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That's right I remember that story. I guess I will put in a maxi fuse and a 30amp ... or I may go back to the 2 step oem system and add some wire. I like my setup now, but obviously this didn't work. I did like this setup lol.
How is your fuel pump wired now? The reason I ask is because simply adding a higher current fuse and/or better fuse holder won't necessarily solve the problem if it's root cause is a weak connection elsewhere in the circuit from battery (power supply/bus) to the fuel pump (load), and that includes the ground paths. I like to run a minimum 10AWG gauge wire circuit from battery all the way to the pump, for a single Walbro 450 or equivalent pump electrical load.
Lots of fuel pump rewire jobs that I've seen reuse the existing OEM bulkhead connector in the tank (because it's easy), which will be a problem if your pump draws more current than the OEM pump. Those puny terminals in the OEM bulkhead connector are a current flow choke point, even when the connector is brand new - and you guessed it, more current = more heat = blown fuse.
How is your fuel pump wired now? The reason I ask is because simply adding a higher current fuse and/or better fuse holder won't necessarily solve the problem if it's root cause is a weak connection elsewhere in the circuit from battery (power supply/bus) to the fuel pump (load), and that includes the ground paths. I like to run a minimum 10AWG gauge wire circuit from battery all the way to the pump, for a single Walbro 450 or equivalent pump electrical load.
Lots of fuel pump rewire jobs that I've seen reuse the existing OEM bulkhead connector in the tank (because it's easy), which will be a problem if your pump draws more current than the OEM pump. Those puny terminals in the OEM bulkhead connector are a current flow choke point, even when the connector is brand new - and you guessed it, more current = more heat = blown fuse.
^^This! Seen it many times. Double check the inside of the fuel pump bulkhead connector… they can’t handle to extra amps of aftermarket pumps and will eventually fail.
MANY aftermarket fuse holders are CRAP. They really don't handle the amperage they should.
Just a general lesson from someone who has blown his fair share of motors - typically when a motor lets go from a broken apex seal or similar detonation-related failure you lose a lot of power, get rough idle, and the car runs rough, but it WILL run. It's VERY uncommon to have a motor completely lose ALL compression.
Terry, glad it's something easy to fix! Hope you see you at DGRR!
How is your fuel pump wired now? The reason I ask is because simply adding a higher current fuse and/or better fuse holder won't necessarily solve the problem if it's root cause is a weak connection elsewhere in the circuit from battery (power supply/bus) to the fuel pump (load), and that includes the ground paths. I like to run a minimum 10AWG gauge wire circuit from battery all the way to the pump, for a single Walbro 450 or equivalent pump electrical load.
Lots of fuel pump rewire jobs that I've seen reuse the existing OEM bulkhead connector in the tank (because it's easy), which will be a problem if your pump draws more current than the OEM pump. Those puny terminals in the OEM bulkhead connector are a current flow choke point, even when the connector is brand new - and you guessed it, more current = more heat = blown fuse.
So this is Sakebomb's rewire set up that bypasses the oem 2 stage. It plugs into the factory harness. I also have a Fuellabs through bulkhead connectors running 2 smaller extra power and an extra ground . These are mil spec 14g with an extra 14g ground thrown in. This is for the Supra TT pump.
I am actually considering a quick fix of running an additional power and ground through bulkhead with a damn switch... that way if the fuse blows or the relay fails i have a whole redundant system lol..... seems unnecessary and overkill, but here I am.
If the fuse wasn’t blown you had a faulty fuse holder. What you experienced only generally happens when people over fuse the wire amperage rating. Since that was a 20 amp, you need to amp probe out your pump to see what it’s pulling while running. I made a post in Howard’s thread about his mishap, tho his was a mini fuse holder not atc like yours. He also boosts the voltage up higher which in turn reduces the amperage. The one in the sakebomb garage kit is an atc which is widely used in the auto industry. I have the same setup as you , Supra pump, sakebomb bypass and relocated battery. I do know that Chris @ banzai uses Supra or now that they are discontinued the walbro pump with the stock resistor without issue. I would investigate your fuel pump before I made any changes.
If the fuse wasn’t blown you had a faulty fuse holder. What you experienced only generally happens when people over fuse the wire amperage rating. Since that was a 20 amp, you need to amp probe out your pump to see what it’s pulling while running. I made a post in Howard’s thread about his mishap, tho his was a mini fuse holder not atc like yours. He also boosts the voltage up higher which in turn reduces the amperage. The one in the sakebomb garage kit is an atc which is widely used in the auto industry. I have the same setup as you , Supra pump, sakebomb bypass and relocated battery. I do know that Chris @ banzai uses Supra or now that they are discontinued the walbro pump with the stock resistor without issue. I would investigate your fuel pump before I made any changes.
~ GW
So your running a 20amp fuse? I have an ARD alternator which holds an unbelievable steady voltage and is high amperage. I know that obviously doesn't affect the draw from the pump, but the pump has more than enough juice. What should I be looking for on the pump? It is a maybe 2.5 year old supra pump with maybe 10k miles now.. probably less. Looking for amperage draw and that's about it? I mean I can pull it and check all connections etc. I could add another ground... lol my car probably has 20 additional grounds as is.
Do you have a build thread so I can see how your running? Or a quick description?
...He also boosts the voltage up higher which in turn reduces the amperage ...
~ GW
Boosting voltage will raise the amperage, given a fixed resistance the voltage is applied to. The only way increased voltage will reduce amperage is if the wattage stays the same. That would require some sort of feedback wattage/amperage control.
^ I don’t disagree with you. That is ohm’s law. Pretty sure the boost a pump does just that with the controller. It has some sort of internal feedback control. Hence why Howard was only running a 20 amp fuse for all that pump output. The op does not have anything like that on his though.
Testrun,
You can buy a cheap amp probe that does dc stuff online. It doesn’t need to be a super expensive one. You don’t need to read down to .01 amp. I would repair that with a maxi fuse holder that was rated for 32v dc and at least 30amp. That doesn’t mean fuse it for 30 amps tho. They seem to be better quality. Like dale said, most of them are crap. You can then put your amp probe clamp around it and see what it’s reading. I can check mine this weekend and let you know. The issue is knowing what it’s doing as the fuel pressure is rising. Most rising fuel pressure regulator is are one to one. As the pressure increases so does the load on the pump. Not sure what it’s going to read at full tilt. Here (RRE Instructions ) is an amperage vs voltage that I found a while ago when I was searching for which pump to use.
I think you just got a bad fuse holder. It happens. I would still check it out to make sure.
So 21 amps is the max showing I would think the 20 amp is pushing it. I will check all the wiring to make sure it isn't shorting anywhere and I guess just add another inline maxi fuse at 30 amps or so.
I can shorten some of the wires a bit more which can lessen some resistance. I can't imagine needing to add more wire than what I have.
you know.... sometimes old modified cars do things out of character once or twice and then never again. not the explanation anyone is looking for I'm sure but we've seen it quite a few times. most recently on an FD we built, the fuse in the harness for IGN coils blew a few seconds after start up. we replaced it and a few thousand miles and plenty of starts later, it hasn't happened again and likely wont. there may not necessarily be anything "wrong", it could have just been a freak occurrence. following up on the reccommdations wouldn't hurt and doing what you described wouldn't hurt either but don't lose yourself trying to find a problem that may or may not be there
If you’re showing 21 amps of load on a 20 amp atc then you’re on borrowed time. What size wire is the sakebomb kit from the battery? I can’t remember off the top of my head but I think it’s 12 ~ which is good for 25 amps on dc. I believe it’s 12 because I have a 25 amp fuse in mine, and I would have checked that on install. I’ll amp probe mine out this weekend and report back.
If you’re showing 21 amps of load on a 20 amp atc then you’re on borrowed time. What size wire is the sakebomb kit from the battery? I can’t remember off the top of my head but I think it’s 12 ~ which is good for 25 amps on dc. I believe it’s 12 because I have a 25 amp fuse in mine, and I would have checked that on install. I’ll amp probe mine out this weekend and report back.
~ GW
DC Chart ;
Please let me know what you find on your's. the 21amps Injust saw on a chart. I didn't check mine yet.
Oh I see. You need to calculate your fuel pressure to know the amperage draw. I don’t know what your base fuel pressure is, but assuming it’s 43.5. ( the book says stock is 36 ) and you are running 13 psi that you stated earlier in the thread, that’s 56.5 psi. That’s under 19 amps according to the chart.
Yeah, it could just be the fuse holder itself. Also I only had a 20amp fuse in there... I thought it was a 25 or 30. Supra TT pump.
3scary to think something so simple can blow the motor. This happened I shut off the throttle abruptly. Could have been worse and happened with my foot down. Car idles the same as it did before. Smooth and power seems normal... out of boost lol I just rigged up a quick fix to drive it home. Can you believe AAA never came?
the problem is the wire gauge is not thick enough to support that amperage
I thought the same when I 1st got the harness, but there are so many others using it and a lot of the gauge people use for the fuel pump seem small to me. How is it Inhave the issue? It is a Supra pump. It isn't like it's a damn hellcat or something....
You need to calculate your amperage draw to size your wire. The chart I posted has the info. I will probe mine today. Not sure if that will help you but may give you an idea if yours is higher than mine by a fair margin.
You need to calculate your amperage draw to size your wire. The chart I posted has the info. I will probe mine today. Not sure if that will help you but may give you an idea if yours is higher than mine by a fair margin.
~ GW
Understood, but I also need to keep in mind that I have 2 other short 14 gauge wire along with the factory with this kit. I guess what I am trying to say ts I don't see how the hell my supra pump could be demanding so much compared to anyone else with the same pump. I know it is getting 14v solid for sure. I am getting ready to work on it, just trying to figure out what type of fuse holder to stick in there. Another spade type or what.....
I checked this today. I draw right around 8.5 Amps while at idle. I do not have a way to check this at full tilt. The only way to do that would be to send it somewhere like RC engineering. They could bench test the flow rate verse, psi verse, amperage draw. If you follow the chart I posted and do the calculation for your max fuel pressure. I think you’ll find you’re under the 20 amp mark. I think you just got a bad fuse holder.
I checked this today. I draw right around 8.5 Amps while at idle. I do not have a way to check this at full tilt. The only way to do that would be to send it somewhere like RC engineering. They could bench test the flow rate verse, psi verse, amperage draw. If you follow the chart I posted and do the calculation for your max fuel pressure. I think you’ll find you’re under the 20 amp mark. I think you just got a bad fuse holder.
~ GW
I will go with a 30amp maxi fuse. I believe that is more than adequate and still small enough should I have a short. I will. I will check all the wires. I forgot how I have the added wires ran at this point.
Remember that the job of the fuse is to protect the wire (and relay, and connectors) from burning or melting. If all of your wire and relay and connectors in the circuit are capable of handling 30A safely, then it's safe to swap fuses. But if even just one other piece of the puzzle will be harmed by 25A then it's not safe to swap fuses to a higher rating.
25A is too much for 14AWG wire, the wire might not melt but it will get noticeably warm and possibly feel hot to the touch after carrying 25A for a few minutes. It's also less efficient, if you have a multimeter you can probably measure that the voltage at the fuel pump is at least 0.75V less than the voltage at the battery, the heat is generated because that section of too-thin wire is absorbing (wasting) energy that could have gone to the fuel pump.
I saw that you mentioned a maxi fuse, that's a good idea. I've pulled 30A and 35A through an ATC size fuse and the fuse holder started to melt.
[QUOTE=scotty305;12556282]Remember that the job of the fuse is to protect the wire (and relay, and connectors) from burning or melting. If all of your wire and relay and connectors in the circuit are capable of handling 30A safely, then it's safe to swap fuses. But if even just one other piece of the puzzle will be harmed by 25A then it's not safe to swap fuses to a higher rating.
25A is too much for 14AWG wire, the wire might not melt but it will get noticeably warm and possibly feel hot to the touch after carrying 25A for a few minutes. It's also less efficient, if you have a multimeter you can probably measure that the voltage at the fuel pump is at least 0.75V less than the voltage at the battery, the heat is generated because that section of too-thin wire is absorbing (wasting) energy that could have gone to the fuel pump.
I saw that you mentioned a maxi fuse, that's a good idea. I've pulled 30A and 35A through an ATC size fuse and the fuse holder started to melt.
I will drop it to a 25. If I need a 25 besides a possible short I have other issues. This thing is supposed to only pulls 21amps max from what I understand. I will donsome more research on it. It's been over a year I played with the pumpnand wiring. It isn't like this just happened the instant I put it in.
If you want an excuse to buy a new tool, local hardware stores like Lowes or Home Depot might carry a clamping DC current meter. You can use that to measure the current going to the fuel pump, and most of them have a 'max' mode where the tool will store the maximum measurement. You could rig that up to measure your fuel pump's max current draw during normal driving, just clamp it around one of the wires (not both wires, the two different current directions would cancel each other out).
Be sure not to get the cheapest clamping current meter at the store, the cheapest ones usually measure AC current only (like house wiring), you need to step up at least one tier to get the ones what will also measure DC current (like car 12V systems, or solar panels). I have an Ideal 61-747, it works well.
The sakebomb relay kit is a piece of 12 for that fuse holder. That’s only rated to 25 amp. I would not fuse past that. Having a higher rated fuse holder is fine since they have a better rating. That’s why I suggested the 32v rated stuff in a 30 amp size. Not to fuse at 30 amp tho. You do not want to fuse for higher than your minimum wire size.
Update. This had to be the fuse holder itself, but I am taking a couple extra steps.
keeping Sakebomb's harness as it seems like good quality with a 50amp relay. I have 2 additional 14 gauge wires through bulkhead going to the relay for power and another 14 gauge through nulkhead for grounding. I am putting a 12 gauge from relay to battery running it through a 30 Amp Maxi fuse. There is no way in hell this is not adequate for my set up. Unfortunately I will not be making it to the Dragon this year, but I am taking it to the track on the 16th of this month. I will jump on the oval and check the tune and see if anything gets heated up on the wires, relay, or fuse.
My 12gauge should be here on the 14th. If I have any other issues I will report back. But considering this done.
Ok... I took it to the track today for some 4th a d 5th pulls on the oval and now the damn relay is hot... The drive there was about 45 min with a bunch of pulls to try and see how things are on boost. The 50amp relay which is in the rear left compartment behind strut was smoking hot.... I let everything cool and hopped on the track and relay got really warm again..... the fuse never got hot nor did the wires, but the relay would.
Maybe I should have changed the relay our after the fuse holder melted..... I upgraded the wire from bat to relay to 12 gauge and remember from relay to pump there are 2 othe 14g spliced in within a few inches from the exit of relay to the pump....
Sakebomb!!.... it may be time to go back to the good old oem setup with some additional wire....
04-07-23, 10:53 AM
