mr2's. fires. ground potential. what you NEED to be doing to your car right now.

[TomsMR2]

we've all heard stories about mr2's going up in flames! its heart breaking for the most part.. but the truth is, its very largely preventable!

many mr2s over the years have gone up in flames due to car fires.. sometimes its due to age, sometimes its due to poor mods and swaps. in this day and age its not uncommon to have a chassis with a completely different drive train in it. thats all fine and dandy, theres nothing inherently wrong with swapping drivetrains.

however, the grounds on these cars are CRITICAL.

as most of you know.. mr2's have a battery in the front of the car, in what we call the "frunk". this is the main power source for all critical power. while great for weight balance, this can create a problem with providing high amperage draw circuits, such as the starter, with an appropriate ground path.

a lot of people dont understand what "ground potential" is. to simplify the concept.. a ground is a ground is a ground is a ground. a ground wire from the negative terminal to the chassis is just as good as a ground from the negative terminal to the engine block, or the transmission.

what happens in an engine.. the engine block grounds itself to the head via the studs, the engine block grounds itself to the transmission because it physically touches metal to metal, and is bolted securely. because of that, the head is equally grounded to the transmission, through the block, and vise verse. this is called "ground potential". since all components are jointed, very securely, though a LOT of metal, they all have the same potential to carry electricity back to the battery.

they just need a something between them, and the battery to carry electricity!

this makes all those components good grounds! toyota knows this and has provided a simple ground strap from the chassis to the transmission.. a connection more than adequate to be safe and secure.

what happens is that people do swaps, or just old age kicks into effect, they leave that critical ground loose, or connect it poorly, or get corrosion between the points. electricity still does its thing and finds another path back to the battery.. usually through the throttle cable, or other greased, highly flammable lines! this causes fires almost every time!

the end result is a bad fire.. all because of one, very simple connection missing... the ground back to the battery.

so whats this mean to you? this means YOU can prevent your car from electrical failure and fires.. extremely easily, and cheaply! everything electronic in your car will last longer if you put effort into your ground system. i seriously havent even changed a single light bulb in my car in 7 years.. secure grounds make secure components.. and secure components last longer, give better fuel economy, and run smoother.. not to mention safer.

so to the meat and potatoes. in your frunk, connect a thick wire, 8ga or lower is good.. from the negative terminal to ANYWHERE in your frunk. theres multiple threaded holes, choose any of them. sand the paint off before you make the connection, you can apply dielectric grease (sold as "spark plug grease" at autoparts stores) to prevent rust. now clean up the existing factory ground wire too, sand down that connection and apply grease. this gives a good metal to metal ground in the frunk.. which grounds your battery to the entire chassis.

now your WHOLE chassis is a very good, reliable ground! lets move to the engine.

toyota provided us with a good ground here again.. but lets freshen it up. they're old cars now, corrosion happens! remove your airbox (na's and turbos have it in the same location, its applicable to both). you will see a black, fat wire connected under it. unbolt that connection and sand off wire terminal, and sand the chassis where it bolts to as well.. again apply grease.

this really covers you for most things.. but lets take it a step further. this is VERY cheap insurance against many, many problems.. buy another ground wire from the autoparts store and connect it to your engine. you can use any hole on your engine, transmission, or cylinder head. again, theres a bunch of pre threaded holes to use, connect it to any of them. since youve already grounded your chassis to your battery, any part of the frame becomes an excellent ground!

you've created what toyota calls "redundant grounds". they're just safety backups, just in case. modern toyotas have already done these steps for you because it makes reliable cars.. it creates an equal ground potential throughout the car.

this might cost you 15 or 20 bucks in wires, and 15 or 20 minutes of your time. but it WILL save cars!

lets not see any more lost projects this year!

[Ku-sama]

been there, done that.

great write up though.

I'm going to be redoing the big 3 in my car, so yeah, I'll take pics.

[PETC]

Thank you for this Tom, although this may be common sense to some, I'm sure many know nothing of this concept, and hearing how to prevent something as major as a fire is good advice. I vote we sticky this post personally, it's an incredibly important topic that has not been covered very well.

I keep a little 5 lb fire extinguisher in my 2, but I've heard many stories of people emptying the contents of them onto a fire and having it continue to burn.

If I may add something, if your car is on fire, your instinct may be to immediately attempt to put it out if you have an extinguisher, but first try to identify what kind of fire it is. If you smell fuel, chances are you have a fuel fire, but if it just smells of burning and then all of a sudden you're on fire, probably electrical, in which case it would be in your best interest to disconnect the battery before attempting to extinguish the fire.

I always keep the following things in my MR2 just in case:

1. Flash light: never leave home without one. Seriously.
2. Fire Extinguisher: It may not work all the time, but in an early detection scenario it can be the difference between leaning against your car and smoking a cigarette to calm yourself down, or standing on the side of the road smoking a cigarette watching your car burn to the ground as the fire department approaches in the distance.
3. Pliers: Seriously.
4. Small Socket Set: You never know.
5. 1 Gallon of Toyota Red
6. 1 Quart of synthetic motor oil
7. C-Clamp: Very useful for pushing down brake pistons if for some reason you need to do that, and very tiny.
8. Brake Piston Tool: A little cube that you can use to push down other kinds of brake pistons. The MR2 has two kinds, one that needs a C-Clamp and one that needs one of these.
9. 1 bottle of DOT3 brake fluid
10. 1 Bottle of MT90 Redline gear oil
11. BFB: A big ****ing bar, never leave home without one.
12. Rags/Shop towels: Sooooo nice to have....
13. Extra belts: I have these, most people don't... and while I wouldn't pull over to change an AC belt on the side of the road, an alternator belt is a 10 minute job, and is the difference between being towed home, or driving home yourself.
14. Multimeter
15. Knife

[Don't Worry, It's Just Me]

^ Sounds like a nice list of things to have.

[LegendaryT2]

subscribed

[TreyMR2]

Great write up. Might save a few MR2's and other cars. Good info to be putting out there for all the newer people.

[LegendaryT2]

electricity is quiet a wonder, after some autoschooling and reading a bunch of grounding info/tips i still dont understand it. gotta reread this maybe 2 more times to get it

[TomsMR2]

honestly, electrical work is the easiest, and hardest thing you can do on a car.

i cant count how many 15 foot long ground wires ive seen because the person wants to make a "proper" ground back to the battery. (dont ever do that by the way, MAXIMUM ground length is 18 inches).

it can be a little hard to get, but once it clicks its really quite simple!

[LegendaryT2]

usually it not the work that gets me but how it works

[328FTW]

I did this when I first got my 2 and it instantly solved the starting issue the car had because the PO just thought the starter was bad, I was 15 then and it was one of the first basic essential things I was taught to do to a car.

And I also keep a lot of tools in my 2 like PETC does although not quite as extensive unless it is a long trip. The fire extinguisher is a car saver, saved me twice, once from a blown cv that set the car on fire and again when an oil cooler line blew next to the exhaust. I don't like towies they generally damage everything unless you get one of the 3% the give a damn.

[Ashmen]

Would a grounding kit be recommended then? And how would it be installed in a 2 since all the ones I've seen would connect to the battery then the ground points in the engine bay.

[TomsMR2]

if you can get a cheap grounding kit, sure go for it.. mostly grounding "kits" are just cheap audio ground cables marked up 5 times what they otherwise cost. all you need is large diameter cables.

i outlined what needs to be grounded in the first post. anything more than that is too much. if you buy a grounding kit, throw away the silly "distribution block", as its worthless, and just use a couple cables out of the kit. ground the block to the chassis, and reground the negative post to the firewall. clean up the factory grounds and you're done!

the factory toyota grounds really are good enough.. but things happen, especially with older cars! the extra 2 grounds ensure that things dont happen and you enjoy your car for a long, reliable time

[TomsMR2]

if you ever dig through a toyota wiring harness, you'll find something called common grounds.. its those clusters of small diameter brown wires all crimped together and grounded in one spot. its usually 5 wires or so. again, this is for ground potential.

toyota does this to ensure that a group of sensors all has the same, equal ground. if that ground gets a little corrosion, it'll give an equal (but worse) ground to all sensors and they will read appropriately.

what we're trying to do is make the entire car a common ground with the same potential for everything.

if you want to quantify your ground quality, or potential.. you can easily check it with a multimeter for a more scientific approach.

connect a multimeter to the ground clamp directly at the battery. set your meter to ohms and test multiple spots on the car with the other probe.. to test for bad grounds, test the resistance between the negative post and the chassis of the car, on clean, bare metal.. you can test at the frame rails or something. write down that measurement, it should be very low, fractions of an ohm.

now test directly from the negative terminal to the engine block, cylinder head, and transmission. you SHOULD have an extremely equal measurement between all the engine components.. and ideally, your engine will have the same impedance as your frame rail. if your engine has more resistance, you've just verified a poor ground between the engine assembly and the frame.

you can also disprove the junky ground "kits" using this method. take a piece of metal and a block of wood or something. place the wood on your trunk and lay the metal ontop. measure resistance between the piece of metal and your engine. it will be an open circuit (no connection!). now attach a piece of wire from the block to your engine. your resistance will now be very, very low.. maybe .001 if you have an amazing meter that reads that low. now attach another wire.. still .001. and another, still .001.. and then keep in mind we're talking about components that wont be effected by even .01 resistance and you can see that adding on tons of wires does nothing once you've got a good ground, you cant get better.

[canadam]

Does anyone have a list of grounds that are in the engine bay that is a little more intuitive than the ground pages listed in the BGB? I want to be sure I've done this, as well as connected all OEM grounds before I put the battery in this thing.

[car0linab0y]

I was going about 70 when the car lost power all of a sudden, got back on the gas and it seemed fine for about 15 more seconds, then it shut off and started smoking. I coasted to the shoulder and sat in the car on the phone for a few minutes thinking it just broke down. A few minutes later, I had to get out and call the fire department. Does this look like a result of the throttle cable acting as the ground wire? I thought the engine blew before reading this post.

[PETC]

Originally Posted by car0linab0y

I was going about 70 when the car lost power all of a sudden, got back on the gas and it seemed fine for about 15 more seconds, then it shut off and started smoking. I coasted to the shoulder and sat in the car on the phone for a few minutes thinking it just broke down. A few minutes later, I had to get out and call the fire department. Does this look like a result of the throttle cable acting as the ground wire? I thought the engine blew before reading this post.

Yes and yes.

You got luuuucky!!!

[BrokeMoFuGgA]

Atleast the car wasnt totally ruined and is fixable

[BRAUVIC]

He makes an outstanding point. I have done my own maintenance for years. I do projects and custom stuff all the time, but when I stop to think about it... I never pay attention to my grounds. Well here is first hand work of what can happen if you don't keep up with grounds:

[car0linab0y]

Originally Posted by car0linab0y

I was going about 70 when the car lost power all of a sudden, got back on the gas and it seemed fine for about 15 more seconds, then it shut off and started smoking. I coasted to the shoulder and sat in the car on the phone for a few minutes thinking it just broke down. A few minutes later, I had to get out and call the fire department. Does this look like a result of the throttle cable acting as the ground wire? I thought the engine blew before reading this post.

So based on my first pic, what part is this that burned up, because I need to replace it asap. Forgive me for not knowing the parts of these cars, I'm a V8 guy. This is the first import I've owned since I REALLY got into cars. I didn't even drive it long enough to have to pop the hood more than twice before it caught fire.

[TreyMR2]

Thats where it links the trottle cable from the pedel to the cruise control cable and the trottle cable going to the trottle body. I have 2 so if you can't find a good price on one let me know.