I recently helped my son rebuild the carb on his 73 I6-200 and it now has trouble starting. The car had sat for almost 2 years and had a lot of crud and water in the carb so we soaked it good and blew out all the passages that we could find. The engine will start pretty easily with a squirt of starting fluid and then idles decently. When it is running tapping the throttle does provide a nice squirt of gas but there is no such squirt when the engine is not running. I assume that is why it won't start on its own, no initial fuel in the intake from pumping the throttle. Why wouldn't the accelerator pump work with the engine not running?
If accelerator pump operates with engine running, the only logical reason it isn't when setting is there's no fuel in bowl... If that's the case it should be operating just after engine shutdown...
The engine does not re-start immediately after shut down (without starting fluid) nor does the pump operate at that time. I did find a site that indicates the accelerator pump discharge is from a very small port near the top of the bore but mine is discharging in the main discharge nozzle similar to this pic. But only when the engine is running.
I gotta admit that's a interesting display... But it's showing discharge from venturi booster, not the accelerator pump... That only functions with manifold vacuum, or in other words engine running... Here's the one for for pump function... Usually no "squirt" issues are related to upper pump spring incorrectly installed... Could also be related to problem in discharge circuit(weight, ball, plugged passageway etc)... If inlet check ball is missing the pump won't function...
I saw that same GIF but did not see any fuel coming from there. When the engine is running there is an obvious squirt of fuel as shown on the GIF I posted. This evening I was looking at it again with the engine cold and located the 'pump jet'. I also did discover that there is a small squirt of fuel when I slowly applied the throttle. And the engine started right up after I did that. That jet is further down the throat than I was expecting and my viewing angle might have contributed to me not seeing it earlier. Would the speed at which you depress the gas pedal have any effect on the function of the pump? Wouldn't think so but it is the only thing I did different tonight.
The quicker the throttle is opened the faster the stream should be... I dunno why it works opened slowly, sorta points at linkage/spring or maybe the check ball I mentioned earlier... It's no doubt going to have to be opened again...
Thanks helping me with what to look for. The carb was pretty nasty when I opened it the first time and I may have not gotten something as clean as it should be.
