Tired motor

7173Mustangs.com

Help Support 7173Mustangs.com:

1973 Mach-1

Active member
Joined
Jun 29, 2016
Messages
31
Reaction score
22
Location
Phoenix AZ
My Car
Arizona car, 1973 Mach-1, Still has its original 351 Cleveland engine and its original C-6 trans, All original body panels, most of original paint. Interior is restored.
You've probably been over this multiple times, but here is the diagram that I used when re-plug-wiring my car.
HO_firing-order.gif
 

PeteG41

Well-known member
Joined
May 18, 2022
Messages
180
Reaction score
57
Location
Tempe, AZ
My Car
351c 2v, FMX Transmission. Ordered from Sanderson Ford in Phoenix, 99k original miles.
You've probably been over this multiple times, but here is the diagram that I used when re-plug-wiring my car.
View attachment 64518
Absolutely nothing wrong with a reminder! If anything this will give me a diagram to clean up the routing. The trick is going to be finding the timing marks. Didnt see any with a quicish look, might have to go the other route and pull plug 1 to feel it get to TDC.
 

swice

Active member
Joined
May 12, 2019
Messages
27
Reaction score
12
Location
arkansas
My Car
1973 mustang convertible
I’m just a carport mechanic, but your engine is definitely not firing on all cylinders, I’m sure you’ve done this but check the re check the distributor cap ( make sure it’s not cracked), rotor, points, wires, etc. I’ve seen water/debris in the fuel line do this, so re check the fuel filter, make sure no water in the fuel or tank. Seems like it would “tap” harder if valve or lifter issue, dunno for sure. It wouldn’t run at all if too much was wrong, so don’t lose hope, eventually it’ll come togethe!
 

PeteG41

Well-known member
Joined
May 18, 2022
Messages
180
Reaction score
57
Location
Tempe, AZ
My Car
351c 2v, FMX Transmission. Ordered from Sanderson Ford in Phoenix, 99k original miles.
I’m just a carport mechanic, but your engine is definitely not firing on all cylinders, I’m sure you’ve done this but check the re check the distributor cap ( make sure it’s not cracked), rotor, points, wires, etc. I’ve seen water/debris in the fuel line do this, so re check the fuel filter, make sure no water in the fuel or tank. Seems like it would “tap” harder if valve or lifter issue, dunno for sure. It wouldn’t run at all if too much was wrong, so don’t lose hope, eventually it’ll come togethe!
Definitely appreciate the positive reinforcement haha I also assumed if it was a really big issue it wouldn't want to run at all, but thats me being optimistic. The tank is new, filter going to the carb is new, and the cap is also new. However, I have not checked the points. It was on the list but the carb rebuild was first since I knew I was getting spark, I had high hopes that was my problem. Rebuild exposed a bad fuel pump that I spent yesterday getting done. Wasn't getting fuel to the carb after the rebuild, and the line going to the pump had fuel, so I knew it was 99% a bad pump. Pretty sure it was the original one that I took off and replaced.
 
Joined
Jul 27, 2021
Messages
823
Reaction score
599
Location
East Texas
My Car
1971 Mustang Mach 1 M code 351 4 speed
Hopefully you do not have any dead cylinders because of mechanical issues. You can definitely have good compression on all cylinders and still have 1 or 2 not firing because of other issues. One easy way to check is to just fire up the engine and let it idle, then remove one spark plug wire from the distributor cap. when you remove one wire from the cap, you should see the engine idle drop and it should run worst as you are basically killing one cylinder. Do this to each and every cylinder, you should notice a marked difference as soon as you remove a spark plug wire when the engine is running. If you remove a plug wire and there is no difference in how the engine runs, well, there is your dead cylinder. Another easy way is with a water bottle, just leave the engine on idle till it warms up, and just squirt some water on the exhaust manifold right at the exhaust ports. On good cylinders water will evaporate almost immediately, and on a dead cylinder you will see the water linger quite a bit before it evaporates, it is a marked difference and easily noticeable from a good cylinder and a dead one. If you have a infrared temperature gauge you can look at the exhaust temperatures on the exhaust ports, a dead cylinder will be hundreds of degrees less hot than a running one, again it will be obvious when you see it. If and when you find a dead cylinder you will need to figure out why. You could have bad plug wires, bad plugs, or maybe some internal engine issues. A bad distributor cap could be a remote possibility. One of the first thing to do is to change a plug wire from a know good cylinder to a known bad one and see if the issue moves to the other cylinder, if it does you probably have a bad plug wire. Double check your firing order, it may be as simple as that.
 

PeteG41

Well-known member
Joined
May 18, 2022
Messages
180
Reaction score
57
Location
Tempe, AZ
My Car
351c 2v, FMX Transmission. Ordered from Sanderson Ford in Phoenix, 99k original miles.
Hopefully you do not have any dead cylinders because of mechanical issues. You can definitely have good compression on all cylinders and still have 1 or 2 not firing because of other issues. One easy way to check is to just fire up the engine and let it idle, then remove one spark plug wire from the distributor cap. when you remove one wire from the cap, you should see the engine idle drop and it should run worst as you are basically killing one cylinder. Do this to each and every cylinder, you should notice a marked difference as soon as you remove a spark plug wire when the engine is running. If you remove a plug wire and there is no difference in how the engine runs, well, there is your dead cylinder. Another easy way is with a water bottle, just leave the engine on idle till it warms up, and just squirt some water on the exhaust manifold right at the exhaust ports. On good cylinders water will evaporate almost immediately, and on a dead cylinder you will see the water linger quite a bit before it evaporates, it is a marked difference and easily noticeable from a good cylinder and a dead one. If you have a infrared temperature gauge you can look at the exhaust temperatures on the exhaust ports, a dead cylinder will be hundreds of degrees less hot than a running one, again it will be obvious when you see it. If and when you find a dead cylinder you will need to figure out why. You could have bad plug wires, bad plugs, or maybe some internal engine issues. A bad distributor cap could be a remote possibility. One of the first thing to do is to change a plug wire from a know good cylinder to a known bad one and see if the issue moves to the other cylinder, if it does you probably have a bad plug wire. Double check your firing order, it may be as simple as that.
Tons of useful info, thank you! I know when I did the compression test I got good readings for cylinders 1-3, 4 and 5 were spotty, 6 was 30, retested, and it went to 90. Cylinder 7 gave me 151 but thats when the compression gauge started giving me some issues. In the back of my mind I was nervous to let it sit there and idle based on how bad it sounded, and from the shaking I didn't want to jeopardize a motor mount or cause damage to the engine. But then again if check out the cap/wires and those check out, and I am still not running on 8 there's already the possibility of the motor being hurt. No infrared gauge yet but seems like it would be a very useful little tool. Tapped out my tool budget for the next week or so with the floor jack/stands, but will give the water bottle a try. I know the plugs are new, but I do not believe the plug wires are. I will for sure get it to idle, and when I find a dead cylinder swap a good wire onto that and see what happens. If nothing fixes it, is my next step pulling off the valve covers to see if anything looks lout of place? I am getting some smoke, of course no smoke when I went to look at it, which maybe makes me think a stuck valve? Forgive me if I am way off. Definitely a learning experience, based on the fact the fuel pump took me a few more hours than it should have.
 
Last edited:
Joined
May 28, 2011
Messages
3,765
Reaction score
159
Location
Phoenix
My Car
'73 mustang convt.
Will be doing the compression test again this week with a full time functioning gauge. Probably a dumb question but if I have a dead cylinder or 2, whats my next plan of action? I am a "carport mechanic", so pulling the motor is far above my paygrade. Is it possible the timing is so far off that its running this poorly? Popping the valve covers off wouldn't be the worst thing, I am sure the gaskets are pretty shot anyways based on the transmission leak that just started.
It's hard to predict what to do until the numbers are known. If it iis just one cyl then it could be a stuck valve, collapsed lifter, bent pushrod or.... You pull the valve cover and take a look. If it is two adjacent cyls then blown head gasket or warped head might be the issue.

I don't personally believe that the timing being so far off will make it run in the way we see in the video. There is some unhappiness in one or two of the cyls. If the firing order is off, yes, but too much or too little initial advance won't make it run that way.
 
Joined
May 28, 2011
Messages
3,765
Reaction score
159
Location
Phoenix
My Car
'73 mustang convt.
We both posted at the same time. Do you have a timing light with an RPM indicator? One check I do is move the timing light from one plug wire to the next, they should all show about the same RPM. If one doesn't, it's bad.
 

1973 Mach-1

Active member
Joined
Jun 29, 2016
Messages
31
Reaction score
22
Location
Phoenix AZ
My Car
Arizona car, 1973 Mach-1, Still has its original 351 Cleveland engine and its original C-6 trans, All original body panels, most of original paint. Interior is restored.
Just another thought...
Start it up at night. That way you might see some cross-arcing in the plug wires (if there is a split in a plug wire).
 
Joined
Jul 31, 2014
Messages
98
Reaction score
38
Location
Seattle
My Car
71 conv,429cj, 4spd 3.5 N-case, it's not an original but the running gear is correct.

69 Fastback, it's a project. going to be a built BBF with a Lenco 5spd. Looking to get the car in the mid 8 to low 9 sec and still be streetable. I just hope I get it done before I am too old to drive it. lol.
My opinion is you have a vacuum leak. Feather the throttle enough to keep it running while you or someone else spray’s carb cleaner. I would start by spraying around the base of the carb.
 

PeteG41

Well-known member
Joined
May 18, 2022
Messages
180
Reaction score
57
Location
Tempe, AZ
My Car
351c 2v, FMX Transmission. Ordered from Sanderson Ford in Phoenix, 99k original miles.
Just another thought...
Start it up at night. That way you might see some cross-arcing in the plug wires (if there is a split in a plug wire).
That’s actually a great idea. I thought about just getting new plug wires so I know where I’m starting but would love to use that money for other parts
 

PeteG41

Well-known member
Joined
May 18, 2022
Messages
180
Reaction score
57
Location
Tempe, AZ
My Car
351c 2v, FMX Transmission. Ordered from Sanderson Ford in Phoenix, 99k original miles.
My opinion is you have a vacuum leak. Feather the throttle enough to keep it running while you or someone else spray’s carb cleaner. I would start by spraying around the base of the carb.
I actually found a small one last night. There’s so many useless vacuum trees and lines on this. The plan is to leave the essentials, like the tranny and distributor line, and eliminate the rest
 

PeteG41

Well-known member
Joined
May 18, 2022
Messages
180
Reaction score
57
Location
Tempe, AZ
My Car
351c 2v, FMX Transmission. Ordered from Sanderson Ford in Phoenix, 99k original miles.
We both posted at the same time. Do you have a timing light with an RPM indicator? One check I do is move the timing light from one plug wire to the next, they should all show about the same RPM. If one doesn't, it's bad.
I do have a timing light but not with the rpm. I was also finally able to locate the timing mark, so getting in there with a paint pen to make my life a little easier
 

Ron Tanzi

Well-known member
Joined
Jun 10, 2014
Messages
347
Reaction score
76
Location
United States
My Car
1972 Ford Mustang Mach 1 bright red, standard black interior,pb,ps
gauge package.rim blow steering wheel,15" magnum 500s,351 C 2bbl running a 4bbl Holley 600,MSD 6a with stock distributor and Pertronix,Comp cam mild grind, The Engine(rebuilt by me in 2002 for the second time the first rebuild I did was stock in 1995) made 305hp and 358 lb ft on the dyno. 9" 2.75 rear end,Global west sub frame connectors,620 front coils.Rear defroster. My parents bought my car brand new the year before I was born. I cherish it like my child.
Will be doing the compression test again this week with a full time functioning gauge. Probably a dumb question but if I have a dead cylinder or 2, whats my next plan of action? I am a "carport mechanic", so pulling the motor is far above my paygrade. Is it possible the timing is so far off that its running this poorly? Popping the valve covers off wouldn't be the worst thing, I am sure the gaskets are pretty shot anyways based on the transmission leak that just started.
If you come to the conclusion that you have 2 dead cylinders then I would most definitely pull the the valve covers and investigate. I doubt it is an ignition timing issue. If you what I suggested IE: stuck valves you would not have to pull the engine. It may be possible to unstick them, possibly without removing the heads. If a valve or 2 or 3 had hung up and a pushrod became displaced that is even more doable with the heads on. Years ago my neighbor who also had owned the Ford dealership that my car came from had a 30K mile 71 Grande 302 that sat for 16 years he started it with the 16 year old gas still in it and it ran for a while. Once it cooled down the varnish from the ancient fuel on the valve stems caused the majority of the valves to seize in their guides which bent pushrods and partially pulled the pressed in rocker arm studs out of the heads. Of course I had to pull the heads on that bad Larry.

Ron
 
Joined
Sep 12, 2015
Messages
6,068
Reaction score
1,062
Location
SW Ontario
My Car
1971 Mustang Mach 1, M code, 4 speed.
That’s actually a great idea. I thought about just getting new plug wires so I know where I’m starting but would love to use that money for other parts
Just my thought on this as it's typically the way I roll, just go buy a set of inexpensive plug wires and try them. If it fixes it, great, buy a really good set later when funds allow. If not, well at least you have a set of newer wires if ever you need them.
OR, do as 73 Mach 1 suggest. That's a great idea too.
 

PeteG41

Well-known member
Joined
May 18, 2022
Messages
180
Reaction score
57
Location
Tempe, AZ
My Car
351c 2v, FMX Transmission. Ordered from Sanderson Ford in Phoenix, 99k original miles.
If you come to the conclusion that you have 2 dead cylinders then I would most definitely pull the the valve covers and investigate. I doubt it is an ignition timing issue. If you what I suggested IE: stuck valves you would not have to pull the engine. It may be possible to unstick them, possibly without removing the heads. If a valve or 2 or 3 had hung up and a pushrod became displaced that is even more doable with the heads on. Years ago my neighbor who also had owned the Ford dealership that my car came from had a 30K mile 71 Grande 302 that sat for 16 years he started it with the 16 year old gas still in it and it ran for a while. Once it cooled down the varnish from the ancient fuel on the valve stems caused the majority of the valves to seize in their guides which bent pushrods and partially pulled the pressed in rocker arm studs out of the heads. Of course I had to pull the heads on that bad Larry.

Ron
Awesome advice. This motor has been rebuilt, and one of the cylinders was sleeved although the PO couldn't remember which one. Odd to think a 99k mile car had that catastrophic of a failure. I definitely won't rule the varnish part out, based on what the inside of the carb looked like, and the old fuel filter that was attached. pulled it off, tapped it on the table, and started making a small pile of gunk. If everything checks out and still not running well, the valve covers will come off. Easy to check for bent push rods or maybe overtightened rockers. Obviously the less invasive the better.
 

PeteG41

Well-known member
Joined
May 18, 2022
Messages
180
Reaction score
57
Location
Tempe, AZ
My Car
351c 2v, FMX Transmission. Ordered from Sanderson Ford in Phoenix, 99k original miles.
Just my thought on this as it's typically the way I roll, just go buy a set of inexpensive plug wires and try them. If it fixes it, great, buy a really good set later when funds allow. If not, well at least you have a set of newer wires if ever you need them.
OR, do as 73 Mach 1 suggest. That's a great idea too.
Thats what I was leaning towards as well. Obviously we all hate the idea of just throwing parts at it in the hope it fixes it, but its also possible something that simple could do it. I have no clue the age of the wires, but based on the oil filter and fuel pump I pulled off, they definitely arent new.
 
Joined
Jul 31, 2014
Messages
98
Reaction score
38
Location
Seattle
My Car
71 conv,429cj, 4spd 3.5 N-case, it's not an original but the running gear is correct.

69 Fastback, it's a project. going to be a built BBF with a Lenco 5spd. Looking to get the car in the mid 8 to low 9 sec and still be streetable. I just hope I get it done before I am too old to drive it. lol.
In your first post, you said it runs smooth at 2000rpm, then drops like it’s going to die, then shoots back up. This sounds to me like a vacuum leak. I would think you can hear the leak. You mentioned a lot of vacuum trees. Check around the carb and the intake manifold runners. Maybe a wrong base gasket.
I hope it’s something simple.
 

PeteG41

Well-known member
Joined
May 18, 2022
Messages
180
Reaction score
57
Location
Tempe, AZ
My Car
351c 2v, FMX Transmission. Ordered from Sanderson Ford in Phoenix, 99k original miles.
In your first post, you said it runs smooth at 2000rpm, then drops like it’s going to die, then shoots back up. This sounds to me like a vacuum leak. I would think you can hear the leak. You mentioned a lot of vacuum trees. Check around the carb and the intake manifold runners. Maybe a wrong base gasket.
I hope it’s something simple.
Yeah in the video when I give it some gas it completely clears up. Sounds terrible from an exhaust leak but the shake is gone. I found one plastic tee that I need to cap. There is a ton of extra emissions parts on it that aren't being used, so I am going to eliminate those. I know I need the vacuum line from the dist. to the carb, and the line to the transmission, but the plan is to clean up the rest. Just don't want to start capping lines that I actually need. Also trying to figure out what the 4 vacuum lines go to on the back of the firewall, right in the middle.
 

1973 Mach-1

Active member
Joined
Jun 29, 2016
Messages
31
Reaction score
22
Location
Phoenix AZ
My Car
Arizona car, 1973 Mach-1, Still has its original 351 Cleveland engine and its original C-6 trans, All original body panels, most of original paint. Interior is restored.
"Also trying to figure out what the 4 vacuum lines go to on the back of the firewall, right in the middle."

If they vanish into the firewall, at least one of them is the vacuum control for the heater/air conditioner controls.
 
Top