Fuel Pump Current Monitor/safety cut

This has been a thought of mine for quite some time since I damaged an engine (older project with older ECU) due to a lean condition where my fuel pump died…

2 years ago when I built my new setup (Evo 8) I switched over to MaxxEcu which straight away gave me so many more options & safety cuts etc.

Whilst I have things like Lean Fuel safety cuts activated, the previous mess has left its mark lol and I’ve had this idea on my mind and wondered how I would go about setting it up . Even just from a logging point of view it would be interesting to monitor..

I’m aware that I could have something setup where in the event of a loss in fuel pressure I could have a complete safety strategy in place or even just a 4d table and when it saw loss in pressure it could pull timing etc..

What I would like to do is have some way of monitoring Current draw on the fuel pump supply wire, we could log the current and from that then populate a table and then let’s say it was suddenly pulling more current (or less) then a safety could be implemented to reduce power or cut the engines power.

The first thing that pops to mind is a PDM and you could easily do it this way, as we all know, a lot of ECU manufacturers do their own PDM units which work hand in hand with the main ECU to provide safety strategies etc via fuel pump control.

I don’t unfortunately have a PDM and therefore have no easy way of dealing with my ‘brain wave’ which got me thinking and i noticed that many modern cars have a test procedure built into them, and also in most decent Diagnostic Scan tools And that procedure is a Compression Test. Obviously they don’t do the test the way we all know but it’s done by current draw. You crank the engine for a period of time and the diag tool then gives a set of results, it’s more of a cylinder to cylinder comparison result from what I’ve saw, I’m sure it’s done via the starter motor cable and when a cylinder is on a compression stroke then obviously it draws far more current whilst it overcomes the load…

Ive noticed a small circular device that goes around the main battery cable that I can only assume works as an amps clamp and the ECU gets its info from there..

I think you’ll see where I’m going with this! And yes! Could we get one of these sensor devices and use them as current monitoring but this time put it directly around the fuel pump wire to monitor current draw? I know this is a very long winded way of asking such a basic question but I can’t help but think it’s worth putting out there and even if it’s worth experimenting with and more importantly how would one go about setting it up, surely this has got to be worth a look into?

thanks

You might just be overthinking this. How will you tune the current load that is too much? And how does this relate to the pump output?

To me it seems like it would take significant testing (or a reproducible case you are tryin go fix) , and you still might not catch the case where a failed crimp causes the pump to have less voltage and not produce the expected pressure, vs. the high load case where the pump is doing it job, just needs more current to get it done.

Just use the MaxxECU to alarm, or stop the engine if the fuel pressure is too low. That is what you really care about, right?

BTW, I believe the right thing to do is compensate for the lower pressure with increased pulse width, so the engine still runs fine. But generate the low fuel pressure alarm, so you can look at the logged data and see the conditions that caused the low fuel pressure.

I'd agree with David on this. Current draw would require a lot of testing to create the data needed and would vary wildly with temperatures.

Monitoring fuel pressure is quicker and simpler to set up and repeatable. I'm not sure how the Maxx would do this but on the Link ECU's I've got the injectors compensating for drops in fuel pressure, and if it drops too low, it'll start limiting the engine. This has less variables so will be a safer way to set it all up.

Using current draw is a handy diagnostic tool if you have multiple pumps and are trying to find a failing pump. PDM's do this well, as current draw is usually something you can log

Understood. I’m already monitoring fuel pressure along with many other pressures, crank case , coolant etc.

I suppose it was more of a ‘thought’ I like to log and review data - I’m one of those people who has to know EVERYTHING! So I thought it would be interesting to see the current draw along with pressure etc as the boost pressure increases, I’m guessing that at 5 bar fuel pressure (rising rate system with 3 bar base and near to 2 bar of boost) the current draw would be a good bit higher.

Like I say it would just be interesting to see, I spotted the amps clamp thing on various different cars and had this idea of adding it in to my setup. Also from the day my old engine was damaged due to a bad pump, it’s something that you never forget! If there’s a way to come up with another safety strategy then I’m all over it.

I know that temperature will affect current etc but I didn’t realise the readings would be wildly different from run to run, I’ve learned something I suppose.

Appreciate the input guys, Thanks

Understood. I’m already monitoring fuel pressure along with many other pressures, crank case , coolant etc.

I suppose it was more of a ‘thought’ I like to log and review data - I’m one of those people who has to know EVERYTHING! So I thought it would be interesting to see the current draw along with pressure etc as the boost pressure increases, I’m guessing that at 5 bar fuel pressure (rising rate system with 3 bar base and near to 2 bar of boost) the current draw would be a good bit higher.

Like I say it would just be interesting to see, I spotted the amps clamp thing on various different cars and had this idea of adding it in to my setup. Also from the day my old engine was damaged due to a bad pump, it’s something that you never forget! If there’s a way to come up with another safety strategy then I’m all over it.

I know that temperature will affect current etc but I didn’t realise the readings would be wildly different from run to run, I’ve learned something I suppose.

Appreciate the input guys, Thanks

OK, I find using a PDM and logging currents for all the circuits is a very handy diagnostic tool. Using a current sensor would be a useful diagnostic, but I was trying to steer you away from using this as any input that would stop the engine running.

I can only think of one case where I found the current could tell me something I that would be useful for an dash alarm. That was a coolant pump, which only used about 60% of the normal current when cooling system wasn't fully bled. We were having overheating issues -- and when we finally got the system fully bled, then pump current went from 7-8 amps up to 11-13 amps -- and the overheating problem was solved. So an alarm could advise checking the coolant system for leaks, of course so could a pressure sensor.