Hard to start after 2 days, fuel drain is possible. Why?

Yes, once running, the slightest covering of the carb will choke the motor out, so that is not expected.

SE Georgia, it was probably 68-72 degrees. The reason I question spark is my tach was very erratic. Not slowly moving 150-200 RPM, but immediate jumping like something was signaling shut off and then back on. I did notice this several times recently, but now am paying more attention to it.

The tach needle moves quicker than a motor will change speed erratic. I wanted to add this line...

I know you ask this to Mark, but once I start driving my car, it has no issues with hesitations. Vary smooth if the gas pedal motion is smooth.





Mike

 

the tach works normally when everything is warmed up?

 

Yes, no erratic behavior.

 

Did this combination ever start well and if so, this is a new problem?

 

It used to be a whole lot better. If the car sat for a week or two, it may take 5-6 seconds of cranking and then I would stop. Then I would depress the throttle twice and it would start within 3 seconds after that. And I did not have the erratic tachometer readings. I could bring up and hold the idle near 1800 - 2000 RPM and it would slowly vary 100-150 RPM as the motor would surge over several seconds as expected. After 60 - 90 seconds, the car would idle on its own.



Currently, after the car is warmed up and I have driven it around, I can hit the key for less than 2 seconds and will idle all on its own with no need for accelerator movement.




Mike

 

Any way to post a video of the event happening? It sounds lean to me.

 

Not only would there be a drain, but it will siphon fuel when running.

 

Of the tach behavior?

I may be able to do that tonight after I get home, it will be late though.



Mike

 

Yes

 

Dry cranking as a habit is horrible way to kill an engine. I gave up on this problem years ago (had the carb open in December 2015 for the first time in 20 years and saw no evidence leakage past epoxied plugs). The fuel evaps off after two days (a function of formulations made for fuel injection). I use maybe two cans of starting fluid a year driving the car Saturdays most weeks. Spritz yer carb and go.

 

No, after a couple of days, with the air cleaner off, show the pump shot by pumping the throttle twice and having your phone or camera recording over the air horn so we can see it. Next, have a helper crank the engine while you "man the throttle" to keep it running and you can run the camera or have a 3rd person do that. It's so hard to know what everyone's skill sets or tuning abilities are on the internet.

 

Can do.

I will wait until Monday to do this. I am working out of town this weekend and gives me the perfect opportunity to give it a few days. Monday evening will be 5 days sitting.






Mike

 

can you elaborate? isnt it dry either way until it builds oil pressure?

 

yes badbrad, please elaborate.. instantly firing the engine with little to no oil in the rod bearings vs. turning it over with the starter is worse how? pounding the crank journals against the bearings with no oil cushion vs the pressure of the compression stroke only? even if for only 8 seconds? how can that possibly be?

 

An engine that instantly fires should have enough of an oil film on the bearing surfaces to provide adequate lubrication until pressure builds.
Feather the throttle if it does fire right away until pressure builds.
DO NOT hammer the throttle:shock:
When I start my GS cold, you can hear if pressure has been established without looking at the gauge, you can hear the mains bang bang bang very lightly, it doesn't happen often, but when it does its not doing any damage as I'm not hammering the throttle.
Every new LS powered truck we have in the shop does the same thing after initial fire, DRAAAAAP
I can tell when somebody is moving a Silverado or Tahoeou:

 

Just a couple things to add: ethanol fuel evaporates faster than pure gasoline. Also, the qjet bowl is small and when shutting off hot the evap process is sped up.

Also, there are qjet fuel filters that have a anti-siphon check ball in them. They help but may reduce flow at WOT.

 

OK, got the SunCoupe out today. Pushed it out of the garage to get better lighting and used my iPhone to video the action. I uploaded the videos on YouTube for you to watch. I hope I got good enough angles. I believe I see fuel squirting when first attempting to start the car.

I went into the car to start again to show the tach operations. You can see some erratic behavior, but it has been worse before at times.

I let the car sit for about 10 minutes after the first video. I did keep it running for maybe 30 seconds longer in the video. After the 10 minutes and the heat moved through the motor, I turned the key and within a second it was idling on its own without touching the gas pedal.

Then I did another video after pulling the car back into the garage to choke the carb checking if it appears to have a vacuum leak and it does not seem to me to be an issue.


Starting test

https://youtu.be/7UqwuSYtMiM


Vacuum test

https://youtu.be/vI4HsleLFek

 

Next time you go to start it cold--- pump the accelerator to the floor 5 times, and hit the key.

It should fire.. if it does, but does not start, do it again.

What I see there is normal cold starting with no choke on a Q-jet.. they can be really cranky.




JW