Carbs and fuel pump relay, my solution Options

[hcdmueller]

I am running carbs on my 2056 so I performed the simple mod as described by SirAndy in the Tech Articles. One thing I have noticed with my car is that my fuel pump runs continuously with the key switched on. The fuel pump is a rotary one that I bought from the Type4Store.

I didn't like that fact that my pump kept running so I took matters into my own hands. I modified a Bosch CIS fuel pump relay to work with my car. It needs a signal from the negative side of the coil to provide power to the fuel pump. So unless the engine is cranking or running it won't start up the pump. Nice to have the extra safety margin as well. The relays are easy to find in the junk yard. I only paid a couple dollars for 3 of them.

[r_towle]

Interesting idea.
What are you thinking for the long term storage/ first spring start?
That would be when you have no fuel left in the bowls of the carbs...it all evaporated.

That is what I like about the FI setup, on Djet anyways...I can turn the key to run three or five times to prime the system and then it starts on one crank...It seems alot nicer to the starter circuit to me.

Rich

[hcdmueller]

You can put the original relay back in and the fuel pump will run continuously. I soldered a jumper wire off the tach signal wire on the relay board. I can switch the relays in a matter of seconds.

[shane]

I am running carbs on my 2056 so I performed the simple mod as described by SirAndy in the Tech Articles. One thing I have noticed with my car is that my fuel pump runs continuously with the key switched on. The fuel pump is a rotary one that I bought from the Type4Store.

I didn't like that fact that my pump kept running so I took matters into my own hands. I modified a Bosch CIS fuel pump relay to work with my car. It needs a signal from the negative side of the coil to provide power to the fuel pump. So unless the engine is cranking or running it won't start up the pump. Nice to have the extra safety margin as well. The relays are easy to find in the junk yard. I only paid a couple dollars for 3 of them.

Was going to hook up my carb fuel pump today off my oil pressure sender today and was reading about my options here. Haven’t got out my multimeter yet but this seems to make sense, is anyone using this method or a reason this method doesn’t work or is a bad idea. Thanks.

[Tbrown4x4]

I have this:

https://www.revolutionelectronics.com/Fuel_Pump.html

It primes for 3 seconds and then waits for an ignition signal.

[DickSteinkamp]

Was going to hook up my carb fuel pump today off my oil pressure sender today and was reading about my options here. Haven’t got out my multimeter yet but this seems to make sense, is anyone using this method or a reason this method doesn’t work or is a bad idea. Thanks.

If it is a pressure switch that turns the green light on and off, yes, it will work. When no oil pressure you can wire it to ground the fuel pump and prevent it from running. However, you will also need a signal from the starter when it is turning to power the fuel pump so that it will provide fuel to the carb if the float bowl is low. This set up is commonly used in boats to prevent an electric pump from continuing to run if a fuel line breaks.

If your oil pressure sending unit is for a gauge, no. That sending unit is a variable resistor based on the pressure it sees, not an on/off switch.


In Shane's example, isn't the pump going to continue to run if the engine stops in a position where the distributor is energizing the coil? (Or am I too hung up on points type ignitions?)

[shane]

I do have points, I’m thinking you are correct if I run the fuel pump relay off the negative side of the coil and the points are closed when the engine is off the pump would continue to run. But wouldn’t it also be a constant pulsating ground? Idk if the relay cares much or if it’s going to shorten the life of the relay and pump? Sounds like I’ll just keep it simple and run the relay off the stock oil pressure switch. I have a freshly rebuilt carb I’m thinking I’ll always have the tiny bit of gas it takes to start the engine and turn on the pump.

[hcdmueller]

Never expected to see this again.

The Bosch CIS relay is looking for the high voltage pulse from the coil, similar to the tachometer. No pulse, no energizing the relay. Just hooking up voltage won't do it.

I've never seen that controller. Looks good. The 3 second prime would avoid the issues of dry carbs if the car sits a while.

I don't hook to oil pressure switches. My engine holds oil pressure pretty well after shut down. I don't know how much of a difference it would make, but the less time the fuel pump runs after the engine shuts off, the better.

[mlindner]

Tbrown4x4, That sounds like a great product, thanks for sharing. Mark

[913B]

I have this:

https://www.revolutionelectronics.com/Fuel_Pump.html

It primes for 3 seconds and then waits for an ignition signal.

(IMG:style_emoticons/default/clap56.gif)
Thank you for the link

[SirAndy]

I have this:
https://www.revolutionelectronics.com/Fuel_Pump.html
It primes for 3 seconds and then waits for an ignition signal.

(IMG:style_emoticons/default/clap56.gif)
Thank you for the link

(IMG:style_emoticons/default/agree.gif)

That looks like it would do all the things ...
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[Ansbacher]

The Revolution thingy looks OK but a 3 second prime for carbs is no where near enough down here in hot Florida. The 356 I used to have and my present 914 with carbs always require(d) about 10 seconds of prime. If that thing was adjustable I would consider it.

Ansbacher

[DickSteinkamp]

The Revolution thingy looks OK but a 3 second prime for carbs is no where near enough down here in hot Florida. The 356 I used to have and my present 914 with carbs always require(d) about 10 seconds of prime. If that thing was adjustable I would consider it.

Ansbacher

I think you would just need to turn the key on and off and on a few times.

[SirAndy]

The Revolution thingy looks OK but a 3 second prime for carbs is no where near enough down here in hot Florida. The 356 I used to have and my present 914 with carbs always require(d) about 10 seconds of prime. If that thing was adjustable I would consider it.

I think you would just need to turn the key on and off and on a few times.

(IMG:style_emoticons/default/agree.gif)

[Tbrown4x4]

The Revolution thingy looks OK but a 3 second prime for carbs is no where near enough down here in hot Florida. The 356 I used to have and my present 914 with carbs always require(d) about 10 seconds of prime. If that thing was adjustable I would consider it.

Ansbacher

I have no experience with this, because I daily drive mine. I will say it always fires up right away no matter how cold or rainy. (I did park it for a few days last winter when we had some snow.)

(IMG:http://www.914world.com/bbs2/uploads_offsite/i.imgur.com-17338-1569769399.1.jpg)

I would like to mount some stud tires and try it out, but I'd hate to stuff it into a guard rail.

Anyway, I also like that if the module fails, it can be bypassed easily by clipping the wires in and out of the module for the fuel pump power, or (God forbid) snapping a Scotchlok across them.

[DickSteinkamp]

There are (at least) two times you want your fuel pump to stop operating wether you have a fuel injection or carb equipped engine.

1. When you get in an accident.

2. When a fuel hose or line breaks or a fuel hose clamp fails.


For the first case, one one of the inexpensive inertia safety switches is a good solution. All cars have been equipped with these since the 1990s.

An inertia switch won't protect you in the second case, however. Without some additional device, the pump will continue to dump fuel until the ignition switch is turned off.

Adding an oil pressure switch or a the Revolution thingy would work OK for a fuel injected engine. I think the engine would stop pretty quickly with a major fuel line failure due to the drop in fuel pressure.

A carbed engine, not so fast. It would run until the fuel in the float bowl(s) was exhausted. Not a good thing. Especially if the fuel being dumped was feeding a fire.

I don't know any way around this, however. Ideas?

[Ansbacher]

I think you would just need to turn the key on and off and on a few times.

That means to get at LEAST ten seconds of prime I would have turn my key four times. Sounds like a lot of unnecessary wear and tear on a switch that fails often.

[porschetub]

I think you would just need to turn the key on and off and on a few times.

That means to get at LEAST ten seconds of prime I would have turn my key four times. Sounds like a lot of unnecessary wear and tear on a switch that fails often.

(IMG:style_emoticons/default/agree.gif) and it would be a bit of a pain,IMO 3 seconds wouldn't even get a six on carbs started,when my car has sat for a while the bowls were dry,thought I had a hard start problem till I found this out when the car was first put in storage.
I do think it is a great safety device however,didn't someone mention an oil pressure sender that turns off the pump when the oil pressure drops to a low set point or none @all ?.

[shane]

I had the carter oil pressure safety switch in place of the standard oil pressure switch. It allows the fuel pump to run whenever the starter is cranking, And you keep your oil light function also. But mine stopped working I’m pretty sure it had something to do with having the engine upside down on a engine stand for about a year or so. But it seems like a good way to go, so I just replaced it with a standard oil pressure switch and used a relay to operate the pump when there’s oil pressure and another relay to operate the pump when the engines being cranked to start. I also added a medium loud buzzer when the key is on but the cars not running so I don’t forget and leave the key on when I’m working on the car.

[HansJan]

I have this:

https://www.revolutionelectronics.com/Fuel_Pump.html

It primes for 3 seconds and then waits for an ignition signal.

Just installed this today.
Works great.

Only took 20 minutes to install.
Then (because it’s me) it only took me 1hour to find that I reversed the wiring on the pump.