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914World.com _ 914World Garage _ Help...I'm electrically stumped

Posted by: cuddyk Apr 30 2016, 08:24 AM

Hi Guys,

I posted earlier about my fuel pump not working. Before I went on a goose chase to find another, I thought i'd check the circuit (I may be learning from my mistakes after all).

Anyway...I pulled the black and white leads off the fuel pump, hooked up my multimeter and turned the ignition switch to "on". Zero point zero.

Moved around the relays on the board and no change. I assume those two leads are positive and negative and they should show 12V with the switch on, no?

Any ideas? Thanks so much for your help. I SO want to get on the road this weekend...

Posted by: r_towle Apr 30 2016, 08:28 AM

1)
Hook up 12 Vdc directly to the fuel pump, does it run?
2) can't help you from there without year, make, model, stock or not, carbs or FI...

Rich

Posted by: cuddyk Apr 30 2016, 08:30 AM

Thanks man. Will check the pump directly. My car is a 73 2.0 (with a McMark-built 2056). Dual IDF 40 carbs.

Posted by: McMark Apr 30 2016, 08:34 AM

Fuel pump is wired with stock wiring? Do you have the ground from the relay board to trip the fuel pump relay on?

Posted by: cuddyk Apr 30 2016, 08:40 AM

Just tested...the pump works when directly powered.

Mark...I believe it's stock wiring. Yes, the pin is grounded on the relay board. No change from the way it's been. What's weird is that the pump was working fine yesterday. All I did since then was disconnect and reconnect the battery (with the key off and out). Maybe a surge when the battery was reconnected? Is it possible that all the round relays blew?

The wiring at the pump is one black and one white. Pic attached. Thanks so much for your help. Attached Image

Posted by: JRust Apr 30 2016, 08:44 AM

For a temp solution you can run the power down from your coil. That will turn it on with your key still.

Posted by: anderssj Apr 30 2016, 08:52 AM

Don't forget to check the fuse on the relay board--sometimes that fuse looks good, but corrosion on the tips means no current. A quick way to check is to see if the heater fan in the engine compartment comes on when the level on the cockpit floor is pulled up. If the fan doesn't come on, fuel pump won't either (at least on my '72).

Hope this helps!

Posted by: cuddyk Apr 30 2016, 08:53 AM

You guys are like therapists...just talking to you helps solve problems.

FIXED. I did the headlight test on all the relays and found a bad one. Replaced it and voila...12V at the fuel pump.

Thanks for helping my brain get into logical mode. That's not easy to do!

Posted by: timothy_nd28 Apr 30 2016, 08:55 AM

Could be a faulty ignition switch. With the key at the "on" position, try nudging the key in this direction and sequence: up up, down down, left right, left right, B then A. Have the meter near by and see if it flinches as you move the key.

Posted by: cuddyk Apr 30 2016, 09:02 AM

Many thanks, all!

Posted by: r_towle Apr 30 2016, 11:30 AM

Cool, now go drive it!

Posted by: cuddyk Apr 30 2016, 10:40 PM

Done! Took my first drive after a shit ton of winter work. So great. And I won a bet with my wife that the car would once again move under its own power. So I got that going for me. Which is nice.

Posted by: ClayPerrine May 1 2016, 05:40 AM

QUOTE(JRust @ Apr 30 2016, 09:44 AM)

For a temp solution you can run the power down from your coil. That will turn it on with your key still.

This is a BAD idea. Running power to the fuel pump off the coil will cause the voltage to the coil to drop and you will get a weak spark.

Posted by: JOEPROPER May 1 2016, 06:29 AM

Good stuff cuddyk! When you get a chance, cruz that '73 over to White Plains so i can check out your progress.

Posted by: Rob-O May 1 2016, 09:25 AM

QUOTE(cuddyk @ Apr 30 2016, 08:40 PM)

Done! Took my first drive after a shit ton of winter work. So great. And I won a bet with my wife that the car would once again move under its own power. So I got that going for me. Which is nice.

Nice Caddyshack quote. Not sure many caught that.

Posted by: napasteve May 1 2016, 09:42 AM

Sounds like a Cinderella story

Posted by: cuddyk May 1 2016, 10:07 AM

QUOTE(Rob-O @ May 1 2016, 11:25 AM)

QUOTE(cuddyk @ Apr 30 2016, 08:40 PM)

Done! Took my first drive after a shit ton of winter work. So great. And I won a bet with my wife that the car would once again move under its own power. So I got that going for me. Which is nice.

Nice Caddyshack quote. Not sure many caught that.

Gunga lagunga!
(Or as my iCrap is trying to say...Hungary Laguna)

Posted by: r_towle May 1 2016, 03:18 PM

QUOTE(cuddyk @ May 1 2016, 12:40 AM)

Done! Took my first drive after a shit ton of winter work. So great. And I won a bet with my wife that the car would once again move under its own power. So I got that going for me. Which is nice.

What was the bet?
I mean, was it worth it?

Posted by: cuddyk May 1 2016, 10:27 PM

QUOTE(r_towle @ May 1 2016, 05:18 PM)

QUOTE(cuddyk @ May 1 2016, 12:40 AM)

Done! Took my first drive after a shit ton of winter work. So great. And I won a bet with my wife that the car would once again move under its own power. So I got that going for me. Which is nice.

What was the bet?
I mean, was it worth it?

youll have to ask her if it was worth it

Posted by: cuddyk May 1 2016, 10:31 PM

QUOTE(JOEPROPER @ May 1 2016, 08:29 AM)

Good stuff cuddyk! When you get a chance, cruz that '73 over to White Plains so i can check out your progress.

Def! I just have to have my gray haired mechanic friend check my work first. I wrenched too many things that could strand me or worse. i usually get good grades, but this isn't my day job

Posted by: rhodyguy May 2 2016, 08:15 AM

Refer to the 'fuel pump power for carbs' in the classic thread forum. I used the coil method for a short period. A fuse would blow at the worst possible time. Use the stock pump power wires and change to the appropriate connectors for your pump.

Posted by: 76-914 May 2 2016, 07:52 PM

This is a BAD idea. Running power to the fuel pump off the coil will cause the voltage to the coil to drop and you will get a weak spark.
[/quote]

QUOTE(rhodyguy @ May 2 2016, 07:15 AM)

Curt was describing a "test" method if I read this correctly. He never said to run like that. The OP wanted to verify that the pump was good or kaput.