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PWM Control of Dual Bosch 044 Fuel Pumps

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Hi Guys

I'm considering running my dual Bosch 044 pumps via pwm control from the ecu.

I'm looking at reducing both pumps to 50% at idle / low load and increasing output as load increases.

I'm wanting to avoid the fuel heating and noise issues associated with running the pumps at 100% all the time.

I'm interested if anyone has had any specific experience using pwm control with 044's and if they had any issues or reliability problems with running the pumps like this.

You can't directly PWM control the pumps. This needs to be done through a speed control module such as the Motec DHB controller. If you were using a conventional relay you won't be able to modulate it fast enough to get any real control.

Many late model cars of course now incorporate fuel pump speed controllers which can be functioned via the ECU. The downside is that often these aren't designed for high performance use and hence they may not be able to provide sufficient current to support a high flow fuel pump.

Thanks Andre

I didn't explain that I'm looking at controlling the pumps through a solid state relay like the jaycar sy4086.,-30VDC-100A-Switching/p/SY4086

The 044 pumps are a durable pump but I'm not sure how they handle lower voltages.


An engine cooling fan controller should work.

Ah that makes more sense. Yes a solid state relay should work in that application. I don't see any potential risk or problem with delivering the pumps a lower voltage. They will simply operate slower and at some point the flow will not be sufficient to match demand and the fuel pressure will drop.

You're right Dynodom, any device designed for speed control on a DC motor will do the job. My concern is more centred around the devices maximum current capability. While a Bosh 044 pump is only likely to draw 10-12 or so amps , some of the larger pumps on the market can exceed 20 amps and I would be worried about the chance of a fan controller (or a factory fuel pump speed controller) handling that. Of course we are only likely to want to speed control a pump when it's a big one too so that makes this concern more relevant.

Hi Marty how did you go with jaycar solid state relay?

Why don't you just get one in tank pump? You've got a Walbro 400 and other really high flow pumps. Why are you so worried about fuel temperatures? That's mostly an emissions issue. What engine is this, what is done to it, and what fuel?

Any high flow pump is going to make extra heat by circulating more fuel then the engine will use. He has 2 044 pumps most probably connected to a surge tank. So a single intank won’t cut it.

A lot of Australians are running surge tanks with dual 044 pumps for high boost rotary/4s where the in tank single performance curve doesn't really cut it at the base+boost pressure for big power levels or they want a surge tank, for some reason walbro doesn't have an inline version of the 450l/h pump (perhaps that is a thermal management thing?). In rx7s at least fuel surge is a known killer and the new b2a kit is the only off the sheft in tank surge I'm aware of. There are quite a few people running those SSRs for that purpose, haltech were even rebranding them?

Hi Guys,

I don't want to create a new thread, because this topic is exactly what I want to do for my BMW s65 v8 engine (M3 build).

However I want to drive the pumps from the PWM output of a Cosworth IPS32.

There I would like to use 2 channels both capable of 25A cont. but only with a PWM frequency of 5kHz.

I read somewhere the OEM controllers use as high as 20kHz for smoother operation.

The IPS32 also has 20kHz PWM outputs (50A), but I wanted to use them to drive the 2 current eating radiator fans.

Any thoughts on this?

A lot of cheaper ecus can't pwm close to 5kHz so I wouldn't worry about using those outputs.

Hi guys, I'm a bit late to join this thread, but I'm looking at doing the same with my twin 044 pumps. I was looking at using 2 Hella SSR

using PMW from the ecu. I'd be interested to hear some opinions on this idea from you guys, especially Andre and the HPA guys.

I dont think the hella relays will handle PWM with the current that a 044 pulls for very long. I use them on some of the sports cars I work on but the fuel pumps would only pull probably 10A max in those. Even though the Hella datasheet says they are good for 22A continuous, PWM of inductive loads is pretty hard work for it, there are some posts on the Link forum where some guys have tried them with bigger pumps and found they overheat quickly.

You will either something like a Motec DHB or the common Ford/Jaguar fuel pump control module.

Thanks for that info Adam. Do you know if the Motec DHB can be used with other aftermarket ecu's or is it just for Motec units? Also, if anyone knows the part numbers for the Ford/Jaguar fuel pump control module, that would be a great help?


Aston Martin Range Rover Sport Fuel Pump Electronic Module Genuine 7H42-9D372-AA

Attached Files

I use Crydom 60 amp SSR's when PWM'ing fuel pumps, part number: DC60D60

They work awesome. You do need to mount them to a metal surface, preferably a heat sink. You also MUST wire in a fast recovery diode across the load, I usually overkill it and use an IXYS: DSEP60-06A

Attached Files

Hi Sapphire,

The MoTeC DHB's can be used with any ECU that has suitable outputs.

I have done exactly this, running 2 044's in PWM from separate outputs from my ECU... I used a Sabertooth 2x32A unit with regenerative turned off (this reduces the amp capability hence using 32amp per pump) ... I then additionally use the 5V output of the unit via a relay to activate my lifter pumps.

Of cause I could have simply used a similar single higher amp version and controlled both of them from a single ecu output, but i wanted to only have one active at idle and genuine 044's do have an effective one way valve in them.