Well, now that she's down for the winter, I want to figure out where my fuel system is messed up.
Here's the problem: if I turn the key on w/ engine off I get 0psi at the rail. I need to turn the key on and off a bunch of times to get it to show any pressure. (10x will bring it up to about 20psi)
Problem 2. Idle fuel pressure is at about 45-50psi and under load / boost it doesn't move much. (@10psi I might see it raise 5-7psi)
this is a racetronix w-body pump. Any ideas where to start?
check the voltage at the relay and at the pump might be a good start, next would be to make sure the little tube hasn't come off the pump and is on there nice and tight.
Ryan Thompson wrote:Well, now that she's down for the winter, I want to figure out where my fuel system is messed up.
Here's the problem: if I turn the key on w/ engine off I get 0psi at the rail. I need to turn the key on and off a bunch of times to get it to show any pressure. (10x will bring it up to about 20psi)
Problem 2. Idle fuel pressure is at about 45-50psi and under load / boost it doesn't move much. (@10psi I might see it raise 5-7psi)
this is a racetronix w-body pump. Any ideas where to start?
do you have a return or returnless fuel system?
problem 1
aftermarket pumps do not hold line pressure when pump shuts off. once the pump turns off rail pressure drops drastically. when you turn the key to the on position the pump will only run for 2-3 seconds. this is normal for an aftermarket pump. it requires extra cranking time to get the engine started.
problem 2
unless you have a boost reference fuel pressure regulator the fuel pressure is not going to vary much.
I would drop the tank and check the connections on the pump. I'm betting you have something loose. You should be able to turn the key one time and get your pressure.
FU Tuning
Addicted to meth wrote:I would drop the tank and check the connections on the pump. I'm betting you have something loose. You should be able to turn the key one time and get your pressure.
oh dont recommend that! people just disregard that when you tell them to check that!
I agree with him though. something is bleeding the pressure off/not allowing it to build.
I had this problem was the small line to the pump vantrial line so ya 3 votes for pull tank sucks I know I did it 3 times hahaga double check everything
Yes its a return system on a 2005 Sunfire. Its just the factory fuel pressure regulator on the rail, and it hooks up to vacuum so it sees boost. I thought I read the stock fpr will raise fuel 1:1 for boost.
I have 8 months of winter so I dont mind pulling the tank. I know I wasnt 100% cinfident in the venturi tube when i hooked it up cuz its fastened with a zip tie. anyone know where I can get a steel clamp like installed from the factory?
my fuel pressure gauge shows zero unless the car is running. it will jump to 35-40 while the pump primes with key on engine off, but then goes back to zero. like someone said above, the aftermarket pump doesnt HOLD the pressure. it pumps and pumps and pumps, but as soon as its told not to pump all pressure goes away. nothing wrong there.
Ryan Thompson wrote:Yes its a return system on a 2005 Sunfire. Its just the factory fuel pressure regulator on the rail, and it hooks up to vacuum so it sees boost. I thought I read the stock fpr will raise fuel 1:1 for boost.
I have 8 months of winter so I dont mind pulling the tank. I know I wasnt 100% cinfident in the venturi tube when i hooked it up cuz its fastened with a zip tie. anyone know where I can get a steel clamp like installed from the factory?
the factory fuel pressure regulator does not raise 1:1 for boost. it raises the fuel pressure up to 0 psi(atmospheric pressure). above that there is no raise in pressure. you need to replace the stock fuel pressure regulator with a 1:1 boost reference fuel pressure regulator. this is an option as any good tuner doesnt need this. it is fine to tune with a constant fuel pressure so the 1:1 really isnt needed.
Thanks for clearing that up Joe. So I guess my only problem is the lack of fuel pressure on startup. I'm going to try and find a stainless steel clamp small enough for that venturi hose. And check voltage
to answer your question I think those clamps that come on the factory are not buyable I looked all over for em ended up just getting a small pinch clamp at ace......ace is the place lol
When you do the pump, you are supposed to trim a little bit off the end of the venturi line where it was connected to the pump. What happens is, it stretches and the clamp holds it on and its formed to the factory nipple on the pump. For mine he had to cut a little bit off the end and then re attach it. So far so good!
in case you don't find them at Ace, Autozone has a box of FI clamps that are small enough, trouble is you gotta buy the whole box
Yeah I trimmed the end like you are supposed to. But it still wasn't super tight. I looked all over for a clamp too, but never found one obviously.
well id keep a eye out that zip tie may come back to bite you later on
