Vacuum and fuel issues

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Les - 28 Jun 2003 05:29 GMT

Hoping for help from the group.
The little red beast decided it did not want to run on anything less than
full choke a couple of days ago. First tried to solve the problem my
favorite way. Park it for a few days and hope the malady cures itself.
Having failed with that method my next MO is to get down and dirty with it.

IT is a '76 with a 1275 lump(year unknown) with a myriad of vac lines off
the carb and manifold running to a canister under the left fender. The
canister is loose and flopping about (will remedy that). A small thin line
exits back into the engine bay, joins with a line off the carb and connects
to the distributor. That seems intact but spark does not seem to advance.
There is another hose exiting the can and takes a right turn for the tarmac
and joins a block that includes the fuel line from the petrol tank (BTW mech
fuel pump seems to be outputing ok, pumped a litre of fuel with a few spins
of the starter) and the vac line parallels the fuel line back to the tank.
Back to the right turn in this vac line; a rubber join tube in the hard
lines was seriously cracked and I replaced it, then the engine would not
start. Disconnected the join tube it starts with full choke. Push choke in
eng dies. Put finger over hose coming out of canister, eng dies. Must
feather throttle and clutch to get car to roll and does not run smooth nor
is the any power. And there I am!
Any thoughts from the group aside from referencs to tall cliffs and boat
anchors. I have been through the AutoData manual and there is no reference
at all to the vacuum system. Is the Haynes manual any better?
Dazed and Confused in the Colonies

Les

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oli - 01 Jul 2003 11:48 GMT

hello lez

both the current and the older versions of the Haynes manual are crap at
actually telling you what does what. they are fine at telling you how to
rebuild your carb and how to rebuild all associated parts BUT they do no
tell you how to connect the bastard back up ! what i have found as a good
rule of thumb and may be a good start for you to source your problem is.
there are basically 4 connections to an su carb.

1. distrib advance (small 4mm pipe coming off the back off the carb mounting
plate and sometimes can be found coming out of the exhaust manifold)
2. large pipe 7 or 8mm about in diameter... this is your crankcase/engine
breather connection
3. float vacuum. higher of the 2 remaining pipes (both should be the same
diameter) this should take a feed from your air filter
4. fuel in (self explanatory)
(there may also be a connection into the manifold that provides vacuum to
the brake servo)

i find that the best way to sort probs like this is to block off 2 and 3 and
see how it behaves then, this will tell you if you have a vacuum leak (as
you are having to enrich the mixture with choke and or extra throttle i
would say you have a vacuum leak) if you do have a brake servo then check
its connections aswell and replace if it looks dodgy (do not block this off
and go for a drive or your will have no brakes)
ive had the same symptoms myself and it was a vacuum leak, pipe looked fine
but i connected it on an airline at work with a pressure gauge on it and it
held no pressure at all. replaced the pipe and the engine behaves lovely
now.

hope this helps... if it doesnt... i was not here.... i did not say this !

ttfn
Oli

> Hoping for help from the group.
> The little red beast decided it did not want to run on anything less than
[quoted text clipped - 23 lines]
>
> Les

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