FUEL VAPOURISATION

[tr7mgb]

My MK2 VITESSE suffers from fuel vapourisation after a run, leave it 20 mins and it starts ok, until then no chance

what i've done

checked ignition system
re routed fuel pips around back of engine
wrapped manifold

still have the problem

i do have pancake filters fitted, i read somewhere that these can cause issues sucking in hot air, should i return to air box with ducted air?

still running manual fan (plastic type), manual fuel pump and engine shields are fitted although tried without them, no change

running BP unleaded ultimate (97 octane)

not fitted carb shields yet - are they any good?

I am convinced its fuel vapourisation as engine runs and starts fine when sat with bonnet open, but obscures driving!!!!

any ideas?

[esxefi]

pipes round the back of the engine will be exposed to more heat from the block.
run them to the front and even extend them to run through the area of the radiator.you could even add extra pipework to create a cooling coil arrangement in a cold air stream to help supress vapour locking.petrol is volatile and will evaporate quickly.(especially the new stuff)
carb shields do work,and as you mention try to cobble up some sort of cold air feed.temperature control is a fine balance and small improvements all add up. :)

mind you this time of the year is a bit unusual to be experiencing vapour lock,your problem could lie elsewhere. :-/

[nang]

I've run my line from pump to carb across the back in rubber ,fuel line grade. Had no problems even in New Zealand summer (>30 degrees C.
I do have a full length heat shield. Running K & N 's with no cold air intake.
Tony.

[Nick Jones]

I think the problem may slightly different to what you imagine.

I had similar problems with mine.  It was heat soak, but causing the fuel in the float chambers to expand and overflow into the carb throat, flooding the engine.  Quickest start came from holding the throttle wide and cranking until it fired.  There would be a puff of black smoke and a fuelly smell when it did go.

Check the float levels first (possibly a bit high) and also that the needle valves are in good shape as fuel expanding in the feed lines around the engine might also force more fuel through into the float chambers.  A heat shield between carbs/manifold/exhaust manifold will also reduce the heat transfer to the carbs in the first place.

Good luck......

Nick

[69vitesse]

Pancake filters loose you power, @ 6BHP, and suck in lots of the hottest air in the engine bay to cook your carbs.
Put the FAR superior factory airbox and hoses back, and fit some carb shielding, the new Zercotec mat is extremely effective.

[Pete Lewis]

My Vit 6 has std air box, 631 unwrapped manifold, plastic fan and side shield removed for access, used rubber fuel lines
and she will  idle all day without missing a beat,

yours could also  be  related to coil temperatures , theres some rubbish condensers about ,
or just  set on the rich side of normal, and under bonnet temp just over comes the fuel/air ratio and wont restart.

if you revert to std airbox, don't use the convoluted tubes make up some from 1.5" waste pipe   flare the end and its nice and smooth air flow.... very cheap too

worth a check of the tappet clearances
if the rotor arm has a rivet in it...get a genuine one (lucas or delco)

check the coil 12v is correct polarity

Pete

[tr7mgb]

thanks chaps

tried a few things today, heat shield fitted, new coil, adjusted float height, some improvement, but still not right

the problem is not idling, this it will do all day bonnet open or closed, temp reads just below half regardless.

the problem is restarting when hot, after 10-15 mins its ok (for example, go for a drive, stop at petrol station, by the time that i've been into shop and paid, go back to the car and no start, wait 15 mins and it fires up).

tappets? i have no tappet noise, so are they are a tad too tight, might be worth a reset of the tappets, what gap is recommended? hot or cold?

condensor??? neve thought of that might be worth a try then

[esxefi]

tappets could cause that,if they were too tight you might get the odd backfire through the carbs and/or exhaust as the seats slowly burn away :(

sounds fuel or even electrical related(something going open circuit or breaking down when hot)I had a problem with the low tension wire years ago,conductors broken inside the sheathing,it got hot and would not start,few minutes later all was well.

replaced it and it was ok.

try some testing of sparks or using a multimeter for breaks.

[nang]

Do you have SU's fitted ? If you do you have waxstats on them ?
Tony.

[ferny]

Coil getting hot?  Not sure if it's bolted to the engine on a vitesse.

[mpbarrett]

do you have electronic ignition? If so and its a RetroRocket system then you must make sure it has an earth connection between the dist body and the plate holding the sensor. Otherwise you will get probelms very similar to fuel vapourisation...
regards
mike

[Pete Lewis]

put a workshop manual on your easter wish list,  all this generation of engines tapets are 0.010" set cold
Pete

[tr7mgb]

Workshop manual is well thumbed, but purpose of asking is that sometimes the manual is not accurate, or someone knows better.

anyway

points, condensor, dodgy lead from dizzy to coil, tappets (3 were very tight), timing and colour tune all done

its a different car!!! all problems gone, it even starts better.

not sure what fixed though, don't care either

thanks for all the suggestions,