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Roll start in a 7MT?

Techun

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Which electronic fuel injected vehicles are those? You aren’t powering the ECU and fuel pumps/injectors with a barely turning alternator.
Good luck. I carry jumper cables.
Lots of 1990s cars while in high school in the 2000s. Saturns, vws, Hondas, etc.
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kodiakisland

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Lots of 1990s cars while in high school in the 2000s. Saturns, vws, Hondas, etc.
That’s cool. Above posters say they can roll start theirs with dead batteries, so I stand corrected. I guess we’ll be good to go when our batteries die.
 

Techun

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That’s cool. Above posters say they can roll start theirs with dead batteries, so I stand corrected. I guess we’ll be good to go when our batteries die.
It depends on how dead the battery is, and how the alternator functions. The broncos have computer-controlled alternators* so you would MAYBE need some initial electricity to power it. There's a chance a spinning engine provides initial power which can run that module, I'm not sure.

*If you watch your voltage while driving you can see that generally the alternator functions while decelerating, and not while throttle is applied.
 

SVTLightning

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That’s cool. Above posters say they can roll start theirs with dead batteries, so I stand corrected. I guess we’ll be good to go when our batteries die.
That’s cool, there is a difference between drained and dead. If the thing has accessory power but not enough to crank engine is pretty normal.
 

Bmadda

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I've roll started mine, but only ran a few seconds with a ton of errors. Too much complicated electronics and not optimized well enough to permit starting this way which is a major shame.
You are correct
It depends on how dead the battery is, and how the alternator functions. The broncos have computer-controlled alternators* so you would MAYBE need some initial electricity to power it. There's a chance a spinning engine provides initial power which can run that module, I'm not sure.

*If you watch your voltage while driving you can see that generally the alternator functions while decelerating, and not while throttle is applied.
From the description/operation section of the shop manual:

" Under certain circumstances, the charging system may have a concern but still keeps the battery charged while the vehicle is running. The LIN is normally used to initiate charging, but with a fault in this circuit the generator self-excites or begins charging on its own. The charging system warning indicator is illuminated and/or the corresponding message to notify the driver of the condition is displayed and the generator operates in a default mode (approximately 13.8 volts)."

Most computer controlled alternators work this way, in the absence of a signal from the PCM, they will default to "one wire" mode, but will set fault codes...so if the alternator can be spun at enough speed to self excite when push starting, it could generate enough current to get coils/injectors/fuel pump to run...certainly won't be happy about it!
 

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You are correct

From the description/operation section of the shop manual:

" Under certain circumstances, the charging system may have a concern but still keeps the battery charged while the vehicle is running. The LIN is normally used to initiate charging, but with a fault in this circuit the generator self-excites or begins charging on its own. The charging system warning indicator is illuminated and/or the corresponding message to notify the driver of the condition is displayed and the generator operates in a default mode (approximately 13.8 volts)."

Most computer controlled alternators work this way, in the absence of a signal from the PCM, they will default to "one wire" mode, but will set fault codes...so if the alternator can be spun at enough speed to self excite when push starting, it could generate enough current to get coils/injectors/fuel pump to run...certainly won't be happy about it!
For the 6G, yes I could believe that it may depend on battery level. ALSO when I mentioned roll starting with errors, if I didn't say, it only ran for a short bit and I wouldn't consider it drivable.
 

kodiakisland

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I don’t know man. The signals in this thread be like:

Ford Bronco Roll start in a 7MT? 35CB5401-9C3F-4D73-9AF8-0C5494885881


So which is it, it will or won’t work with a dead battery, which is when you most likely need to roll start a vehicle? The alternator definitely does produce everything you need, or it doesn’t. It works, but not.
If it’s some battery, how many volts did you have when you got a positive test? How dead was the battery? How many volts required to power everything needed?

Or, is it just being tested with a fully charged battery capable of starting and running all electronics on the Bronco on its own?

I’m not saying I don’t believe you, but it’s hard to keep it straight when it definitely works and when it doesn’t, because people argue one definitive thing in one post, then back track in another. People want to say it doesn’t need a battery because of every other vehicle they’ve owned, but yeah maybe it needs some battery. People say yeah it worked, but wasn’t drivable. Some have a maybe worked on a full battery, maybe.

When it did work, and that means able to drive down the road without doing anything else, was the battery dead, depleted below starting but still there, or fully charged? 100%, when does roll starting work? Repeatable?

I’ll still carry the jumper cables just in case I can’t roll start it whenever I need to.
 
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Bmadda

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For the 6G, yes I could believe that it may depend on battery level. ALSO when I mentioned roll starting with errors, if I didn't say, it only ran for a short bit and I wouldn't consider it drivable.
If it's not drivable, then what use is it? In my mind "starting" means the vehicle runs...not just makes a fart sound. So what you are saying is it failed to push start?
 

Figmo

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Keep one of these in every one of my vehicles. Found these are way better than the Harbor Freight models. Those will lose power after long storage periods. Had to jump a guy once and grabbed the Harbor Freight unit out of my truck - dead. So I grabbed one of these I had in the wife’s car that had been under the seat for over a year….fired his truck right up. Apparently, those little jump packs are not all the same.

https://suzuki.roadlessgear.com/12v-portable-jump-start-power-station
 

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If it's not drivable, then what use is it? In my mind "starting" means the vehicle runs...not just makes a fart sound. So what you are saying is it failed to push start?
I was only describing exactly what happened when I tried to push start it. I NEVER claimed it was viable and I believe I was pretty darn clear in the full text of original comment about it starting that it didn't lead to anything useful. Most of the follow up comments had to do with someone claiming EFI engines wouldn't ever roll start which is wrong because my Bronco II 2.9L EFI had no issue roll starting even with very dead battery, but that is another vehicle entirely
 

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I was only describing exactly what happened when I tried to push start it. I NEVER claimed it was viable and I believe I was pretty darn clear in the full text of original comment about it starting that it didn't lead to anything useful. Most of the follow up comments had to do with someone claiming EFI engines wouldn't ever roll start which is wrong because my Bronco II 2.9L EFI had no issue roll starting even with very dead battery, but that is another vehicle entirely
I used to roll start my 89 Ranger with 2.9L all the time, never had a problem other than not going fast enough to to it, and I just pushed harder the next time.
 

Bmadda

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I was only describing exactly what happened when I tried to push start it. I NEVER claimed it was viable and I believe I was pretty darn clear in the full text of original comment about it starting that it didn't lead to anything useful. Most of the follow up comments had to do with someone claiming EFI engines wouldn't ever roll start which is wrong because my Bronco II 2.9L EFI had no issue roll starting even with very dead battery, but that is another vehicle entirely
You are correct, push starting EFI has always worked. Been many years since I tried also (manual transmission is so rare now when do you get an oppotunity?). No real reason a Bronco shouldn't be able to be push started, sounds like the computer just refuses to accept that it happened. Could probably be fixed w/software/adding a switch etc to tell the computer whats happening
 

kodiakisland

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I suppose it's my fault for not specifying an EFI vehicle made in the last decade with a dead battery. I don't consider the vehicles made in the 80s and 90s to be any where in the same ballpark in the fuel/spark area to have even considered that just because they worked, any vehicle made in the 20s would work. Todays computers and fuel systems are not the same as the 80s. I wouldn't even consider them close enough to compare, so that's why I really wasn't in the mindset that if it worked in the 80s, it damn well will work in the 20s. I just wasn't thinking throttle body era vehicles to be in the same class when discussing the Bronco.

So I'll take the blame for that. Definitely my fault and I was not clear. Something made in the last decade. Seems as adamant some are it works with a dead battery would be able to show it does, but like I said before, I'll be prepared for other means of self rescue until someone actually shows it can work with a dead battery. As I said in the first post, it needs gas. I just don't see how it's going to get it without a good battery, but I am certainly willing to be shown the light.

I wonder about modern Jeeps. They still make them in a MT, right? Surely someone here in this thread knows if they roll start on a dead battery. Do they? They must if it always has worked and always will work. IDK though as I don't own a Jeep. I do own a MT Tacoma though, and know I better have plenty of juice if I want to roll start it. At least it has a key to put the electronics in the on position and clutch over ride switch, but it still needs power.

Surely there are some other Jeep and Tacoma owners on here with MT made in the last few years. How do you roll start your vehicle with a dead battery? Maybe there's an easy work around.
 
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Bmadda

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I think I might have accidentally uncovered the problem w/push starting a 6g Bronco. The computer is programmed to prevent it. Starting mine the other morning, with shifter in neutral, my foot slipped off the clutch a mere fraction of a second after the engine started. The engine instantly shut off! I restarted, then tried simulating that result, and it seems that not only does the computer lock out cranking the engine unless the clutch is depressed, it has a strategy to shut the engine down if the driver's foot were to accidentally slip off the pedal at startup. If I release the pedal normally the engine continues to run in neutral, but if I start it and immediately slide my foot off the pedal it will shut down. Speculation on my part, but I believe this computer strategy is what prevents 6g from being push started, and what we would need is a way to tell the computer that a push start is being attempted, or have it programmed to allow it under certain conditions
 

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I've been thinking about this.

I've roll started my Subaru a number of times. But it has a key ignition, so I can turn on the ignition without activating the starter. The Bronce has push button start, so how do you turn on the ignition without also activating the starter?
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