Brakes causing electrical problems

[Wing0tj]

Has anyone ever had a problem with ALL of the electronics flickering when the brake pedal is pushed? This doesnt happen when I have a full tank of gas... but as soon as I get to 3/4 tank and below it seems that there is a power problem from the tail lights going on. It gets to the point that when Ihave no gas left and I hit the brakes ALL lights and electronice shut off for a second. I have a rewired fuel pump so I supposed that could have a part it in. If anyone has any suggestions as to what might cause this help would be appreciated.

 

[NitrousPete]

What did you tap into for the ground on the fuel pump? Also, what did you tap into for power for the pump relay, and relay main?

It sounds like what you have going on is a voltage drop when you hit the brakes. Logic would say that the reason you're affect by your fuel level is it's somehow affected by the position of the fuel sending unit, which is nothing more than a variable resistor. Basicly when you hit the brakes something is drawing power through the sending unit circut, most likely you're backfeeding current through the sending unit and powering up a ground side somewhere.

Sorry if this isn't too clear, I know what I'm thinking but I'm having a hard time explaining it, but hopefully it will give you an idea. Look for a pinched wire somewhere that the brake light wiring and sending unit wiring might share, like in a conduit, perhaps under a carpet or somewhere you may have run the wiring for the pump. You can try disconnecting the sending unit and see if the problem disappers. If not, pull out all of your brake light bulbs and try it. More than likely the power is feeding through the bulb, then backfeeding into a bad ground somewhere thus drawing power from another circut because the power isn't being dissipated to the chassis but back through the other ground wire sharing the circut. If that's what you have your electronics wired to, it will give you a problem. Most of the electronic stuff is fairly voltage sensative.

Another thing to try would be wiring your electronics directly to a dedicated (and fused) circut to the battery, or through a relay. Basicly the idea is to remove anything from the factory wiring that wasn't designed to be there.

Good luck, hopefully I havn't confused you more than you were

Keep me posted and let me know if you have questions.

 

[NitrousPete]

Here's another question while I'm thinking of it; if you hold your brakes down for 30 seconds or so, does the gas gauge move?

 

[Wing0tj]

ok your post is pretty intense haha, but I do understand what you are saying. As for the fuel pump rewire, I followed the instructions on vfaq, I used the relay they say to and I have some fat wire directly from the battery powering it.

Another thing is that my gas gauge does act kind of wierd, today for instance I filled up and half tank, and I only needed 4.2 gallons of gas, Im pretty sure that the gas tank is larger than 8~9 gallons... I will check the thing with holding the brakes down also.

I will check the relay and the ground I used, but otherwise I dont think that I have the brakes and the fuel pump inter-twined in anyway. If there are specific places that I should look let me know, you kind of mention certain things but in technical terms (sending unit) off the top of my head right now I dont know what or where that is.

 

[91gsxboosted]

Hey man if you want I'll help you look at it I live in grafton

 

[Defiant]

Make sure your positive terminal isn't shorting out to the hood or a strut bar.

 

[Wing0tj]

Ok, well on the drive how Im I tested the brake pedal down and the gas gauge does go down, also when I flipped the brights on same thing, all the dash lights flickered and my cd player died for a second.

All I can think of are bad grounds... but idk where

Defiant how would I know if the positive terminal was shorting? and what could I do?

 

[Wing0tj]

What ever my problem is it is very off and on, also today this happened, when I turned hte engine off but left the key in the on position nothing worked, except the CEL, Bat light, and Coolant light. Besides those no dash lights, no headlights, taillights, seatbelts radios or andything, but when the car is on everything is fine.