Hot fuel cavatating external pump!
03-03-2020, 05:23 PM
#1
Hot fuel cavatating external pump!
Like the title says, I have hot fuel cavitation causing me to loose pressure with my external 340Lph pump.
I have a racetronics intank pump and hot wire that is normally on. The second pump that is cavatating is turned on by a hobbs switch set at 3psi.
Car is a 1999 C5 with rear mounted twin turbo set up.
I daily drive the car and like my 15psi blast or two getting on to the expressway in the morning's.
I converted from the returnles 1999 style fuel system to a full return from the rail with a 1:1 boost referenced fuel pressure regulator. (Regulator is in between the two rails)
Adding a small transmission style cooler on the return side from the regulator definitely has helped but it's still not enough.
On cooler days I can now drive all day with the fuel cooler installed and I build pressure in boost like I should.
Anything over 60F outside air temp and after about 20 minutes of driving my external pump starts cavatating as soon as it kicks on and I don't build pressure in boost. Which makes me very lean at 15psi on a new forged motor..
Looking for opinions at this point, texas summer is only going to make the issue worse.
Do I add a second fuel cooler? (Still might not be enough come 100F days in july and August)
Or use some heat reflective tape on the rails and put heat sleeves on the lines? (Would look like crap but might work, that stuff blocks out a ton of heat)
Or use a small trunk mounted fuel cell just for the second pump so it's never hot from constantly being recirculated in the rails / engine bay. (Might be best option, would just have to keep it filled and watch the level)
As a last resort I could ditch the external pump and do a dual in tank.. (I'd rather not)
I confirmed this hot fuel issue about an hour ago. I pulled a bunch Of timing from my tune so it would be somewhat safer, Then went and drove for good 20 minutes while data logging and rolled into it, sure enough pressure actually droped off instead of climbing with boost. After that I stopped and added about 5 gallons of 93 to the tank and quickly got back out on the road and rolled into it again, sure enough fuel pressure was climbing again in boost, hot fuel issue confirmed.. help
I have a racetronics intank pump and hot wire that is normally on. The second pump that is cavatating is turned on by a hobbs switch set at 3psi.
Car is a 1999 C5 with rear mounted twin turbo set up.
I daily drive the car and like my 15psi blast or two getting on to the expressway in the morning's.
I converted from the returnles 1999 style fuel system to a full return from the rail with a 1:1 boost referenced fuel pressure regulator. (Regulator is in between the two rails)
Adding a small transmission style cooler on the return side from the regulator definitely has helped but it's still not enough.
On cooler days I can now drive all day with the fuel cooler installed and I build pressure in boost like I should.
Anything over 60F outside air temp and after about 20 minutes of driving my external pump starts cavatating as soon as it kicks on and I don't build pressure in boost. Which makes me very lean at 15psi on a new forged motor..
Looking for opinions at this point, texas summer is only going to make the issue worse.
Do I add a second fuel cooler? (Still might not be enough come 100F days in july and August)
Or use some heat reflective tape on the rails and put heat sleeves on the lines? (Would look like crap but might work, that stuff blocks out a ton of heat)
Or use a small trunk mounted fuel cell just for the second pump so it's never hot from constantly being recirculated in the rails / engine bay. (Might be best option, would just have to keep it filled and watch the level)
As a last resort I could ditch the external pump and do a dual in tank.. (I'd rather not)
I confirmed this hot fuel issue about an hour ago. I pulled a bunch Of timing from my tune so it would be somewhat safer, Then went and drove for good 20 minutes while data logging and rolled into it, sure enough pressure actually droped off instead of climbing with boost. After that I stopped and added about 5 gallons of 93 to the tank and quickly got back out on the road and rolled into it again, sure enough fuel pressure was climbing again in boost, hot fuel issue confirmed.. help
03-03-2020, 08:54 PM
#3
Drifting
A lot of pumps are made to be in tank and the fuel actually keeps it cool. Is the your pump designed to be an external pump?
Last edited by silver408z; 03-03-2020 at 08:55 PM.
03-04-2020, 07:26 AM
#4
Melting Slicks
How are your lines routed and do you have a fuel temp sensor installed anywhere to be sure it's actually cavitating due to heat and you don't just have a bad pump? Also, do you have a check valve installed where the secondary pump Y's or T's into the OEM fuel feed line? I've heard of issues where the larger external pump will overpower the in tank pump and actually try to push fuel backwards down the OEM fuel feed line.
03-04-2020, 05:47 PM
#5
Secondary pump is meant to be ran as an external. It's the 340lph pump that comes with the UPP kits. The pump is mounted just behind the tank on the rear cradle where it gets good airflow. Lines are -8 feed into a filter (not sure the micron rating, it came with the UPP kit) then from filter to the pump. From the pump it goes -8 all the way up to a check valve, from there -8 to a Y block that reduces to dual -6 lines, one line goes to each rail.
The factory pump uses stock lines up until the engine bay where there is a -6 Y block that has two -6 hoses going to each rail as well but on the opposite side as the -6 lines from the other pump. The regulator is in between the two rails with a T fitting. ( -6 lines from the intank pump connect to the T fitting on each rail which is on the end of the rail, the regulator is in between each rail off of the T fittings.
Return line from the regulator is a -6 that runs to my fuel cooler that's mounted in the cutout where my front license plate used to be, then it's a-6 back to the tank from there.
No temp sensor to check temps. I'm just going off of the fact that it's a non issue on cold days, and on hot days when it wont build pressure if I add a few gallons of fresh gass then go roll into it real quick it is better. The issue comes back after15 minutesor so of driving after I top off the tank.
All that in my mind confirms hot fuel is the cause. (All testing I described has been done with 3/4 or more in the tank)
im ballparking here but I'd guess the car is around 700whp. I know -6 lines are a bit smal but with feeds going into all 4 corners of the rails and running a good amount of 50/50 meth I don't see an issue with what I'm working with.
I don't intend to push the car any higher HP wise for a while, when I go down that road I will definitely be going bigger on all the lines, pumps, ect.
As far as where I'm getting my 700whp guess from it's a forged 5.7 with a Turbo cam and twins on 15lbs of boost. (6speed T56 car, not an auto) I made 580whp / 641wtq on a mustang dyno at only 5,800rpm on smaller turbos with the stock motor and no cam at 9lbs of boost. So that's where I'm getting my 700whp guesstimate.
The factory pump uses stock lines up until the engine bay where there is a -6 Y block that has two -6 hoses going to each rail as well but on the opposite side as the -6 lines from the other pump. The regulator is in between the two rails with a T fitting. ( -6 lines from the intank pump connect to the T fitting on each rail which is on the end of the rail, the regulator is in between each rail off of the T fittings.
Return line from the regulator is a -6 that runs to my fuel cooler that's mounted in the cutout where my front license plate used to be, then it's a-6 back to the tank from there.
No temp sensor to check temps. I'm just going off of the fact that it's a non issue on cold days, and on hot days when it wont build pressure if I add a few gallons of fresh gass then go roll into it real quick it is better. The issue comes back after15 minutesor so of driving after I top off the tank.
All that in my mind confirms hot fuel is the cause. (All testing I described has been done with 3/4 or more in the tank)
im ballparking here but I'd guess the car is around 700whp. I know -6 lines are a bit smal but with feeds going into all 4 corners of the rails and running a good amount of 50/50 meth I don't see an issue with what I'm working with.
I don't intend to push the car any higher HP wise for a while, when I go down that road I will definitely be going bigger on all the lines, pumps, ect.
As far as where I'm getting my 700whp guess from it's a forged 5.7 with a Turbo cam and twins on 15lbs of boost. (6speed T56 car, not an auto) I made 580whp / 641wtq on a mustang dyno at only 5,800rpm on smaller turbos with the stock motor and no cam at 9lbs of boost. So that's where I'm getting my 700whp guesstimate.
03-04-2020, 05:55 PM
#6
How are your lines routed and do you have a fuel temp sensor installed anywhere to be sure it's actually cavitating due to heat and you don't just have a bad pump? Also, do you have a check valve installed where the secondary pump Y's or T's into the OEM fuel feed line? I've heard of issues where the larger external pump will overpower the in tank pump and actually try to push fuel backwards down the OEM fuel feed line.
Since its only an issue I'm seeing on hot days after driving for 10 / 15 minutes I don't think it is back flowing issue but its a possibility that I haven't checked off yet though so thanks.
03-04-2020, 06:39 PM
#7
Melting Slicks
Check valve is in place. You just gave me an idea though, going to run it at idle while the fuel is still cool and I'll crank the pressure up to the max ideal fuel pressure in boost and just jumper wire the Hobbs switch for the second pump so I can see if it back feeds the intank pump or does anything else weird.
Since its only an issue I'm seeing on hot days after driving for 10 / 15 minutes I don't think it is back flowing issue but its a possibility that I haven't checked off yet though so thanks.
Since its only an issue I'm seeing on hot days after driving for 10 / 15 minutes I don't think it is back flowing issue but its a possibility that I haven't checked off yet though so thanks.
How old is your intank pump? Have you tested voltage?
Have you watched your battery voltage once the engine gets warm to make sure the alternator isn’t going bad and dropping voltage at higher engine temps?
Just a few more questions to help you sort this out.
I also originally overlooked the rear mounted twins portion previously. With the pump mounted on the cradle, the twins could definitely be generating enough radiant heat to hurt your pump.
Last edited by Turpid porpoise; 03-04-2020 at 06:42 PM.
03-04-2020, 11:54 PM
#8
Are the fuel lines routed near your exhaust in any locations?
How old is your intank pump? Have you tested voltage?
Have you watched your battery voltage once the engine gets warm to make sure the alternator isn’t going bad and dropping voltage at higher engine temps?
Just a few more questions to help you sort this out.
I also originally overlooked the rear mounted twins portion previously. With the pump mounted on the cradle, the twins could definitely be generating enough radiant heat to hurt your pump.
How old is your intank pump? Have you tested voltage?
Have you watched your battery voltage once the engine gets warm to make sure the alternator isn’t going bad and dropping voltage at higher engine temps?
Just a few more questions to help you sort this out.
I also originally overlooked the rear mounted twins portion previously. With the pump mounted on the cradle, the twins could definitely be generating enough radiant heat to hurt your pump.
The in tank pump is not even a year old, I installed it and the hot wire maybe 5,000 miles ago.
Alternator was an issue in the past, took me forever to figure that one out but now I monitor voltage and with the new alternator I dont drop below 13v at any point during my pulls.
Everything from the exhaust manifold back is heat wrapped and the turbos have blankets. The pump shouldn't be picking up radiant heat from them with where I have it.
I'm leaning more and more towards the 2.5 gallon fuel cell option just for my external pump. I've found some nice ones with a level sensor for under $100. I did some math and my 340lph pump should go through about 1.5 gallons a minute.
I'm in boost on a 1st through 3rd gear romp for only a few seconds at most so a 2.5 gallon cell shouldn't need topping off all that often. Especially since this is a street car and I dont get to open it up all that much. If this was a track car it probablywouldbe a different story. I figure if I feel like getting fancy with it I might even add a small transfer pump wired to a float switch so I dont actually ever have worry about topping the fuel cell off. Any hot fuel that does get transferred into the cell should cool rather quickly since the cell is aluminum.
I haven't pulled the trigger on the fuel cell idea yet but I'm getting close. Having to sit out TX2K this year beacuse of a hot fuel issue sucks.
03-05-2020, 07:00 AM
#9
Melting Slicks
Unfortunately yes, the fuel line from my external pump is near the exhaust (obviously not touching) charge pipes are in the rocker panels though so the trans tunnel was really my only routing option. That's all on the discharge side of the pump though so it should be ok since boiling point is raised when a fluid is put under pressure.
The in tank pump is not even a year old, I installed it and the hot wire maybe 5,000 miles ago.
Alternator was an issue in the past, took me forever to figure that one out but now I monitor voltage and with the new alternator I dont drop below 13v at any point during my pulls.
Everything from the exhaust manifold back is heat wrapped and the turbos have blankets. The pump shouldn't be picking up radiant heat from them with where I have it.
I'm leaning more and more towards the 2.5 gallon fuel cell option just for my external pump. I've found some nice ones with a level sensor for under $100. I did some math and my 340lph pump should go through about 1.5 gallons a minute.
I'm in boost on a 1st through 3rd gear romp for only a few seconds at most so a 2.5 gallon cell shouldn't need topping off all that often. Especially since this is a street car and I dont get to open it up all that much. If this was a track car it probablywouldbe a different story. I figure if I feel like getting fancy with it I might even add a small transfer pump wired to a float switch so I dont actually ever have worry about topping the fuel cell off. Any hot fuel that does get transferred into the cell should cool rather quickly since the cell is aluminum.
I haven't pulled the trigger on the fuel cell idea yet but I'm getting close. Having to sit out TX2K this year beacuse of a hot fuel issue sucks.
The in tank pump is not even a year old, I installed it and the hot wire maybe 5,000 miles ago.
Alternator was an issue in the past, took me forever to figure that one out but now I monitor voltage and with the new alternator I dont drop below 13v at any point during my pulls.
Everything from the exhaust manifold back is heat wrapped and the turbos have blankets. The pump shouldn't be picking up radiant heat from them with where I have it.
I'm leaning more and more towards the 2.5 gallon fuel cell option just for my external pump. I've found some nice ones with a level sensor for under $100. I did some math and my 340lph pump should go through about 1.5 gallons a minute.
I'm in boost on a 1st through 3rd gear romp for only a few seconds at most so a 2.5 gallon cell shouldn't need topping off all that often. Especially since this is a street car and I dont get to open it up all that much. If this was a track car it probablywouldbe a different story. I figure if I feel like getting fancy with it I might even add a small transfer pump wired to a float switch so I dont actually ever have worry about topping the fuel cell off. Any hot fuel that does get transferred into the cell should cool rather quickly since the cell is aluminum.
I haven't pulled the trigger on the fuel cell idea yet but I'm getting close. Having to sit out TX2K this year beacuse of a hot fuel issue sucks.
03-05-2020, 08:37 PM
#10
Not a whole lot of room in the C5 for all that since it's a street car and I pull the top off and put it in the trunk on nice days. Not a bad idea though.
I just went ahead and pulled the trigger on a 2.5 gallon fuel cell and everything else to make it work.
Another benefit of the fuel cell route I just thought of is that if I ever decide I want to fill it up with some high octane $h!t like 112 or 116 I can and I wont be burning through that expensive fuel unless I'm in boost and the second pump is on.
I just went ahead and pulled the trigger on a 2.5 gallon fuel cell and everything else to make it work.
Another benefit of the fuel cell route I just thought of is that if I ever decide I want to fill it up with some high octane $h!t like 112 or 116 I can and I wont be burning through that expensive fuel unless I'm in boost and the second pump is on.
03-06-2020, 09:25 AM
#11
Melting Slicks
Not a whole lot of room in the C5 for all that since it's a street car and I pull the top off and put it in the trunk on nice days. Not a bad idea though.
I just went ahead and pulled the trigger on a 2.5 gallon fuel cell and everything else to make it work.
Another benefit of the fuel cell route I just thought of is that if I ever decide I want to fill it up with some high octane $h!t like 112 or 116 I can and I wont be burning through that expensive fuel unless I'm in boost and the second pump is on.
I just went ahead and pulled the trigger on a 2.5 gallon fuel cell and everything else to make it work.
Another benefit of the fuel cell route I just thought of is that if I ever decide I want to fill it up with some high octane $h!t like 112 or 116 I can and I wont be burning through that expensive fuel unless I'm in boost and the second pump is on.
Last edited by Turpid porpoise; 03-06-2020 at 09:25 AM.
03-06-2020, 05:08 PM
#12
Melting Slicks
If it's only 60degF outside...the chances of fuel temperature being the problem is zero.
More likely a plumbing or other issue.
Pumps like that MUST have a good clean uninterrupted gravity supply of fuel.
More likely a plumbing or other issue.
Pumps like that MUST have a good clean uninterrupted gravity supply of fuel.
03-06-2020, 08:43 PM
#13
On 60 degree days it works fine, it's on the 70+ days that I'm seeing issues. Well when I install the cell it will definitely be gravity fed. Right now its about level with the tank but it's got a good 5ft of -8 line that it has to go through before it gets to the pump. That will also be getting fixed once I install the cell, going to have as short of a run of hose as possible and as straight as possible.
03-06-2020, 09:21 PM
#14
I'm hoping that all of these changes help me build a bit more pressure too. Even with 2 pumps I dont see a 1:1 rise in pressure. Theres a pretty good delay sometimes, I ve been at 5lbs of boost and not even gotten back up to my base pressure before. When everything is working, At full boost (15psi) I still only see 67 / 68fuel psi. My base pressure was set at 60 so I should be seeing closer to 75psi.. is my base pressure maybeset too high at 60psi? (255lph in tank and 340lph external)
03-07-2020, 04:30 AM
#15
Melting Slicks
On 60 degree days it works fine, it's on the 70+ days that I'm seeing issues. Well when I install the cell it will definitely be gravity fed. Right now its about level with the tank but it's got a good 5ft of -8 line that it has to go through before it gets to the pump. That will also be getting fixed once I install the cell, going to have as short of a run of hose as possible and as straight as possible.
03-07-2020, 04:35 AM
#16
Melting Slicks
I'm hoping that all of these changes help me build a bit more pressure too. Even with 2 pumps I dont see a 1:1 rise in pressure. Theres a pretty good delay sometimes, I ve been at 5lbs of boost and not even gotten back up to my base pressure before. When everything is working, At full boost (15psi) I still only see 67 / 68fuel psi. My base pressure was set at 60 so I should be seeing closer to 75psi.. is my base pressure maybeset too high at 60psi? (255lph in tank and 340lph external)
Do you need 60psi base ? Do you have enough injector to not need to run so high ?
But if you're starving the pumps or pump on the supply side, you can never expect the system to work correctly. But some regs just dont always perform 1:1. But there are so many variables that can affect this too. Reg type, placement, vac/boost source, any leaks or restrictions etc etc