EFIDynoTuning Forum

So I think I am still dealing with my fuel pump overheating my fuel. Its better than it was before because I dont have boiling issues but I get a pretty big swing in my fuel trims if I drive the car for a few hours vs 30 minutes. I currently have a on3 triple hat with dual 340lph pumps and an 03 cobra tank. The first pump runs off the computer, the second is activated by a Hobbs switch set at 3psi. I was thinking of switching out my main pump for a 190 or even 155lph pump and leave the secondary 340lph in there for when it goes into boost. I ultimately want to switch back to e85 so I need some overhead but I thought switching to a small main pump will help with the heating issues since I wouldnt be recirculating the fuel nearly as much. As a refresher, I completely rebuilt the fuel system last year. The regulator is in the rear. I have a 8an supply and a 6an return with 8an behind bars rails. the supply line from the rear to the front is wrapped in fiberglass insulation and reflective tape to reduce heat absorption. Will I have any issues running mismatched pumps or should I replace both pumps with 190s?

Anybody?

Have you thought about running the return fuel through a cooler before returning to the tank. Couldn't a simple power steering cooler from a car help?
you could put it under the car where is could get some air flow.

Not enough information.
Are your pumps in series or parallel?
Why is your regulator at the rear?

You could hit the pumps with less voltage and trigger 12V power with a switched relay. A concept similar to factory gen 2 Lighting trucks fuel systems. Just a thought “spin the pumps less until you need them”

jcbryant wrote: ↑2021 Jun 06, 23:17 Have you thought about running the return fuel through a cooler before returning to the tank. Couldn't a simple power steering cooler from a car help?
you could put it under the car where is could get some air flow.

Yes i have. I found a 6an cooler but I really don't have enough room under the car. The car sits pretty low too so under car options are limited

m-barans wrote: ↑2021 Jun 07, 00:04 You could hit the pumps with less voltage and trigger 12V power with a switched relay. A concept similar to factory gen 2 Lighting trucks fuel systems. Just a thought “spin the pumps less until you need them”

I don't need 680lph. I'm only making 560whp. My car is 99% street car so streetability is the most important thing. I have thought about what you mentioned which could be done with a 5 pole relay and a resistor but i feel using a small pump or pumps is a better option in the long run.

A 155+340 or dual 190s will both meet my needs. I really like the idea of running a 155 and 340. It should solve all my fuel heat issues

Can you somehow take a temperature measurement of the actual fuel in the tank? Or even use infared thermometer on the bottom of the tank. If the skin of the tank is near ambient i would think the temp is not a problem. It could just be adding air bubbles somehow. I think I saw a video about the cavitation problem.

red5.0fogger wrote: ↑2021 Jun 07, 09:30 Can you somehow take a temperature measurement of the actual fuel in the tank? Or even use infared thermometer on the bottom of the tank. If the skin of the tank is near ambient i would think the temp is not a problem. It could just be adding air bubbles somehow. I think I saw a video about the cavitation problem.

I think cavitation is unlikely. The return line goes all the way to the bottom of the tank. It doesnt seem to matter if its full or half a tank. If I drive for a few hours, the fuel error is adding 8-10%. If I check them 30 minutes after warmup, they are 0 to 2% off. Im gonna get a gauge to monitor the fuel temps to verify. I dont have a infared thermometer.

It's my opinion that you don't need 2 pumps. I'm willing to bet one 340lph pump will be fine for your hp. Did you run new wiring to the pumps and what gauge?
I had a similar issue until I went to heavier gauge wiring from the battery to the pump. I now get a good 14v at the pump.
As an example; I ran a 190lph pump on a 400hp 347 with 34lb injectors. I never ran out of fuel.