Engine dies after 45 seconds?

[Flanders 46]

I've just finished getting my engine all together and got it fired up for the first time the other night. WOO-HOO!

 

Unfortunately, it runs for 45 seconds to a minute before stopping. It will start again after a lot of cranking, but then die shortly after. Starting it up a 3rd time just won't happen. This behavior occured two nights ago when I first got it started, and again last night when I was doing some debugging.

 

When I manually activate the throttle of the car, I see gas squirt into the carburetor. This occurs when the car is 'cold' and even after it dies after running for a minute. While it's running, I have gently moved the throttle as well, and the engine responds appropriately. When the engine stopped (after 45 seconds) I opened up the carb's float sight plug and peeked inside. I could see the fuel in the bowl, and it came right up to the sight plug level which (according to the instructions) is exactly where it should be. I believe the fueling is working just fine.

 

I have suspicious about my spark. I know the pertronix is getting a nice ignition-fed 12V, so I don't think lack-of-voltage the problem. Even after the car stopped, if I leave the key in the IGN position, I see 12V on the pertronix. I've been reading not to leave the key in the IGN position with the engine off for long periods of time, as this could pooch the Ignitor. Maybe this was done last year some time? I'm speculating, but at this point I'm not sure what else it could be. I have a Pertronix Flamethrower distributor with the IgnitorII inside it.

 

Any other thoughts on why it would run for 45 seconds only before dying? The electric choke on the carb (Holley Avenger) is wired up, and the carb is brand-spanking new.

[MustangChuck 16]

If you hold the throttle open, will the car stay running longer? I had a similar problem in that the car would fire, run for a few second and die. If I kept it at WOT, it would run. The problem ended up being I had too much return spring and the butterflies were snapping shut and choking the engine.

 

Chuck

[LoneWolf2U 136]

What coil are you using? a stock coil will overheat with 12v constant power.

[dzahm 10]

I hope this is not your problem- I had this happen to me on an engine one time (not mustang) but main tolerances were too tight- When the engine warmed it tightened more causing it to die. It would start up (after a minute of cooling) then die again pretty quick (since its now warm)- Third time- you had to wait a while till it cooled. I was very lucky the motor didn't completely sieze up; but just to throw it out there.

[Pakrat 1,043]

Just for the sake of argument and a no cost way to rule it out, try disconnecting the choke and see what happens. When I first took possesion of my car I had a similar problem and had to keep tethering my gas pedal to keep it alive until it warmed up on cold starts, warm starts were fine though. Once I disconnected the choke though it was fine, I could let it sit all winter and with just 1 & 1/2 pumps of the gas pedal and holding it at the half way when cranking it would fire the first time after that and stay running unassisted.

[Flanders 46]

MustangChuck -- the choke is still opening the butterflies, so I don't think that's the issue. I haven't tried WOT yet -- I just got the engine back together, so I was going to be gentle for a little bit longer :)

 

I'm using a flamethrowerII coil to go with my Pertronix Flame Thrower distributor (with Ignitor II).

 

Pakrat -- I'll do more choke testing tonight, but when I first fired it up I noticed I didn't have the electronic choke wired up at all. Car started fine. After it died the first time, I properly wired the electronic choke and it started again (with a higher idle) and then died again after 20 seconds.

 

dzahm -- I'm pretty sure my tolerances are good. The last time the engine was fired up, it drove across Canada in 4 days last year. I took the engine out to replace the rear main seal (had to loosen all the mains to do this) and core plugs. Oil pump and water pump were replaced, but otherwise nothing was touched in the engine.

 

My shaky finger is pointing at the ignitorII module.

[69gmachine 15]

My shaky finger is pointing at the ignitorII module.

 

From everything you've reported I agree it sounds like the ignition; either the module or the coil. Do you have a known good replacement you can swap in for one or the other?

[Flanders 46]

From everything you've reported I agree it sounds like the ignition; either the module or the coil. Do you have a known good replacement you can swap in for one or the other?

 

The coil is brand spankin' new, so I have high confidence in it. I had problems during my cross-country trip, where the pertronix wasn't getting 12V (resulting with intermittent problems with the ignition). I've since fixed the wiring, but I'm wondering if the Ignitor somehow got fried.

 

Earliest I can get a replacement here is Monday. I'll post results...

[jag 10]

This sounds just like the problem I had earlier this year. It was my Pertronix II. I have since gone back to coil and points. The car runs great. Try just putting points back in. That will let you know if it is the Pertronix or something else.

JAG

[Flanders 46]

well, I put my old distributor back in and VROOM it runs for more than 45 seconds :) There's definitely something pooched with the Ignitor II.

 

No receipt though, so I'll see if I can find a replacement over the weekend.

[Lemon Owner 11]

With your pertronix installed run a wire from the positive battery to positive coil terminal. this will deliver constant 12 volts and bypass the ignition switch. If this allows your engine to run properly you know you have a voltage drop through the ignition. I found this out the hard way over the weekend when the lemon just flamed out and wouldn't start. I did as above and she started and drove it home. I replaced the ignition switch and now she seems back to her annoying self.