So I can't figure this out. I'm hoping one of you guys can help me. After my '73 Chero 500 has been sitting for a day or two, I will go to start it and it will crank and crank but it acts like it is not getting any gas. If I shoot a short burst (1/2 a second spray) of starting fluid or carb cleaner into the intake and then crank it, it fires right up and runs great. Any ideas?
First thing that comes to mind is the accelerator pump in the carb. Tomorrow morning, before trying to start it the first time, remove the top of the air cleaner, manually hold the choke plate open, and work the throttle linkage once. You should see two healthy squirts of gasoline [one in each primary bore]. If there's no accelerator shot, then it's time to rebuild the carb. It either has a worn pump diaphragm or perhaps it has leaked all the fuel from the bowl overnight. If you do have a good accelerator shot, then I'd suggest that you go through the ignition system -- may be too weak to fire a cold engine on just gasoline. And then maybe do a compression test on it.
More likely that the carb is leaking internally into the manifold where it evaporates leaving no fuel in the float bowl. Time for a rebuild. If you're interested in joining Capitol Rancheros truck club, shoot me a pm and I'll give you the details. Jax
Any ideas? >ring +++++++++++++++ I'll just add one more comment, hope this doesn't insult anybody. It may be that in this modern age of EFI motors, people don't really understand the right way to start a carburetor car. The expectation goes like this: pump the gas pedal all the way to the floor, once, and let it up somewhat slowly, THEN try the starter. This protocol is required to allow the automatic choke to fully close, and gives it an initial shot of raw gasoline, and it also allows all that linkage to set the fast-idle cam up so it will run fast for a bit. Then, once it's running [and it should fast idle with no further action] -- give it a little gas pedal, and let off again. This action lets the 'vacuum pulloff' gizmo on the carb open the choke plate a bit, and simultaneously back off the fast-idle cam by a bit. It should still [ideal setup!] continue to idle, just not quite as fast as before. Each time you operate the gas pedal it provides an opportunity for the auto choke to release a bit more, which will also slow the fast idle. By maybe 4 - 5 minutes of running, the choke should be fully open and idling at expected warm-idle speeds. Hardly any carb works ideally, but that above is the way it is supposed to work. And of course, this discussion assumes it's still the stock carb.
Thanks for the input guys. It is the stock 4bbl carb. I already knew the bit about operating the choke, but thanks. The choke seems to work fine.
rumor has it that the stock 2bbl will even run with the top off? but i think you need to replace the center stud to close off a vacuum leak. >2seater ++++++++++++ Yeah, they will, but there's a huge pucker factor when you do that. The top plate is what keeps the float pin in place, and if not restrained it'll float right out of the seats that constrain it, and then you've got raw gasoline running down the sides all over the hot motor. Not recommended at all. I think I have seen that [removing top plate on a running motor] in a Ford book, recommended as a way to check the actual fuel level in a running motor. I agree with you about a Motorcraft carb not leaking gas out of the bowl, but Holleys surely will.
I have the exact same problem with my "stock" 4-barrel carburetor on my '73 GT 351c. As it was explained to me, that square horn looking thing at the top of the carburetor goes directly to the bowl. After stopping the engine, the gas starts to evaporate through it. With the engine not running to replace the gas, the level decreases and the float opens allowing the gas in the line to flow all the way back to the tank. Later when you go to start the engine, there's no gas in the carburetor, so you have to crank the engine longer to pump the gas all the way back up from the tank and refill every thing. I have a semi-transparent gas filter on the fuel line and while it isn't immediate, after shutting off the engine the gas in the filter disappears. It's the combination of the gas evaporating in the bowl and the line draining back to the tank that causes the hard starting.
That's what I thought was happening, especially since my driveway is up hill, but even if I let it crank for 10 or 20 seconds, it doesn't fire. Is there any way to stop it? BTW, my accelerator pump is working fine.
That's what I thought was happening, especially since my driveway is up hill, but even if I let it crank for 10 or 20 seconds, it doesn't fire. Is there any way to stop it? >ring +++++++++++++ Uhmmm ... Mike's theory is very plausible, except that I'm near certain there's a check valve in the fuel pump -- necessary to the design** -- that would prevent that if it were not leaking??? So, maybe a new fuel pump is the answer. BTW, 15 - 20 seconds isn't nearly long enough to crank fuel all the way from the tank to the carb bowl. The pump will get many more strokes than from cranking in just a few seconds of running. Which reminds me I need to change the pump on my car -- gradually replacing all the old stuff for reliability reasons. I wonder if electric pumps will allow reverse flow? **has to seal in that direction when the cam strokes the pump diaphragn -- so the pump can suck more from the tank. There's also a check valve on the inlet side of the fuel pump. Think both are closed at rest, but they could be leaky. Now that I look, I see lots of reports on the web claiming fuel drains back into the tank while the motor is off.
All that I've used don't. And all that I used required a fuel return line to the tank (and don't use the vent line to do it).
carburator trouble I have the had the same problem on my 60 t-bird was a easy fix, added a in-line electric fuel pump that when I turn the key on it fills my fuel line in seconds and the car starts on the first try.
All that I've used don't [bb: allow reverse flow]. And all that I used required a fuel return line to the tank (and don't use the vent line to do it). >72gtva +++++++++++ Uhhh ... return from what? You use some sort of EFI-style pressure regulator, or ??? Got a part number?
If you believe the engine driven fuel pump is weak or non-functioning, I'd say replace it. Also, if you still don't have enough fuel pressure, add an inline electric fuel pump just forward of the fuel tank. I did that on my '78 because the fuel would leak back into the tank. Now, if she has sat for a couple days without running, I turn on the key for 20 ~ 30 seconds to let the pressure in the fuel lines build up some, then depress the gas pedal to the floor once and let it up and start the engine. Works pretty good. Good Luck Bob Jones
Thanks Bob, I have found that's what works. I just get a little tentative about letting a starter crank for that long.
Bob has an electric pump that he is allowing to run for those 30 or so seconds before he ever cranks the starter. With fuel pumped up to the original fuel pump his Ranchero starts almost instantly without grinding his starter. The factory style pumps have check valves built into them that can wear out or get held open by a tiny bit of grit. I'd replace your pump and add a good filter in the hose that connects the pump to the gas line on the frame.
For a electric fuel pump, I would go with the holley blue electric fuel pump. This pump is very easy to install, and pretty fair priced. This is the one that I have on my 72, and after having this on my car for the past 5 months, I would never go back to a diaphragm pump. You have to think of it this way, with a mechanical pump, you are pumping fuel through a pump which is pretty much the same temp of your motor causing your fuel not to be put in a mist as well as cooler fuel would be resulting in the loss of some power. Tomorrow, or when I get a chance I will take a pic of my setup. Dave http://www.summitracing.com/parts/HLY-12-802-1/
Well as for wiring it up, if you wanted to take the easy/ lazy way you could just wire it up to a keyed ignition source. But if you want to do it the safer way like me which is also easier on your electrical, get yourself a four pin relay and wire it up to that. Also another good idea would be to get yourself a oil pressure switch that shuts off the fuel pump if your oil pressure cuts out. I brought one for mine, but I haven't gotten around to wiring it up yet, and I really should as this is a safety item that would prevent your fuel pump from running on if you had a under hood fire, or flipped your car. I will try to get those pics for you soon. Dave
