Can't Keep It Running

[Valhallo]

Hey guys,

I know there are a lot of people on here who know a LOT more than me about these cars, or mechanics in general, so I'm hoping someone has an idea or some input.

My 73 coupe has run great for the past couple of years, but just these last weeks it's been giving me some trouble. A couple of weeks back as I was driving the mustang, it almost seemed as if the engine completely stalled on me for 1 second, then everything returned to normal. Over 2 weeks it went from happening once in 4 days to the point where I was going for a test drive and the engine completely puttered out on me. Now I can't get it to stay running for the life of me.

I guess you could say that it idles REALLY rough. I can turn it over and get the engine started with a lot of babying, but as soon as my foot's off the pedal she's dead again. If i don't give it any gas, it just cranks and cranks, but when I open the throttle all the way, it starts up, but then it is violently irregular.

I'm having a hard time putting my finger on the problem. I don't think it's a fuel problem because the carb is full of fuel, the engine starts and there is combustion in the engine. I also doubt it's a carb problem, as I just rebuilt it this last year. I tested my vacuums, but I can't be 100% sure they're perfect. I can't imagine it's a vacuum though, as the condition deteriorated over time. I also recently replaced my distributor cap, rotor, etc.

It's difficult to explain exactly what's going on with the engine starting, so I figured a video might help.



Any ideas anybody? All input is very much appreciated, because I have no clue what to try next.

 

[Machman]

Does the engine have high mileage? Do you think the timing chain may have jumped a notch?


I forgot to ask did you check the points gap in the distributor? I had a car years ago that at some point refused to hold a gap. I would adjust it perfectly then in a day or two of driving the car it would slowly slip closed. I eventually got another dizy as I got tired of continually adjusting the points.

It may not be the cause of your problem but it is easy to check.

 

[JimNiki]

Hey guys,

I know there are a lot of people on here who know a LOT more than me about these cars, or mechanics in general, so I'm hoping someone has an idea or some input.

My 73 coupe has run great for the past couple of years, but just these last weeks it's been giving me some trouble. A couple of weeks back as I was driving the mustang, it almost seemed as if the engine completely stalled on me for 1 second, then everything returned to normal. Over 2 weeks it went from happening once in 4 days to the point where I was going for a test drive and the engine completely puttered out on me. Now I can't get it to stay running for the life of me.

I guess you could say that it idles REALLY rough. I can turn it over and get the engine started with a lot of babying, but as soon as my foot's off the pedal she's dead again. If i don't give it any gas, it just cranks and cranks, but when I open the throttle all the way, it starts up, but then it is violently irregular.

I'm having a hard time putting my finger on the problem. I don't think it's a fuel problem because the carb is full of fuel, the engine starts and there is combustion in the engine. I also doubt it's a carb problem, as I just rebuilt it this last year. I tested my vacuums, but I can't be 100% sure they're perfect. I can't imagine it's a vacuum though, as the condition deteriorated over time. I also recently replaced my distributor cap, rotor, etc.

It's difficult to explain exactly what's going on with the engine starting, so I figured a video might help.

matey, I would go back to basics.

confirm TDC ... ( to confirm "0" is where it should be)

adjust timing to suit.

check that all sparks are firing (short to ground and watch for spark)

check and confirm points are working as they should (check gaps)

check carby mixtures, idle speed and power valve isn't ripped.

get a vacc gauge installed.

from the vid, it looks like a serious timing issue.

with these old beasts, it really isn't hard to diagnose.

A simple process of elimination usually finds the culprit.

Let us know what you find...

cheers...

 

[marks73]

From the video it appears that it jumped time. Find the timining mark on your harmonic balancer and line it up with the pointer. Find the #1 cylinder spark plug wire on your distributer cap. Remove the cap while using your finger to point directly where the #1 plug wire is. Your rotor should be in direct line with your finger. (It may be pointing 180 degrees but that's o.k.) If it's not directly in line with your finger it's jumped time.

 

[cobrajet99]

From the video, it appears as though the chock flap is not opening up at all. I know that it doesnt open while cranking, but did you try to manually open the flap while cranking?

 

[will e]

My first suggestion is to not mess with the carb until you have pretty much eliminated the ignition as the source of your problem.

You said it had a few moments of issues while driving and now you can't get it to run. You also indicated you changed cap/rotor. Did changing the cap/rotor make it worse? (Did you put the rotor on 180 degrees backward, easy to do and it will 'run' but not very well)

Like Jim said, go back to the basics.

First thing first. Do what Mark said. You need to confirm the timing isn't way off. Get a timing light. THey are cheap and they are helpful. Hook it up to #1 spark plug wire, have someone crank the motor, watch your fingers and see where your timing is. Cranking it should be about 10 degree before TDC on a stock motor. I say about because each motor is different. At this point you are just checking to see if you are close. THe motor will run a lot better than yours if you are only a few degrees off what would be your best spot.

If you are way advanced or retarded (15 or 20 degrees away from 10 degree before TDC) you can move the distributor to get you close again. See if this helps. If you are not even in 'the ball park' or don't see the marks at all then it is possible you have the rotor on backward. If this appears to be the case.

I would confirm it is on the compression stroke by placing a finger over the #1 hole and have someone turn the crank by hand. Then confirm the rotor is pointed towards the #1 cyl on the cap. (Mark the #1 location on the housing since you won't be able to see it with the cap off) and that the timing mark is at or near TDC.

 

[Valhallo]

Crap, I didn't even check the timing! I'll either be stopping by my buddies house to borrow his timing light, or maybe its time to go buy my own. Ive tried holding the choke flap open while cranking, but same problem. When I installed the cap and rotor it ran great for a while, so I don't think that's it. I'm gonna start with the timing and if its still giving me grief try your other suggestions. I'll hopefully post results later today.

Thanks for all the help guys. I hope this gets it running again.

 

[Valhallo]

Well, I hooked the timing gun up and gave it a run, but the light didn't come on consistantly. I'm figuring that it's an electrical problem than, right? Shouldn't the spark plug fire every rotation whether or not the timing is off? I replaced the ignition coil, but that didn't do me any good, so now it's back to the drawing board.

 

[Don C]

Is the little ground wire connected that runs from the body of the distributor to the screw that holds either the condensor or points in place, and is the condenser connected to the points? Either of these not connected can cause these types of symptoms.

 

[Fordication]

That does look like an ignition issue. Do you still have points? What should his degree be for a 351C and is that a factory carb?

 

[NoLimitssjca]

I haven't posted in the "what I do for a living section" yet, but I've been I've made a career of Technical support. I noticed you said "I also recently replaced my distributor cap, rotor, etc.". A couple of others have suggested this might be ignition related and I agree. This looks to me like a classic example of the points not being tightened enough. They are fine at first but as time goes on they get farther apart. The car runs rougher and rougher an best under full throttle (of course).

Check those points. You'll either see they drifted to far out to be moved or the ground has come loose.

 

[OLE PONY]

Is the little ground wire connected that runs from the body of the distributor to the screw that holds either the condensor or points in place, and is the condenser connected to the points? Either of these not connected can cause these types of symptoms.

Many years ago traced a similar problem to the short ground wire in the distributor. Replacing it fixed my problem.

If the timing light was not firing consistently, maybe the plug wire is bad.

On a different occasion the pin that holds the gear on the bottom of the distributor broke and the gear was spinning at a different speed than the shaft and rotor. This also created a timing issue and eventually the car would not start. Something easier to check before pulling the timing chain.

 

[will e]

Yes, it should fire consistently. Try it on a few other wires and see if they are firing consistently or not.

 

[bluee]

Helpful post Its very true and this is one and only which I was looking for. So its my pleasure to have this thread. Thanks for sharing such a nice information over here.

 

[cobrajet99]

So, did you ever get to figure out the problem with your car yet and if you did,, the outcome?

 

[Valhallo]

After a long month, it is finally up and running again! After a bad ground wire (thank you ole pony) and a shorted condenser, it is back on the road. I don't believe I've ever posted pictures, so after I wash it ill put them up here.

 

[OLE PONY]

Glad you got it going without a major repair.