How do I adjust dual carbs?

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katy
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Post by katy »

Well the front carb is still running overly rich, but I may have found the problem. The car has a "Bugpack" electric fuel pump on it, putting out about 3 PSI. I see in the workshop manual that the stock SU pump only puts out 3/4-1 PSI.
The fuel from the pump goes to the front carb first and then some is rerouted to the rear pump.
I'm going to try and source an adjustable fuel pressure regulator that I can use to decrease the pressure.
In the meantime I think I'll hook up a temporary gravity feed system to check it out. Sorta like an IV pole. :D
Any thoughts on this?
:o
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katy
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Post by katy »

Oops, I meant to say that some of the fuel is rerouted to the rear carb. :oops:
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eastona
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Post by eastona »

Yes, I know what you mean, it goes to the first float chamber, then a little connecting pipe to the other carb.

It could be it. that may be enough to unseat the float(s) and constantly pump a little extra fuel through the jet.

Be careful with a gravity fuel system. It may be fine for tuning up and testing your theory, but I wouldn't drive like that. (I'm just a scaredy cat around fuel!)

oh, just reread, an IV pole LOL :lol: I guess you can't drive like that!

Andrew
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katy
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Post by katy »

While running on the gravity feed did make a difference I still can't get it to idle properly, maybe not enough pressure that way.
While running on the electric pump, I disconnected the wire to the pump and that made a difference also.
I also tried another 'lectric pump that I have and it also puts out 3 PSI.
Am trying to source a reasonably priced fuel pressure regulator that I can use for a permanent fix, once I get and install one we'll take it from there.
Oh well, one of these days I'll figger it out, in the meantime there's lots of other issues that need attended to.
:lol:
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MarkyB
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Post by MarkyB »

In what way was it not idling properly?
Why not just get a standard SU pump rather than a fuel pressure regulator?
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katy
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Post by katy »

It doesn't idle properly because the front carb is running way overrich, even w/the jet adjusted all the way up. At this point I'm suspecting the higher fuel pressure may be the problem.
To get a new SU pump would cost me about $140-$150, a fuel presure regulator is worth around $30.
I'd rather check it out w/the $30 solution than the $140-$150 one. :o
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MarkyB
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Post by MarkyB »

:o I didn't realise the price difference would be over $100.
Good luck with it.
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