Pop and now No Start

[1983 911SC]

Took our 1983 911SC to the hardware store and she ran great like she always has. Never a cough or a sputter from the 105K mileage 3.0L. Always runs flawlessly.

Parked her for 90 minutes and then went to continue some errands. While starting she popped and now won't start. The engine ignites but doesn't continue to run. The"pop" was not a loud back fire, something much less, but definitely a "pop". Let her sit for a while and then tried again, same scenario. Not sure were to start the troubleshooting. Any ideas?

[ninelevenick]

I would poke around the engine compartment to make sure all connections are secure. Also, swap the fuel pump relay with a another one in your fuse panel.

[RSBob]

Remove the air cleaner and filter to see if your pop off valve is stuck open, if you have one. It may also have blown out of place and will need to be secured back down until it can be epoxied.

[pete3799]

Check that the pop off valve in the air box is seated..... if you have one.

[RSBob]

Yeah, what Pete said .

[McLovin]

You have a vacuum leak somewhere.

[SalParadise]

Probably blew the box if there is no pop-off. Hopefully the pop-off is just popped and not closing, if not you probably smoked the plastic box.

[ninelevenick]

We can't just throw around worst case $$$ scenario conjecture here. For one, a small "pop" noise from the intake does not indicate a blown air box. That would be a "bang!" Even then that wouldn't automatically lead to a cracked box. The OP needs to pragmatically go through the motions of checking the easiest and most obvious first.

[john walker's workshop]

Pop-off valves pop out all the time. May just need a reglue.

[1983 911SC]

Yes indeed, the pop-off valve has separated from the air box. Now time to re-epoxy and evaluating whether or not this can be done with the air box in place. Thanks for the diagnosis.

[stlrj]

Originally Posted by 1983 911SC

Yes indeed, the pop-off valve has separated from the air box. Now time to re-epoxy and evaluating whether or not this can be done with the air box in place. Thanks for the diagnosis.

Only one way of finding out...


Cheers,

Joe

[HarryD]

Originally Posted by 1983 911SC

Yes indeed, the pop-off valve has separated from the air box. Now time to re-epoxy and evaluating whether or not this can be done with the air box in place. Thanks for the diagnosis.

I have reinstalled mine. Just clean everything up, wipe it down, make sure you have a snug fit and epoxy back in.

When I did mine, I left the old epoxy in place to act as a template to hold the valve.

[pmax]

Originally Posted by 1983 911SC

Yes indeed, the pop-off valve has separated from the air box. Now time to re-epoxy and evaluating whether or not this can be done with the air box in place. Thanks for the diagnosis.

Not sure we can conclude the toilet seat is the definitive cause of the backfire.

[HarryD]

Originally Posted by pmax

Not sure we can conclude the toilet seat is the definitive cause of the backfire.

The backfire typically results from a lean mixture that denotes suddenly. The flapper valve popping out is the symptom and results in the car not running due to the massive amount of unmetered air from the popped out flapper.