ultima fuel delivery issue
Discussion
Hi guys my name is soroush and I bought an ultima with a ls7 motor a few months ago, love the car but its had some issues, guess thats what you get when you buy and dont build it yourself. Any way I have had a fuel delivery issue with this car since I bought it, when the car is cold everything works fine and and it starts right up and drive idles great, but as it warms up or gets hot the pressure drops and basically kills the car and you cant really start it again until it sits for a few minutes, so far we have looked at the pump driver to make sure its working properly, we have replaced the fuel pump and looked into the requlator all seem to be working properly but for whatever reason when the car gets hot it cant pressurize the line with fuel, the only area we have not looked at is the tank selector valve, but since our issue is heat related I cant imagine there would be an issue with the selector, so basically every time it gets hot no fuel.. we have been chasing this issue on and off for a few months now, any ideas from a different prespective is greatly appreciate it. thanks in advance..
here is a pic
here is a pic
Boss: I'm not one for trying one thing after another until you stumble upon a solution that you think works, Then at the worst possible time you realize that its still not fixed. Pull the motor, throw the damn selector valve in the trash along with everything else in the fuel system including the fuel rails. take the tanks to a competent fabricator and put sealed access doors in the top of the tanks. Install in-tank fuel pumps in each tank with filters. Then install the little plastic lines and pickup points in the corners of the tank. Connect the two tanks with a 1 inch or bigger size tube connected to each tank with a short piece of fuel rated hose and clamps. tee the two pump outlets to the inlet for the fuel rails. In a stock system Chevy runs the fuel pressure regulator internal to the pump so the fuel rail is capped at one end. Some might argue for an external regulator mounted after the fuel rails since you would need to run a regulator in each tank. send the excess fuel off the regulator back to one of the tanks. You will get folks that argue for 6 pumps, catch cans, supply cans, and a partridge in a pear tree I will tell you that I run one external pump and filter just slightly lower than the left hand tank, a connector between the tanks, the output of the pump is teed to supply the two fuel rails. there is a fuel regulator that is feed from both fuel rails after the injectors and the output goes to the left hand tank. 5 years in So Cal 115 degrees is the hottest that the car has seen in traffic and I have never had a problem there or on the track. P.M. if you want a good source for the intank stuff. Ultima owners meeting near San Francisco on the weekend of April 11. Lee
69boss said:
Hi guys my name is soroush and I bought an ultima with a ls7 motor a few months ago, love the car but its had some issues, guess thats what you get when you buy and dont build it yourself. Any way I have had a fuel delivery issue with this car since I bought it, when the car is cold everything works fine and and it starts right up and drive idles great, but as it warms up or gets hot the pressure drops and basically kills the car and you cant really start it again until it sits for a few minutes, so far we have looked at the pump driver to make sure its working properly, we have replaced the fuel pump and looked into the requlator all seem to be working properly but for whatever reason when the car gets hot it cant pressurize the line with fuel, the only area we have not looked at is the tank selector valve, but since our issue is heat related I cant imagine there would be an issue with the selector, so basically every time it gets hot no fuel.. we have been chasing this issue on and off for a few months now, any ideas from a different prespective is greatly appreciate it. thanks in advance..
here is a pic
you need to be a little more specific.here is a pic
How long from start up does it take before the issue appears?
What ECU are you running?
What pumps are you running?
What regulator do you have?
Hi, sure , im running the aeoromotive pump that comes with a ls7 installation kit including the supplied regulator, and controller from aeromotive as well, the engine ecu is a 2006 z06 ecu thats all I know about the ecu, the problem is heat related so it varies how long after I start the car for it to occur, if im running it hard it will occur faster 10 to 20 min if I just cruise it will take a bit longer, 30 min, but when it gets hot if happens every time. it doesnt seem to like running at low rpms if im running it hard it seems to do it less but once slowing down it becomes more prominent obviously it doenst like less demand on the pump I imagine the fuel is not flowing fast hence overheating somehow.
A couple of additional questions.
1. If you run lean on fuel, the engine ECU will store an error code.
Example: Lean condition bank 1 and 2. Do you have this type of error code stored?
If not, its likely not a fuel delivery related problem.
2 Are both fuel tanks verified to be full when it happens?
3. Do you have the optional fuel sump tank installed? (Sorry can't see you pic in case it's shown)
4. Does the sound (pitch) of the fuel pump change when the problem occurs?
5. Does it happen when running on either fuel tank 1 or 2 ?
6. Have you inspected or changed the fuel filters?
7. You mentioned that the fuel pressure decreases when hot. What is the pressure when cold and hot?
1. If you run lean on fuel, the engine ECU will store an error code.
Example: Lean condition bank 1 and 2. Do you have this type of error code stored?
If not, its likely not a fuel delivery related problem.
2 Are both fuel tanks verified to be full when it happens?
3. Do you have the optional fuel sump tank installed? (Sorry can't see you pic in case it's shown)
4. Does the sound (pitch) of the fuel pump change when the problem occurs?
5. Does it happen when running on either fuel tank 1 or 2 ?
6. Have you inspected or changed the fuel filters?
7. You mentioned that the fuel pressure decreases when hot. What is the pressure when cold and hot?
that seems like a long project although i can definitely see the advantage of it, I wanted to sort this problem out first to get used to the car on the track then I have other ideas and plans for the car in the future, but as it is right now its not fun to drive and i cant imagine im the only one running this set up and having so many issues with fuel delivery, I personally think its vapor locking but I cant see where or how?? first we thought the pump was getting way too hot and boiling the fuel so we replaced it but now I think it has to be in the lines somewhere, I have felt the tanks right after shutting the car off and the tanks are not that hot.
GTR-P said:
A couple of additional questions.
1. If you run lean on fuel, the engine ECU will store an error code.
Example: Lean condition bank 1 and 2. Do you have this type of error code stored?
If not, its likely not a fuel delivery related problem.
2 Are both fuel tanks verified to be full when it happens?
3. Do you have the optional fuel sump tank installed? (Sorry can't see you pic in case it's shown)
4. Does the sound (pitch) of the fuel pump change when the problem occurs?
5. Does it happen when running on either fuel tank 1 or 2 ?
6. Have you inspected or changed the fuel filters?
7. You mentioned that the fuel pressure decreases when hot. What is the pressure when cold and hot?
I would imagine if the pressure drops in the line the car will go lean?? I haven't had the computer codes checked but im sure they would have a lean code bc of fuel pressure droping, we did have the car tuned on the dyno so we know the tune is good.1. If you run lean on fuel, the engine ECU will store an error code.
Example: Lean condition bank 1 and 2. Do you have this type of error code stored?
If not, its likely not a fuel delivery related problem.
2 Are both fuel tanks verified to be full when it happens?
3. Do you have the optional fuel sump tank installed? (Sorry can't see you pic in case it's shown)
4. Does the sound (pitch) of the fuel pump change when the problem occurs?
5. Does it happen when running on either fuel tank 1 or 2 ?
6. Have you inspected or changed the fuel filters?
7. You mentioned that the fuel pressure decreases when hot. What is the pressure when cold and hot?
it does it when both tanks are full,
I dont have the optional fuel sump tank
there is a noise that comes through the reulator right before the pressure completely drops , its like you can tell its about to drop, but its not from the pump seems to come from the regulator like its running and whinning really loud. like cavitating fuel inside the regulator(this happens at idle then when you rev it up the noise stops but if you keep driving the car will eventually just lose pressure and die
I have not inspected the fuel filters, only bc again the problem is always heat related
the pressure is always what it should be around 45psi, until the problem begins then it just take s few seconds it drops to zero the car dies.
What you need to do is get some data, some facts, so you can diagnose the problem. I would suggest the following:
1) Get a couple of lengths of wire, and "T off" the wires that attach to the fuel pump. Run these wires into the cabin, and connect to a normal multimeter, set in "DC voltage" mode. This will allow you to monitor the voltage that the controller is applying across the pump. Broadly speaking, this voltage is proportional to fuel flow. By writing down what that voltage is when the car is running normally (check when cold, at light and heavy engine loadings / speed etc).
Now, when the car starts to have it's issue, if the voltage on the pump is exactly the same as when it is operating normally, you know you have a mechanical issue, rather than an electrical one.
Assuming you aren't actually loosing fuel (ie no leaks!) then the only way the fuel pressure can drop is:
1) due to the pump slowing down (delivers less fuel)
2) the pump cavitating (can't deliver enough pressure) you can generally hear this happening) due to a faulty pump or a blockage in the supply pipes or tank pickup
3) The mechanical pressure regulator (if fitted) failing to close fully (jamming open when hot) resulting in too much fuel flowing back to the tank, and fuel rail pressure dropping etc
So, start with the basics, and move one step at a time to identify the fault!
1) Get a couple of lengths of wire, and "T off" the wires that attach to the fuel pump. Run these wires into the cabin, and connect to a normal multimeter, set in "DC voltage" mode. This will allow you to monitor the voltage that the controller is applying across the pump. Broadly speaking, this voltage is proportional to fuel flow. By writing down what that voltage is when the car is running normally (check when cold, at light and heavy engine loadings / speed etc).
Now, when the car starts to have it's issue, if the voltage on the pump is exactly the same as when it is operating normally, you know you have a mechanical issue, rather than an electrical one.
Assuming you aren't actually loosing fuel (ie no leaks!) then the only way the fuel pressure can drop is:
1) due to the pump slowing down (delivers less fuel)
2) the pump cavitating (can't deliver enough pressure) you can generally hear this happening) due to a faulty pump or a blockage in the supply pipes or tank pickup
3) The mechanical pressure regulator (if fitted) failing to close fully (jamming open when hot) resulting in too much fuel flowing back to the tank, and fuel rail pressure dropping etc
So, start with the basics, and move one step at a time to identify the fault!
Max_Torque said:
What you need to do is get some data, some facts, so you can diagnose the problem. I would suggest the following:
1) Get a couple of lengths of wire, and "T off" the wires that attach to the fuel pump. Run these wires into the cabin, and connect to a normal multimeter, set in "DC voltage" mode. This will allow you to monitor the voltage that the controller is applying across the pump. Broadly speaking, this voltage is proportional to fuel flow. By writing down what that voltage is when the car is running normally (check when cold, at light and heavy engine loadings / speed etc).
Now, when the car starts to have it's issue, if the voltage on the pump is exactly the same as when it is operating normally, you know you have a mechanical issue, rather than an electrical one.
Assuming you aren't actually loosing fuel (ie no leaks!) then the only way the fuel pressure can drop is:
1) due to the pump slowing down (delivers less fuel)
2) the pump cavitating (can't deliver enough pressure) you can generally hear this happening) due to a faulty pump or a blockage in the supply pipes or tank pickup
3) The mechanical pressure regulator (if fitted) failing to close fully (jamming open when hot) resulting in too much fuel flowing back to the tank, and fuel rail pressure dropping etc
So, start with the basics, and move one step at a time to identify the fault!
good Idea I have not checked the voltage across the pump, I will do that next, should give us some more clues. thanks!!!1) Get a couple of lengths of wire, and "T off" the wires that attach to the fuel pump. Run these wires into the cabin, and connect to a normal multimeter, set in "DC voltage" mode. This will allow you to monitor the voltage that the controller is applying across the pump. Broadly speaking, this voltage is proportional to fuel flow. By writing down what that voltage is when the car is running normally (check when cold, at light and heavy engine loadings / speed etc).
Now, when the car starts to have it's issue, if the voltage on the pump is exactly the same as when it is operating normally, you know you have a mechanical issue, rather than an electrical one.
Assuming you aren't actually loosing fuel (ie no leaks!) then the only way the fuel pressure can drop is:
1) due to the pump slowing down (delivers less fuel)
2) the pump cavitating (can't deliver enough pressure) you can generally hear this happening) due to a faulty pump or a blockage in the supply pipes or tank pickup
3) The mechanical pressure regulator (if fitted) failing to close fully (jamming open when hot) resulting in too much fuel flowing back to the tank, and fuel rail pressure dropping etc
So, start with the basics, and move one step at a time to identify the fault!
It's worth noting that pump priming issues caused by cavitation on the inlet to the pump can be fuel temperature related. This is because the vapour pressure of the fuel depends on it's temperature. What happens is that as the pump "sucks" fuel from the tank at its inlet port, the pressure at that point falls (as it must do to "suck" fuel in) If this pressure falls below the vapour pressure of the fuel, the liquid fuel "boils" and turns to vapour. The pump cannot efficiently pump vapour (as it is designed to move liquid fuel) and so it can struggle to pressurise the fuel rail enough to start the engine). This is an issue, because if you can't start the engine, there is no bulk fuel flow, and the fuel sitting in the system close to the pump will just get hotter and hotter, and even more cavitation will occur! it's a viscous cycle in fact.
I have seen this effect negated on a very hot race car that came into the pits by using a Co2 fire extinguisher to chill the pump and local fuel lines to allow the engine to start!
I have seen this effect negated on a very hot race car that came into the pits by using a Co2 fire extinguisher to chill the pump and local fuel lines to allow the engine to start!
Max_Torque said:
It's worth noting that pump priming issues caused by cavitation on the inlet to the pump can be fuel temperature related. This is because the vapour pressure of the fuel depends on it's temperature. What happens is that as the pump "sucks" fuel from the tank at its inlet port, the pressure at that point falls (as it must do to "suck" fuel in) If this pressure falls below the vapour pressure of the fuel, the liquid fuel "boils" and turns to vapour. The pump cannot efficiently pump vapour (as it is designed to move liquid fuel) and so it can struggle to pressurise the fuel rail enough to start the engine). This is an issue, because if you can't start the engine, there is no bulk fuel flow, and the fuel sitting in the system close to the pump will just get hotter and hotter, and even more cavitation will occur! it's a viscous cycle in fact.
I have seen this effect negated on a very hot race car that came into the pits by using a Co2 fire extinguisher to chill the pump and local fuel lines to allow the engine to start!
I suspect that's exactly what's happening, but how to go about solving the problem without having to carry a full bottle of co2 everytime you want to start the car I have seen this effect negated on a very hot race car that came into the pits by using a Co2 fire extinguisher to chill the pump and local fuel lines to allow the engine to start!
my next project was to wrap all the lines as to get rid of as much radiant heat as possible and wrap the headers to to lessen the general heat in the engine compartment, I dont know where else to look, I will also run a test on the pump make sure its getting enough juice but all our other tests with verifying the pump controller showed that the pump is performing as the controller is dictating, the only other thing is that im not familiar with the ecu so i dont know if there some weird setting in there thats kicking in when the car gets hot that somehow affecting the pump. I dont know what had to be done to retrofit that computer to the ultima, if any of the operations of the computer had to be shut down in order to make it work with the ulitma etc etc. Max_Torque said:
Also, somewhat counter intuitively, if cavitation is an issue, running the pump slower can help, rather than trying to run it faster! If your fuel pump controller can be calibrated for pump speed vs engine speed, then try a much lower speed demand!
oddly enough when the car was build someone installed a bypass switch for the pump controller, I wonder if this is normal on all builds or did these people knew something? like the car keeps dying and we need to run the pump full blast to get it to prime the lines.. when the car dies I can flip the switch to bypass the controller and honestly sometimes it works and sometimes it still doesnt work. the pump controller is set to run the pump on minimum current to keep the pressure at 45psi then its set to go full blast at 2700 rpm so the pump is not being over run but it is still possible that its getting hot or the fuel is getting hot. we also opened up the regulator and checked it , it looked clean but if the spring is getting old and not sealing the bypass I guess it would not allow the pressure to build up, but why when only hot?Edited by 69boss on Monday 3rd March 20:15
Two things worth considering:
LS7's run at 60psi??
We had an issue where the suction side of one of the oil lines collapsed when it got hot, due to the pressure drop (I assume the hose softened slightly when it got hot) - it had actually delaminated inside, and cost us an engine.
It could be that the same is happening to your fuel lines, although I find it pretty unlikely. Worth getting underneath and checking - if the original builder used cheap imitation Aeromotive hoses it could be the source. Also check no kinks etc anywhere in the lines.
LS7's run at 60psi??
We had an issue where the suction side of one of the oil lines collapsed when it got hot, due to the pressure drop (I assume the hose softened slightly when it got hot) - it had actually delaminated inside, and cost us an engine.
It could be that the same is happening to your fuel lines, although I find it pretty unlikely. Worth getting underneath and checking - if the original builder used cheap imitation Aeromotive hoses it could be the source. Also check no kinks etc anywhere in the lines.
macgtech said:
Two things worth considering:
LS7's run at 60psi??
We had an issue where the suction side of one of the oil lines collapsed when it got hot, due to the pressure drop (I assume the hose softened slightly when it got hot) - it had actually delaminated inside, and cost us an engine.
It could be that the same is happening to your fuel lines, although I find it pretty unlikely. Worth getting underneath and checking - if the original builder used cheap imitation Aeromotive hoses it could be the source. Also check no kinks etc anywhere in the lines.
interesting i have had to deal with collapsing hoses before but mainly radiator, definitely worth looking into, thanks! as for the pressure you are right we are actually running 50 psi maybe still too low, but thats what we were told.LS7's run at 60psi??
We had an issue where the suction side of one of the oil lines collapsed when it got hot, due to the pressure drop (I assume the hose softened slightly when it got hot) - it had actually delaminated inside, and cost us an engine.
It could be that the same is happening to your fuel lines, although I find it pretty unlikely. Worth getting underneath and checking - if the original builder used cheap imitation Aeromotive hoses it could be the source. Also check no kinks etc anywhere in the lines.
Just wondering how high the fuel pump is in the engine bay? Is it at floor level? If not it may be struggling to get a good suction which could be worse with heat due to the vaporisation issue. I would also increase the supply pressure up to 60psi. I have a kinsler stack system that likes 65psi. 45 seems a little low to me but I'm not an LS expert! Cheers. Mart
Davrianman said:
Just wondering how high the fuel pump is in the engine bay? Is it at floor level? If not it may be struggling to get a good suction which could be worse with heat due to the vaporisation issue. I would also increase the supply pressure up to 60psi. I have a kinsler stack system that likes 65psi. 45 seems a little low to me but I'm not an LS expert! Cheers. Mart
yes pump is at or slightly below floor level, definitely below the tanksCan you clarify what you mean by pump controller in your post? Do you have a variable voltage pump controller attached to the fuel pump? (My factory supplied kit from 2009 did not include one.) Or, are you describing the L/R dash toggle switch that switches the fuel selector pollak valves and fuel gauge.
The E38 ECU which is the one that you most likely have, has a programmable setting for variable speed or fixed speed fuel pump.
The factory recommended fuel pressure at the regulator is 60PSI or 65PSI (I can't remember which is correct right now). This would be the setting for fixed speed pump operation.
Your regulator may be faulty. You can purchase rebuild kits from Aeromotive for items that can jam or tear like the diaphragm. Its worth removing it for inspection.
The E38 ECU which is the one that you most likely have, has a programmable setting for variable speed or fixed speed fuel pump.
The factory recommended fuel pressure at the regulator is 60PSI or 65PSI (I can't remember which is correct right now). This would be the setting for fixed speed pump operation.
Your regulator may be faulty. You can purchase rebuild kits from Aeromotive for items that can jam or tear like the diaphragm. Its worth removing it for inspection.
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