wire to fuel pump wire, fuse gets very hot

 rewired my fuel pump to pull power direct from the battery via a relay?Fire310

For Pete's sake - connect them properly. The fuel pump relay needs to be controlled by the ECU, else an "engine running" circuit like charge sensing, air flap, or ignition (spark) sensing etc. This is to ensure the pump STOPS in an accident etc - ie, ignition on, fuel line severed etc. Charge controlled is the most common and easiest - eg: (Thanks to Tezza) ....where Reg means the charge lamp aka D+ or L wire from the alternator (else its regulator), and Start is the starter-motor's +12V from the ignition key to "prime" the system. [If the alternator or regulator fails, just disconnect the D+ or L wire and the relay should turn on so that you can limp home.] (The above fig is from the last post at the12volt.com/installbay/forum_posts.asp?tid=107789.) And DO NOT use oil pressure signals for fuel pumps - that went out with draining carbies and stiffening capacitors. But there are many variants of the above circuit including manual bypass & prime (aka - milking the tank), or using an SPST relay and diode connecting the various inputs (Starter, Charge, air-flap, bypass).

Kmn5- In the future if you run across any similar type problem with extensive heat in any circuit run a simple voltage test right off the rip. If you were to test the circuit you wired for your fuel pump disconnect the feed to the pump (at the pump) and arrange your relay input and output to be normally closed therefore allowing voltage to be applied without it being energized while still using the contacts in the relay for the test. Connect your voltmeter to the battery and the the end of the wire feeding your fuel pump. Any difference in potential from the battery to the end of your feed will be displayed on your meter. Lets say it read 1 volt, you now know that even with the load disconnected you are dropping a volt somewhere in the circuit which means there is resistance and resistance will induce heat. Also if the battery is too far away from the feed use 2 calibrated meters testing each 12 volt signal to ground and subtract the difference giving you the same number of dropped voltage as the first test. Once you have figured out how much voltage you are dropping unintentionally break the circuit in as many places as you can and use an ohmmeter to do the rest. write down the resistance read in each portion of the circuit and use ohms law to figure out how much voltage drop is normal for each. If there is actually an abnormality in the circuit you will be able to find it very quickly. everything should read almost a direct short so you should not have a problem identifying the issue. Although "crushing the fuse holder" haha sounds like a very quick fix for this issue it is not the right answer. troubleshooting is very important. If you have an electrical issue unplugging and plugging it back in different configurations until it works is not a professional way to do things. As a rule of thumb if your circuit was intended to pull 30 amps you need to use at least a 10 AWG conductor. All those guys that told you that when you first posted this problem were right. When you installed a giant fuse block on a 30 amp circuit all you did was introduce a heat sink to dissipate the heat generated by faulty wiring. I professionally recommend to you that you replace your conductors with the correct rated AWG standard and you will never burn down your vehicle. In no way should a 30 amp circuit need a fuse block to operate properly. You still have an issue but with a bandage on it. Good luck to you and if you have any more issues and would like the correct answer and not some mickey mouse backyard tips feel free to contact me.Kodi H. Almeida

almeida.kodi wrote: Kmn5- In the future if you run across any similar type problem with extensive heat in any circuit run a simple voltage test right off the rip. If you were to test the circuit you wired for your fuel pump disconnect the feed to the pump (at the pump) and arrange your relay input and output to be normally closed therefore allowing voltage to be applied without it being energized while still using the contacts in the relay for the test. Connect your voltmeter to the battery and the the end of the wire feeding your fuel pump. Any difference in potential from the battery to the end of your feed will be displayed on your meter. Lets say it read 1 volt, you now know that even with the load disconnected you are dropping a volt somewhere in the circuit which means there is resistance and resistance will induce heat. Also if the battery is too far away from the feed use 2 calibrated meters testing each 12 volt signal to ground and subtract the difference giving you the same number of dropped voltage as the first test. Once you have figured out how much voltage you are dropping unintentionally break the circuit in as many places as you can and use an ohmmeter to do the rest. write down the resistance read in each portion of the circuit and use ohms law to figure out how much voltage drop is normal for each. If there is actually an abnormality in the circuit you will be able to find it very quickly. everything should read almost a direct short so you should not have a problem identifying the issue. Although "crushing the fuse holder" haha sounds like a very quick fix for this issue it is not the right answer. troubleshooting is very important. If you have an electrical issue unplugging and plugging it back in different configurations until it works is not a professional way to do things. As a rule of thumb if your circuit was intended to pull 30 amps you need to use at least a 10 AWG conductor. All those guys that told you that when you first posted this problem were right. When you installed a giant fuse block on a 30 amp circuit all you did was introduce a heat sink to dissipate the heat generated by faulty wiring. I professionally recommend to you that you replace your conductors with the correct rated AWG standard and you will never burn down your vehicle. In no way should a 30 amp circuit need a fuse block to operate properly. You still have an issue but with a bandage on it. Good luck to you and if you have any more issues and would like the correct answer and not some mickey mouse backyard tips feel free to contact me.

"Them is fighting words"...Aren't they...?

M.E.C.P & First-Class

Go slow and drink lots of water...Procrastinators' Unite...Tomorrow!

So are you saying it was NOT a faulty fuse holder...Rather something else...!? ( I gave up reading your post)  Who mentioned to upgrade the wire...? Such an old post...So many people currently that need help and this was your first post...? How did you single out this post...?M.E.C.P & First-Class

Go slow and drink lots of water...Procrastinators' Unite...Tomorrow!

Wow, I didn't realise you could experience a voltage drop with ablolutely no current traveling through the wire.  No load on the wire = no current draw.  No current draw = ZERO voltage drop.   M-I-C-K-E-Y M-O-U-S-E  Mickey Mouse.

Well there you go Idiot (Sir...) - we learn something every day! Kodi should have added "assuming power at the pump" else test that first... I know that is obvious to some, but after having a qualified mechanic unable to test electric fuel pumps (despite my suggestions - like a battery at each of its terminals (after disconnecting etc)) thereby causing me 4 hours of grief pulling the pumps from my spare vehicle - only to find out later "it wasn't the pumps".... Mind you, a mechanic that works on an EFI vehicle and doesn't even have a test light.... Misses the bad battery fuselinks (that I forewarned 3 months earlier).... And blows up the EFI ECU through his repeated testing.... But at least he was qualified. (I call him "Mechanic" because you beat him to his name. Reminds me of why golf is called golf.)    PS - small world - last night a colleague dragged up an old "unbelievably moronic" post about controlling fuel pump relays. I guess now well read about (Bosch) alternators being self-exciting too....?

well mr idiot. i will explain this once since u thought it would be funny to try and insult me. if you apply a 12 volt signal to wire and add a resistor in the middle of that wire you will be able to test before the resistor and after the resistor with no ground hooked up and you will have dropped voltage across the resistor. you will not drop all of the voltage because you are not hooked up to a ground providing a path for current. if you hooked up the ground with a single resistor in place you would drop all of your voltage across the resistor being that it would be acting like a load. since you have disconnected the ground all you will read is the voltage dropped from the resistor due to its resistance properties. all you are measuring is the potential of voltage. no one said anything about current.ask yourself do you need a ground hooked up to read voltage? the answer is no. all you need is a difference in potential from ground to positive. they don't need to be connected. simply put lets say you hook up a wire and test it at the source (battery terminal) you tread 12 volts then you go 100 feet down the wire and test again. you will still read 12 volts. a wire although it is a conductor still has resistance so that means that with your theory that there would be no way to test voltage except at the terminal unless ground is hooked up. voltage dropped across a load to create work is different than voltage dropped because of high resistance in a conductor.and as for you old sparky you jumped on the band wagon with idiot and now you seem to be just as electrically uneducated.Kodi H. Almeida

you can give up reading it all you want my tommy but that doesn't change the fact that there is a right way and a wrong way to do things. if you read the original post kmn5 states that other forums guys were telling him to upgrade the wire and they were right. although replacing the fuse holder may have bandaged the problem it is not the right answer. if he is pulling 30 amps on that circuit 12 guage wire will not hold up forever. end of story. although i am new to all of this 12 volt install stuff I have been to school for electronics/electricity not just a book and a test and I assure you there is only one right way. electricity can cause problems and alot of damage and unless one knows the right way to do it they do not need to be doing it at all.Kodi H. Almeida

wheres the captain now mr idiot?Kodi H. Almeida