Ignition problems 440

thethee

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It will be worse once the engine is hot. I found the same problem before. I found that my cam would idle very nice with about 16* advance, and got rid of a bog that I was experiencing when trying to launch hard from idle. Unfortunately that was too much when trying to start the engine hot because ignition would happen too early and fight the starter, so I had to cut the timing back. It started fine when cold though.

This sounds real familiar. Mine idles super smooth and is real responsive at 17.5 degrees advance and starts real good when cold. BUT it has a tough time starting when hot, so I'll back down the advance a couple of degrees and see what it does.

As for your other problem with the engine cranking at a normal rate but not starting, I suspect your ignition was not firing while you were cranking. No ignition therefore not kicking back against the starter.

Excellent point, I hadn't even thought about that.
 

thethee

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But still, this has me wondering. When I looked online for timing settings I found a lot of threads on F_BO forums and moparts and such that mention something along the lines of "mopar BB like a lot of advance" and "needs more timing with todays bad gas" and a lot of those mentioned running 17-19 degrees advance. Or would that be okay for non-stock 440's and too much for completely stock?
 

Big_John

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But still, this has me wondering. When I looked online for timing settings I found a lot of threads on F_BO forums and moparts and such that mention something along the lines of "mopar BB like a lot of advance" and "needs more timing with todays bad gas" and a lot of those mentioned running 17-19 degrees advance. Or would that be okay for non-stock 440's and too much for completely stock?

Are they running that much advance in a '75 Imperial with the vacuum advance still hooked up? I'll bet the answer is no. You have a bunch of guys here telling you that you may have too much initial advance and to try backing it off a few degrees before you go diving into anything else. First, they have owned/own these cars and second, it's just common sense to try something that takes literally minutes with no cost.

We're thousands of miles apart, so trying to help can be a little tough to get it right. This may be the problem... It may not be too... But if it is, and you want, you can look at some options with having your distributor reworked to bring more advance in faster. @halifaxhops can help with that.
 

Big_John

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Usually a bad ballast will exhibit the opposite behaviour of what you describe: it fires while cranking but dies when you let off the key, because the ballast is bypassed while cranking. I have no experience with the dual ballast though, only single ballast and 4-pin ECU.

The dual ballast uses one side while cranking and the other side when running. So if the cranking side goes bad, and that seemed to be what always happened with them, they will fire when you let off the key.

Of course, it can go the other way too....
 

thethee

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Are they running that much advance in a '75 Imperial with the vacuum advance still hooked up? I'll bet the answer is no. You have a bunch of guys here telling you that you may have too much initial advance and to try backing it off a few degrees before you go diving into anything else. First, they have owned/own these cars and second, it's just common sense to try something that takes literally minutes with no cost.

We're thousands of miles apart, so trying to help can be a little tough to get it right. This may be the problem... It may not be too... But if it is, and you want, you can look at some options with having your distributor reworked to bring more advance in faster. @halifaxhops can help with that.

Sorry, I didn't mean to come across as questioning you guys and your experience! Just trying to learn since I'm pretty new to all this and didn't know things like timing would be that different with different applications but now I do :)

Will definitely back off the timing a bit before anything else as it, like you said, takes little time and no cost!
 

halifaxhops

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Start there it should definitely help. Hey where is your vacuum advance line going to the carb or the manifold?
 

Big_John

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Sorry, I didn't mean to come across as questioning you guys and your experience! Just trying to learn since I'm pretty new to all this and didn't know things like timing would be that different with different applications but now I do :)

Will definitely back off the timing a bit before anything else as it, like you said, takes little time and no cost!
I just reread what I posted and it did sound a little grumpy... Didn't mean it like that, but it is early in the morning here... and it was a rough night.

We were all new at this at one point in time.
 

halifaxhops

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What carb? Most go to the lower passenger side the ported vacuum.
 

halifaxhops

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I just reread what I posted and it did sound a little grumpy... Didn't mean it like that, but it is early in the morning here... and it was a rough night.

We were all new at this at one point in time.
We will get him through it, thats what coffee is for!:rofl:
 

thethee

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I just reread what I posted and it did sound a little grumpy... Didn't mean it like that, but it is early in the morning here... and it was a rough night.

We were all new at this at one point in time.
Ah yes, the time difference. Early mornings can be a pain, that I'm not new to haha.

What carb? Most go to the lower passenger side the ported vacuum.

Thermoquad. Looked it up and it should be correct, ported vacuum.
 

halifaxhops

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Should be right then. Hey does the idle drop when you take the vacuum advance line off to check the timing? Should not be advancing at idle.
 

Mike66Chryslers

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The dual ballast uses one side while cranking and the other side when running. So if the cranking side goes bad, and that seemed to be what always happened with them, they will fire when you let off the key.

Of course, it can go the other way too....
Ok. I thought that one side was a resistor which was always in-circuit, but they later redesigned the ECU to move that resistance inside so it was no longer required. Your explanation makes sense for his symptom.
 

halifaxhops

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I had a crazy one on my worked big cam 440, I kept breaking starter noses of due to kickback on hot start only. Turned out that when I was cranking hot for some reason the vacuum advance was advancing. I know it should not Eddy carb. Went to a full mechanical distributor I made up and it is fine now relay weird one there. Took forever to figure it out.
 

thethee

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Yes I do, will hook it up to the carb to see if it pulls vacuum at idle and/or on hot start
 

halifaxhops

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Do that and after it is say not kicking in the vacuum advance retard the timing a few degrees and try to hot start it again that should give us something to work with.
 

Big_John

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Ok. I thought that one side was a resistor which was always in-circuit, but they later redesigned the ECU to move that resistance inside so it was no longer required. Your explanation makes sense for his symptom.
I'm really oversimplifying the explanation and I've tried for a while to wrap my brain around how the 5 pin ECU gets power through the dual ballast resistor, especially at "start".

The way I understand it, the 1.2 ohm side is in use all the time, feeding the ECU on start and run, and then the coil on run only, but the 5 ohm is used on 2 of the pins of the ECU during start and only 1 pin on run.

It would seem like it shouldn't start or run at all with the 5 ohm resistor side bad, yet I've had that failure (not start, fire on key release) more than once and seen it several times (phone call.. "Hey John, my car won't start...") and been told by pros that it is a common problem.

I'll even go as far as saying the ballast resistor failure rep that Mopars have can be traced to the 5 ohm side of a dual ballast resistor!
 

Mike66Chryslers

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I'm really oversimplifying the explanation and I've tried for a while to wrap my brain around how the 5 pin ECU gets power through the dual ballast resistor, especially at "start".

The way I understand it, the 1.2 ohm side is in use all the time, feeding the ECU on start and run, and then the coil on run only, but the 5 ohm is used on 2 of the pins of the ECU during start and only 1 pin on run.

It would seem like it shouldn't start or run at all with the 5 ohm resistor side bad, yet I've had that failure (not start, fire on key release) more than once and seen it several times (phone call.. "Hey John, my car won't start...") and been told by pros that it is a common problem.

I'll even go as far as saying the ballast resistor failure rep that Mopars have can be traced to the 5 ohm side of a dual ballast resistor!

I was curious enough that I looked-up a wiring diagram. This is not the most nicely drawn diagram I saw but it is colour-coded and well-labeled, so helps with the explanation.

1-gif.gif


We know that the ignition switch was designed to only power one of the START or RUN circuits at a time, and the other circuit is open. The best explanation I've seen for the 5-ohm BR connected to ECU pin-3 is that it was to provide lower voltage for the digital electronics in the ECU, and they got rid of the need for it later because they redesigned the voltage regulator inside. ECU pin-1 is the main power pin, but if the pin-3 explanation is correct, it was power for only the analog electronics in the original 5-pin style ECU.

When the key is in RUN: The red circuit is powered from the battery. Both resistors of the dual BR are powered , and the ECU gets full voltage to pin-1. The coil gets reduced voltage through the 1.2-ohm resistor.

When the key is in START: The pink circuit is powered from the battery. The coil gets full power, not through the BR. Current flows in the opposite direction through the 1.5-ohm resistor. The ECU is powered through the 1.5-ohm BR. Assuming that the current draw of the ECU is small, this won't have a negative effect on its operation. (Since millions of cars were wired this way, it's safe to say that is the case.) The 5-ohm resistor is also powered this way, so the actual voltage seen at ECU pin-3 may be reduced during cranking.

If the 1.5-ohm resistor is failing such that it has high resistance, you may see the symptom of engine ignition during cranking but dies in RUN because the coil isn't getting enough power. If the resistor is completely broken, the engine shouldn't start at all, since either the ECU or the coil is unpowered at any time.

Possibly if the 5-ohm resistor (and possibly both resistors) is failing in a high-resistance condition, you may get the case where the engine won't fire in START because the combined resistance is too high so the voltage is too low going to pin-3, but will fire in RUN.
 
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