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EFI Fuseable Link


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Zmaster:

The wire from the positive terminal of your battery is the positive voltage feed for the EFI control unit. The control unit has it's own positive and negative voltage source. The EFI wiring harness is a whole separate harness including voltage feeds directly from the battery. The connector in the negative line is probably just so the battery cable can be removed without having to pull the entire EFI harness out. In the day, the positive probably had one also. (I'm guessing) Problem is, the battery cables have probably been replaced once or twice during the thirty years since the car was made. Aftermarket battery cables generally have only the one thick wire. (this next part I'm just guessing so don't take it as gospel) I think, one of the few applications that do include a second smaller wire is for fords, and that wire is a fusible link on those fords. So... someone may have replaced the cable with one that had a fusible link. I'm not sure where/how the EFI control unit is fused. Mine does not have a fusable link or inline fuse on those two wires. Mine are connected directly from the battery. That is how it has always been and I never questioned that it needed one. I think short protection may be provided by the FI relay. If anyone knows better please speak up. A good look at the wiring harness may provide an answer. Hope this helps

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right now I'm starting to think it will be easier to buy a used EFI harness and throw out the old one. but i don't know anymore. I will try and wire upp my efi harness directly to the battery, and ditch the stock battery connections, and hard wire it in

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Zmaster:

I have been studying the wiring harness schematics and trying to figure this out. The wiring harness diagrams I've been studying are found here

http://www.autozone.com/az/cds/en_us/0900823d/80/1d/1d/80/0900823d801d1d80/repairInfoPages.htm

I have one that came with my factory service manual as well. The schematic for the 77 and 78 both show the hot (positive) going from the battery to the fusible link on the inner fender. The schematic for the 76 shows a hot running directly from the battery to the EFI control unit. This is how my car is wired. My car was manufactured in 6/77. I'm guessing it has the harness shown in the 76 schematic. FYI the schematic does show a fusible link inline in the hot wire leading to the EFI control unit. (although no indication of amp rating) I have a 78 parts car and I swear it is wired the same way but will be checking soon. If you decide to swap out the whole harness, bare in mind that there are differences between years in the harness, the control unit's pin out, the AFM and automatic versus standard tranny.

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Guest 280zfast

I am having the same problem with my 1975 280z coupe My fuel pump is reading 0.03 volts while the engine is cranking I don't know if this is normal or not, I have never come across a problem like this before, and I don't know how to fix this either If someone has any advice or information, i can really use it to help me.

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280zfast:

There is a link to a wiring harness schematic above. To understand how the fuel pump gets power you need to dowload and read the EFI bible. (search bible or EFI bible on this site) When cranking the fuel pump should be getting full voltage. There is something wrong, could be a few different things. The wiring is thirty years old. Try to isolate the problem. Get the fuel pump off the car and bench test it. Apply 12 volts to the pump and see if it runs. Check the wiring harness, the wires run down the passenger side sill and then through the floor just behind the seat. Check the harness for broken or frayed wires.

What happen to zmaster?

Edit: OK I see from your other post you have the bible

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Guest 280zfast

my little brother zmaster was banned for a week because he asked too many specific questions he wanted answered, and posted pics with things circled so the visual learning people can see Exactly what he was talking about. but oh well his ban ends on friday...so i am asking questions on my own to help him with his fuel pump problem. so we will trace the wire from the pump to the relay... Oh and he did bench test the fuel pump with 12volts and it runs, and pumps gas really good.

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Guest 280zfast

by the time his ban is up on friday he will be taught to approach questions a whole lot better. sorry little bro didn't mean to hijack your thread.

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my little brother zmaster was banned for a week because he asked too many specific questions he wanted answered, and posted pics with things circled so the visual learning people can see Exactly what he was talking about. but oh well his ban ends on friday...so i am asking questions on my own to help him with his fuel pump problem. .....

 

That is wrong. Zmaster was not banned for asking too many specific questions with circled pictures, (we like that). Zmaster was “suspended” for asking questions that he has the resources to answer on his own, yet continually asked those questions after being told where to find those answers on his own, and some of those questions are NOT conducive to this forum. This forum is NOT mechanics 101. If a person either wont, or cant understand or comprehend what it is he looking at or for in a service manual, this forum is not for them. This forum is dedicated to extreme performance modifications to Z cars, not routine maintenance, not restoration, or extremely basic troubleshooting. Those sort of questions do NOT belong on this forum!

 

These 2 threads linked here are WHY Zmaster was suspended for 7 days, read them in this order…

 

http://forums.hybridz.org/showthread.php?t=132418

 

http://forums.hybridz.org/showthread.php?t=132448

 

As an aside, how are you going can you prove to me that you are NOT Zmaster signing back up prior to the 7 day suspension?

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not yet but i think i know what the problem is. I tested the fuel pump with a volt meter, while I turned the key to the on position and the voltage read 0.03 volts so i think i may have a short in the wire somewhere. maybe I will ren a wire from the power side of the fuel pump relay all the way to the fuel pump to see if that fixes the problem.

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I tested the fuel pump with a volt meter, while I turned the key to the on position and the voltage read 0.03 volts so i think i may have a short in the wire somewhere.

 

Sounds like the safety feature to shut the fuel pump off is working correctly. To assist in troubleshooting it - remove the white/black wire from the starter solenoid to test if the relays are turning the fuel pump on when the key is in the 'START' position, and/or opening the flap in the AFM w/ a screwdriver to test if the relays are turning the fuel pump on with the key in the 'ON' position. Is some debris possibly jammed in the pump causing a 'no-pump' condition?

 

maybe I will ren a wire from the power side of the fuel pump relay all the way to the fuel pump to see if that fixes the problem.

 

Just so I understand, you want to run a new wire from the INPUT of the relay or the OUTPUT of the relay to the fuel pump? Is it even connected at the bullet connectors (behind the passenger seat)?

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