Really? Since the pump does not put that much pressure into the system and what is returned to the tank did not go into the delivery system how much heat does it really add? Have you measured that? Dean
Need help with lift pump sump, nowhere to install
- Thread starter pavetim
- Start date
It goes from the lift pump to the hpfp, then gets pressurized from to about 5000 psi at idle to 25000 psi at higher power settings, you can bet it does heat up, how much I don't know. Don't most duramax trucks have a fuel cooler?
I do know that on Boeing airplanes, the hydraulic fluid only pressurizing to 3000 psi, is routed through the fuel tanks for cooling.
I do know that on Boeing airplanes, the hydraulic fluid only pressurizing to 3000 psi, is routed through the fuel tanks for cooling.
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most of the heat probably comes from the engine itself and only a small amount from the pump. as you probably already know, liquid is not compressible so it's not the pressure increase that is going to add any heat but the resistance of the fuel to the mixing and churning that happens inside the pump and to a smaller degree at the lines and injectors.
with that being said, all the prior years had a fuel cooler but the LML it was left out. probably because the piezoelectric injectors return far less fuel then the solenoid type. thus allowing for it to cool down more before it makes it back to the tank and not heating the tank as much either. whatever it was, the engineers didn't see it as necessary for that model.
the fuel, off the top of my head, heated up to between 200° to 250° . I don't think too many got much higher then that unless they had some pump problems or other issues. I know the CP4 pump, while it was chewing itself up or grinding it's internals just before dieing could get hot enough to boil the fuel. seen that first hand.
The way I see it the limits of the stock fuel system is a good fuse as the trans won’t last long at much higher power levels anyways. Upgrade the trans, upgrade the fuel system and air.
That said I don’t get the sump thing either. Drawstraw pretty much solves any issues plus gives you a nice return. Other than sloshing, all the water and debris collects in the lowest part of the tank which in the case of a sump would be there. Some places water isn’t an issue, and others it is depending on environment but just the same, anything other than fuel that gets into the tank I’d just as soon like to leave there.
Plus it not only makes for a good place for fuel thieves to empty your tank there’s an increased chance of knocking it off or having a leak depending on where you drive your truck.
That said I don’t get the sump thing either. Drawstraw pretty much solves any issues plus gives you a nice return. Other than sloshing, all the water and debris collects in the lowest part of the tank which in the case of a sump would be there. Some places water isn’t an issue, and others it is depending on environment but just the same, anything other than fuel that gets into the tank I’d just as soon like to leave there.
Plus it not only makes for a good place for fuel thieves to empty your tank there’s an increased chance of knocking it off or having a leak depending on where you drive your truck.
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You should log a max effort stock motor lml fuel return temp. Also, look at the fuel limiting temperature in the files. Of all of the generations.
I'm quite aware of those tables as I do my own tuning. I have not seen any increase in temperature from a lift pump. fuel temp was more directly related to engine temp and to some degree exhaust temp. this makes sense because the fuel flows through the injectors which are sticking right into the combustion so a hotter tune will impart more heat into the injectors which will heat the fuel.
what you would really need to do to settle the argument would be to have a temperature sensor right after the output of the CP3/CP4 and compare it to the return temperature if it is the same or close then the pump is adding the temp. if the return is hotter than the temp is coming from the injectors/combustion. another test would be to just use the DVT controls to jack up the pressure and watch the temperature. it's been a while but I don't remember seeing any significant change in temperature from doing this
I never stated there was an increase in temp from a lift pump? The increase in fuel pressure at the cp3/cp4 is what generates the heat. There is a slight cooling effect caused after that by the small orifice in the fittings to the rails themselves, but the heat shed there is directly related to flow through the orifice. So if the tune is commanding higher rail pressure but not a lot of volume, the source of the majority of hot fuel returning to the tank is from the pump itself. Not a lot of heat is gained or lost in the low pressure plumbing in a stock truck.
It's an easy thing to isolate and figure out the contributions, just separate the pump return from the injector returns and plumb it in after the sensor and compare logs
I agree with your statement but the issue is in regards to a FASS lift pump. What fuel is not used to feed the CP3 or CP4 goes thru a pressure bypass on the FASS unit. This is aerated fuel is returned to the fill hose going to the fuel tank. That in itself should not be an issue. Now I can see were we know are feeding a bit of pressure to the CP3 or CP4 where before it sucked fuel from the tank would cause a slight increased rail pressures but that is part of what is needed to make more power. What is returned from the main fuel system runs thru an cooler just in front of the fuel tank to aid in cooling the fuel before going into the tank at the sending unit. Dean
I think I see where some confusion started, you thought I was talking about the hot return fuel coming from the Fass and I wasn't, I thought it was just understood by most here that it comes from the high pressure system and is directly related to higher rail pressure command because it is a topic most of us have discussed and logged at length in years past. I should've been more specific originally and not made that assumption.
There is no issue at all with the fass pump excess fuel returning to the tank. I just want to make that extra clear. It isn't even aerated fuel. It isn't hot. And if returned into the filler neck or elsewhere, it does not cause any change in the pump suction.
Probably my mistake since the whole thread was about installing a lift pump I assumed you were referring to the return from the lift pump. No worries, thanks, Dean
Well I modified the stock sender I cut the bottom off the basket, put 4 big semi circular notches to help with flow and since the sump has a tube coming out of the return port to help with cavitation I basically had to cut off the whole black piece off the bottom. The one thing I am worried about is when I cut it off there was a metal piece inside like a flat spade and I thought it had something to do with where the second white wire hooked up, the wire with a female terminal end but there is no metal where the connector goes in, it just goes into plastic so not sure what that's for. You guys have me worried I messed up a fuel temp sensor but I don't see anything g that the metal piece I cut off even goes too. Should have gotten pics
could have been the wiper or resistive element. the wires should just attach to the resistive element. there should be no wires inside or at the bottom. only running down to the sender