I have noticed when i drive the car for more than an hour or thereabouts, i start loosing fuel pressure and the pumps whine more as though they are cavitating. There are heaps of people all over the internet having this issue but hard to find solutions. Even aeromotive have the symptom in thier faq. I have twin walbro 255 in tank both running full speed constantly. I am wondering if its the amount of fuel returning to the tank causing it to heat up and vaporize as it enters the pumps or if it could be the fuel line being too close to the dump pipe. Solutions would be to wire the second pump to a hobbs switch so its only on when in boost to minimise the amount of fuel circulating. Or to move/shield the fuel lines even more than the stock setup plus maybe add a fuel cooler. Thoughts? Experiences?
From a specific cavitation standpoint, it is unlikely. Your fuel would be getting VERY hot for this to be an issue. Generally with a flooded suction to the pumps and a small lift is should not present it self. Can you measure your fuel temperature in the rail? Does the LS have a fuel temp sender? If you can find the temperature you can work out the vapour pressure and do the NSPH calcs. Working out the NSPHr of the pump will be a lot more difficult.
No fuel temp sender. The reason i think its heat related is it only happens after long drives. Once the car has cooled down the pressure is back to normal (60psi base) and the pumps quieten down
considered adding a fuel cooler? in the wa climate and with your beastly applicaation, its probly a good thing to have regardless of wether this is the actual cause of your problem.
I think you will find the fuel is getting overheated. It is a common problem with LS engines running a return line fuel system and constant speed pumps. If it is overheated fuel then you will find the fuel pumps are too hot to touch and the fuel tank is also hot. The fuel pumps will not last long if they are overheating. A cooler on the return line should help.
yeah I haven't checked current but voltage is fine at around 14.5v. I've used pretty beefy wiring so that's one thing I'm sure is ok. Each pump has its own battery feed and relay. yes this thread was just to see what the general consensus was. I'll be looking to add a cooler.
I've had this problem . My main pump is now variable controlled by the electronic fuel reg. It still showed symptoms at 1/4 to 1/2 tank on a hot day . So I have the lift pump now 2 speed controlled at 7 and 12 volts . Which has allowed me to go under 1/8 of a tank . Now I'll add a fuel cooler as a back up as I wanted to fix it as much as possible without it .. Otherwise it would just be a bandaid fix to me I could also have set the lift pump on a switch hi/lo switch for freeway cruises on low tank
My dumps are very close too .. All though HPC coated still generates a lot of heat .. Might have to wrap them as well if that solves/helps the problem .. .
Isn't there a thread around here somewhere that got trashed by those against cooling the fuel ? :rofl:
i think there is yeah. what of it lol. you of all people know better than to suggest new things around here......
run a methanol/dry ice slush inside a fuel cooling container for the drags. should come out nice and cold. if your problem is street related.... got no idea. cant imagine a typical heat exchanger will do much?
It's a street related issue so any mechanism needs to be maintenance free. Controlling the speed of the pumps and therefore the amount of fuel being circulated is a HUGE factor for usability, running the pumps at full speed all the time actually generates heat in the fuel system. Circulating the fuel through the rails excessively takes heat from the engine & transfers it to the fuel system. Control the fuel pressure & flow efficiently & if you have a heat issue THEN look at a cooler on the return line
specialty z run hobs switches on all there dual pump setups with check valves to keep the system primed.. didnt you have your fuel cap drilled for emmisions and carbon canister to get over the pits.. could be something that simple dude !!
