how it sounds when working.

What happens in the 'bypassed' state with the engine running if you remove the filler cap?

If you leave the hose from the tank to the canister open to atmosphere, reconnect the other disconnected hose to the canister and disconnect the plug on the purge valve you'll be pretty close to the previous models without the evaporative control. Worth a try?

Reply to
Dougal

Its a bog standard 3.9 v8i - cant find mention of boost.

When I have the purge feed tucked into the one from the tank, then the canister is bypassed - ie it aint in the loop. If i leave both pipes to air, engine is rougher than a heinz 57 mongrel.

The only two things that havent been changed on the setup at the moment are the ECU and the fuel filter - and after the last couple of hours i've given up on the filter :-( Are there tail kits available for the filters so i can just drop it into the line?

I think its prolly fair to say "ignore the canister" unless anyone has any ideas about it causing rough running (like a miss but not quite).

Si

Reply to
GrnOval

If both hoses are open to atmosphere you are sucking in extra air into the plenum via the outlet hose from the canister - hence the rough running.

Does anyone know how the purge valve works? Is it a simple on/off device with two ports or is it more like a changeover device with three ports?

Reply to
Dougal

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.