Debating Standalone (MegaSquirt) with dual speed fuel pump

[johnb7]

Hey guys,

I have been debating this for a while now. My Bosch 044 fuel pump works great. Unfortunately, the longer it runs, the hotter the fuel gets, the louder it gets. I mean REALLY loud. A lot louder than when I first started driving. This is actually considered normal for this pump, but it still makes me nervous/annoyed.

So as a preventative measure, I have been debating using the stock MK3 fuel pump relay and resistor. Using a spare output on my MegaSquirt, I could have the fuel pump at low speeds at cruise and idle (say less than 3000 RPM). I also would use a timer to keep the high speed mode active for a minimum of 5-10 seconds to prevent it kicking back down on shifts or other brief RPM drops.

So this evening I hooked up my fuel pump and ran it through the resistor just to see how much of a difference it would make and how much heat it would generate. I did this without the car running. Pump sounded like it was at half speed. Wire and relay temps stayed ambient. My concern was that the Bosch 044 pump would pull too much amperage for the resistor. After 10 minutes or so, the heat sink settled at about 200F with ambient air temps at about 70F and no air movement. Seems a little high, but I have found indirect references to other people doing this with similar setups, and people claiming the resistor will get well over 150F.

So is this just a bad idea as a whole? Do those resistor temperatures scare anyone? I am guessing I should put it somewhere with at least some air flow to help. Anyone ever checked their MK3 fuel pump resistor to see how hot it gets on a stock pump after lots of cruising and idling?

Let me know your thoughts.

-John

[Muchbzy]

Didn't I hear someone say once that you can use a MKIV pump? I thought I remember something about them being cheaper and quieter. Just a thought.

[johnb7]

Didn't I hear someone say once that you can use a MKIV pump? I thought I remember something about them being cheaper and quieter. Just a thought.

If I had an internal pump I would have done that. Not really interested in converting to internal pump.

-John

[Daves2JZGTE]

Never run less then 1/4 tank unless on a road trip and you will be fine I have been running my 044 external for years with. No problems but yes pump is louder after it worms up

Side note check your tank for sediment build up sender hole is ez to check

[ABQMK2]

John, have u thought about a weldon fuel pump controller. Im running.one. it pulses the pump. Uses a potentiometer also a switch to full on. Works with standalones too. Aeromotive makes one too.

200° sounds really hot for a resistor. But im just saying that with no merit.

[BillyM]

Complexity is the mother of failure.
All it would take is a single failure and "pop"...

I'd feel better about a small radiator/cooler in the return line if heat is your issue.



This is pretty standard in the diesel world (much higher pressures/temps)

--billyM

[johnb7]

Dave,

I already decided on the 1/4 tank rule. I wish the pump sat a little lower in comparison to the tank. Even on a full tank it still warms up after a half hour of driving. Tank has been replaced and is squeaky clean.

Jake,

I could build an extra standalone for $300. PWM is awesome but too expensive. I agree that the resistor was probably too hot. I already found an alternative if I decide to go with this.

Billy,

I guess I should gather some data on how hot my fuel gets. That would only be effective it it got pretty hot. I agree that if I thought I could avoid this extra complexity, I might go for it. Its worth checking out I guess.

Thanks for the input.

-John