Dam those twin carbs !

[EDCivic]

In there hay day Honda have made 100,000's of thousands of these dual carbs/engines/models combo's for years
and after the last 20 odd years the dual carby issues must surely be as common as the sun rises in the morning !
I have posted before about my issue re switch engine off and momentarily fuel continues to pour into the
inlet manifold flooding the engine. The weird thing is that ocassionaly it will be come good for a few weeks then returns back to its flooding routine
I've read through many posts but have had not seen an adequate response as to how to fix this ?
Surely there must only be 2 or 3 areas to look at or am I just kidding myself. Some back ground...the original carby (385,000k's) behaved exactly the same as
the carby that is on it now (220,000k's) which was swapped out in its entirety. The fuel pump, charcoal canister and the magic prince of darkness have all been swapped out and a new fuel filter fitted.
I am running out of ideas. Any help would be hugely appreciated as other than this the car has served us well for over 14 years and 395,000 k's.

[dove grey 64]

Checked the return line isn't blocked?

[EDCivic]

Will check...one thought I had was the 2 way valve located near the petrol tank. Can that cause this as it is about the last component that I haven't touched. I appreciate that these are old cars now but both carbs behaving the same way is just to coincidental ???

Please keep those suggestions coming.

[dove grey 64]

Thats why I think your return line may be blocked. Just sounds like fuels going in but not going out.
How many k's per tank? My D15b4 gets 600ks from 42l.

[EDCivic]

We get around 540 (it's an auto)...even with the way it is currently behaving it's still pretty good economy as once it get's over it's starting issue it runs like a Seiko watch ! That's why I'm stumped at what the issue is i.e. if it was a sticky float or needle it should be getting terrible fuel economy, but it's not, so the issue is centred around that period after the engine is switched off.

[dove grey 64]

Im assuming these have a single return line or both get plumbed into one spot, I would disconnect the return line from the carbs and plumb it into a coke bottom, drill a small hole in the lid and feed the pipe into that.
See if after shut off the excess petrol runs into the bottle as it should and see if its easier to start.
I guess another possibility is if your petrol tank is under too much pressure, how is the filler cap? When you undo it is there a loud sucking noise or not?

[EDCivic]

Not sure if there is a return line as the diag (attached) shows the return is from the fuel pump ??? Regarding the filler cap, it will have a sucking noise from time to time but I'll need to check again.

[EDCivic]

OK.....cap has a slight sucking sound when removed. Today I pulled up and with engine still running, removed the petrol cap to release any pressure issues, and then switched off the engine. Came back 30 minutes later and could smell petrol and sure as eggs ......crank, crank, crank, crank, cough, splutter, cough and much like the start of the "Phoenix" as it fired up into life http://www.youtube.com/watch?v=AwYzAF9bZLI (good movie). Still need to check the return line over Easter as I'll have plenty of idle time then. Not sure if I buy a carby service kit for it off eBay for $150 (http://www.ebay.com.au/itm/221166522261?ssPageName=STRK:MESINDXX:IT&_trksid=p3984.m1436.l2649) and fit it to the original carby ???