Electric Fuel Pump Failure

[MMC757]

I wonder if the pump circuitry has some sort of safety feature that's being triggered, then gets reset when you cycle power.
Have you verified if voltage is making it to the pump housing itself when its not running?

It might be a worth an email to the manufacturer for some tech support.

 

[Indycars]

Have you verified if voltage is making it to the pump housing itself when its not running?

The relay contacts for power are dropping out, so the pump would not be getting any power.

 

[PotvinGuy]

If you want the pump to be on while cranking, it needs to be wired like this:

That is, both the operating current (pin 87) and the control current (pin 85) need to come from Always On. If either of them come from Switched Power, then the pump will be off while cranking, since Switched Power comes from the ACC terminal, which is dead during cranking.

Could it be a voltage spike in the system when the starter engages ?

Highly unlikely. Now the system voltage will drop while cranking since the starter draws lots of current (just as an aside, are you using a stock starter? I changed to one of those small geared starters and it made a giant difference; the motor spins faster and the starter draws less current).


The thing that vexes me now is does the pump and the FP still go off while driving? And why would toggling the pump switch fix it? I've been poring over the schematics and can't find any reason.

 

[MMC757]

The relay contacts for power are dropping out, so the pump would not be getting any power.

What I meant was have you verified this is true or are you assuming it is?

 

[MMC757]

...The thing that vexes me now is does the pump and the FP still go off while driving? ...

You could install an LED indicating light at the pump to show if its powered or not.

 

[Indycars]

(just as an aside, are you using a stock starter?

No, it's a PowerMaster mini starter.

https://www.summitracing.com/parts/pwm-9526



Below is my relay board with 4 channels.

The thing that vexes me now is does the pump and the FP still go off while driving?

Yes ???? The pump goes off when the starter cranks over, so yes there would be no pressure when I'm driving.

And why would toggling the pump switch fix it?

It's not making sense to me either. Some kind of interaction between the starter and fuel pump relay power contacts ??? Power is still present on the coil, but the power contacts are NOT made.

I've been poring over the schematics and can't find any reason.

Much appreciated !
.

 

[old round fart]

Can you temporarily leave the relay out of the circuit?

 

[Indycars]

Can you temporarily leave the relay out of the circuit?

I have a stand alone Hella relay that I'm going to try.

 

[PotvinGuy]

Yes ???? The pump goes off when the starter cranks over, so yes there would be no pressure when I'm driving.

So the pump goes off and then stays off after the motor has started? Or does it come on and then go off while you are driving?

It's not making sense to me either. Some kind of interaction between the starter and fuel pump relay power contacts ??? Power is still present on the coil, but the power contacts are NOT made.

Whoa! The pump relay has power (pin 86 is ground and pin 85 is +12) and pin 87 has +12 but pin 30 has none? That's a bad relay, as shown in this professional rendering:


...and the toggling thing fits: the relay is flakey and sometimes makes contact and sometimes doesn't.

 

[Indycars]

So the pump goes off and then stays off after the motor has started? Or does it come on and then go off while you are driving?

The pump stays off until I flip the rocker switch off/on and then I'm OK.

The pigtail for the Hella relay was labeled wrong, so that took me a few minutes realize. This
time I went direct to the info on the relay case and labeled the wires myself.

This did not fix the problem, but it did make it slightly different. Now when I turn the key to the
Run position, the pump comes on very briefly, less than 0.5 seconds and then goes off. Until you
turn the key Off and then back to run. I'm getting power from Always On fuse panel.

 

[PotvinGuy]

Time to play elimination. Hook the pump directly to Switched Power; no relay, no switch,, and use a fuse that can handle the pump. After the motor starts and the ignition switch is back at RUN, the fuel pump should go on and stay on. We are now down to the pump or Switched Power as the source of our discontent.
Drive and see. If the FP drops, check other things on Switched Power (ALT light, voltmeter) to see if they are off.
I'm beginning to suspect the anti-theft switch or relay.

 

[Indycars]

I put a jumper across the switch in my console and the pump started working. So I went back
to the relay on the circuit board from the Hella relay and it still works. It's a lighted switch, so
maybe that has something to do with it. I had already purchased another switch panel, so I
have some spare switches. With the new switch I can get the pump to work or the light to work,
but not both.

It's still mind blowing how the switch would work until the starter was engaged !

 

[PotvinGuy]

Ah, the plot thickens...

With the new switch I can get the pump to work or the light to work,
but not both.

So in one position the pump works and in the other position the light is on?

I assume you want the light on when the switch (and load) are on? Or light on all the time? How do the other switches work?
And how do you have the switches wired, i.e. which terminal goes where.

 

[Indycars]

So in one position the pump works and in the other position the light is on?

No, I'm not talking about the position of the switch. What I'm saying is when I move the wires
around on the switch, that's when I can get only the light or the pump to work, but not both.
Yes, I am flipping the switch during this process and can get only one to work at a time.

This is the way it's been wired.

I assume you want the light on when the switch (and load) are on?

Yes, that's correct.

BTW, I cut the old switch open and tested the light from inside the switch. It was
no good. The light is what I would call a neon light.

 

[Rip VW]

Just a casual observation I noted but the switches you are showing are AC rated switches NOT dc rated. The amperage rating in AC amps is not the same as DC amps. There is a big difference between the two. AC rated switches should not be used for switching DC Loads there to light and won't last long.

Check out this article about switch ratings... https://www.electronicdesign.com/te...ng-the-right-switch-know-your-ac-from-your-dc

 

[PotvinGuy]

Neon is unlikely, that's for 110 VAC. Yours should be a 12v incandescent or an LED.
This is the switch insides:

But we need to know which pin is which. A common configuration is this:

Then pin 1 goes to ground, pin 2 goes to the FP relay and pin 3 goes to the anti-theft switch. Try that and lemme know.

 

[Indycars]

Just a casual observation I noted but the switches you are showing are AC rated switches NOT dc rated.

I see what you are saying. They are marketed as a 12vdc switch on Amazon. The lights do work with 12 volts. I cut a used switch open and the contacts look like new. All the switches do is control a relay, so they carry only a small amount of current.

I do appreciated you reading and pointing out things that might make a difference !

www.amazon.com/gp/product/B007XXA5HA/ref=ppx_yo_dt_b_asin_title_o06_s00?ie=UTF8&psc=1

 

[Indycars]

I did away with the Impact Switch for now. The starter has been moved to constant
power, but the fuel pump is still on Switched Power. Don't need the pump while I'm
cranking the engine.

My son is out for a test drive, time will tell if I have it configured correctly. Better for
him to get stranded than me if it quits again !!! LOL !

#1 - Goes to ground
#2 - Goes to the relay coil
#3 - Goes to the switched fuse panel (12v)



I guess the looks of it makes me think neon bulb.

 

[PotvinGuy]

I guess the looks of it makes me think neon bulb.

Ugly little critter. I can't tell if it's incandescent or LED.

 

[Island Girl]

Ugly little critter. I can't tell if it's incandescent or LED.

Sure looks like a filament across the top to me . . . of course if it lights with applied power in either direction, that would be a sure way to tell.