Questions about PWM fuel pump control & relays

[matthunter1448]

About your diagrams, why are you taking 12V for the pump from the main relay and not the fuel pump relay? Also if you do use that 12V source for your pump, you can also use it for the input side of your SSR which may make it easier for your wiring (or not).

Jean

I thought the ssr is the fuel pump relay? So your saying if I use his first diagram. To use the 12v source from a fuel pump relay on the input and output side. Instead of the 5v. Would the diode still be needed?

[racingmini_mtl]

About your diagrams, why are you taking 12V for the pump from the main relay and not the fuel pump relay? Also if you do use that 12V source for your pump, you can also use it for the input side of your SSR which may make it easier for your wiring (or not).

Jean

I thought the ssr is the fuel pump relay? So your saying if I use his first diagram. To use the 12v source from a fuel pump relay on the input and output side. Instead of the 5v. Would the diode still be needed?

You're correct that the SSR is used instead of the fuel pump relay and that's a brain fart on my part. You can still use 12V as a source for the input side but you don't want it to be powered when the MS isn't. And the diode has nothing to do with the input side so you need it regardless of the power source on that side.

One thing I'm curious about now is what the recommended wiring becomes with a PWM fuel pump control. You obviously can't wire the injectors and ignition from the fuel pump SSR so you no longer have "safe" power source that is only available when the MS is ready.

Jean

[jb007]

About your diagrams, why are you taking 12V for the pump from the main relay and not the fuel pump relay? Also if you do use that 12V source for your pump, you can also use it for the input side of your SSR which may make it easier for your wiring (or not).

Jean

I thought the ssr is the fuel pump relay? So your saying if I use his first diagram. To use the 12v source from a fuel pump relay on the input and output side. Instead of the 5v. Would the diode still be needed?

You're correct that the SSR is used instead of the fuel pump relay and that's a brain fart on my part. You can still use 12V as a source for the input side but you don't want it to be powered when the MS isn't. And the diode has nothing to do with the input side so you need it regardless of the power source on that side.

One thing I'm curious about now is what the recommended wiring becomes with a PWM fuel pump control. You obviously can't wire the injectors and ignition from the fuel pump SSR so you no longer have "safe" power source that is only available when the MS is ready.

Jean

Your'e right Jean the FP pin does not operate as a fuel pump pin ie it does not turn on when the MS is ready for injection if you use another general purpose I/O pin. If you are using the FP pin for PWM and the 12V power from the main relay you should have a safe system as the PWM only occurs when the MS controls it. Or have I missed something?

Matt, You have to use the +5V instead of +12V because the FP pin is using 0V to turn on the SSR eg most SSR's need minimum of 3V so the voltage differential is 5V when the FP goes low. Now if we we use 12V as Jean has suggested, then when input goes low we get a 12V differential, SSR turns on. But wait when the input goes high back to 5V, the SSR sees 12V - 5V a 7V differential, and this will keep the SSR on. Or have a finally gone senile in my old age?

Jim

[racingmini_mtl]

Jim,

The FP pin does not output 5V; it's grounding the output when the CPU signal is on. That's how it operates a relay in the normal non-PWM mode.

If you rely on what you're seeing on the JimStim, you have to consider that you have a fuel pump LED that is powered by 5V so it will look like the output goes between 0 and 5V. But the 5V is coming from the JimStim through the LED and not from the fuel pump output.

And my concern about a "safe" 12V source is not for the fuel pump because, as you say, the SSR is controlled by the ECU so it will only turn on when the MS is ready. It's more for the injectors and ignition coils which will be powered before the ECU has completed its boot up. We're talking about milliseconds or a fraction of it but that's still enough in some cases to have a spark. And if the engine stalls, the injectors and coils would remain live which is not desirable.

Jean

[jb007]

Jim,

The FP pin does not output 5V; it's grounding the output when the CPU signal is on. That's how it operates a relay in the normal non-PWM mode.

If you rely on what you're seeing on the JimStim, you have to consider that you have a fuel pump LED that is powered by 5V so it will look like the output goes between 0 and 5V. But the 5V is coming from the JimStim through the LED and not from the fuel pump output.

And my concern about a "safe" 12V source is not for the fuel pump because, as you say, the SSR is controlled by the ECU so it will only turn on when the MS is ready. It's more for the injectors and ignition coils which will be powered before the ECU has completed its boot up. We're talking about milliseconds or a fraction of it but that's still enough in some cases to have a spark. And if the engine stalls, the injectors and coils would remain live which is not desirable.

Jean

Thanks for that. But because I'm also using the Generic PWM A output for Fan control and it does not support a negated (inverted) O/P will it work with the FIDLE pin?

What is the point of having gone to the trouble of providing a PWM Fuel Pump feature that is not safe. If you select a different O/P pin for PWM control then the FP pin cannot be used for fuel pump relay control. Really what should have been done is make the FP pin only for relay use as originally intended, and one of the other pins for PWM control! Simple!

Edit: So senario goes like this, software says its ok to start injecting... turns on FP pin and starts to PWM the other designated O/P pin. s***! Emergency, software shuts the FP off, which then the FP Relay turns off stopping spark, fuel etc.

I'm seriously considering ditching the PWM of the fuel, but still monitoring the fuel pressure with my pressure sensor. Hopefully when this problem is resolved, then I'll return to it.

Thanks Jean for your help in this matter!

Jim

[racingmini_mtl]

Really what should have been done is make the FP pin only for relay use as originally intended, and one of the other pins for PWM control!

That is also be what I would prefer to see, at least as an option. But note that I did put "safe" in quotes because while it is the most foolproof way to have any setup safe, it is not the only way and it will depend on what is being used.

So I may be over emphasizing a minor issue but it does goes against what has been strongly recommended for a while now and what is in the manuals as the way to wire things up. So I'd like to have some feedback for James and Matt and others to see what they think and what they would propose. Hopefully they do see this and reply. Or I may need to contact them about it.

Jean

[jb007]

Really what should have been done is make the FP pin only for relay use as originally intended, and one of the other pins for PWM control!

That is also be what I would prefer to see, at least as an option. But note that I did put "safe" in quotes because while it is the most foolproof way to have any setup safe, it is not the only way and it will depend on what is being used.

So I may be over emphasizing a minor issue but it does goes against what has been strongly recommended for a while now and what is in the manuals as the way to wire things up. So I'd like to have some feedback for James and Matt and others to see what they think and what they would propose. Hopefully they do see this and reply. Or I may need to contact them about it.

Jean

I have a feeling that James commented on one of the PWM posts about this issue, I'll have a look and report back. I'm a little worried now for safety sakes on not using the FP relay for its original intention. I've got to get my Mini on the road by mid Sept for a 2000km road trip.

Jim

[matthunter1448]

i agree that safety is a big concern wondering if this will be fixed in the next update would like to be able to use the fuelpump wire for the main relay and another output for pwm since i will be running two pumps (one for surge tank and one for pwm) but i thought about this can't you use a general output and set it up to come on only when it sees rpm or the fp wire is on?

[jb007]

Hi guys, I was wondering if any of you had implemented the PWM of a fuel pump or a returnless system in the last 3 months since I last posted?

I finally got the Mini started and I used DIYAutoTune's wiring diagram to wire up the FP and Main SSR relays. with their wiring, the FP can either be used as a simple on/off or PWM controlled by the FP Pin (DB37).

I've had some issues with my new 'replacement' pump that sits in the fuel tank. In the on/off mode, it appears to be overloading the Aeromotive low pressure fuel regulator. I can get the pressure down to the 12PSI my GM TBI injector requires but I think the flow rate is very high causing the PSI to fluctuate. It also could be the regulator... I wasn't happy with it when I had the fuel injection running before this recent rebuild...

I would like to try the pump in a returnless mode, maybe it will all come good then, otherwise I'll be looking for another lower pressure pump. The Mini Spares place the pump comes from, state that this replacement pump (Walbro brand) is a near drop-in replacement for the Rover Mini SPI and MPI fuel systems, 1 Bar and 3 Bar respectively. One thing is for sure the pump is bloody loud, and if I can't get it running quieter, it will definitely be ditched!

Jim

[jsmcortina]

Perhaps easier to add another standard 3bar regulator in there as an intermediate step, tee the return lines together?

James

[jb007]

Perhaps easier to add another standard 3bar regulator in there as an intermediate step, tee the return lines together?

James

Thanks James, I've found the specs of the pump since posting. I need around the 1 Bar 10-15PSI any more and the injector would have to low pulse width at idle. 3 Bar pumps were for the later MPI Rover Mini. I will look time permitting tomorrow morning to get the pump running under PWM, as I have a 30PSI fuel sensor in the fuel line, so hopefully I can do closed loop PWM. Do you recall anyone else using this feature, and if so how did it go?

I've also read that the only difference between the SPI and MPI fuel tanks, was the MPI had bituminous sound deadening panels on it. I have some DynaMat which might help.

Here's the specs f the pump:

Walbro In-Tank Fuel Pump Kit

Fittings In (mm):- 8mm
Fittings Out (mm):- 22.5mm
Pump:- Walbro 5ca401
Voltage DC:- 12v
Flow Ltr/Hr (Max):- 180 Ltrs
Flow Ltr/Hr @ 1 Bar (14.6psi):- 144 Ltrs
Max Pressure (Bar):- 2
Length (mm):- 128mm
Diameter (mm):- 36.8
Weight (Kg):- 0.3

Applications:- Rover Single Point Injection
Rover Mini 1.3 (Spi) 92>


Cross Reference Numbers:-

Rover WFX100811
Rover WZX10045