Sorry if this is a little long. Just wanted to give some background first.
Ever since I've had my Vette, 1993 - LT1, it's had a hard start
condition after turning off the engine and sitting for an hour or so.
It would always take several seconds of cranking to get it started.
A gas smell was always noticeable too. If it sat overnight or just
maybe 30 minutes, it would fire up immediately. I replaced the
injectors with Bosch III's maybe 3 years ago. It didn't help the
problem. I just learned to live with it. Since then, I've replaced the
optispark, plugs, wires, fuel pump, pressure regulator, icm, etc... Not
because of the hard start problem, but the car had about 140,000
miles on it and was just a good time to do it. I've driven it maybe
5,000 miles since everything was replaced. Runs fine with no problems
other than the hard starting after sitting.

I took it to get an emissions test today. The testing center is about
1/2 mile from my office. The car had been sitting for a few hours and
took several seconds to start as usual. When I got to the testing
center the coolant temp had just hit about 180 deg. Pulled in, got my
test, and failed. HC was at 820 and CO was 1.30. Last year HC was
146 and CO was .34. I thought the higher readings this year might be
due to the fact that the car wasn't really heated up before the test
and it have dumped more gas in because of the hard start?


Brought it home tonight and hooked up the fuel pressure gauge.
Turned on the ignition and it read about 41psi. 10 minutes later, it
read around 30psi. Clamped off the pressure line and the gauge
seemed to leak down a little slower. Not sure if the hose was totally
pinched. Clamped the return line and couldn't tell much difference.
Turned the switch on again and pinched the pressure line. I took the
clamp off the line just a few seconds later. After the clamp was
removed the gauge read about 28psi. Following the chart in the FSM,
I kind of think the pulse dampener on the fuel pump could be leaking,
but I really don't know how long the system should hold a constant
pressure. Since it doesn't drop immediately and there isn't a lot of
difference when either line is clamped, I'm not sure if it is the
injectors, pulse dampener, or check valve in the fuel pump. No codes
either.


I guess I really have two questions. 1. Does anyone think this problem
could have caused the car to give a high HC reading since it really
didn't have time to heat up? 2. What are your comments on the time
it takes for the fuel pressure to leak down?

Thanks for any help.

 

Leaking fuel injectors can cause the hard start you are describing. It should not drop 10lbs in 10 min. I think that is too much.

I would key it up, then pinch off the return line and supply line at the rubber hoses on the tank. Use good hose pinch off pliers. Then try the test again, if it drops off. It is very possible you have leaking fuel injectors.

I would pull the vacuum hose of the fuel pressure regulator and see if it is wet inside the hose as well.

 

Thanks for the response. I did pinch the pressure and return hose off. No real change and still leaks down. Will have a new set of injectors on the way shortly. Just hope that was partly to blame for the failed emissions test too.