Electric fuel pump conversion

[spidernut]

I'm converting from a mechanical to electric fuel pump on my 79 stock Spider and am amazed at the bazillion ways people recommend wiring these things. I have a question for the experts in this process and want to bounce my logic off of others with extensive mechanical and electrical experience. My goal is to eliminate the hard starting problem caused when the car sits for long periods of time....a common problem with the ADHA carbs (and no I can't change the carb because I live in the Communist Republic of Califgomorrah so don't suggest it).

My goal is to bring up the fuel pressure to the carb prior to cranking the motor to make cold starts faster and create less stress on the starter. This would necessitate eliminating an oil pressure safety switch since the pump would only run when the motor is cranking - as it is the mechanical pump also pumps only when the motor is turning over so I see no benefit to using an electric over mechanical pump for this purpose. I will be installing an intertia switch for safety reasons, so I'm not terribly worried about eliminating the oil pressure safety switch. Thoughts?

Also, I like the idea of using a relay in the system. I've seen a multitude of ways to wire the relay. The one that makes the most sense also would only activate the pump when the motor is cranking - again, I need the pressure prior to the motor cranking over.

I'm thinking it would make the most sense wiring a fused circuit from the red wire on the coil to an inertia switch and then to the fuel pump and eliminate the relay and oil pressure safety switch. The other option I thought of is to T it into the fuel line and plumb it as a priming pump with a toggle switch....not my first choice though.

Thoughts? Suggestions?

[RoyBatty]

Hi John,
My carb'd 75 has no safety provisions in it's fuel pump wiring.
Key in the run position brings the electric pump online.
Not saying it's not a good idea, just gonna suggest that before you install more complicated systems, just get the basics installed first and flesh out any problems. THEN install the safety devices.
Make any possible troubleshooting easy with the basic system install.
Good Luck

[JEEPER]

I have a 79 that I've had since new. Fiat paid for and installed an electric fuel pump under warranty when the car was about 4 years old. They used the wire in the trunk that was factory, for an electric fuel pump. I believe it was blue with a red tracer. The only problem I have had, is that the electric fuel pump I had was only putting out 1 1/2 PSI. When I put my foot into it I would read zero. My new fuel pump puts out 4 PSI and may go down to 1 1/2 when you step on it.

[spidernut]

Jeeper,

I had already traced the blue/red and blue/white wires from the trunk back to the relay panel beneath the glove box. At the glove box, they connect to nothing so there's no power. Do you know what they plugged the relay panel end into?

[vandor]

I liked best what one of my friends did. He had the same hard starting problem when the car set, but otherwise the mechanical pump worked fine.
Both the mechanical and electric (not all electric ones) pumps are flow-through when not operating, so he simply left the mechanical pump in place and added an electric pump to the trunk. The electric pump is operated via a pushbutton on the dash, so it's only on when the button is pushed.
He operates the electric pump for ~10 seconds before starting the car and then the car starts easily and the fuel is pumped by the mechanical pump.

Around 1970 Fiats had a separate pushbutton for the windshield washer, I found him one of those, so the prime button was an original Fiat part

[124Germ]

I really like the idea about the push button priming system as I also have the same issue with my 72. Wonder what I could find as an original Fiat part to re-purpose for this priming system.

Any idea what size or type of electric pump I would need for this?

Thanks for the great idea guys.

[124Germ]

I was just thinking about this and wonder if you could tie it into the cigarette lighter. when you push in the lighter to heat it up it would turn on the electric fuel pump, when it pops back out it would turn off the pump. I seems to remember the lighter heats up in about 10-15 seconds.

But now, for the life of me, I can't remember if I even have one or where it is......I guess I've been away for it for too long...

[spidernut]

I'd not recommend running it to the cigar lighter since that's a live circuit even without the key in the ignition. If the switch failed with the circuit activated, your pump would be running. I can't imagine a safe way of making the cigar lighter itself operate as a switch.

Re the 75 wiring, I had seen in the wiring diagrams that it was a direct wire to the ignition. I'll avoid that since the ignitions are already overloaded circuits, but I'm leaning in that direction - but will still install an inertia switch.

Csaba - I was unaware that these were flow-through pumps...I was envisioning T-ing into the line using check valves to stop back flow to the tank. I'll have to consider that since all I really need is a priming pump. The mechanical pumps are far more reliable than the electric pumps and I like the idea of keeping it.

[cjd]

I also like the Vandor idea of the push button, but would prefer a spring loaded toggle under the dash with it in a pull, so a knee would not hit it and set it off. On the pressure, get a low pressure pump, 1 1/2 pounds to 2 1/2. Ask for the ones for a Triumph or MG. All you need to do is get the bowl filled before starting as the needle and seat will shut off when the float is up to proper level.

Wayne

[tartan18]

This is what I am installing on my 1975. I haven't hooked it up yet but I did test it and it works as advertised. This device is a bit on the pricey side but safety was my motivation. Just my opinion as I have no connection with this vendor other than buying it.

http://revolutionelectronics.com/Fuel_Pump.html

[vandor]

We carry pumps that are made in the US, so they do not regularly fail, like the cheap Chinese ones.
They are Facet brand:

http://www.autoricambi.us/product/FU7-4 ... -Electric/

[btoran]

I use a plainly obvious switch to activate the electric fuel pump on my 1975. it also acts as a theft deterrent. underneath the radio (on the left) is a switch with a headlight symbol on it. pull it out and the fuel pump is on. push it in and the pump is off. i know it's there (i installed it) and it's defeated me a few times.

[JEEPER]

Jeeper,

I had already traced the blue/red and blue/white wires from the trunk back to the relay panel beneath the glove box. At the glove box, they connect to nothing so there's no power. Do you know what they plugged the relay panel end into?

No I don't know and the Fiat is in storage and I can't get to it until spring. My stock mechanical pump is still mounted to the engine but, both lines were removed and spliced together.

[spidernut]

Jeeper...I consulted my wiring diagrams. The two wires are for the power antenna on the 79 but aren't hooked to anything from the factory at either end.

[JEEPER]

Jeeper...I consulted my wiring diagrams. The two wires are for the power antenna on the 79 but aren't hooked to anything from the factory at either end.

The dealer must have tied the blue/red to something. When you turn the key you get power to the fuel pump. When I get it out of storage I'll see where the Fiet dealer tied it in in 1982.