Author Topic: 1973 Cheyenne C20 - Start Up Issues  (Read 1338 times)

Offline BADGE73

  • Newbie
  • Posts: 45
  • 1973 Cheyenne Super C20 Camper Special
1973 Cheyenne C20 - Start Up Issues
« on: July 09, 2021, 01:41:46 PM »
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
"Firemen never die, they just burn forever in the hearts of the people whose lives they saved."

Offline Shifty

  • Junior Member
  • ***
  • Posts: 937
  • I bleed Bowtie red...
Re: 1973 Cheyenne C20 - Start Up Issues
« Reply #1 on: July 09, 2021, 02:42:54 PM »
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. 

87 V20 Standard Cab Longbed (current)

87 R30 3+3 Longbed (days of yore)

98 C2500 ext cab longbed

Offline BADGE73

  • Newbie
  • Posts: 45
  • 1973 Cheyenne Super C20 Camper Special
Re: 1973 Cheyenne C20 - Start Up Issues
« Reply #2 on: July 09, 2021, 04:21:41 PM »
So start by checking into the carbs needle and seat?
"Firemen never die, they just burn forever in the hearts of the people whose lives they saved."

Offline Shifty

  • Junior Member
  • ***
  • Posts: 937
  • I bleed Bowtie red...
Re: 1973 Cheyenne C20 - Start Up Issues
« Reply #3 on: July 09, 2021, 05:14:18 PM »
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? 
87 V20 Standard Cab Longbed (current)

87 R30 3+3 Longbed (days of yore)

98 C2500 ext cab longbed

Offline Knochen

  • New Users
  • Posts: 1
  • Newbie
Re: 1973 Cheyenne C20 - Start Up Issues
« Reply #4 on: July 09, 2021, 09:48:40 PM »
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. 

Offline JohnnyPopper

  • Senior Member
  • ****
  • Posts: 2526
  • Old Goof
Re: 1973 Cheyenne C20 - Start Up Issues
« Reply #5 on: July 10, 2021, 01:45:39 PM »
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.
1957 Apache 3100 235 Inline 6, 3 on the tree
1973 C-20, 3+3 454 4BBL TH400  Water Injection
1978 K-10, 350 4BBL TH350 NP203 M.M. Part time Kit/Hubs
1980 C-10 under construction

Offline TexasRed

  • Junior Member
  • ***
  • Posts: 727
Re: 1973 Cheyenne C20 - Start Up Issues
« Reply #6 on: July 10, 2021, 06:50:40 PM »
If this is the original Quadrajets, it may be something like the well plugs leaking and need to be epoxied.