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Converting from EFI to Triple Weber setup

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Have not regretted this for a moment - Expensive though...            Aug '76 359550   280     bored - stroked - 10.5/1     New (Spanish) Webers  44 s

 

Remove:  fuel pump - pulse dampener - filter -  all fuel distribution lines in engine bay - bosch FI  computer and harness at LH footwell -

 

Retain: Steel back to front fuel line.

 

Unused: Fuel return line (cap off)

 

New: Fuel Pump - buy a good quite low pressure unit... / Wiring ( with some form of auto shut-off, in the event of an accident )  - fuel filter - pressure regulator -

                  engine bay braided hose & AN fittings for distribution to  banjo fittings - Webers - rebuilt and cleaned - even new ones -  the correct size for your specific engine build -                  linkage mechanisms - velocity stacks  -    air filter (s) -     header heat shield   -   

                 -  an old Weber   expert          for tuning...

IMG_0098.JPG

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Looks 

3 hours ago, 280zzzzz said:

Have not regretted this for a moment - Expensive though...            Aug '76 359550   280     bored - stroked - 10.5/1     New (Spanish) Webers  44 s

 

Remove:  fuel pump - pulse dampener - filter -  all fuel distribution lines in engine bay - bosch FI  computer and harness at LH footwell -

 

Retain: Steel back to front fuel line.

 

Unused: Fuel return line (cap off)

 

New: Fuel Pump - buy a good quite low pressure unit... / Wiring ( with some form of auto shut-off, in the event of an accident )  - fuel filter - pressure regulator -

                  engine bay braided hose & AN fittings for distribution to  banjo fittings - Webers - rebuilt and cleaned - even new ones -  the correct size for your specific engine build -                  linkage mechanisms - velocity stacks  -    air filter (s) -     header heat shield   -   

                 -  an old Weber   expert          for tuning...

IMG_0098.JPG

Looks Rad man...Oh your a local Vancouver guy. Good to see some local s30s.

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My apologies for reviving this thread but I'm in a bit of a pickle.

 

I've removed all of the above-stated items

but when it comes to the removal of the Wiring harness that goes to the Bosch ECU,

is the wiring that connects the fuel pump to the ignition switch bundled up in the same harness?

also, the wiring for the Alternator and the started, and even the ignition coil?

I'm just looking for advice on how to handle all the wiring for the items to remain. 

do i need to wire up the new fuel pump? if so, this is what I was looking at 240z fuel pump wiring

 

I can attach pictures of what I'm working with if I need to

thanks in advance

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What year vehicle? I assume 75+ because EFI.

 

What are you planning for your fuel pump? Mechanical? Electric near the tank?

 

How about any kind of automatic shut-off?

 

By default (at least on my 77) the fuel pump is switched on by the flap in the AFM and also while cranking. This way, the pump doesn't run unless the engine is running.

 

I've seen a number of users with electric pumps mirror this setup, except with an oil pressure switch instead of the AFM flap, which will work with both carbs and EFI.

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78 280z

I bought a carter low PSI electric pump to replace the stock one near the tank.

the idea was that I would just replace the stock pump and use the original +/- wires, but it doesn't look like that will be possible

the other route was to use these instructions and apply it to my 280z.

but the other problem is that by removing the EFI wiring harness I'm afraid that it might remove other essential connections from the ignition switch to the alternator, starter, etc.

if I follow the instructions linked they require an oil pressure switch in the install

 

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Why dump the return line? 

 

You can plumb the triples setup exactly like the stock EFI.

 

TANK ==> PUMP ==> FILTER ==> CARB CARB CARB ==> FUEL PRESSURE REGULATOR ==> RETURN LINE ==> TANK

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17 minutes ago, bradyzq said:

Why dump the return line? 

 

You can plumb the triples setup exactly like the stock EFI.

 

TANK ==> PUMP ==> FILTER ==> CARB CARB CARB ==> FUEL PRESSURE REGULATOR ==> RETURN LINE ==> TANK

the plumbing is pretty straight forward. I have no issues there plus the return line is optional.

it's the electrical that I have no knowledge about. I'm concerned that by removing the wiring harness I'll lose wiring that connects the ignition switch to the starter, pump, ignition coil, etc.

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EDIT: The following information is for 77 (and prior) cars, the 78 is quite different in this area.

 

If I recall from when I removed my EFI harness, there is a plug (maybe two) underneath the dash on the driver's side that connect the EFI harness to the rest of the electrical system. Besides that and the two wires to the battery, I don't think there are any other connections you need to worry about.

 

Take a look at this wiring diagram http://www.atlanticz.ca/zclub/techtips/wiringdiagrams/F77ZCAR-WIRING1.pdf

 

That is for a 77, but it should be mostly accurate and should give you an idea of the way the system works. The diagram for the 78 was broken, and 77 is in color.

 

The 6-pin connector on the bottom just left of center is the one I'm thinking of. IIRC this is the only connection between the two harnesses and carries ignition on and fuel pump positive. I think everything you need is right there, connection wise. You just need to add a relay (and possibly an oil pressure switch).

 

Also I recommend you run a return line on your fuel system because it's already there and you'll have more consistent fuel temperatures making for easier tuning.

Edited by ZHoob2004
Correctness

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17 hours ago, jjcatfish said:

78 280z

I bought a carter low PSI electric pump to replace the stock one near the tank.

the idea was that I would just replace the stock pump and use the original +/- wires, but it doesn't look like that will be possible

the other route was to use these instructions and apply it to my 280z.

but the other problem is that by removing the EFI wiring harness I'm afraid that it might remove other essential connections from the ignition switch to the alternator, starter, etc.

if I follow the instructions linked they require an oil pressure switch in the install

 

 

It's possible and should be very easy.  1978 uses a different fuel pump control system than the other years.  The relays are in the engine compartment.  Since it doesn't use the AFM anymore you should be able to keep full functionality of the fuel pump control system.

 

I've found that trying to use other people's instructions directly doesn't work well.  Study them and the wiring diagram and make your own decisions.  The fuel pump control is explained in detail in the FSM and the wiring diagrams are free all over the internet.  In color even.

 

Good luck.

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OK, I got bored on my lunch break and decided to look into this further. It appears the 78 model year differs rather significantly in this area, and you should disregard basically everything I said.

 

It appears that the 78 cars already utilize an oil pressure switch from the factory, and the system is basically done for you. Nissan seems to have just ignored the switch in the AFM and instead actuate the fuel pump via a combination of the oil pressure switch and whether or not the alternator is producing power, meaning you will lose fuel if you lose either oil pressure or alternator voltage (which I think is supposed to ensure your water pump is running).

 

Besides removing the EFI harness, I'm not sure you even need to do anything except turn the key.

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