Car amperage question

Need Help? Willing to Help? Post it here.

Moderators: flogger, SilverYota, JimR, Thorox

Post Reply
g3joshua
Posts: 43
Joined: Wed Mar 11, 2009 12:55 am

Car amperage question

Post by g3joshua » Wed Jul 14, 2010 12:04 am

Not sure if this is the right section but it appears to be right. As per my car it has a trunk relocated battery with a 100 amp fuse between the battery and the chassis (engine harness).

I've always done fine with that 100 amp fuse but a few days ago when it was around 96 degrees outside I popped the fuse trying to get the car running again. Checked all the wiring, it was good, since I never touched it since the last time I started the car. Today I replaced the fuse with another 100 amp fuse and it popped again. It seems to blow right as the car actually starts.

So that is the problem and here is my question: is it true or just a urban legend of sorts that the hotter it is outside the more amperage the vehicle will use to start and run? If this is true then a 100 amp fuse may not be enough to keep my car going...since I have never driven my car when it's this hot outside, weather said it felt like it was 107 today so yeah it was hot here.
Nah, Just a Nerd!

Bullitt2954
Posts: 422
Joined: Sun Apr 12, 2009 5:54 pm
Location: Jane, MO
Contact:

Post by Bullitt2954 » Wed Jul 14, 2010 8:59 am

Heat, age, distance, and splices all increase resistance in a particular piece of copper wiring. NFPA 70 (NEC) has tables and equations for de-rating wire according to ambient temps and distance.

I would caution you about putting a substantially-larger fuse on the car "just to get it running". Fuses should be sized to protect the Wiring - NOT to the load.

What gauge wire did you use, and how long is it? Did you replace the positive-cable entirely, (going with a larger gauge) - or did you just "extend" the cable to your new battery location?

It is quite-possible that the starter itself is drawing nearly everything it can through the cable, with nothing "left over" for electronics. When it "starts", the fuse reaches its tipping-point and does what fuses do.
-Scott Creech, #54STF - Hyundai Veloster "The BluMeanie!"

Parfois, on fait pas semblant

"The key to happiness is; If you cannot learn to do something well; learn to enjoy doing it poorly..."

g3joshua
Posts: 43
Joined: Wed Mar 11, 2009 12:55 am

Post by g3joshua » Wed Jul 14, 2010 3:05 pm

I'm using 4 gauge wire, and yes I replaced the whole positive battery cable. I picked up "high dollar" Stinger brand power wire about 5 years ago and relocated the battery to the back to make room for the front mount intercooler :)

After reading your post I picked up a 175 amp fuse to give that a try. From what I found on the internet 120-200 is a safe range for my car and they don't seem to make a cheap 150 fuse that I can find locally so I'm going to give this a try when it cools off a bit, way to hot outside right now.
Nah, Just a Nerd!

User avatar
SilverYota
Posts: 501
Joined: Tue Mar 11, 2008 7:03 pm
Location: Springfield, MO
Contact:

Post by SilverYota » Wed Jul 14, 2010 8:44 pm

Good idea on waiting for it to cool down as fighting fires can be very exhausting. There was nothing in Scotts reply that should have led you to believe putting a bigger fuse in was a good idea.

http://www.powerstream.com/Wire_Size.htm Here is a chart that shows the max load for 4ga wire is 135A, so if you do put a 175A fuse in you should find the problem rather quickly, hint: there is a good chance it will be in the same area as the smoke :).

You should start by unhooking both ends of the starter cable and making sure it isn't shorted to the chassis. If it isn't grounded out get the starter checked at the local parts store. Still not the problem, start checking the wiring for shorts to ground and begin with all aftermarket wiring (many cars have burned to the ground over a poorly wired radio).

Hope this helps and looking forward to seeing you out there this weekend.
Last edited by SilverYota on Thu Jul 15, 2010 10:54 am, edited 1 time in total.
Matt Longpine
'88 MR2

g3joshua
Posts: 43
Joined: Wed Mar 11, 2009 12:55 am

Post by g3joshua » Thu Jul 15, 2010 1:37 am

Well I had already gone over the wiring a handful of times and nothing was wrong so I just picked up whatever size fuse I could find just to give it a test. Let's just same I'm stupid. My father found the problem and what was actually causing the system to overload and it's in the middle of being fixed.

Kind of sucks when all I know is what I've done to this car or problems I've had with this car before. So here was another stupid problem that was my fault that I know now....at least it wasn't my wiring :)

Thanks for the help, I bookmarked that information in case I need it later on.
Nah, Just a Nerd!

Bullitt2954
Posts: 422
Joined: Sun Apr 12, 2009 5:54 pm
Location: Jane, MO
Contact:

Post by Bullitt2954 » Thu Jul 15, 2010 9:02 am

So, what was the problem?

I'm glad you found it, BTW. It's really hard to diagnose these things over Teh InterpRon's; a problem (and solution!) that you've experienced might help someone-else down the line.
-Scott Creech, #54STF - Hyundai Veloster "The BluMeanie!"

Parfois, on fait pas semblant

"The key to happiness is; If you cannot learn to do something well; learn to enjoy doing it poorly..."

g3joshua
Posts: 43
Joined: Wed Mar 11, 2009 12:55 am

Post by g3joshua » Sun Jul 18, 2010 12:12 am

Well you can go ahead and laugh at me because I did.

The new injector I got, well I was informed it was just tested in another engine like me, right. Well guess not since the lower seal ring wasn't on the injector. The upper ring was. I didn't know any better or what it should look like. I installed the injector and after a few time checking the electronics to make sure everything was fine (so the fuel pump has primed a hand full of time). Which is not a problem since normally all the extra fuel that keeps getting primed just recirculates back to the tank right...well not when the lower seal ring isn't on the injector so it filled my 3rd cylinder with fuel.

So when I went to the start the car it would try to turn the engine over and well it wasn't possible so the starter was pulling a crap ton more juice and pop goes the fuse. I never noticed it couldn't turn over since the fuse would also pop.

Being nervous about starting the car with the larger fuse I asked my dad to look the car over. He tried to turn the engine by hand of it wouldn't. So I pulled the coils and plugs to take any compression off the motor. When I turned the crank a bit and on the up stroke on cylinder 3 out came a big splash of fuel and that is when I knew what had happened and slapped myself.

Today I put a small fuse back in and all new injector seals (and yes the fuel was removed from the cylinder). Car still won't start, cranks over just fine and dandy but won't actually start. Got to hot to work on it so I'll take a gander tomorrow. And yeah the seal is what it was, no fuel went into the cylinder after that.

I'm going to try to make it out tomorrow if I can make it but since the car is down I promised my parents to help haul some hay so if I can get the single load from Kansas to Neosho, MO earlier enough I'll show up just to watch.
Nah, Just a Nerd!

Post Reply

Who is online

Users browsing this forum: No registered users and 1 guest