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Hello all so here's my issue and I've tried a few things but I'm not familiar with the rx7s at all. So I'm working on a 1987 rx7 n/a the issue I'm having is the fuel pump won't run I'm getting 12v to the pump and it will only run when I jump ground so I went through cleaned the ground behind the cluster on the frame rail on the front left engine bay the ground under the intake manifold and grounds in the trunk but no avail. I tried closing the replay under the dash that has the big yellow plug on the relay side the fuel pump relay and still nothing. Tried jumping the yellow plug on the passenger side strut tower still no go even tried opening the afm alittle and nothing. But if I run a ground from the pump to the body the car runs but obviously that's not a fix the pump will run 24/7. Any information would be greatly appreciated I have searched and searched and just cannot find a solution to this issue.
Electrical gremlins are tough to solve at times. Homefully you have a digital multimeter. There is a good disection on the fuel pump sender on here recently. Start ohming the cabling from the fuel pump on the fuel pump to the sender body. I believe the sender body ground is tied to one of the leads on the outside of the seding unit, check that. Then, check the cabling from the sending unit to the molex connector by the shock tower. After that I am lost. Best of luck to you. Report back with progress if possible.
Edit: It is obvious that the spot where you have the added groung wire is good to the pump. Check from there forward.
Electrical gremlins are tough to solve at times. Homefully you have a digital multimeter. There is a good disection on the fuel pump sender on here recently. Start ohming the cabling from the fuel pump on the fuel pump to the sender body. I believe the sender body ground is tied to one of the leads on the outside of the seding unit, check that. Then, check the cabling from the sending unit to the molex connector by the shock tower. After that I am lost. Best of luck to you. Report back with progress if possible.
thank you and yes it's been a pain and I have checked over everything I possibly could from what I found the pcm sends the ground but can't confirm. The car ran before it had the fuel tank filter and pump replaced due to rust. Basically I got my hands on the car at my work and was told if I can get it fixed properly I'll get a permanent 1 dollar raise so im determined to fix it since no one else has been able to.
Have you checked the connector behind the carpet by rear driver side speaker? Back probe both ends of the connector and check for continuity. I'm not 100% sure where this connector leads to, but page 50-34(wiring diagram) in the FSM shows where the wiring runs. Check this connector to the next and so on.
Section 15-162 in the FSM shows the connector by the speaker.
Have you checked the connector behind the carpet by rear driver side speaker? Back probe both ends of the connector and check for continuity. I'm not 100% sure where this connector leads to, but page 50-34(wiring diagram) in the FSM shows where the wiring runs. Check this connector to the next and so on.
Section 15-162 in the FSM shows the connector by the speaker.
yes I did back probe and have power where I need it but no ground to the pump if I remeber correctly it was a blue wire with yellow tracer.
Back probe and check for continuity at the connector. Back probe and check for ground on both sides of the connector.
I did back probe there's no ground at the blue/yellow wire which is the ground to the fuel sender from the reading I've done apperently that controls the pump itself and the fuel gauge. I do have continuity through the sender to the plug so wiring off the fuel sender is good. I was trying to find a wiring diagram but everything is for the turbo 2 and I can't really find anything on what sends the ground trigger to the pump. The car does run if I jump a ground to the pump but that doesn't fix the issue at hand lol.
I did back probe there's no ground at the blue/yellow wire which is the ground to the fuel sender from the reading I've done apperently that controls the pump itself and the fuel gauge. I do have continuity through the sender to the plug so wiring off the fuel sender is good. I was trying to find a wiring diagram but everything is for the turbo 2 and I can't really find anything on what sends the ground trigger to the pump. The car does run if I jump a ground to the pump but that doesn't fix the issue at hand lol.
You are at the shock tower in the back? You just need to trace from there to the front? You will need a long piece of wire now. Look for the blue/yellow wire in a loom that runs down the driver side under the carpet. I would start near the driver foot well close to the rocker panel. If it isn't there, keep looking. Once you find it, test it with the meter and the long wire and check for ground again. If you have access to a wire toner and probe, this might speed things up. I am not sure what one will or won't do to sensors or the ECU. So ... use with caution. If you have the time and the pateince, we will get you the raise.
You are at the shock tower in the back? You just need to trace from there to the front? You will need a long piece of wire now. Look for the blue/yellow wire in a loom that runs down the driver side under the carpet. I would start near the driver foot well close to the rocker panel. If it isn't there, keep looking. Once you find it, test it with the meter and the long wire and check for ground again. If you have access to a wire toner and probe, this might speed things up. I am not sure what one will or won't do to sensors or the ECU. So ... use with caution. If you have the time and the pateince, we will get you the raise.
yes im at the driver side rear strut tower i did pull back the harness a bit and starr uncovering it. I wanna figure out where it goes so i can test that length if wire from front to back. I assume ot runs to the pcm? But not sure until i start start stripping back the wiring harness and chasing it.
So this is the plug on the driver side kick panel that has the blue/yellow wite in it i checked for continuity and its good so no broken wire now to try and figure whats suppose to trigger the ground and fix it.
Page 50-36 & 50-37 in the S4 FSM shows the wiring diagram for an NA. It looks like the fuel pump grounds via the black wire from the connector to ground near the rear passenger side near tail lights (#25). Check this ground / continuity to the FP connector. You said you cleaned this ground, but not sure if you checked the actual wiring to the ground.
Page 50-36 & 50-37 in the S4 FSM shows the wiring diagram for an NA. It looks like the fuel pump grounds via the black wire from the connector to ground near the rear passenger side near tail lights (#25). Check this ground / continuity to the FP connector. You said you cleaned this ground, but not sure if you checked the actual wiring to the ground.
the wire on the body harness side or fuel sending unit side?? Neither of them had ground but used a cornwell test light that tells power or ground and voltage I have no ground at the harness but I do have ground at the body ground.
the wire on the body harness side or fuel sending unit side?? Neither of them had ground but used a cornwell test light that tells power or ground and voltage I have no ground at the harness but I do have ground at the body ground.
He is refering to the black wire at the connector near the driver shock tower that goes to the pump. Those other wires or body harness wires are not your ground wires. The black wire terminates by the rear light. Ohm the black wire to ground from every point from the pump to the last point before final termination.
If this is good, the ground isn't the problem. You could have a bad relay or ignition switch.
wilfff is giving good advice here, I will duck out now unless you get stuck.
He is refering to the black wire at the connector near the driver shock tower that goes to the pump. Those other wires or body harness wires are not your ground wires. The black wire terminates by the rear light. Ohm the black wire to ground from every point from the pump to the last point before final termination.
If this is good, the ground isn't the problem. You could have a bad relay or ignition switch.
wilfff is giving good advice here, I will duck out now unless you get stuck.
So this plug here from the body harness to the sending unit. The black ground on the sender side is blue/yellow on the body harness side I did check it for a break with my multimeter for continuity and came back good from the driver side kick panel to the plug at the strut tower.
That connector has a black wire on it, that is your ground. Or so says the gentleman with the schematic.
yes the wiring from the sender to that plug is black but change to the blue/yellow tracer on the body harness side of that plug I checked for continuity fron the sender side to the green plug in the driver side kick panel and it tested good. I assume the pcm sends the ground to the pump I'm just not sure how this system works I'd rather not rewire the whole car to a more modern relay setup. I tested the fuel pump relay under the dash and it's good even closed the circuit by closing the relay by hand I pulled the cover off it and nothing changed still no ground at the sender. I tried manually opening the afm I read that controls the pump but that did nothing same goes for the yellow 2 wire plug on the passenger side front strut tower. I've tried to find other people that may have had this issue but it seems like everyone else loses power to the pump I have 12vs to it if I run a jumper ground from the black wire on the fuel sender to the body the pump runs. So I'm assume the pcm is not sending the ground signal to the pump.
This black wire is in your harness. I can barely see it in your picture. Trace it to the loom where it disapears. Do you see a splice? Find the end of that wire. it is not the other three. Those are seperate. You might get continuity through them but they arent the same wire. This is why an ohm meter is necessary. I have gotten continuity on a circuit before between the positive and negative sides before. If you aactuallu ohm then the resistance it is extremely high compared to a dead short.
Trace the black wire and remove the plastic bits near the rear light and look for a black wire with a lug screwed to the frame. There is a possibility it is disconnected.
Dont worry about those other wires until you test properly for a good connection on the black wire.
This black wire is in your harness. I can barely see it in your picture. Trace it to the loom where it disapears. Do you see a splice? Find the end of that wire. it is not the other three. Those are seperate. You might get continuity through them but they arent the same wire. This is why an ohm meter is necessary. I have gotten continuity on a circuit before between the positive and negative sides before. If you aactuallu ohm then the resistance it is extremely high compared to a dead short.
Trace the black wire and remove the plastic bits near the rear light and look for a black wire with a lug screwed to the frame. There is a possibility it is disconnected.
Dont worry about those other wires until you test properly for a good connection on the black wire.
Ok awesome thank your for the info I'll check it out tomorrow I was so focused on the blue/yellow wire to check the others in the harness. There was a chassis ground that ran through the harness in the back that was bolted to the right rear kind around the tail light area I did pull that and clean it. I'll check that next and take pics of rhe ohm readings and check for continuity as well. Is that black wire on the fuel pump harness??? I don't remember seeing a black wire on the harness side of wiring ill double check tomorrow. I didn't installed the new fuel tank or pump is it possible there's another plug that the fuel pump wiring from the sender would fit into??? Maybe the person prior to me plugged the sending unit into the wrong body harness plug.
Clean this, I think ground 25 goes to this point. And it looks crusty as hell.
Just search the FSM and it will tell you everything you are looking for...
If your wire color is different due to the fuel pump not being OEM or any other reason, base it on the location of the pin on the connector. Connector R-03 as shown on the connector above should be the fuel pump side. Trace that B(black) wire to ground 25. L(blue) is not a ground, it is power based on the diagram.
Jeff76 is correct, he is leading you in the right direction as well. His comments about ohms is also correct, a continuity test will not really give you any indication on if there is a short.
Clean this, I think ground 25 goes to this point. And it looks crusty as hell.
Just search the FSM and it will tell you everything you are looking for...
If your wire color is different due to the fuel pump not being OEM or any other reason, base it on the location of the pin on the connector. Connector R-03 as shown on the connector above should be the fuel pump side. Trace that B(black) wire to ground 25. L(blue) is not a ground, it is power based on the diagram.
Jeff76 is correct, he is leading you in the right direction as well. His comments about ohms is also correct, a continuity test will not really give you any indication on if there is a short.
ok awesome ill take a look at it tomorrow and report back with updates I didn't clean the ground at the sender but I will. I looked up in our system and it says it's a 1988 I was going off the sticker on the door that it said 87 so I was wrong lol. I'm gonna check the wiring tomorrow and go from there.
Also if you are not aware the Factory Service Manual is easily available online for RX7s. Just google "RX7 FC FSM" and it will come up. Wiring Diagram Section page 50-36 & 50-37 are what I clipped in my previous reply.
Also if you are not aware the Factory Service Manual is easily available online for RX7s. Just google "RX7 FC FSM" and it will come up. Wiring Diagram Section page 50-36 & 50-37 are what I clipped in my previous reply.
that's great thank you. I just wanna get this car fixed and running so the owner can have it back. The previous person to work on it is no longer with us so idk what all was done and wasn't done I did noticed someone deleted alot of solenoids under the hood but that shouldn't be an issue. Since the car did run before we got it the fuel tank was full of rust so we replaced the tank pump and filter and serviced the injectors then all of a sudden wouldn't run. Unless if they replaced the fuel pump motor in the oem sender and wired it wrong... hmm I'm gonna check the wiring and also check the fuel pump now that I think about it just to confirm it was install properly.
So I want to thank everyone that helped me with this issue. It turned out whoever put the pump in plugged it into the wrong plug lmfao it now runs again they had it plugged into the plug on the left lol I plugged it in on the right plug in the pick and it fired right up lmao.
No problem. I told you check the connector ahaha. Glad it ended up being an easy fix. I think the other connector is for the power antenna; also explains why the wiring color may have been confusing. Cheers.
No problem. I told you check the connector ahaha. Glad it ended up being an easy fix. I think the other connector is for the power antenna; also explains why the wiring color may have been confusing. Cheers.
much appreciated for sure I ended up getting 2 dollars an hour raise lol I think it's funny that no one else could figure it out. But because I went the extra steps to fix this car he was happy about it and it runs again so im greatly to everyone that helped me fix this issue.
01-30-24, 05:01 PM
