PR280z Posted September 29, 2013 Share Posted September 29, 2013 Running electromotive fuel pump and 750cc injectors with 30amps relays that are just not cutting it. They keep dying out. Can i run some 60- 80 amps relays?? Quote Link to comment Share on other sites More sharing options...
Domzs Posted September 29, 2013 Share Posted September 29, 2013 Don't see why you would need 60-80 Amp. relays , those components don't draw that much . What do mean by " keep dying out " ? Quote Link to comment Share on other sites More sharing options...
PR280z Posted September 30, 2013 Author Share Posted September 30, 2013 If not the injectors the fuel pump stop working . Once i replace with new 30amps relays they start working again until they give out again. Quote Link to comment Share on other sites More sharing options...
Domzs Posted September 30, 2013 Share Posted September 30, 2013 Use an amp meter to check current draw on each relay , are they fused ? Make sure all your connections are good and tight . Quote Link to comment Share on other sites More sharing options...
PR280z Posted September 30, 2013 Author Share Posted September 30, 2013 (edited) ok Domz., I need to check on that, but would a 60 amp relay cause any harm or would they last a little more? Thanks. Edited September 30, 2013 by PR280z Quote Link to comment Share on other sites More sharing options...
DuoWing Posted September 30, 2013 Share Posted September 30, 2013 (edited) What size wire are you running to your pump? I was having issues where after driving my Z at higher(freeway) speeds for a bit my fuel pump would get loud. I was also seeing a loss in fuel pressure until I shut the car off for a bit. The relay was also getting quite hot. I started measuring voltage and was seeing as much as a full 1v drop from the relay output to the + terminal on the pump. What finally fixed my problem was thanks to JeffP and some other help here. I now run a 70amp relay like they give you with those Electric fan kits and I also run 10 gauge wire straight from a maxifuse terminal connected to battery, to the relay, then a 10 gauge wire from the relay back to the pump. I run a 10 gauge wire from the pump - to a grounding point in the back of the car. I have yet to finish adding another ground wire from the back of the car running back up to the front for my star ground setup, but after this I then was only seeing a voltage drop of at most .3v, the pump was no longer getting loud and I wasn't experiencing the pressure drop. This is on my 76' I was originally using the stock wires which are far too small in my opinion. Also if you happen to be running an external pump like I am, make sure you're not making it work to pull the fuel to the pump. I mounted mine lower to make sure it was being gravity fed from the tank. Also external pumps seem to like being mounted horizontally better. Edited September 30, 2013 by DuoWing Quote Link to comment Share on other sites More sharing options...
PR280z Posted October 2, 2013 Author Share Posted October 2, 2013 Thanks dou wing for the reply. i need to do an overall check on my set up. Quote Link to comment Share on other sites More sharing options...
cgsheen Posted October 2, 2013 Share Posted October 2, 2013 ok Domz., I need to check on that, but would a 60 amp relay cause any harm or would they last a little more? Thanks. Amperage is kind of "volume of current". It's sort of like how much water can flow through a given size pipe. Having a relay that will handle more amperage than the stock relay in and of itself can do no harm (except it may be "masking" other problems that might be present in your electrical system). A relay is just a switch (or set of contacts) that's operated by an electromagnet. It's amp rating is how much electrical current the switch mechanism inside can safely pass through. Too much current creates resistance which creates heat which oxidizes contacts which creates even more resistance which creates even more heat which - ya, leads to even more problems... Having said that, I have to agree with Domz. I just don't see why your fuel pump would be drawing that many amps (although I've never put an amp meter on a fuel pump). Still, pumps come with specs. Electric motors always have a specified amp draw. You should be able to find out real quick how many amps your fuel pump should draw. My thinking is: why would you ever need a relay rated much higher than the fuse that protects the circuit. Quote Link to comment Share on other sites More sharing options...
DuoWing Posted October 2, 2013 Share Posted October 2, 2013 I think the real problem comes from running such small gauge wire over such a large distance. If you're using the stock wiring you're running from the fusible link, to the relay, to the back of the car at the pump, which isn't even a straight shot. It goes through a grommet then back tracks a little to get over to the pump. Then your ground wire isn't even at the back of the car if I'm not mistaken, the ground for the pump then comes back in and runs back towards the front of the car and gets grounded in with the main harness. So you have a loooong way for that electricity to travel just to run this electric motor. Quote Link to comment Share on other sites More sharing options...
NewZed Posted October 2, 2013 Share Posted October 2, 2013 I'm no electrical expert but somewhere along the line I've learned or suspected that current draw increases with load in a DC motor. I Googled around and found what looks like a reputable source that illustrates it. It's at the bottom of the page linked below. So the fact that your fuel pump's DC motor is drawing so much current that it's killing 30 amp relays is a sign that your pump is working very hard. Harder than it seems like it should be if you have a typical return-style 280Z fuel system regulated to about 36 psi. You might examine the flow path for the fuel and see if you have obstructions, like a blocked filter or maybe you're using a 240Z return line and it's too small for the pump volume. In short, your pump might be drawing too much current because it's working too hard. I would focus on the fuel flow path first, not the electrical draw. http://www.me.umn.edu/courses/me2011/arduino/technotes/dcmotors/motor-tutorial/ Quote Link to comment Share on other sites More sharing options...
PR280z Posted October 2, 2013 Author Share Posted October 2, 2013 C:\Documents and Settings\adelberto medina\My Documents\My Pictures\2011-11-09 001 this is what im using Quote Link to comment Share on other sites More sharing options...
Domzs Posted October 2, 2013 Share Posted October 2, 2013 C:\Documents and Settings\adelberto medina\My Documents\My Pictures\2011-11-09 001 this is what im using Unable to see what you are posting . Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted October 2, 2013 Share Posted October 2, 2013 I'm no electrical expert but somewhere along the line I've learned or suspected that current draw increases with load in a DC motor. I Googled around and found what looks like a reputable source that illustrates it. It's at the bottom of the page linked below. So the fact that your fuel pump's DC motor is drawing so much current that it's killing 30 amp relays is a sign that your pump is working very hard. Harder than it seems like it should be if you have a typical return-style 280Z fuel system regulated to about 36 psi. You might examine the flow path for the fuel and see if you have obstructions, like a blocked filter or maybe you're using a 240Z return line and it's too small for the pump volume. In short, your pump might be drawing too much current because it's working too hard. I would focus on the fuel flow path first, not the electrical draw. http://www.me.umn.edu/courses/me2011/arduino/technotes/dcmotors/motor-tutorial/ As someone who works in the industry, that is exactly right. Is your fuel pressure correct? If the return is blocked or the regulator is defective, your fuel pressure would be sky-high and cause the fuel pump current to get very high. Your pump will fail soon under those conditions. Quote Link to comment Share on other sites More sharing options...
PR280z Posted October 2, 2013 Author Share Posted October 2, 2013 my pump:[/img] Uploaded with ImageShack.us Quote Link to comment Share on other sites More sharing options...
PR280z Posted October 2, 2013 Author Share Posted October 2, 2013 (edited) sleeperZ, what would be the ideal psi on the regulator ? i`m at 12psi of boost. Edited October 2, 2013 by PR280z Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted October 3, 2013 Share Posted October 3, 2013 Ideally you would run the pressure where your injectors are rated to flow. Most are 300kPa, or about 43.5psi, some are 250kPa, or about 36 psi. Your pressure regulator should be referenced to your manifold pressure, so your pump needs to flow enough for all your injectors at rated pressure plus your boost pressure, so your pump need to flow 57 gallons/hour at about 60psi, assuming you have a 6 cylinder. Quote Link to comment Share on other sites More sharing options...
PR280z Posted October 3, 2013 Author Share Posted October 3, 2013 Thanks, and yes L28et inside: [/img]Uploaded with ImageShack.us Quote Link to comment Share on other sites More sharing options...
Domzs Posted October 3, 2013 Share Posted October 3, 2013 Wires to your pump do look small . Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted October 3, 2013 Share Posted October 3, 2013 Wires to your pump do look small . I agree. I would rewire both power and ground wires. Quote Link to comment Share on other sites More sharing options...
PR280z Posted October 5, 2013 Author Share Posted October 5, 2013 I`ll get to it this weekend .thanks! Quote Link to comment Share on other sites More sharing options...
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