69mustangcali

Hey everyone, I recently tried starting my classic mustang again since I bought it. I originally test drove it without a problem but once I actually paid for it everything went to crap. We were able to start it up again by pouring in a little bit of fuel in the carb but a few miles down the road and I'd lose all power. After feathering the accelerator I would get power back but it would die again almost instantly.

Flash forward to now where I've tried to get it running again. After getting the carb rebuilt and putting in a new fuel pump I tried to start it but all it does is crank. To be honest it sounds like it's cranking rather slowly/erratically but I'm unsure. Anyway while cranking it I pulled off the fuel line and sure enough fuel spurts out including when I hit the accelerator. However, even with this and me spraying starter fluid down the carb nothing happens. So its not fuel.

Today I did a ghetto test of the spark by taking out one of the spark plug cables and putting in a spare one. Then, I touched it to the intake bare metal and asked a friend to crank it. Sure enough, I could see a little spark flicking back and forth on the plug. (I also put in brand new spark plugs 2 days ago).

I assume the next natural step is compression testing... But to save me some time and money since I don't have a tester yet do you guys have any idea what else it could be??

Gun Jam

I wonder if its really weak spark. Ive had this cause similar issues.

Here is a fair dinkum example of a quality spark. it could jump a lot further but then it tends to loop over to the coil ground wire. This is a MSD A6 digital box. Notice the color, jump distance, and sound. Not shown: the hole it left in the vicegrips.

Try a similar test will it jump out of the coil neck?

69mustangcali

I don't know.. that seems rather unlikely considering how easily gas burns. I did put new spark plugs though so what could cause super weak spark? Is it my coil?

Gun Jam

Yes the coil is a likely source. If you are running points there could be excessive gap, low power to the coil could cause an issue as well.

I always love it when someone immediately dismisses a possible solution directly based on a perceived "science" with no attempt to investigate at all. It means there's a 75% chance im right....

69mustangcali

Haha alright alright believe me I won't dismiss anything I've seen weirder crap so I will believe anything. As for low power to the coil unless it's gone bad there's no way because the battery is new and fully charged.

The points theory does seem pretty feasible. I'm not super comfortable dealing with the distributor though because I have no clue how to set timing and such and I have a very limited understanding of how it works. So YouTube I guess and then we'll see what happens haha.

Gun Jam

Or there is a loose bolt
wire corrosion
partly broken wire
bad ground


A multi meter might be a wise investment at this point...Ive always got one in the glove box

Ps make no mistake its not about making you believe anything its about getting you to go out and do a 30 second test free of cost that would allow you to compare results and make an informed decision on your own.

See....You posted a question and I was like **** yeah I had the same thing happen! I found the issue and resolved it I noticed things during this troubleshooting process. So I bet it might be the same issue here.. So I go out, build a tripod out of cardboard box, set up a demonstration, film it, upload it to youtube, explain the results, provide the link and alls you gotta do is mimic the test I showed you and let me know what you saw. But instead its like "yeah naw can't be" its free and very easy at least try it out...remember im not the one who's asking questions / looking for help. I just want to help you avoid unnecessary cost and wasting time.

Starfury

Run the test, as Gun Jam recommended. I don't know if an OE coil with points is going to give you quite as big of a spark as Gun Jam's, but even 20kV should jump out of the coil tower.

Adjusting points isn't hard, and you could probably get away with the match book trick (google it) to get it close. Upgrading to a Petronix or similar drop-in electronic ignition module is a good idea though.

You should invest in a digital multimeter (DMM) as suggested, as well as a timing light. Essential tools for any classic car owner. If you can, fork for an adjustable timing light; you don't realize how valuable they are until you actually use one.

There are many critical components to igniting the mix in a combustion chamber. Weak spark, improper plug gap, improper air/fuel ratio, poor compression, incorrect timing, all of these can cause a no-fire situation. The fact that the car ran initially but now won't ignite even starter fluid leads me to think the same as Gun Jam, that your problem is likely ignition related.

67mustang302

Contrary to what you may believe, gas does NOT burn easily...at least not inside of a combustion chamber. Trying to get adequate ignition to drive pistons is difficult when you consider fuel mixture, atomization, temperature, compression, turbulence, resistance across the plug gap (which varies greatly with many of the aforementioned), molecular distribution of the mix, flame front propagation, chamber and piston design (both of which affect flame front propagation).

Just to name most of the impediments to making gas burn.

With enough compression or boost pressure and a weak ignition system, you can actually blow the spark out (technically the flame kernel), just like blowing candles out on a cake.