Have a 71 with a 351C 2v. Replaced the leaking fuel pump and now the car starts fine at first startup of the day, but if it sits for an hour or two (at lunch or at a car show), it is very hard to start, I have to keep pumping the gas to get it to start. Never needed to do this with the previous pump, even when it was leaking. It isn’t heat soak as this just started and the weather is cool with the temp gauge all the way down. Can anyone offer insight?
At least it isn’t leaking anymore…
Your fuel pump has very little to do with hard starting issues. There should still be plenty of fuel in the bowls of your carb, as it won’t have had time to evaporate. Even if your pump is not working, if there’s gas in the carb bowls, it should start and run.
So that leaves only a few other fuel-related issues. It sounds like you probably ruled out two of these:
If there is a fuel leak and gas drips out of the bowls while it sits, you may have to crank for a while in order for the fuel pump to refill the carb!
Also, while I do agree that in cold weather with a cold engine, percolation is unlikely, with modern gasohol, there are often problems with the fuel boiling. You can hear this if you stop your car after driving it for a while, and lift the hood. You may also see fuel shooting out the carb vents as it boils, if you take off the air cleaner lid. Using a phenolic spacer to insulate the carburetor from the intake may help, and there are other tricks you can use to try and keep your fuel system cooler.
With your need for fuel enrichment however, I’m thinking this is just a simple adjustment needed for your carb: The choke is misadjusted, and stuck wide open. It would explain your cold start woes, and need for extra pumping!
Grim, thanks for the reply. This didn’t happen with the old leaking pump, it was as soon as the new one was installed this began. I didn’t think much of it as the car started right up after installation and then I didn’t drive it for a few days as the weather was bad. So in troubleshooting, looking at the very last thing that changed prior to the issue, it was the pump replacement. I had it out today and just sitting for 15 minutes will produce the issue, yet if I get gas, it starts right up.
I did hook up a vacuum gauge to make sure the carb screws were set correctly and they are.
I’ll go back and check routing of the fuel lines.
Next time your in the situation you are describing this happens in, remove the air cleaner lid, look down in to the carburetor and hand pump the throttle or have somebody do so from in the car. If you do not have gas squirting out of the accelerator pump nozzles then you know you have no gas in the float bowl. While new parts sometimes are not any good, I’m thinking Grim is on the right track.
Better check your coils output. Might be bad after motor cools a little.
Update: well not much of one. Still have the issue. Carb squirts fuel when hitting the throttle so the bowls aren’t draining. Pointed an IR thermometer into the carb and it was 115F internally, 107F on the outside of the bowl. I dont think that is hot enough for evaporation and boiling. Air temp was 75F.
If I go out the next day, two pumps and car fires right up.
Drive the car for a while, shut it off and get gas, fires right up. Drive it for a whie, turn off, go into the drug store for 10 minutes, car will spin over for 8 seconds then gradually catch and fire up, then its fine unitl I need to shit if off again for longer than 3-5 minutes
During the heat of the summer I never had this issue so I still dont think it is vapor lock or boiling.
John, perhaps this is an issue with HOW you are starting the car when warm?
When cold, you need some enrichment, so you need to step on the gas at least once to put a squirt of fuel down the throat (which also sets the choke and flips it closed if it’s not already).
But when warm, your choke should be open already. Does it need more enrichment? Pumping the gas more than once might be necessary. If it’s set a bit rich at idle, it may already have too much, and your best option would be to push the pedal down (which yes, will squirt) but then hold it there so more air can get in. As it catches, you can let off.
Experiment! Pumping the pedal adds fuel, holding the throttle open to different positions will let more or less air in. Once you find what your engine “likes” you can duplicate the process.
Ford usually recommended one pump, then holding the throttle 1/4 open on warm start, if I recall correctly.
Here’s a link to the repro start instructions that were attached to the sun visor of new cars
Thank you Pacifica, I do have those instructions from the original owners manual.