| nozzle drip [message #263566] |
Mon, 06 October 2014 11:21  |
appie
Messages: 902
Registered: April 2013
Location: denmark
Karma: 2
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Well maybe not just a drip
I have been looking to fix this for some time and it makes me nut
idle is unstable
vacuum at idle low around 15-17 hg at 800 rpm going over 20 at 1000 rpm
revs rising when i put my hand over the carb
a haze of petrol is coming out of the nozzles at idle
double cheked ignition
carb is flat
can´t find any vacuum leaks
choke opens completly
Any idears anybody?
Appie
eleganza 76 "Olga" now sadly sold
6 wheel discbrake
Quadrabags
Springfield stage 2 462 olds
Manny tranny
( pictures at http://www.gmcmhphotos.com/photos/g6489-olga.html
Fulltiming in Europe july 2014 til july 2016
Denmark
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| Re: nozzle drip [message #263577 is a reply to message #263566] |
Mon, 06 October 2014 12:46  |
An87ttype
Messages: 157
Registered: September 2012
Karma: 0
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Senior Member |
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You can try and adjust the idle screw until you have zero vacuum at the ported spark port on the carburetor. It's the port that goes to the "Cristmas tree" on the front right of the manifold and needs to have no vacuum at idle. If there is zero vacuum there, nothing can get sucked from the nozzles. If your idle is too low at this setting, you may need to advance the timing and mixture a bit. Qjet adjustments can be frustrating, but once set, they are great carbs. I'm no expert, but this has worked on many a Qjet I've had over the years.
Is your vacuum steady at idle? Or jumpy? If its jumpy, you may have a vacuum leak in the manifold by one of the cylinders. This sometimes forces you to adjust the idle too high.
Good luck, it sounds like your having a great trip...
1975 Eleganza II
Hudson Valley NY
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| Re: [GMCnet] nozzle drip [message #263596 is a reply to message #263566] |
Mon, 06 October 2014 15:43 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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Yep, one that is not likely to make you too thrilled. Sounds like classic
timing chain stretch to me. You know the remedy. Verify by removing the
mechanical fuel pump, shine a light into the hole and using a stiff wire
like oxy/acetylene welding rod with a hook bent on the end. Reach in there
and hook the chain. Pull it towards the hole and push it away from the
hole. 1/4" movement is probably ok, 1/2" is not O.K. Ball Park figures
here, there are precision specs. out there but not in the KOA campground
where I presently am. At idle speed the chain snatches and causes irregular
valve, ignition timing, and erratic oil pressure. If it skips a tooth, It's
not a good thing.
Jim Hupy
Salem, Or.
78 GMC ROYALE 403
On Oct 6, 2014 9:21 AM, "lenze middelberg" wrote:
> Well maybe not just a drip
>
> I have been looking to fix this for some time and it makes me nut
>
> idle is unstable
> vacuum at idle low around 15-17 hg at 800 rpm going over 20 at 1000 rpm
> revs rising when i put my hand over the carb
> a haze of petrol is coming out of the nozzles at idle
>
> double cheked ignition
> carb is flat
> can´t find any vacuum leaks
> choke opens completly
>
> Any idears anybody?
>
> --
> Appie
> eleganza 76 "Olga" ( pictures at
> http://www.gmcmhphotos.com/photos/g6489-olga.html
> Volvo v70
> Denmark
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
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| Re: [GMCnet] nozzle drip [message #263604 is a reply to message #263596] |
Mon, 06 October 2014 18:21 |
Bullitthead
Messages: 1411
Registered: November 2013
Karma: 5
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Senior Member |
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Increasing rpm when holding hand over carb means that the system is running lean. Hand over carb is same as applying choke, which richens the mixture. Must be a small piece of dirt in one of the fuel passages. Sometimes you can clear it out with very strong vacuum by running the engine fast (about 2500 rpm) and fully closing the choke or using your hand to block the airflow and the high vacuum may pull the blockage through the passage. If that doesn't work, take the carb off and clean the passages with compressed air from the opposite direction of normal flow. You can tell which side is blocked by adjusting the idle screws and the one that does not make a difference is the blocked side. Sometimes removing the idle screw and applying compressed air to the screw bore can clear it, or possibly shoot some carb cleaner in there to dissolve the dirt and then replace the screw and start her up. Be careful with the compressed air, don't do that operation with the engine running.
Terry Kelpien
ASE Master Technician
73 Glacier 260
Smithfield, Va.
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