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Sun May 27, 2018 2:47 pm

I searched and found many threads on the installation of a fuel pump relay. I am requesting a schematic to install a 5 pin 30/35 amp relay. I'd rather not use the generator light/oil pressure light as a latching mechanism for the safety circuit. Can the ignition coil ne used for the latching circuit? Thanks for your insight.

Sun May 27, 2018 2:57 pm

Sun May 27, 2018 3:11 pm

Thanks Glenn, Because electricity is PFM to me, 31b goes to the (-) on the ign coil, correct? Also a good place to mount it... Thanks

Sun May 27, 2018 3:23 pm

Also will a 35 amp relay be too much? I found a nice one with a mounting bracket...

Sun May 27, 2018 4:42 pm

c.ruber wrote: Also will a 35 amp relay be too much? I found a nice one with a mounting bracket...

Take note, the relay Glenn is showing is NOT a standard SPDT relay it has special circuitry to only trigger for about 2-3 seconds to bring up fuel pressure then cuts off till it sees a series of plusea on the input line from coil to trigger relay on continuously while engine is running....

There is also this option...

http://revolutionelectronics.com/Fuel_Pump.html

Dale

Sun May 27, 2018 4:50 pm

Dale M. wrote: Take note, the relay Glenn is showing is NOT a standard SPDT relay it has special circuitry to only trigger for about 2-3 seconds to bring up fuel pressure then cuts off till it sees a series of plusea on the input line from coil to trigger relay on continuously while engine is running....

Dale
correct, it's a VW Rabbit (A1) FI relay. The part number is in the picture.

Mon May 28, 2018 11:03 am

The fuel pump controller that Dale M. posted looks nice. Anyone else used it? pros/cons?

Mon May 28, 2018 11:09 am

c.ruber wrote: The fuel pump controller that Dale M. posted looks nice. Anyone else used it? pros/cons?
It works exactly like the Rabbit relay. 31b is the tach signal.
Quote: It monitors the tach signal to limit when the fuel pump can operate. When the key is first turned on, the fuel pump is allowed to operate for three seconds, priming the fuel system. After these first three seconds, the pump is only allowed to run when the engine is running; if the engine stops, so does the fuel pump.

The relay is $30 (1/2 the price).

Tue May 29, 2018 7:52 am

If I knew about the DALE relay I would have gone that route for safety.

I hated the fact that one thin 40 year old wire was going from way back at the battery to up front to the key switch and the fuse box and then back to the rear of the car to the Coil, which also powered the back up lights on a stock bug. Now the thin wire only goes to about 2 feet and only acts as a power on signal to two 50amp relays used on the rear window defoggers.
My coil, Jacobs ignition, back up lights, fuel pump, Strobes ( yes ) etc. are all hooked up to the box in on the drivers side rear floor.

The relays are in Parallel so if one fails the other takes over.

OK yes can crash an burn. Hopefully I can get to the fire extinguisher !!!!

Wed Nov 07, 2018 3:26 pm

I'm about to install a Carter fuel pump on my bus, and found this post.

The Relay looks easy enough to understand (except the 31b, which i'm not sure where its supposed to connect), but my question now, is where is best to place that relay in a bus?

My first though was next to the other relay in the kick panel, but is it a good idea? Under the bus is obviously not the best. Inside the engine compartment?

Wed Nov 07, 2018 3:30 pm

31b goes to the 1 (-) post of the coil.

Wed Nov 07, 2018 5:26 pm

On other vehicles I have used a normally open oil pressure switch on the ground side of the relay. No prime function but it was never an issue. All you have to do is key the ignition on and ground the oil pressure switch lead to prime the carb.

No oil pressure no fuel.

But this was on v8’s that hold a little more oil pressure than an ACVW

Wed Nov 07, 2018 6:34 pm

The Early Porsche 911 used power being generated I think as the trigger, Nothing at all wrong with it. I copied the Idea on mine and used a $5 Radio Shack relay my circuit works great just so long as I rev the engine a little to start the charging. It seems to need a bit of a rev. My radio shack relay loads the Alternator D+ enough it causes it. So that makes this Rabbit relay a better Idea. But here is mine:

I had this Idea for doing it off of the Oil light but have not tried it:

I had to come up with a fuel line shut-off Solenoid for mine in case my carbs don't stop the gas which has been happening lately. I guess the CB Performance Fuel Pumps still let gas gravity feed to the carbs.

Thu Nov 08, 2018 5:53 pm

Anyone running a fuel pump relay with MSD ignition -i.e. when you can’t run a wire to the coil?

Thu Nov 08, 2018 6:11 pm

The common relay hooked up to the oil light switch seems the best to me.

Thu Nov 08, 2018 8:00 pm

neil68 wrote: Anyone running a fuel pump relay with MSD ignition -i.e. when you can’t run a wire to the coil?

Ummm.... Tachometer output **MAY** drive relay...

MSD WDTN states tach output is a 12 volt square wave with a 30% duty cycle... Page 9 of PDF file below...

https://documents.holley.com/catalog_wiring_diagrams.pdf

MSD tech support probably could confirm if it would operate fuel pump relay...

https://www.holley.com/support/

Dale

Fri Nov 09, 2018 5:15 am

Neil,

I have a mallory 6 al2 (very similar to MSD CDI) and a Mallory pump as well as a CSP fuel pump relay (same terminals as Glenn's).

I had to fit a MSD tach adapter (8910 : for white wire triggering and points) to have the relay activated which would in turn prime the fuel pump for ca. 3 seconds.

Now that I have switched to as MSD distributor I have just bought a MSD 8920 Tach adapter that works with mag pickup distributors. https://www.holley.com/products/accessories/tach_adapters/parts/8920

I will hook up the relay (31b) to the violet wire of the 8920 tach adapter. Tach wire will attach there too.

It seems that it is the way to go to have the relay working.

If you guys think that I am wrong, please let know :wink:

Fri Nov 09, 2018 7:26 am

1950split wrote: Neil,

I have a mallory 6 al2 (very similar to MSD CDI) and a Mallory pump as well as a CSP fuel pump relay (same terminals as Glenn's).

I had to fit a MSD tach adapter (8910 : for white wire triggering and points) to have the relay activated which would in turn prime the fuel pump for ca. 3 seconds.

Now that I have switched to as MSD distributor I have just bought a MSD 8920 Tach adapter that works with mag pickup distributors. https://www.holley.com/products/accessories/tach_adapters/parts/8920

I will hook up the relay (31b) to the violet wire of the 8920 tach adapter. Tach wire will attach there too.

It seems that it is the way to go to have the relay working.

If you guys think that I am wrong, please let know :wink:

Try it both ways (with or without tach adapter) and let us know...

Dale

Fri Nov 09, 2018 7:24 pm

I tried to use the tach wire from the Mallory Hyfire to trigger the fuel pump relay. It did not work.

Then I wired the tach adapter (msd 8920) as per the diagram for voltage triggered tachs and connected the relay to the same wire as the tach and now it works perfectly ! :D

Hope this helps!

Fri Nov 09, 2018 9:35 pm

The tac signal could be used it was a square wave, Sign wave, Saw Tooth or (Just the points signal with some kind of isolation) with a True RMS chip to buffer it and then a Comparator Circuit and appropriate driver to run the fuel pump relay.