Backfire, then no start

[78sc]

Hi all,

It's been a while since I've been driving my 911 or been around these forums. Thought I'd ask you all a question as I get back into enjoying these 911's we like so much.

So, I got mine running again and had been driving it for about a week. One morning last week, I went to start it and it backfired pretty good and then would not start. If I let it sit for a couple of minutes, and tried again it would try to start but then just crank. All these attemps to start were with my foot off the gas pedal. So I took my non-fun car to work and when I got home again, all it does is crank and not even a hint of wanting to fire.

My question is, where do you guys think I should start the troubleshooting? The airbox has a pop-off valve installed. I can't see any cracks in the airbox, but I'm sure there is a lot I can't see with just the airfilter cover removed.

Thanks.

[timmy2]

Is the pop off valve seated on its o-ring properly?
Basic tune up of ignition and check fuel pressures would be next, spark plugs fouled?

[jtfreels]

Check to make sure that you are getting spark. If so then .... check for vacuum leaks etc.

I had a similar occurrence, and after the backfile got no spark, turned out the "coil" inside the distributor had failed. That is "green" wire related.

Just a thought.

Jay

[McLovin]

Something has cracked/broken off, and now you have a big vacuum leak that is preventing the car from starting.

[kodioneill]

Pop off valve or broken air box.

[RSBob]

If you pop off valve popped completely off like mine did remove the air filter and you will see it unsecured. Clean out old glue or adhesive and mix a 2 part epoxy and reseat the valve and you should be good to go

[78sc]

Thanks for the thoughts guys. I will go hunting for the culprit tonight.

[78sc]

So, I checked spark, that was good. Plugs were not fouled. Couldn't find any hoses that got blown off or any cracks that might cause a vacuum leak. Then realized I couldn't hear the fuel pump. Turned out the fuse was blown. Weird! Replaced that and it started right up.

[timmy2]

Good find, and thanks for updating with your results.
Now go drive it like you stole it!

[arry911]

Originally Posted by 78sc

So, I checked spark, that was good. Plugs were not fouled. Couldn't find any hoses that got blown off or any cracks that might cause a vacuum leak. Then realized I couldn't hear the fuel pump. Turned out the fuse was blown. Weird! Replaced that and it started right up.

I had similar problem the other day turned out the fuse was corroded not even blown, Just put in new fuse and it started.

[Jim Richards]

Coil failure.

[78sc]

Originally Posted by Jim Richards

Coil failure.

Hi Jim...sorry, not quite sure what you mean.