what size diode do I need

34PKUP said:
petehoovie said:
Really? Could be wrong but just wondering how long it will run hooked up like this?


484714
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I see what your confusion is. This diagram is not complete, as it is intended only to show the bypass circuit, and not the normal ignition circuit. The circuit you see here is only active during the time the starter is energized.
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Jack E/NJ said:
Mart>>>Millions of Fords started without a hot wire jump, why would we need one now?>>>


Agreed. I never had to use one either. When I switched to 12v, I got the 2-terminal solenoid described by bobH just in case. Same price as the single terminal. So why not. But never had to use the bypass terminal. Always started except when the resistor burned out. It does get hot.
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To Mart, and Jack.... Agreed. I've never had a need for this on my cars, no matter if they are original (old) 6V Fords, or the more modern stuff that I play with. I've got two old heaps that are on 12V, and I have never hooked up this bypass. No problems. I only tried to respond for the benefit of the OP, that asked how to do it.
And, by the way, I believe the diode is drawn backwards (for 6V positive ground), as indicated in some of the above posts. I make the assumption that if messing with this stuff, one can figure out which way to put the diode. And, on another note, of course Mart is correct regarding the relay. A relay could do this job, also.
(If the diode is put in backwards, you will NOT get battery voltage to the coil. And, worse, you will get coil voltage trying to run the starter when the car is trying to run. The car might not start, and if it does, the resistor circuit will probably eventually burn up. I'm pretty sure the starter would survive this. My opinion, don't mess with this if you are unsure.)
 
Mart said:
Would it be simpler to use a relay to achieve the same goal?
Is this a band aid to try and overcome a problem elsewhere?
Millions of Fords started without a hot wire jump, why would we need one now?
Not knocking it, just curious as to why one would be required.
Mart.
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All your MKIII Cortinas used a 6V coil wired through a resistor, and a hot wire from the starter solenoid. So you got 12 to the coil while you were cranking the starter and 6V for the rest of the time. The hot wire with a diode is a brilliant idea.
 
The 9N tractor like the cars used a wire wound resistor, when cold the resistance is low so more current flows to the points. As the current flows through after about 2 minutes the wire gets hot and the resistance changes, getting higher, reducing the current flow to the points.

Doesn't the original system already accomplish what this bypass does?
 
OKAY


MART and everyone else that "HAS NEVER HAD TO DO....."


Let me go through this ONE more time. I am working on a Ford GP Jeep (Effectively a "proto type vehicle). There were many issues with these jeeps....ONE being ground issues!!! IT only has one ground strap from the body to the frame ORIGINALLY. I am working on adding a couple of more BUT until then.....I would like to at least get it running. IT is "basically" a Ford 9N tractor motor. IT is a fresh rebuilt motor SO it is "somewhat" of a tight motor. The starter is turning the motor BUT it is somewhat slow, Initially, then gets real slow real fast!!!! IT is a supposed rebuilt Ford starter....NOT sure IF it is the issue or NOT....trying to assess that now and IF not then why the drop to my coil........IF i can get it running with a jumper THEN I have also narrowed down my area of focus!!!! I Believe a by product of this IS a voltage drop to the coil AS even when it is spinning "somewhat" slow, I have NO spark at the plugs!!!! NEW...coil, points, condenser, optima battery, carburetor, I have re-re-did the distributor. I would LIKE to get this thing "running" and broke in BEFORE I continue to find & refine the inherent issues with these limited production vehicles!!!!
 
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69a said:
All your MKIII Cortinas used a 6V coil wired through a resistor, and a hot wire from the starter solenoid. So you got 12 to the coil while you were cranking the starter and 6V for the rest of the time. The hot wire with a diode is a brilliant idea.
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This "hot wire" ckt. is especially useful when you have a weak battery...
 
petehoovie said:
This "hot wire" ckt. is especially useful when you have a weak battery...
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Petehoovie


My Optima is up to 6.4V. It seems to "initially" spin the motor a little better SO my plan IS to use it in conjunction with my wet cell via jumper cables for starting.....I've pulled my battery out of the Mercury for my "jumper" power source AND IF need be I have a 12V battery I can swap my jumper cables to and go directly to the starter with that to get it spinning!!! Thoughts???
 
When Nick Alexander sold his Woodie Fleet back in 2009 at Monterey, many of them would not start. His mechanics crew would apply 12 volts directly to the starters of the cars that would not start to fire them up....
s-l400.jpg
 
rockfla said:
OKAY


MART and everyone else that "HAS NEVER HAD TO DO....."


Let me go through this ONE more time. I am working on a Ford GP Jeep (Effectively a "proto type vehicle). There were many issues with these jeeps....ONE being ground issues!!! IT only has one ground strap from the body to the frame ORIGINALLY. I am working on adding a couple of more BUT until then.....I would like to at least get it running. IT is "basically" a Ford 9N tractor motor. IT is a fresh rebuilt motor SO it is "somewhat" of a tight motor. The starter is turning the motor BUT it is somewhat slow, Initially, then gets real slow real fast!!!! IT is a supposed rebuilt Ford starter....NOT sure IF it is the issue or NOT....trying to assess that now and IF not then why the drop to my coil........IF i can get it running with a jumper THEN I have also narrowed down my area of focus!!!! I Believe a by product of this IS a voltage drop to the coil AS even when it is spinning "somewhat" slow, I have NO spark at the plugs!!!! NEW...coil, points, condenser, optima battery, carburetor, I have re-re-did the distributor. I would LIKE to get this thing "running" and broke in BEFORE I continue to find & refine the inherent issues with these limited production vehicles!!!!
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OK.... I'm another 'Jeep-Nut'. And, I'm also working on an old Jeep (47 2A). And, I've had my share of old Jeeps, about 30+, and maybe half dozen of them WWII, and Ford GPW's. (But, never a GP) So, anyway, in the case of my 2A, (with Ford engine) it had been sitting, exposed to weather, for decades. Motor stuck, and everything corroded. So, like you, rebuilt the motor, and it is tight. One-by-one, found corroded starter, and replaced it. Corroded starter solenoid, and replaced it. With the plugs out, got the motor to spin. Temporarily used 12V, to get it spinning. At that point, put plugs in, spun it again and verified spark. So, for first start (this being after I could make the motor spin with the starter, on 12V), I used jumper wires to put 12V on the coil, and also to 'turn the ignition on'. (Can't trust ignition switch or starter button - both corroded and probably unusable.) This is where I am currently at. The engine starts easily, with these conditions. My point being, I haven't attempted (yet) to start it with any of the (so-called) factory wiring. Adding stuff (like a diode circuit), is stuff for a future day. And, I expect in the end, I don't plan to need a 'resistor-bypass'.
In your case, my opinion is, forget all the stuff you are trying, and go directly to 12V, like Pete has suggested, and I am also suggesting with this post.
 
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BobH


Like you, at one time...We had 15 GPW's, 2 GPA's, 2 Willys Slat Grills, M38, m38A1, 3 M151's a Harley WLA and 2 GP's..... SO we know "JEEPS" ...... This one is a challenge to say the least!!!
 
>>>I've pulled my battery out of the Mercury>>>>>>Thoughts???>>>


(1) Put the battery back.
(2) Tie rope between Jeep & Merc.
(3) Ask wife to tow you around block in Jeep.


No diodes. No relays. No jumpers. No starters. Simple. 8^)
 
Right on !!!! My opinion, get this thing spinning and running first. Later, figure out how you want to wire it.
 
Jack E/NJ said:
>>>I've pulled my battery out of the Mercury>>>>>>Thoughts???>>>


(1) Put the battery back.
(2) Tie rope between Jeep & Merc.
(3) Ask wife to tow you around block in Jeep.


No diodes. No relays. No jumpers. No starters. Simple. 8^)
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I Need to make sure I have fire at the plugs....IF i knew that I would have already done the step above!!! NO sparky NO runny!!!
 
If you have 2 batteries use one (12V if possible) to turn the motor and an independently wired 6V job for the ignition (direct if only to run for a short time.

A spark at the right time, compression and some fuel down the carb should get it going.

I'm not sure what the "NEVER HAD TO DO" comment means but as someone who "ALWAYS HAS TO DO" I'm not sure I like it.

Mart.
 
Do you have a spark if you just open and close the points manually? Poke them with a screwdriver and have the king lead from the coil held near the head.

You're right. Ensure spark first. It doesn't have to be turning to do that.

Mart.
 
Mart said:
Do you have a spark if you just open and close the points manually? Poke them with a screwdriver and have the king lead from the coil held near the head.

You're right. Ensure spark first. It doesn't have to be turning to do that.

Mart.
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I can do that tonight!!! Thanks Mart, I didn't think about that!!!
 
Jeeps are swell ! I kinda feel inferior to you guy's as I have only had 4, 2 MB's, 2 M38's. The current M38 is a keeper, nice clean original except paint. Now, I have to agree with many here, get it spinning with 12 volts, check spark, and fire that mother up
 
I know Rockfla said ONE more time, but it's been bugging me. I understand the concept of bypassing the resistor wire or ballast with a jumper. But how is voltage maintained at the coil? The battery voltage is going to be drawn down with the load when the starter is engaged. A diode isn't going to maintain it at 6volts.
Lets say your battery reads 6.4 volts no load.Hit the starter button, starter engages. The battery is going to read say for argument sake 5.9 volts. The coil is going to see 5.9 volts.

A DuckDuckGo search, I don't use goggle anymore, did not show any results.
 
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