Please Help!! Voltage issues or so I think...

[MustangMatt1966]

Hey guys and gals!

I have a major issue that I can not seem to figure out. Just a little background on the car. 1966 Mustang, built 289, 5 speed manual transmission. Battery is in the trunk, powermaster 1 wire alternator and it seems the votage regulator is bypassed and taken out. Car ran great for over a year and just recently I have run into some serious issues.

Under load while driving, the car will fall flat on its face and the volts drop. It seems to still be running but becomes unresponsive. I have to restart the car and it comes back to life. This issue has become dangerous and I have no idea what it is.

I replaced the alternator with a brand new powermaster and the car ran great the first two times out because I thought it was an alternator issue. Took it out last night and the problem has come right back.

I have no idea what can be causing this and it seems to be some sort of electrical demon. Does anyone have any idea what can cause these symptoms?

At first I thought it was the carb because it fell flat on its face like it was not getting fuel at half throttle.

I now know that it has to be electrical. The battery is a red top optima so I know it is not the battery.

I am scared to drive the car because I will get in an accident if this continues. At idle the volts seem to be great but now under load they are dropping which is what I think causes this problem.

I have no idea where to go for help or what to do to resolve this issue.

Someone please help...my baby is not doing so well...

-Matt

 

[2+2GT]

Tell us about your ignition system.

 

[MustangMatt1966]

Mallory distributor, msd blaster coil, mallory plug wires. Not sure what else you all need. Its been a long time since I have been on the forum because the car was running great for so long but it is actually nice to be back. I missed the sincerity of everyone on here and you all were great in getting my baby working at its peak.

The wiring is stock and has been spliced and torn into like any old car over the years has. The problem seems to have come from no where?

 

[Tim65GT]

The wiring is stock and has been spliced and torn into like any old car over the years has. The problem seems to have come from no where?

I think you may have found the answer. Even if your stock wiring harness was not torn into, it is over 40 years old. I'm not saying replace the entire harness, but the important circuits like the Ignition should be considered. The battery feed from the solenoid to the Ignition switch and switched on ignition power to the coil/distributor. Check the coil and distributor connections carefully.

When you say under load, do you mean the engine or the electrical system? Are you sure the volts dropping is the cause or perhaps the result?

 

[6Stang7]

powermaster 1 wire alternator and it seems the votage regulator is bypassed and taken out.

I want to know more about this. Am I correct in assuming that, with a 1 wire alt, the voltage regulator is not needed?

What do you mean by it seems that the voltage regulator is bypassed and taken out? Is the regulator still physically in the car? Have the wires been disconnected from it?

 

[rbohm]

check all your grounds first, but then replace the starter solenoid. remember that all the electrical goes through that one part and it has been known to drive people nuts trying to figure out your very problem. one of my college instructors was trying to figure out why a ford ltd would sometimes fall flat on its face, and at other times accelerate smoothly with no issues. he eventually got a wiring diagram out for the car and found out this bit of information. it seems the movable element in the solenoid gets loose, and from time to time the disc inside will touch the ground in the unit because of the cars normal vibration. when that happens it shorts out the entire electrical system causing a system wide power loss.

 

[MustangMatt1966]

6stang7- The voltage regulator is gone and the harness is still in the car. It has been bypassed by the mechanic that installed the alternator. The car ran great for well over a year with the alternator like this so I find it hard to beleive this is the issue.

rbohm- Replaced the solenoid I replaced first because I thought that was the issue. Then I replaced the alternator...I just seem to be replacing everything when I have a sad feeling it may be something simple that I have overlooked.

How do I go about checking grounds. If I can not figure this out I am very close to taking it to my mechanic to diagnose the issue

 

[MustangMatt1966]

Oh and it falls on its face under power (load) at least half throttle, any more than that the issue creeps back in...

 

[6Stang7]

So by under load, do you mean when you are driving and you try to accelerate? Are you flooring it, or just giving it a little gas? Does this issue happen when you rev the motor in neutral?

 

[MustangMatt1966]

At idle just reving, no issue in fact the volts seem to be better at idle..no issues. While driving, at about half throttle if that, I will try and give it a little and it will fall on its face but it seems to be inconsistent. The problem will happen and then sometimes it doesn’t. Only seems to be while driving.

Does this help? I know it seems vague but I have no idea what this could be either. I am at a loss...

 

[Tim65GT]

At first I thought it was the carb because it fell flat on its face like it was not getting fuel at half throttle.

I now know that it has to be electrical.

At idle just reving, no issue in fact the volts seem to be better at idle..no issues. While driving, at about half throttle if that, I will try and give it a little and it will fall on its face but it seems to be inconsistent. The problem will happen and then sometimes it doesn’t. Only seems to be while driving.

The more you describe your fault, the more it sounds like you may have crap in the fuel tank/line/filter/carb.

What makes you so sure it's electrical?

 

[MustangMatt1966]

Tim,

At first we thought it was the carb/fuel tank but the more and more we investigated, we thought it was electrical.

After replacing the alternator the car ran great! Better than it has for a long time, no hesitation, bogging or falling on its face. Two days later I go to drive it and the problem is back.

Would something in the carb or fuel tank cause it to be that inconsistent?

The fuel tank is original and very well could have gummed up the carb...I just hate having to replace things hoping that it will fix this mystery problem when it seems to keep creeping back?

Calling my mechanic and a little for advice...

Thanks for all of the help, keep the suggestions coming

 

[MustangMatt1966]

Ok, so update....I talked with my mechanic and he says as dumb and overlooked as it might seem, it could be the belt that is causing the issue. If the belt is overtightened and hot (which it is) after driving, he said the belt could be slipping under load which actually might cause it to loose power and the volts would drop.. This makes perfect sense to me and it does seem to point to the issue. he said it slips backwards causing the car to almost stall like it is.

His second suggestion if the belt does not fix the issue is grounds. Because the battery is in the trunk, there needs to be grounds in the rear as well as the front and my battery is grounded to the block. All internal electrical s are grounded to the body so this could be an issue also.

Please advise.

 

[Tim65GT]

His second suggestion if the belt does not fix the issue is grounds. Because the battery is in the trunk, there needs to be grounds in the rear as well as the front and my battery is grounded to the block. All internal electrical s are grounded to the body so this could be an issue also.

Please advise.

How is it grounded now?

With your battery is in the trunk, there needs to be a ground cable from the Neg post to the trunk floor. I used the area just inboard of the right frame rail where the frame lip meets the trunk floor. There should also be a ground cable from the engine block to the frame. I used a sway bar mount bolt. The cables should be at least 2 gauge and all connections should be tight and clean (bare metal).

 

[Tim65GT]

After replacing the alternator the car ran great! Better than it has for a long time, no hesitation, bogging or falling on its face. Two days later I go to drive it and the problem is back.

Would something in the carb or fuel tank cause it to be that inconsistent?

Yes. Dirt and old rust particles are going to float and slosh around but eventually get sucked into the line and clog up the fuel filter or a carb passage. It can be intermittant. You are describing how my car acted when my filter was clogged. It would idle fine, but once in a while it would just die when I try to give it gas like going up a hill.

A simple check is to disconnect the fuel line from the carb and stick it in a coffee can. Have someone crank it and the fuel should flow out pretty good. If it's only dribbles, then check the filter. You DO have an in-line filter right?

 

[MustangMatt1966]

Hey Tim,

Thanks for the help. I do have an inline filter and it is new. That is a good idea about taking the fuel line off of the carb and checking for the flow. I am going to put a new belt on and test the car. If this does not solve the issue I am going to test the grounds and ground the negative terminal in the trunk. I hope one of these two solves the issue. The cable for the battery is def. two guage.

If these solutions do not solve the issue as much as I hate to do it, I might have to take the care to the mechanic

 

[StangDaddy66]

Yes. Dirt and old rust particles are going to float and slosh around but eventually get sucked into the line and clog up the fuel filter or a carb passage. It can be intermittant. You are describing how my car acted when my filter was clogged. It would idle fine, but once in a while it would just die when I try to give it gas like going up a hill.

I agree. My tank is original and after going through about four filters in a month, I decided to clean my tank with the ol' gravel and paint thinner trick. It solved my problem and this sounds EXACTLY like what mine would do with a clogged filter and yes it can be sporadic until it clogs completely. Start with a quick filter swap and see how that does. You would be amazed at how much gunk can be in a 40 something year old gas tank.

At idle, the carb is sipping gas. When you put it under load, the bowls drain faster than the pump can push/pull gas through the clogged filter basically running out of gas.

 

[MustangMatt1966]

Ok, so replaced the belt and grounded the negative terminal in the trunk. Volts were great and the car ran awesome but on the way back with my buddies in the car as a witness, it died. What is funny is I was all over the car the first half of the ride. Pretty much to the floor through 4 grears and not hesitation or stall. Then almost back to my appt. just cruising under a little throttle it did it again! Got it restarted and then at the light to turn into my appt complex, it died. It has never died at idle before so that was new.

We ran the car in the garage for a little and watched the fuel filter. It looks a little more empty than it should be. We agree that it has to be fuel.

Does anyone have a link to replacing the fuel tank with a fuel cell and replacing the new lines ect. I am still going to take it to the mechanic just to get his opinion but would love to be able to do the work myself.

Thanks again for all of the help. You guys pretty much nailed it!

 

[MustangMatt1966]

Thanks Stangdaddy! I think you nailed it along with the others. Do you have a guide to the tank cleaning or a link to fuel cell replacement?

 

[68er]

if that doesn't get it, you might want to check out the coil.

a tired coil may run ok until it gets hot, then start acting similar to what you describe.