The fuelpump fuse and fuelpump relay are located underneath the rear parcel shelf behind the right seat. The main relay and fuel computer also reside there. The fuelpump relay is the taller of the two relays.
The fuelpump power feed circuit is designed such that the fuelpump will be powered only if the engine cranking or the engine is running. There will be NO power to the fuelpumps with the ignition on and engine off.
If you would like the wiring diagrams for your Spider, please provide me your email address in a private message and I'll send them to you.

 

Hi JIM,
following info and question if you have full wiring for 1979 Spider? fuel pump does not have power currently. concerned if it is pump fuse. thank you for your input! cheers jim

 

Fuel pump.....

Thank you Papajam.
I have found them.
I have removed and cleaned the fuse and all looks ok.
Put it all back, and still wont fire up.
(I am a musician, not an electro-mechanic, but I am eager to learn)

 

L-jet is a system. All its bits have to work for it to work at all. See the link in my signature to a page of things you can check at home with a simple Volt-Ohm meter.

One important thing to note is that the computers will not power on unless the system voltage is about 10.5V or higher. During cranking a weak battery, failing starter or poor electrical connections can cause the system voltage to drop below that threshold. Test system voltage by connecting a voltmeter to the battery and see what it measures during cranking. If marginal, charge up the battery & clean all the connections in the battery to starter circuit. Then re-test.

One other thing. An '84 Spider might have an inertia triggered fuel pump shut off switch. If it does, it'd be either a black rectangular item about the size of a cigarette pack or a silver cylindrical item about 1.5" dia X 2-3" long located in the engine bay between the windshield washer reservoir & the hood latch. Press the button on top to reset it. Better still - bypass it. Connect the wires attached to the switch together. They were problematic even when new. On later Spiders it was deleted once they decided the fuel pump relay would shut off the fuel pumps once the engine stalled (like in an accident).

 

L-jet is a system. All its bits have to work for it to work at all. See the link in my signature to a page of things you can check at home with a simple Volt-Ohm meter.

One important thing to note is that the computers will not power on unless the system voltage is about 10.5V or higher. During cranking a weak battery, failing starter or poor electrical connections can cause the system voltage to drop below that threshold. Test system voltage by connecting a voltmeter to the battery and see what it measures during cranking. If marginal, charge up the battery & clean all the connections in the battery to starter circuit. Then re-test.

One other thing. An '84 Spider might have an inertia triggered fuel pump shut off switch. If it does, it'd be either a black rectangular item about the size of a cigarette pack or a silver cylindrical item about 1.5" dia X 2-3" long located in the engine bay between the windshield washer reservoir & the hood latch. Press the button on top to reset it. Better still - bypass it. Connect the wires attached to the switch together. They were problematic even when new. On later Spiders it was deleted once they decided the fuel pump relay would shut off the fuel pumps once the engine stalled (like in an accident).

Hi again, There is 12 volts going to the rear tank fuel pump when cranking. There is 12 volts going to fuel pump under the rear wheel well passenger side when cranking... Don't seem to hear any pump because the starter motor drown out the noise. The 2 fuel pumps go to a fuel filter. Maybe I should remove the house and see if fuel is coming out? From there it goes into a 5 port manifold and to the injectors. When I crank the engine, I hear a relay clicking near the computers. Not sure if injectors are getting any signals...

 

Great advice sir. Many thanks. I am going to get onto that over the weekend and see what shakes.
Just a quick question.....Assuming the fuel system has an excess return pipe (I see two pipes down there so I am guessing that's the case), can I cause damage by temporarily bypassing the system and wiring a fused switch to the fuel pump/battery so I can turn the pump on and off from the dash??? Only to see me through till the gremlin is found, caught and humanely disposed of?

 

What you propose will not damage anything. However, it will take the safety aspect away in that the fuel pumps* will run continuously. Normally, the fuel pumps would stop if the engine were to die/stall (as in an an accident). Thus I would advise only doing it for a temporary testing period - don't leave it that way.

* there are two fuel pumps - the main pump under the car & an in-tank pump inside the fuel tank.

 

Thank you GHNL.
Safety advice duly noted and will be only for testing (its not on the road yet anyway...I have a way to go before that happens)
B.T.W....Why two pumps?

 

The sole purpose of the in-tank low pressure fuelpump is to provide fuel to the main high(er) pressure fuelpump.
In other words, the main fuelpump can not pull fuel from the tank under all conditions; it must be supplied with fuel.

 

Wow! I have had a couple of 60's and 70's cars in the UK....so much simpler.
OK.
This weekend I have got a lot of work to do......
Cheers loads guys.
Much appreciated. I am enjoying learning something new.
(wish there was something I could do in return..)
Pablo.

 

Great info.

 

Wow I did not think that a small teat in the intake rubber would stop the engine from at least running rough. I will repair the intake rubber in the morning just to see if it then starts on its own fuel. I guess what you are saying is that if there is an air leak, then the computer will not engage the fuel injectors at all?

 

The fuel mix needs to be close to correct. Too much or too little means it may not start/run.