Is this an example of sudden vacuum loss?

[Anonymous]

Engine has been running very well the last few days, since I've cleared up the following issues with my distributor ('66 Mustang 200 w/loadomatic and matching autolite 1100):

1) properly connected the hard vac line (very loose at the carb)
2) lubricated the breaker plate bushing (it was sticking)
3) replaced the two springs (both were shot)

Except for today... I was getting on the interstate and she starts running like crap, won't accelerate, no power. I could manage a wee bit of power out of her if I only slightly pushed the gas pedal. Finally got her off the highway and she choked out. Re-started and voila! No more problem and she's running fine.

My guess is that I lost pressure in the distributor vacuum diaphragm and restarting allowed it to reset itself (kinda like Windows 95). Does that sound like a good diagnosis, or am I missing something important?

I'm not going to bother with a new vac diaphragm if it's bad... I'm just going to replace the dizzy with a rebuilt load-o-matic. I'm very sure that this is the original.

 

[fordconvert]

How old are your points? I had a set that looked good but would stick open sometimes. If that other stuff was stuck or bad maybe just throw another set at it and see if the problem goes away. Also get and ohm meter or test light and flex the wire around that goes between the points and the coil to make sure it doesnt have a internal crack or short somewhere that is killing your ignition when it tries to advance or retard. Also check the ground wire between the plate and the main body if the dizzy.

Good Luck!

 

[Bort62]

Yeah, generally at higher RPM's vacuum leaks are less noticeable. At any rate, a leak as small as a disconnected vac advance line wouldnt even nessicarily be a big problem at freeway RPM. That to me sounds more like a problem with fuel or spark.

 

[Anonymous]

Thanks for the replies!

I Forgot to mention that I'm running a new Pertronix I module and Flamethrower 40k volt coil (installed about a month ago).

Spark or fuel eh? I do believe that I've been having an issue with water in my tank (extremely rough idle as the gas tank approaches empty). I've been running a bottle of heet with each of the last two tanks of gas and things have been running more smoothly. Could it have just been working past some water in the fuel line?

With regard to a spark problem, the ground wire is in place (I know this because I accidentally left it out when I put the Pertronix module in... I had some rough running issues because I left it out, but nothing like what I experienced yesterday on the highway). I'm at a bit of a loss as to what to look for next with regard to spark. :

 

[fordconvert]

Depending on where you are in the world adding something like heat to the gas may be making things worse. Some areas already have quite a bit of crap like that in the gas and adding more just makes things worse. I have heard in some blends of fuels stuff like heat wont mix so when you get low in the tank you could be trying to run on stuff that is not gas.

How is your choke?

How are your rubber fuel lines?

Does your stang have a drain plug in the tank?
Im not sure about the stangs but if they have a sock filter on the pickup in the tank its possible that if there is alot of crap in the tank that when the level is higher the sloshing around keeps the stuff off the filter but when the level gets low it sticks and slows down the flow?

Double check your connections and workmanship on the pertonix, did you have the dizzy out when you installed it? If so how were the bearings? Was there some reason you installed it in the first place or was it just a xmas present to yourself?

 

[Anonymous]

Fortunately, I live in an area where our gasoline is unmolested (not so in Raleigh, about an hour east of me).

Like I said, since running the heet, she's running much better overall. This incident was an anomaly. Drove like a dream to work this morning.

Choke appears to be behaving itself. On cold mornings it takes a couple of tries to get it started, but the choke catches and she idles smooth (if a bit high). Once warm disengaging the choke is not a problem.

Don't know about my rubber fuel lines... i'll give them a look-see.

The tank itself is relatively new (i.e. replaced by PO less than 8 years ago)... that isn't a guarantee that there isn't some junk on the pickup.

I'll doublecheck the pertronix. And no, I didn't pull the dizzy when I put it in. The points were shot and I couldn't find my dwell meter so I opted for the pertronix (found my dwell meter about two weeks later).

Prior to Tuesday morning, I hadn't done anything to the car for several weeks (save the addition of heet). It had been on the interstate and was running fine. Tuesday morning I replaced the springs in the dizzy (loadomatic). Both of the original springs were shot (i.e. when the breaker plate was resting against its stops, both springs were slack and I could see where the heavier spring was stretched open on one end). I got a set of curve springs from Mr. Gasket (set 925d for Ford dizzys) and put those on Tuesday morning. Car drove fine from Tuesday to Friday... but I never took it on the highway until Friday afternoon when this problem ocurred (but less than an hour later I put it on the interstate again, and it ran absolutely fine).

Would a worn out dizzy cause this very intermittent problem?

 

[fordconvert]

Im not sure of the details of the petronix or how sensitive things are with their pickup, I was just thinking that if the shaft wobbles a bit or there is excessive end play that maybe the pickup is not working properly at certain advance settings. At this point it sounds like it could just have had something in the fuel.

 

[addo]

I'm not at all sure the Mr Gasket springs are suited to the Load-o dizzy.

What could be worth checking is a totally non-binding operation of the breaker plate. The grease dries sticky with age. Other wear aspects as mentioned by TJ are less relevant on the Load-o (no separately rotating upper shaft or weights to wear/bind), but still possible.

In terms of rough running as the tank approaches empty - it may be unbaffled and sucking a little air, resulting in a partially filled float bowl. Temporarily hooking in a fuel pressure gauge is a good telltale for such possibles.

Regards, Adam.

 

[Anonymous]

I'm not at all sure the Mr Gasket springs are suited to the Load-o dizzy.

In terms of rough running as the tank approaches empty - it may be unbaffled and sucking a little air, resulting in a partially filled float bowl. Temporarily hooking in a fuel pressure gauge is a good telltale for such possibles.

I'm not sure the springs are suited either, but they seem to be working at least as well as the old springs that were in there (unless the springs caused this problem).

I didn't mention it in an earlier post, but when this problem took place, the tank was more than 3/4 full.