Tyson0317

Hi Guys,

I posted this before with a list of other questions, but did not get a good answer.

I have found out on my '94 V6 SR5 4x4 5-spd that it will not push-start with the battery completely (or nearly) dead. This is frustrating as in my oppinion any stick-car should be startable without a jump.

The idea brought up before was that the computer would need power to activate injectors and this is true. However, with the engine revolving, power should be generated by the alternator and the ECU should come alive. Obviously, this would be a longer-harder push than usual, but it should be doable. My truck would not start while rolling about 1/3mi downhill in gear!

This behaviour also does not happen on my 99' Mitsu 3000GT, or the '05 Audi A5, both of which have electronic injection and electronic ignition.

I suspect that there is some relay or electic actuator that needs to pop for the alternator pump power. Does anyone *Actually Know* what prevents our trucks from roll-starting?

AZkid

*watches thread*

AxleIke

Mine starts just fine with a dead battery on a roll start. So does my brothers 95, my dads 97 and my moms 04.

Just not a dead alternator. Have you made sure the reason your battery is dead isn't your alternator?

turboboost

I've started mine with no battery in it. Seems to work fine.

austinmacry

I had to push start mine for 3 days straight before I replaced battery terminals. 91 4runner

lofreqjeff

I have too a few times with no issues - have you checked the alternator?

Tyson0317

Guys my alternator is fine. This has been a problem for almost a year. I got a slow power leak someplace and if I dont drive for 3-4 days, the battery dies. After a jump, I can drive and start indefinately as long as I dont let it sit for 3-4 days again...

I suspect, that the "mine works fine" crowd have other years and other engine models trucks... Anyone out there having same problem as I?

AZkid

got any mods that involve power?

Magnusian

Since you say if you let it sit for a few days the battery becomes discharged enough for not even a roll start to fix it, I'm going to have to assume that somewhere your power leak is draining your battery charge enough that it's output voltage drops too far for a roll start to be viable over a short distance. Remember, a roll start makes your alternator turn, which in turn charges the battery, but if the battery is discharged enough for the output voltage to be significantly lower than that which is needed to start, it'll have to be rolled further to get the battery back up to the right voltage. The reason why jumping it works is because the donor battery provides the necessary voltage as well as starting amps (which a battery discharged enough for the voltage to be low wouldn't be able to do), and once your alt gets turning at idle, it can handle doing the rest of the job, without a jump it needs a little more time to do this.

Remember, a "dead" car battery is not really a dead battery, a dead battery is one that is discharged to the point where it holds no charge (0Ah/mAh at 0V). Your car will cease to start or operate properly long before it reaches this point, and it's unlikely your battery is getting that bad either, though if you left it for a month, that might be different. What happens is as a battery discharges, the voltage it puts out goes down, with some batteries this happens fast, with others they're able to maintain the voltage for longer, but in the end the voltage always drops past the point where it can no longer power stuff. Your injector and ignition systems require a certain minimum voltage and in the case of ignition a certain minimum of current (the alt can supply this, so a roll start will almost always work with carbed vehicles), because lots of current when meeting a highly resistive path (plug gap) converts to voltage and "sparks" across the path. When your battery drops below this a little, a roll start will work (when the battery is a little low it can still supply enough ignition current), but if it's a lot lower after being constantly discharged for a longer period of time, it'll take a lot more work to get it back to the right level for either system. One must also remember that an alternator supplies current, not voltage, if it outputs 60A, it might be outputting those 60A at less than 12V or 5V, which would recharge the battery, but not help in the voltage department until the battery is charged enough to accomplish the task on it's own.

Basically, fix the power leak, or park further up the hill, your battery's voltage output is way too low for a short roll start to do any good. Your battery and alt are likely both fine, it's the leak that's killing you.

e: For clarification, you can easily assume that even a completely discharged battery can be recharged, but discharging a battery "damages" it due the chemistry of the battery. This is why you need to replace your battery after awhile, even if you've been treating it properly, eventually it just becomes incapable of holding as much charge and it's easier (and more economical) to buy a new one than correct the problem with the battery's internals.1

AxleIke

You stated a 94 V6, which is the 3.slo. I listed a 95, also a 3.slo, also starts fine.

If your battery is REALLY dead, you will need to find a longer hill.

You asked why "we can't roll start our trucks". "We" all can, so yours has another problem, ie, an extremely discharged battery. Also, keep in mind that the more times you discharge a battery that far, the harder time it is going to have keeping a good charge, and eventually, it will stop being able to be charged. Don't ask me why, as I don't know, but I have had that happen to me before.

If it were me, I'd be putting considerable effort into figuring out where that power drain is going, as this sounds like a royal pain in the butt.

desertcamper67

Dead cell in your battery?

shaeff

Never had a problem pop starting any manual car, no matter how dead the battery was, including my '94 4x4 w/ 22re.

Magnusian

It's pretty simple why it happens. The electrodes are always either reducing or oxidizing, depending on whether the battery is being charged or discharged. In the end the electrodes "corrode" enough care of mineral deposits (hastened by not using distilled water to top off the electrolyte) that their surface area available for reaction is reduced beyond a useful point, "killing" the battery, deeply discharging a battery will also cause one electrode to oxidize significantly and the other to reduce just as much, at least this is somewhat reversible. You can do things to slow or even reverse this process, but in the end the battery is going to lose regardless of what you do. The best way to maintain a battery is to always used distilled or any other sort of mineral-free water and to not discharge it significantly. Proper care of a battery can and will make it last far longer (years) than a battery that is not maintained.

Tyson0317

No power mods on the truck exempt for 4 KC lights (which dont leak) and CD head unit (which likely is the cause of the leak).

Again, the alternator is fine. When running, it outputs 13.8V on the dot and charges the battery.

The battery is also fine. After driving to and from work (to charge it), I can easily light up a football field for quite a while with the engine off, then crank and start just fine.

And rolling longer is not a solution. My truck starts VERY easily when there is juice. But when the battery is dead, I have rolled in gear it all the way down a 1/3mi hill (long enough??) without it starding or showing any evidence of generaring electricity.

When the battery dies (after 3-4 days) it really is dead. There is barely enough juice to light the dash warning lights (they are barely noticeable at night) and the dome light does not produce any light.

Magnusian

Fix the power leak.

yoterr

have you pushed your safety cancel button??? if that isnt pushed the truck wont start without the clutch pushed in....rigt? o_0

Lumpy

Ya I agree, might need to have that lil orange light on for it to start.

If it goes dead after sitting for 3-4 days then your not driving enough, either start it more often or pull the neg cable before you let it sit that long.

If you think it's the hear unit draining the bat why don't you pull it? I'd rather get in and turn the key then listen to the radio.

peow130

lol, yoterr, it will if the ignition is on.
that's how you pop-start a vehicle.. get it rolling with the clutch in, and in 1st or 2nd gear, then pop the clutch and it should start.
make sure the ignition is on

91_TOYOTA_4x4

i dont think you need the clutch cancel button on to push start? could be wrong but when my starter decides it doesnt want to work i just turn the key to on then let the clutch out at speed. the clutch cancel just alows the starter to crank when the clutch isnt in right?

this is odd that you cant start it?? i would fix that power drain and maybe get a new battery? idk lol

turkeykiller365

I had a similar problem. Obviously i never tried roll starting because i have an auto but every time it would sit the battery would die. It turned out the problem stopped after i finally got a new battery. I had also thought it was a drain somewhere.