How to Rewire Your Fuel Pump FC3S RX7

How to Rewire Your Fuel Pump FC3S RX7 | Ep 24

Рет қаралды 9,764

5 жыл бұрын

In this episode, I show you 3 different ways to rewire the fuel pump on the RX7. Why rewire the fuel pump? The FC3S has a resistor relay box which varies the voltage to the fuel pump in an attempt to prolong the life of the pump. However, this variance in voltage, combined with 30 year old technology, is not the most reliable means to deliver power to the pump. So, we throw it in the trash! We are more concerned about consistent voltage/pressure than durability of the pump. Protect the engine at all cost!
Old video explaining my Fuel Pump voltage drop:
• Fuel Pump Voltage 101 ...
(It's not my best work, but the proof is there, ~0.5 V drop across the old system)
For any questions / comments feel free to ask below or find me on instagram.
/ rotary_knight
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Пікірлер: 82

@f3archrist 10 ай бұрын

You will forever be my hero for this

@N54OSCAR 5 жыл бұрын

Thank u for passing on the knowledge to the rotary community it is much appreciated please keep it up I enjoy all your videos your doing a awesome job

@cmtcustoms6386 3 жыл бұрын

Awesome video. Good info, detailed diagrams of the circuit. Thanks for putting your time into this!

@AlexFranceschi 3 жыл бұрын

For sure, thank you!

@stingofpurlear8 4 жыл бұрын

I really appreciate the time you put in this man, awesome video

@AlexFranceschi 4 жыл бұрын

Thank you! I appreciate the feedback! It's no easy task putting these detailed instructional videos together!

@stingofpurlear8 4 жыл бұрын

I know it I also have a channel and a fc3s so I know the difficulty of both of these things, but just wanted you to know your video has helped a fellow rotor head! And I'm sure many others so that time and effort is appreciated!

@AlexFranceschi 4 жыл бұрын

@@stingofpurlear8 Super happy to help and I'll def swing by and check out the channel!

@h.j.victory6103 5 жыл бұрын

Thanks for uploading, very good video. Very simple 👍👏🏁

@alexcarrillo7888 5 жыл бұрын

Ya extrañaba tus videos amigo fc✌

@AlexFranceschi 5 жыл бұрын

Gracias!

@TemaPoljanski Жыл бұрын

Legend! Thank you

@dusting3433 2 жыл бұрын

Hey thanks a lot for the time you took to show the ways of fuel I work on cars all the time but never had an rx7 before so I'm a bit nervous because I don't want to screw it up mine is a 1986 and it had sat for awhile motor was froze but I was able to free it and I can run car if prime it by dumping gas down it's throat I hope with this new knowledge I can get the fuel system working again then I can actually drive it so thank you again I can't wait to go out and see if this will work I'll probably try what you called the easiest way and because of the way you showed it should be easy

@AlexFranceschi 2 жыл бұрын

Absolutely, happy to help! Nice work getting the motor to spin and fire up. S4s are a bit different from the S5s like mine, but you can find all of the repair manuals and wiring diagrams online. Good luck and feel free to ask any questions.

@gretastevens1195 9 ай бұрын

My husband sent me this with the intent that I bypass the ‘87’s relay tonight. God help whichever one of us goes to start this thing tomorrow. All jokes aside, thank you for making this. It’s been about 4 years since my ECE100 class and I remembered nothing

@treyw.4278 4 жыл бұрын

Please make a video explaining this for FD’s =) !!!

@jkucukov Жыл бұрын

Cool video, thanks for sharing, I was wondering where the Check connector is located to prime the fuel pump?

@cadenmurray7827 4 жыл бұрын

You the man

@algurdian 11 ай бұрын

Hi Alex , great video! I tried all options but kept having issues so I did the third option and ran a totally new circuit , when I pull the trouble codes the CPU is showing trouble code " 51 - Fuel pump resistor relay." does this affect drivability?? or can I just ignore it as I don't have the Relay resistor anymore.? Is there a way to wire in a resistor to the cpu so the code goes away ? FSM shows there should be .7 to .94 ohms from wire E to wire F. Thanks for your help 1990 NA Vert

@rotary_13b78 5 жыл бұрын

Thanks bro!

@AlexFranceschi 5 жыл бұрын

You're welcome, thanks for watching!

@daesyoung 5 жыл бұрын

previous person cut the relay 4 2 plug in bay. i got another relay but the 2 pin plug touched and now that black yelow doesnt hav power

@AlexFranceschi 5 жыл бұрын

It is difficult for me to fully understand your problem. The relay in the engine bay that you are referring to is the resistor relay behind the passenger headlight, correct? What was cut exactly? Did someone try to splice the wires together, or they simply cut all the wires in the harness?

@rexmemore 11 ай бұрын

So with option 2 did you also do option 1 with it?

@oscurozado5929 2 жыл бұрын

What's the effect of never having the low voltage to the fuel pump if I do option 2 and bypass the resistor relay? How will the engine be able to idle or function in a low load situation at low RPMs? That is, how would the ability to drive like Grandma or slow roll past the police be affected? Would I have high idle all the time? Also, I have a 1988 non-turbo. Based on your response to a previous comment, does all this apply to my car?

@AlexFranceschi 2 жыл бұрын

Low voltage to the pump simply means it may not be able to supply enough fuel pressure to the engine. Low fuel pressure means the engine may run lean (low fuel but a lot of air), not good for internal combustion engines.

@thedieh3628 4 жыл бұрын

Great video. Explained very well. What would happen if I ground the brown wire to the black wire at connector Ba-01 F-08. Would this just delete the resister and ECU loop? Also making the pump run close to 12v in the run and start positions.

@thedieh3628 4 жыл бұрын

Check Connector “Brown” / Ground “Black”

@AlexFranceschi 4 жыл бұрын

Sorry for the delayed response. I can't say for sure what would happen if you did that, it's been awhile since I've done a deep dive into the FC fuel circuit, but in theory, just deleting the resistor relay (option 1 in this video) will be okay. You will have some voltage loss to fuel pump, but it will be better than relying on this old resistor that is over 30 years old.

@thedieh3628 4 жыл бұрын

Alex Franceschi , thanks for the response. I gave myself some extra space while doing what I mentioned above to fix something if I messed up. However, Just grounding the “brown wire”starts pumping fuel the second the car is turned on with this configuration. I think I’ll use your option three at a later time. Great video again.

@keithjohnson1403 2 жыл бұрын

@@AlexFranceschi we did the second option and there must be a volt drop because the fuel relay and pump started to just buzz and not stay open. also the voltage switched back and forth with the brown and one below it on the relay.

@motorpsychohead Жыл бұрын

Hi, I am new to rotary engine and I just got a 1989 rx7 to build for my son. My question is when you choose to go with the method 2 then what did you do to the resistor relay in the engine bay by the passenger headlight ? Did you still remove it or did you leave it untouched and go on with method 2 ? Any answer would be a big help for me and greatly appreciated! Good day !

@AlexFranceschi Жыл бұрын

So, I removed mine completely. There was no need to keep it, but if you want the car to remain OEM and keeps it value as a classic, you can leave it as it is. This is really for people who modify their turbos, increase boost and want the insurance of consistent fuel pump voltage and pressure.

@supradoom 10 ай бұрын

@@AlexFranceschiis there an issue if you are running lown impedence injectors when you delete this? On rtek and have after market injectors.

@SydeshowMO 4 жыл бұрын

Couldn’t have been explained any better bro! I just replaced my fuel sending unit and couldn’t get it to start unless I unplugged the FP harness, start car, and immediately plug the FP harness back. I never primed the system but not sure if that’s the issue or I have a bad GND from FP to body of the frame holding the FP and sending unit.

@AlexFranceschi 4 жыл бұрын

Nice, happy to help! Is everything working okay now? When you say FP harness, is it the stock Fuel Pump harness or a custom one you made?

@SydeshowMO 4 жыл бұрын

Not FP harness but the metal frame that hold the FP and sending unit. Still no luck. I checked voltage today at the wiring harness connecting to FP. IGN on I get no voltage. That said I may have blown a fuse or relay. In didnt disco the batt before removing pump.

@AlexFranceschi 4 жыл бұрын

@@SydeshowMO yeah, check the fuse or relay if you have no voltage at all.

@SydeshowMO 4 жыл бұрын

Alex Franceschi done! Thanks again for making this awesome video! I was able to go to it along with the old one to use as reference. Problem was no continuity from harness to top of screw terminal to FP. Moved everything back to the old frame that holds the FP and sending unit. I get a good 12.9v to the pump at idle. I get 7.95v while cranking.

@AlexFranceschi 4 жыл бұрын

@@SydeshowMO Nice work! Glad you got it working. I never measured the voltage while cranking, but it does make sense because a huge draw is being pulled from the battery.

@trestovall9530 3 жыл бұрын

So you have a question that my Mazda RX7 the has a new fuel pump a new ECM in it and new fuel ejectors and my fuel ejectors are not firing and I can't figure out anything on the wiring to the fuel ejectors or anything that way

@trestovall9530 3 жыл бұрын

Also I forgot to tell you that the fuel rail has fuel pressure to it it's just the fuel injectors don't fire

@AlexFranceschi 3 жыл бұрын

To be honest, I don't think I would be able to help you. But if you have an aftermarket ECU I would refer to their wiring diagram for the injector wiring. If you have an OEM ECU, I would refer to the factory service manual which you can find online.

@arthurraber3839 4 жыл бұрын

Correct me if I'm wrong, but the NA models ('88 FC RX7 5MT in my case) don't come with a relay resistor do they?

@AlexFranceschi 4 жыл бұрын

I think you are right. The S4 turbo systems have the relay resistor, and all S5s have this part. The S4 NA motors do not (what you have). Sorry for any confusion! (I double checked the factory manuals and this seems to be the case)

@arthurraber3839 4 жыл бұрын

@@AlexFranceschi haha, it's all good. Currently diagnosising a fuel pump issue and wanted to make sure I didn't have something else to check. If you don't mind, can I message you on Instagram? I've got a few questions about the the actual fuel pump relay wiring (previous owner did some naughty things to it I'm try to fix)

@AlexFranceschi 4 жыл бұрын

@@arthurraber3839 no problem, shoot me a message anytime. I'll do what I can.

@Hygoog 4 жыл бұрын

After completing the installation for the 2nd option do i simply unplug the resistor relay box and throw it in the trash?

@AlexFranceschi 4 жыл бұрын

Yup! Or you can sell it and make a lil $$$. I kept the bracket for it and actually made a mount for a battery jump post with it. I'll have a new video soon about relocating the battery and some tips/tricks for that.

@Hygoog 4 жыл бұрын

I did the second step and now my car won't start. Checked the power on the fuel pump connector and theres no power at all. Maybe the fuel pump relay went out? It's not even priming anymore even with the jumper connected.

@doraibu.garage Жыл бұрын

Bit confused, if you do option 2 do you also have to do option 1

@AlexFranceschi Жыл бұрын

No, it's either or, not both.

@eddylorenzo5033 Жыл бұрын

Can u do this with stock ecu and injectors fire right? Did u plug back in to the relay under Dash when u cut positive wire please help option 2 would have been great if u showed the full finish make a video on that please

@AlexFranceschi Жыл бұрын

I made this video after I finished everything and have a perfectly running car via option 2. I did exactly as I posted. Not sure what you want to see.

@eddylorenzo5033 Жыл бұрын

@@AlexFranceschi did you plug relay back in under Dash and theother wires to plug u left intact and was that after u deleted everything upfront

@AlexFranceschi Жыл бұрын

Yes, the relay under the dash is still there, I mentioned exactly what I did in the video, you can go back and watch it again. I replaced the power cable to the relay under the dash and removed the resistor relay under the hood. I cut the power wire to the relay under the dash to save the spade that goes into the connector and soldered it on to my new power wire. It's all in the video. You don't need the old power wire that goes to the resistor relay under the hood.

@eddylorenzo5033 Жыл бұрын

@@AlexFranceschi yeah but u still plugged relay under dashboard with power wire out and running direct to the pump wire in back or did u eliminate the relay fuse under Dash or plugged it back thanx bro

@AlexFranceschi Жыл бұрын

Okay, I think you may have misunderstood the wiring diagram. You must have a relay. The relay is still under the dash and plugged in. You simply replace one wire that goes to that relay. The wire that goes to the fuel pump. That's how it's done. You cannot remove the relay altogether. It would not work correctly.

@offthehook7210 5 жыл бұрын

Alex ive got an 84 rx7 gsl and im not getting the fuel pump to work your video is the best ive seen but the plugs are different can you help me

@AlexFranceschi 5 жыл бұрын

I'm not as experienced with 1st gens, but I'll do my best. First off, the gsl is a 12A? Not the 13b? Correct? If so, your relay should have four wires. If there was a way to post pictures in the comments I would show you (if you have instagram you can send me a message there and I can show you the wiring diagram @rotary_knight). Anyway, the power wire should be a blue and white wire. Make sure this wire is getting power at the relay and at your plug for the fuel pump...not sure where they are on the 1st gens. If the power wire has voltage, check your grounds, or you might have to replace the relay. Hope that helps as a starting point!

@offthehook7210 5 жыл бұрын

@@AlexFranceschi ok I'm not sure what 12A or 13b is .but there are 4pins on the relay which i checked the resistance and it is 105 ohms.and there is power going to the relay but no power at the fuel pump plug which only has 2 wires to the pump.i put a jumper at the relay plug and still no power at the pump.on the gas petal art there is a switch and when i. Push it in it triggers the relay thats behind the passenger head light..and i do have an Instagram off the hook.pleasr bare with me im not to good with all of the technology.but i will figure it out

@offthehook7210 5 жыл бұрын

Instagram. Off_the_hook_tattoos

@AlexFranceschi 5 жыл бұрын

@@offthehook7210 got it. Sent you a message on instagram. I'll look up the right wiring diagram for you and see if i can send it over there.

@offthehook7210 5 жыл бұрын

@@AlexFranceschi well i found that the relay plug has power i used a test light grounded to a bolt and it lights up but when i try grounging it to one of the pins i dont get a light or should i say i cant get a ground from any of the 3 remaining pins

@d1zguy864 3 жыл бұрын

on the last option 85 on relay should be ground and 86 power, some relay's have a resistor in them, you always want ground on 85

@AlexFranceschi 3 жыл бұрын

Thanks for the tip.

@BobbyJoe13b Жыл бұрын

Is that 15amp fuse the egi fuse?

@BobbyJoe13b Жыл бұрын

Nvm, it’s the engine fuse 😅

@Hygoog 4 жыл бұрын

I have a 13b 6 port with a T04b T4 turbo, 4x ID1050x, and Haltech Sport 1000. My goal is no more than 10psi. Will I need to move up to the third option or is the second option sufficient?

@AlexFranceschi 4 жыл бұрын

The best way to check is to measure your fuel pump voltage at various throttle positions / engine loads. Make sure the voltage is stable. If it is stable as-is, then you have no need to change it. But if you notice the voltage drops or fluctuates, it may be worth updating the wiring altogether. It's hard to say because our cars are so old. Some of the wiring is still good, but in some cars the wiring is bad. Hope that helps!

@joeybaggettjr9119 4 жыл бұрын

Have question with option 3 if you remove everything up front where do you get the 12v signal from

@AlexFranceschi 4 жыл бұрын

@@joeybaggettjr9119 you run a wire directly from the battery itself and you can use any power wire that is tied to the ignition as your switch source for the relay.

@Hygoog 4 жыл бұрын

@@AlexFranceschi Hey if I go with option 3 does that mean I can no longer use the jump connector to prime my fuel system?

@AlexFranceschi 4 жыл бұрын

@@Hygoog correct, but you could wire in a manual switch and prime it whenever you want.

@AlexFranceschi 5 жыл бұрын

For those who want to skip ahead Generic FC3S Fuel Circuit Explanation: kzfaq.info/get/bejne/nM-oZsRj2LHPgas.html Option 1 - Deleting the Resistor Relay: kzfaq.info/get/bejne/nM-oZsRj2LHPgas.html Option 2 - Bypass the Resistor Relay: kzfaq.info/get/bejne/nM-oZsRj2LHPgas.html Option 3 - Create a New Fuel Circuit: kzfaq.info/get/bejne/nM-oZsRj2LHPgas.html

@teamideall 4 жыл бұрын

for option 1: is this the same process on a s4 car? the resistor/relay has a different plug (round barrel connector) mainly wondering if the wiring is the same between the two or if i have to splice different pins together. using the same A->D & C->F you did here would have a red wire connected to white and blue connected to black on the s4 plug. feel free to dm me directly on instagram, i would be glad to send photos of my resistor relay/ plug as well as the s4 FSM diagram!! @mike__george with two underscores __

@AlexFranceschi 4 жыл бұрын

I'll find you on instagram, I would have to check the wiring diagrams for the S4 to be sure.