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73-87 Chevy _ GMC Trucks => Fuel Systems and Drivability => Topic started by: BADGE73 on July 09, 2021, 01:41:46 pm
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Hey Fellas,
My truck has always had a little bit of an issue starting up, usually takes some pumping of the gas and ignition turn before she starts up. However, the other day I went to start it and she acted like she wanted to turn over and then didn't, I tired again and then nothing. It is a brand new battery, so I went ahead and jumped it and that seemed to get her making music again, however still would not crank.
So I did the ol'gas in the carb and after a couple ounces of gas, she started up. Any ideas? Alternator going? I know the carb needs take off and cleaned or replaced. Any help would be greatly appreciated.
Badge
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Start with your "known issues", like the carb. Keep in mind just how evil oxygenated fuel is to olde rubber, and it will also clean your fuel tank, dropping old stuff into the gas, sometimes plugging the pick up screen, It will soften and "melt" the inside of rubber fuel lines as well, so you may have rubber-slime wreaking havoc with your needle and seat.
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So start by checking into the carbs needle and seat?
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If it will start by the "dump gas into the carb" trick, then it's most likely a fuel delivery/management problem. Either you don't have sufficient fuel pressure and/or volume, which can be a few different things, or it's happening at the carb, which could be few things as well.
Have you seen whether or not you have a nice fan spray pattern of gas when you work the accelerator linkage?
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I have a 80 Scottsdale C20 and always have to pump the accelerator maybe 15-20 times if it has sat for just a few days before it starts. I finally just this week purchased an inline electric fuel pump (Cylindrical Solid State Fuel Pump 12V, 4-5.5PSI, 24"m Min Dry Lift 40007N from DB Electrical for $100) to fill the bowls for an easier start. It requires drilling two 7/16" holes in the frame to mount near the tank select valve - the only place it seemed to fit. I have to cut the fuel line to have room to drill the holes which makes me nervous. Hopefully I can cut off the flow of fuel from the tank by pinching off the short 3" rubber hose that connects to the metal fuel line. But then I will need to put on a longer rubber fuel line and how to do that without getting sprayed with gas I haven't a clue. But from what I've seen on Youtube this seems to be a good fix for the problem.
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That's a good start toward finding what the root cause is as it eliminates the mechanical pump as a suspect.
I guess you could leave the mech pump in place, but I would consider bypassing it. Or removal and plating it off.
So that being said, when you have a positive flow to the carb, and you still have to pump several times, you can suspect the accelerator pump of being shot.
You can replace it without removing the carb, just the top plate.
May as well change out the float needle while in there, and adjusting the float level.
This a minor fix, depending on how long it's been since a rebuild, you may consider taking it out for a rebuild.
Another variable is your timing. If these moves don't fix it, look into where your timing is.
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If this is the original Quadrajets, it may be something like the well plugs leaking and need to be epoxied.