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Join Date: Jun 2009
Location: Santa Fe, NM
Posts: 1,035
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1948 Chev Pickup Mystery Tune-Up Questions
The engine, I believe, is a 235 straight 6 from a 1960 truck, with a very simple one-barrel carb.
It's been running fairly well until recently. Just this past week it started acting funny. Awhile ago, I went through the carburetor and put in new gaskets, etc. And it ran just fine after putting it all back together. Recently, it acts like it is running out of gas. It starts easily with full manual choke, then idles nicely with the choke pushed in to the off position. If I abruptly push the gas, it dies. But I can get it to rev up if I tap-tap-tap the gas. It revs better with the choke on. It all feels like fuel starvation, but I'm not sure from where. Today I replaced the in-line fuel filter, but no change in symptoms. I don't think it's the fuel pump, either, because the symptom of over lean is instant when the gas pedal is pushed. I thought one of the cylinders might not be firing, but all the plugs look just fine. I guess it's the carb. But am not sure what to check next or what to do. Please let me know if you have any diagnostic advice. thanks,
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Scot 78 911SC coupe, sold,, 2019 Macan S "my friends all drive Porsches, I must make amends.." |
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05-08-2010, 06:49 PM
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Somewhere in the Midwest
Join Date: Oct 2001
Location: In the barn!
Posts: 12,499
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Did you fill up the tank recently? Try pumping the gas into a glass and see if it's clean.
I had dirty fue. After a fill up once in my 911 and it behaved somewhat like you described. The fill filter would load up and limit the fuel rate. |
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05-08-2010, 07:37 PM
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Petie3rd
Join Date: Jul 2000
Location: Philly PA
Posts: 4,528
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it sounds like the accelerator pump is either not connected or has a an internal leak or the outlets are clogged. Remove the aircleaner and operate the throttle see if gas squirts into the the intake by pushing the throttle if not then you have your answer, next would be to take the carb apart and inspect it .
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^^^ Stan ^^^ 2019 BMW K1250 GS 2016 HD RK 1988 S4 Auto , Elfenbein Perlglanz, Pearl Gray 1982 5sp Met black and tan sport seats |
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05-08-2010, 07:50 PM
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Registered
Join Date: Nov 1999
Location: Herrin Ill USA
Posts: 1,611
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I've found that on carbed cars that do this, if you rev it up and hold it, pul the choke on full, then turn the choke off, and don't let the engine die it will usuaully suck whatever is clogging it up on through.
When the choke is on, flloorboard it and hold it, it will try to die. Turn the choke off and keep it floorboarded until the engine starts revving up on it's own, and clears the flooding. Repeat as necessary.
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Brent Early85 944 LM6Y Paint Code |
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05-09-2010, 06:51 AM
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Registered
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dirty needle/seat?
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poof! gone |
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05-09-2010, 07:25 AM
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Senior Member
Join Date: Jun 2000
Location: N. Phoenix AZ USA
Posts: 28,943
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Does sound like its running out of gas. The "tap tap tap" thing is getting the thing to rev up using the Accy pump, but the main jets are probably low on fuel.
I would pull the top of the carb off and see what it looks like in there.
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2013 Jag XF, 2002 Dodge Ram 2500 Cummins (the workhorse), 1992 Jaguar XJ S-3 V-12 VDP (one of only 100 examples made), 1969 Jaguar XJ (been in the family since new), 1985 911 Targa backdated to 1973 RS specs with a 3.6 shoehorned in the back, 1959 Austin Healey Sprite (former SCCA H-Prod), 1995 BMW R1100RSL, 1971 & '72 BMW R75/5 "Toaster," Ural Tourist w/sidecar, 1949 Aeronca Sedan / QB |
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05-09-2010, 07:29 AM
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Southern Class & Sass
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As stated earlier, it's the acc. pump.
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Dixie Bradenton, FL 2013 Camaro ZL1 |
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05-09-2010, 08:42 AM
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Feelin' Solexy
Join Date: Oct 2003
Location: WA
Posts: 3,786
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Another vote for accelerator pump. You should be able to take off the air cleaner, look down the barrel of the carb and see the pump put a healthy spray down the barrel when you manipulate the throttle by hand.
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Grant In the stable: 1938 Buick Special model 41, 1963 Solex 2200, 1973 Vespa Primavera 125, 1974 Vespa Rally 200, 1986 VW Vanagon Syncro Westfalia, 1989 VW Doka Tristar, 2011 Pursuit 315 OS, 2022 Tesla Y Gone but not forgotten: 1973 VW Beetle, 1989 Porsche 944, 2008 R56 Mini Cooper S |
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05-09-2010, 09:03 AM
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Registered
Join Date: Apr 2001
Location: Linn County, Oregon
Posts: 48,513
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Quote:
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"Now, to put a water-cooled engine in the rear and to have a radiator in the front, that's not very intelligent." -Ferry Porsche (PANO, Oct. '73) (I, Paul D. have loved this quote since 1973. It will remain as long as I post here.) |
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05-09-2010, 10:41 AM
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Alii&Maui
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Check that the vaccum/machincal advance is working in the distributor.
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05-09-2010, 01:49 PM
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Registered
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Maybe a vacuum leak, just had almost the same symptoms albeit on a 4.2 liter 6. It will run a little lean because of the vacuum leak and when the throttle plate opens it goes too lean to run, tapping on the gas will dribble a little extra fuel then it catches up.
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A nose heavy airplane flies poorly, a tail heavy plane flies once. |
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05-09-2010, 08:15 PM
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Registered
Join Date: Jun 2009
Location: Santa Fe, NM
Posts: 1,035
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Hi y'all
It was a little gob of silicone goo that broke loose and stuck in the main jet. Somebody... not me.. fixed the gasket with silicone sometime in the past. then,, I must admit here,, I might have been a little lax on my clean-up during the last rebuild.. oopsies! runs fine now.. life is good.  S.
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Scot 78 911SC coupe, sold,, 2019 Macan S "my friends all drive Porsches, I must make amends.." |
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05-09-2010, 09:53 PM
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Registered
Join Date: Apr 2001
Location: Linn County, Oregon
Posts: 48,513
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Happy endings to problems are always good!
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"Now, to put a water-cooled engine in the rear and to have a radiator in the front, that's not very intelligent." -Ferry Porsche (PANO, Oct. '73) (I, Paul D. have loved this quote since 1973. It will remain as long as I post here.) |
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05-09-2010, 10:28 PM
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Feelin' Solexy
Join Date: Oct 2003
Location: WA
Posts: 3,786
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Glad to hear you figured it out! There is something uniquely satisfying about working on a car where everything is mechanical, no computer BS... this linkage does this and the device should do that. The more I work on modern cars, the more I yearn for my old '73 VW bug
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Grant In the stable: 1938 Buick Special model 41, 1963 Solex 2200, 1973 Vespa Primavera 125, 1974 Vespa Rally 200, 1986 VW Vanagon Syncro Westfalia, 1989 VW Doka Tristar, 2011 Pursuit 315 OS, 2022 Tesla Y Gone but not forgotten: 1973 VW Beetle, 1989 Porsche 944, 2008 R56 Mini Cooper S |
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05-10-2010, 04:27 AM
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Parrothead member
Join Date: Jul 2003
Location: Monmouth county, NJ USA
Posts: 13,829
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Quote:
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Vinny Red '86 944, 05 Ford Super Duty Dually '02 Ram 3500 Diesel 4x4 Dually, '07Jeep Wrangler '62 Mercury Meteor '90 Harley 1200 XL "Live your Life in such a way that the Westboro Baptist Church will want to picket your funeral." |
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05-10-2010, 10:32 AM
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Registered
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Way cool! I am glad you figured it out.
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A nose heavy airplane flies poorly, a tail heavy plane flies once. |
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05-10-2010, 10:34 AM
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My Camaro
911SC
1979 Porsche 911SC
