Idle jet plugged repeatedly

[quizmaster]

Hi,

I have a 32DHS Weber fitted since 2009.
My good mechanic managed to tune this till the proverbial cup of coffee wouldn't spill anymore.
A couple of thousandsof miles driven since, lots of fun...

This spring, over roughly 500 mi driven, I've had three incidents of engine cutoffs in idle.
I manage to continue to drive by (manually) choking whenever I'm idling, which is no fun.
Apart from the idle dying down, there's backfiring in the exhaust when shifting down gears.
Running at speed is just fine (no choke necessary)

After the first incident, a droplet of moisture was removed from the idle jet, carb sucked clean under vacuum.
It drove like heaven till the next incident.
This time a tiny hair/piece of feather was pulled out, same procedure plus a new filter element was fitted upstream of the carb
After barely 20 mi, third shutdown.

Now, why do I seem to keep trapping anyhting that plugs into my idle jet???
I must filled up the tank three times over the course of the incidents.
I read another post pointing at rust from the tank, so could anyhting be wrong there?

I DID have the tank removed to fit retrobumpers this winter: I understood the tank was emptied and refilled again to facilitate removal.
But if that's at the root of my current sores, shouldn't that purge after 3-4 full gas tanks???


looking forward to expert advice...

[majicwrench]

Oh I feel your pain...........my 72 plugs a couple times a year. Usually. This year plugs every other time I drive it. I am really good at cleaning jet, lots of practice. Took carb apart a few days ago, dried fuel, tiny bit of rust in bowl bottom. Cleaned out, blew and cleaned and blew some more. It doesn't take much, idle jet too small ! Today works well enough, tho idle still not as smooth as it could be, at least it is idling and I can accel without pulling choke out. In mine, there was a lot of debris in emmulsion tube under air bleed jet (can see jet looking down into carb, two of em right together)
I will not be letting fuel dry in carb next winter. And I suspect it will be a few tanks, and maybe another carb cleaning, before I get it all worked out of carb.
Filter should trap anything coming from tank and lines. Is always educational to take old filter and dump out (from inlet side) onto clean paper towl and see what comes out. Other educational thing, take filter off, shake a little w fingers pluggin inlet and outlet, now dump from outlet side. If junk come out, filter aint workin.
Keith

[quizmaster]

Just a little message to close this topic...

Apparently, whatever dirt the idle jet trapped, DID purge out after all.
I've driven 4-5 full tanks since (beginning of June) and apart from the three incidents involving a clogged idle jet hole, it didn't repeat itself anymore.
It's fun, fun fun again !!!

[So Cal Mark]

filling the tank won't purge dirt/rust. You need a high quality filter that will trap dirt down to 1 micron

[sptcoupe]

I've made this comment before in other threads, so I apologize if it is repetitive.

The best filter I have found is the in-line filter from a 1973 Datsun 240Z. There are designed for the fuel injected engine in that car, and to trap dirt to >1 micron. They fit like any other in-line filter, are big, and about $5.00 at any major parts supplier (Autozone, etc).

They are especially effective for IDFs.

[majicwrench]

Filling tank won't purge dirt/rust, but system will get cleaner just from fuel going thru it. My 72 has now purred like a kitten for 1000miles since the last incident. Methinks most of the debris that was causing my issues was in the carb, not coming from the tank. Whatever it is about dried fuel + whatever else was in my carb, it was STUCK to everything. Like I said, I am not going to let the bowl run dry this winter!!
Good hint about the nissan fuel filter!

[quizmaster]

filling the tank won't purge dirt/rust. You need a high quality filter that will trap dirt down to 1 micron

Thanks very much. I will definitely pursue the filter suggestion directly should the idle jet clogging repeat itself.

Quizmaster