Hard Starting

[Edwin Ek]

Hello All,

Need some advice about a difficult-to-start car. Here's the background: '73 S with motor rebuilt about 10K miles ago, 2.2 S pistons and cyliners, Gus Pfister rebuilt mechanical fuel injection pump. Otherwise stock.

Starts great when cold, starts great after sitting for an hour or more, starts great after sitting for a minute or two. However, tough time starting when sitting for 10 minutes to an hour-- the time you would spend running into a store.

When I try in the dead zone, it always fires and almost catches, but never does. Then it just cranks and cranks. Interestingly, because of this difficult starting routine, I bought a Jump-N-Carry jump starter (what the AAA guys often use). When I hook that up, the car cranks a little faster, and then it starts after 30 seconds or so. It makes me think there is some sort of vapor lock nonsense, and the higher cranking speed overcomes that.

Thoughts and suggestions for how to fix?

Thanks,
Ed

[Flieger]

Mine does that sometimes. I put it down to my lack of a thermostat. The car is set up for warm operation so the mixture is too lean to start easily, but the cold start injectors do the trick. I believe they are activated by the thermal time switch on the fuel filter console. In that 10-60 minute time, that switch is not sending the squirt of fuel to the injectors, so the MFI pump is giving too lean a mixture to start since the screw does not cool off like a thermostat would.

That's my theory anyway. Your car may be better with a thermostat.

[edmayo]

Since it starts fine when cold I would assume the cold start system is intact, and on a 73 there is always a squirt of fuel of different duration through the cold start nozzles depending on engine temperature up to about 100 degrees F. This is controlled by a thermoswitch on the breather housing, that may be your culprit.