Carb To Rich? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

bosco200 · 01-11-2011, 12:32 PM

250 inline monojet carb......When I start my truck in the morning to warm up ill go inside and comeback out in about 15 minutes and the gas gauge has dropped this much seen in pic...............its not leaking gas ive checked but it does smell like gas really bad outside my truck...its like its not burning it?

**Wrenchbender Ret** · 01-11-2011, 01:15 PM

The photo looks like a speedo but I get the picture. Check to see if the choke is going off. After it runs for a few minutes the choke blade should be straight up & down.
Check the link from the throttle shaft to the metering rod. They are nortorious for falling out on the early MJ's leaving the metering rod in full rich position. If all that is good you should put a kit in the carb & make sure the float is good & the metering rod is adjusted right. You should also make sure the timing is correct & the vacuum advance is working.

bosco200 · 01-11-2011, 01:37 PM

Yea I didn't have a pic of my gas gauge but the spacing is the same on them...the timing i correct and the choke is electric and if I'm driving it drives fine but still sucks a lot of gas but once I push my clutch in it will start to run at higher RPM

**Wrenchbender Ret** · 01-11-2011, 01:53 PM

If it's a gas smell & not exhaust you must have a leak. Look at the fuel pump while it's running. They can pump gas out the vent holes. I see the markings on the gauge now. Mine drops about that much or a little less on a 20 mile drive to the shop in about 25-30 minute's.

cdowns · 01-11-2011, 02:04 PM

oopps postd twice

cdowns · 01-11-2011, 02:05 PM

under the passenger side cab of the truck theres a rubber section of hose connecting the tubing from the cab to the tubing that goes up the frame to the gas pump// that rubber section sometimes dryrots and leaks

pull a sparkplug or two out and read it to see if carb runs rich

Jacfourteen · 01-11-2011, 03:55 PM

Quote:

Originally Posted by cdowns

under the passenger side cab of the truck theres a rubber section of hose connecting the tubing from the cab to the tubing that goes up the frame to the gas pump// that rubber section sometimes dryrots and leaks

pull a sparkplug or two out and read it to see if carb runs rich

If there was a leak there wouldn't it leak when not running, then when it was running it would suck air causing it to run lean/vapor lock?

Jacfourteen · 01-11-2011, 03:58 PM

If there is no visable leaks I would suspect the choke isn't opening or you have a clogged/stuck needle and float. Also if it smells that rich, check the oil to see if it has a gas smell to it. If so change out the oil asap and get the problem fixed, otherwise you will wash cylinders and scuff them up.

bosco200 · 01-16-2011, 02:26 PM

Ok I got another question....My carb has an auto choke on it and it starts up great and warms up but i doesn't seem like the choke shuts off because I can be driving and when I come to a stop and push my clutch in my truck will rev up and stay at a higher rev than usual...is that a choke problem?

bosco200 · 01-16-2011, 11:39 PM

cmon anybody?

69gmc292 · 01-17-2011, 11:31 AM

I had the same problem with my 292. I found out that the auto choke was staying closed to long causing the engine to run too rich when it is cold. I had to cut and turn the thermo element on the auto choke to adjust the temp that the choke opened.

coloradosean2009 · 01-17-2011, 06:53 PM

Quote:

Originally Posted by Jacfourteen

If there was a leak there wouldn't it leak when not running, then when it was running it would suck air causing it to run lean/vapor lock?

Unless the leak is in the return line.

**Wrenchbender Ret** · 01-18-2011, 11:12 AM

Quote:

Originally Posted by bosco200

Ok I got another question....My carb has an auto choke on it and it starts up great and warms up but i doesn't seem like the choke shuts off because I can be driving and when I come to a stop and push my clutch in my truck will rev up and stay at a higher rev than usual...is that a choke problem?

First make sure the throttle is returning to the idle position & not sticking open a little. These engines used some weird choke systems through the years, till they put the electric choke on them. That is the only one that works right. Some had a wire coil wrapped around the shaft of the choke pulloff. The theory was that the therm. coil would have enough tension to overcome that spring. In cold weather the that didn't happen & caused the condition you describe. I used to cut about half of the coils out of the spring on the choke pulloff & that would cure it. You will have to experament with adjustments till you get it right. Sometimes you can make a shield to keep the cold air off the choke coil.

Jacfourteen · 01-18-2011, 04:54 PM

Quote:

Originally Posted by coloradosean2009

Unless the leak is in the return line.

Do the I6's have a return line?

**Zeke's Garage** · 01-18-2011, 05:01 PM

Quote:

Originally Posted by Jacfourteen

Do the I6's have a return line?

There is a vent line that runs back to the charcoal cannister. My buddy's '72 had a split hose on the vapor line and it would leak a bit if he filled the tank too full.

And yes, if the choke is stuck closed and the cold idle cam step dealie on the carb is still engaged, it will cause the idle to be too high. Usually you can blip the throttle and it will settle down, if everything is working correctly and the choke has opened up all the way.

Something's probably sticking in the choke linkage.

01-11-2011, 12:32 PM	#1
bosco200 Registered User Join Date: Dec 2009 Location: Ste. Genevieve, MO Posts: 526	Carb To Rich? 250 inline monojet carb......When I start my truck in the morning to warm up ill go inside and comeback out in about 15 minutes and the gas gauge has dropped this much seen in pic...............its not leaking gas ive checked but it does smell like gas really bad outside my truck...its like its not burning it? Attached Images Last edited by bosco200; 01-11-2011 at 12:33 PM.

01-11-2011, 01:15 PM	#2
Wrenchbender Ret Registered User Join Date: Oct 2005 Location: Overland Park, Ks. Posts: 5,194	Re: Carb To Rich? The photo looks like a speedo but I get the picture. Check to see if the choke is going off. After it runs for a few minutes the choke blade should be straight up & down. Check the link from the throttle shaft to the metering rod. They are nortorious for falling out on the early MJ's leaving the metering rod in full rich position. If all that is good you should put a kit in the carb & make sure the float is good & the metering rod is adjusted right. You should also make sure the timing is correct & the vacuum advance is working.

01-11-2011, 01:37 PM	#3
bosco200 Registered User Join Date: Dec 2009 Location: Ste. Genevieve, MO Posts: 526	Re: Carb To Rich? Yea I didn't have a pic of my gas gauge but the spacing is the same on them...the timing i correct and the choke is electric and if I'm driving it drives fine but still sucks a lot of gas but once I push my clutch in it will start to run at higher RPM

01-11-2011, 01:53 PM	#4
Wrenchbender Ret Registered User Join Date: Oct 2005 Location: Overland Park, Ks. Posts: 5,194	Re: Carb To Rich? If it's a gas smell & not exhaust you must have a leak. Look at the fuel pump while it's running. They can pump gas out the vent holes. I see the markings on the gauge now. Mine drops about that much or a little less on a 20 mile drive to the shop in about 25-30 minute's.

01-11-2011, 02:04 PM	#5
cdowns Senior Member Join Date: Jan 2003 Location: daytonabeach Posts: 22,956	Re: Carb To Rich? oopps postd twice __________________ 71c-10 350/2004r/4:11 lowered3/4 longbed/dead by hurricane MEANING OF DEATH::::: SOMEBODY ELSE GETS YOUR STUFF DONT BELIEVE EVERYTHING YOU THINK TAKE MY ADVISE;I DON'T USE IT ANYWAY Last edited by cdowns; 01-11-2011 at 02:06 PM.

01-11-2011, 02:05 PM	#6
cdowns Senior Member Join Date: Jan 2003 Location: daytonabeach Posts: 22,956	Re: Carb To Rich? under the passenger side cab of the truck theres a rubber section of hose connecting the tubing from the cab to the tubing that goes up the frame to the gas pump// that rubber section sometimes dryrots and leaks pull a sparkplug or two out and read it to see if carb runs rich __________________ 71c-10 350/2004r/4:11 lowered3/4 longbed/dead by hurricane MEANING OF DEATH::::: SOMEBODY ELSE GETS YOUR STUFF DONT BELIEVE EVERYTHING YOU THINK TAKE MY ADVISE;I DON'T USE IT ANYWAY

01-11-2011, 03:58 PM	#8
Jacfourteen Big Red - Now its a SWB! Join Date: Jun 2009 Location: Oroville, Ca Posts: 1,624	Re: Carb To Rich? If there is no visable leaks I would suspect the choke isn't opening or you have a clogged/stuck needle and float. Also if it smells that rich, check the oil to see if it has a gas smell to it. If so change out the oil asap and get the problem fixed, otherwise you will wash cylinders and scuff them up. __________________ 68 3/4 ton (Project)-350 Small Block, .030 over, 10:1 comp, 3998993 heads, C3BX edelbrock intake, comp cams XE268, Holley 670 SA, long tube headers, dual flow 40's, E-fan, Alum rad, currently under the knife getting shortened and bagged build thread 41 3/4 ton (wife's)-flatbed, fully restored to original 01 Tahoe LT 4WD (my daily driver)-Magnaflow Muffler, Rollin on 22's 02 Ford Mustang Convertable (Wife's Car)-Flowmaster 50, Clear corners, Intake, sittin on 18's

01-16-2011, 02:26 PM	#9
bosco200 Registered User Join Date: Dec 2009 Location: Ste. Genevieve, MO Posts: 526	Re: Carb To Rich? Ok I got another question....My carb has an auto choke on it and it starts up great and warms up but i doesn't seem like the choke shuts off because I can be driving and when I come to a stop and push my clutch in my truck will rev up and stay at a higher rev than usual...is that a choke problem? Last edited by bosco200; 01-16-2011 at 02:27 PM.

01-16-2011, 11:39 PM	#10
bosco200 Registered User Join Date: Dec 2009 Location: Ste. Genevieve, MO Posts: 526	Re: Carb To Rich? cmon anybody?

01-17-2011, 11:31 AM	#11
69gmc292 Registered User Join Date: Mar 2007 Location: tucson Posts: 71	Re: Carb To Rich? I had the same problem with my 292. I found out that the auto choke was staying closed to long causing the engine to run too rich when it is cold. I had to cut and turn the thermo element on the auto choke to adjust the temp that the choke opened.



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