# Electric Fuel Pump Prime Switch

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#### tcmtech

Joined Nov 4, 2013
2,867
Prior to 1995 I can't find any reference to them, so about then. I had no idea either.
My 1989 Ford Taurus had one. That was my first EFI vehicle.

Around 1983 was their first mass produced systems and likely the same time frame the inertia switch system came into use in Ford. That's ~36 years of just one common vehicle manufacturer having them.

#### tcmtech

Joined Nov 4, 2013
2,867
And thusly you are willingly filtering any info not related to your concept even though it relates to issues that have very real potential for doing far more damage than you claim to be avoiding.

I'll condense and summarize it for you.

1. Liability.
If you are planing to make them into saleable kits means you are now liable for any malfunctions that may happen with your homemade DIY system.

2. High potential for catastrophic engine damage due to simple timer failure.

If the timer circuit fails and keep the pump on all the time will have both the electrical and mechanical running in series which could either push the float valve off its seat lead into at minimal flooding the engine or pumping raw gasoline out of the carburetor all over the engine leaving a high potential for a fire.
Or, the added inlet pressure could rupture the mechanical fuel pumps internal diaphragm and seals thus flooding the engines oil with gasoline leading to catastrophic engine damage.

Got insurance? Lots of it?

Got any clue how to ruggedize as solid state circuit to work with a electrical systems that have zero voltage spike protection that are laded with high levels of high voltage noise from mechanical ignition points and mechanical voltage regulators on their generators ans alternators?

Say you design this your way and don't have those sort of issues resolved and I buy one, what's to keep me from suing you into oblivion when your circuit malfunctions and destroys my engine or burns my whole vehicled down and I can easily prove in court you had no clue what you're doing and your whole circuit was based on some free advice you got form some online forum that included sufficient reference and solutions to concerns of such problems you chose to ignore?

#### GopherT

Joined Nov 23, 2012
8,012
And thusly you are willingly filtering any info not related to your concept even though it relates to issues that have very real potential for doing far more damage than you claim to be avoiding.

I'll condense and summarize it for you.

1. Liability.
If you are planing to make them into saleable kits means you are now liable for any malfunctions that may happen with your homemade DIY system.

2. High potential for catastrophic engine damage due to simple timer failure.

If the timer circuit fails and keep the pump on all the time will have both the electrical and mechanical running in series which could either push the float valve off its seat lead into at minimal flooding the engine or pumping raw gasoline out of the carburetor all over the engine leaving a high potential for a fire.
Or, the added inlet pressure could rupture the mechanical fuel pumps internal diaphragm and seals thus flooding the engines oil with gasoline leading to catastrophic engine damage.

Got insurance? Lots of it?

Got any clue how to ruggedize as solid state circuit to work with a electrical systems that have zero voltage spike protection that are laded with high levels of high voltage noise from mechanical ignition points and mechanical voltage regulators on their generators ans alternators?

Say you design this your way and don't have those sort of issues resolved and I buy one, what's to keep me from suing you into oblivion when your circuit malfunctions and destroys my engine or burns my whole vehicled down and I can easily prove in court you had no clue what you're doing and your whole circuit was based on some free advice you got form some online forum that included sufficient reference and solutions to concerns of such problems you chose to ignore?
He'll be ok if Trump wins. There will be no more regulations for businesses - he said he is going to "get rid of them". Right now, I am working on a glass fuel tank. A bit dangerous but look really cool.

#### tcmtech

Joined Nov 4, 2013
2,867
He'll be ok if Trump wins. There will be no more regulations for businesses - he said he is going to "get rid of them". Right now, I am working on a glass fuel tank. A bit dangerous but look really cool.
Can you mount them on the front where the bumper is so everyone can see it and know who brilliantly cool I am?

I want to put on my Ford Pinto so I will need overly complex poorly built a timer to shut the fuel off several seconds before I crash though.

Safety is important to me because it's my daily driver. Not because I am poor but because I have no money because I spent it restoring a 1971 Ford Pinto to exact OEM specs to use as a daily driver after my Edsel burned down due to a failed diaphragm in the fuel pump when my electric primer pump would not shut off due to unrelated homemade fuel system timer malfunction that common $10 junk yard salvage inertia switch could have prevented. #### GopherT Joined Nov 23, 2012 8,012 Can you mount them on the front where the bumper is so everyone can see it and know who brilliantly cool I am? I want to put on my Ford Pinto so I will need overly complex poorly built a timer to shut the fuel off several seconds before I crash though. Safety is important to me because it's my daily driver. Not because I am poor but because I have no money because I spent it restoring a 1971 Ford Pinto to exact OEM specs to use as a daily driver after my Edsel burned down due to a failed diaphragm in the fuel pump when my electric primer pump would not shut off due to unrelated homemade fuel system timer malfunction that common$10 junk yard salvage inertia switch could have prevented.
putting a supplemental pump in parallel with the OEM pump would make so much more sense. SOOOOOOOO much more sense.

#### Deve

Joined Dec 28, 2015
95
The idea is to make the priming circuit so that if it fails, it defers to the oil pressure sensor setup. I do not think a retired guy on SS is much of a target. Good luck getting blood out of a turnip. Yet, I do want to make it right. That is why I came here? And SURPRISE! Most of the above hasn't gotten me any closer to an actual circuit!

I do not want to double the output of the fuel pumps when they are in redundancy. I want to ensure when one goes out, the other is there to take over. Also, I do not think selling an end user an inertia switch out of a junkyard will do anything positive for liability. That's one reason why inertia switches are out of the question. Any ideas on an actual circuit for automatic priming?

http://devestechnet.com/Images/Projects/ElectricFuelPump/FuelPumpSchematiclg.jpg

#### tcmtech

Joined Nov 4, 2013
2,867
It would but what's, simple, reliable and mechanically based is not the point. That's been shown already.

It's got to have a timer, damnit!

#### shortbus

Joined Sep 30, 2009
8,048
I guess I'm pretty dumb about this "primer pump". An electric pump inline(series) with the mechanical pump is going to cut the cranking time how exactly? The electric pump comes on with the ignition and feeds the mechanical pump. The engine will still have to turn over the same number of times to work the mechanical pump to fill the carb bowl, whether it is "primed" or not. The mechanical pump will not allow fuel through its internal valving without the engine turning over the same number of times, "primed" or not.

And what carb is going to allow the evaporation of fuel in the float chamber that fast, in a so called "daily driver" situation? I guess that fuel evaporates faster in other places than it does in Ohio, which has never been a problem for me.

Like I said before, a solution looking for a problem.

#### Deve

Joined Dec 28, 2015
95
Usually when people are trying to keep up, they just sit back and watch the conversation without saying anything if they do not have anything positive to provide. Its about positivity and encouragement. Trying to harsh someones mellow is just indicative of <improper remark stricken by moderator> that none of us have time for. Go to facebook if you want to waste your day. There is always one <insult removed by moderator> but good grief, how did this forum attract all of his friends? Didn't used to be that way.

Meanwhile, I tested the timer circuit and that will work fine. I just need to bench test all of the system. Fuel flow tests as well as electricals. I need to find a timer circuit schematic that will fit this application though. I am using one of those modules from China. The problem with them is the sometimes 10 weeks it takes to get them. I would rather just make the circuit board and solder the parts in myself. Anyone WHO KNOWS know of a schematic out there for a simple timer circuit I can adjust between 2 and 10 seconds?

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#### inwo

Joined Nov 7, 2013
2,419
The 555 inverted monostable in the book is as simple as you may find.
Do you need it redrawn?

#### Deve

Joined Dec 28, 2015
95
Here is the updated block diagram:
http://devestechnet.com/Images/Projects/ElectricFuelPump/FuelPumpSchematicAutolg.jpg

The module allows for adjustment from 0-10 seconds which should be more than enough. I have a few of these lying around, but I would much rather make the circuit from scratch.

http://www.ebay.com/itm/DC-12V-Dela...525145?hash=item51c3a200d9:g:OpkAAOSw-jhUHAOP

I have a test engine with the mechanical pump and an electric pump to play with. I will connect them using fuel pressure gauge to test things before any conclusions. http://devestechnet.com/Images/Restorations/1950B/D50b00757lg.jpg

Again, anyone having electronic knowledge here on All About Circuits, that wants to contribute a 0-10 second timer with relay schematic, it would sure be appreciated. I would defer to someone much better at this than me.

#### Deve

Joined Dec 28, 2015
95
inwo, either yes, or validate the component values and incorporate a relay. I do not want to leave anything to chance. The only thing that concerns me about the way the way it is set up now is, if the module fails, loses power, relay dies, etc. the ground connection would be made and that is undesirable. How to overcome that?

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#### inwo

Joined Nov 7, 2013
2,419
Tell me about the timer you're testing.
What mode are you using? Td on? Td off? One shot?
Do you have a link to instructions?

#### Deve

Joined Dec 28, 2015
95
http://www.ebay.com/itm/DC-12V-Dela...525145?hash=item51c3a200d9:g:OpkAAOSw-jhUHAOP

that is all I have on it. The relay is activated after between 0 and 10 seconds. So before that, is how I have it wired NC. Once the relay is tripped as long as there is power on the module, it stays that way. Does that help?

Specification:
1.Module based on: NE555 chip.
2.Delay modue:delay connect module
3.Input voltage: DC12V
4.Control voltage: AC 0~250V / max. 10A, DC 0~30V / max. 10A the operating voltage: 12 volts DC; (otherwise 5V optional)

Main Chip (NE555) Characteristics:
1.Timing from microseconds to long hours
2.Simple circuit design
3.Precision Pulse Generation / Timing,
5.Monostable Operation
6.Countless Application and Information Sources

#### inwo

Joined Nov 7, 2013
2,419
When testing does output turn on for T then turn off and stay off until input is cycled?

#### Deve

Joined Dec 28, 2015
95
Actually, since I want ground right away with ignition on, I wired it so it runs the pump right away UNTIL the timer kicks in. I don't think I am doing it right, but wasnt sure how to proceed from there.

#### inwo

Joined Nov 7, 2013
2,419
No, that's good. I hadn't thought of that. Doh!
Now it's really simple.

#### Deve

Joined Dec 28, 2015
95
It works but like I said, if something happened to power or the relay died it would always provide ground which is a bad thing. Right?

#### inwo

Joined Nov 7, 2013
2,419
Yes, I think I have a simple circuit to get around that.
Relaxed state is "off".
If really worried about failure, as stated before, an undersized td fuse could blow if pump is on for an extended time.

#### shortbus

Joined Sep 30, 2009
8,048
Usually when people are trying to keep up, they just sit back and watch the conversation without saying anything if they do not have anything positive to provide. Its about positivity and encouragement. Trying to harsh someones mellow is just indicative of some personal problem that none of us have time for. Go to facebook if you want to waste your day. There is always one village idiot, but good grief, how did this forum attract all of his friends? Didn't used to be that way.
It could be that the people giving answers that you don't like are older than you and have messed with old cars, built street rods, hill climb Jeeps, motorcycles and driven old stuff for years. And never once had the troubles your imagining in any of your "project" threads.

I do know that any of the inline out of tank fuel pumps, especially the 6V ones won't allow fuel to be 'pulled' through them when not running, and a mechanical pump won't allow fuel to be pushed through it with the engine not running.

Maybe it's time to join your 'forum' to help over there?

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