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New fuel pump, drove it, then wouldn't start

This is a discussion on New fuel pump, drove it, then wouldn't start within the General Help forums, part of the LSx Technical Help Section category; I put a new 255Lph walbro pump in my t/a last week. i did it by dropping the tank and ...

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    Rice Hungry GottaHaveLS1's Avatar
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    New fuel pump, drove it, then wouldn't start

    I put a new 255Lph walbro pump in my t/a last week. i did it by dropping the tank and i put everything back together and double checked every connection etc. i drove the car for around 50 miles and then i went to start it at my friends house and it wouldn't start. you can hear the motor turning but it wont start. so i figured the hose had popped off cuz that's common for the walbro hose they supply. so i dropped the tank for the second time and took the pump out. everything looks fine, the hoses are all connected and there dont appear to be any splits. what do i do now?

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    check for voltage, continuity, and pressure, its common to change the filter with the pump. I had a similar problem with my truck, the regulator went out so I had to open the valve to manually supply the fuel into the tractor. but its quite the same with out cars. except for the manual valve.

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    I replaced the tank pump in my old daily driver a few weeks ago and I accidently miswired the pump and had to remove the tank again but what I did after I reinstalled the pump I put a little gas into the tank and took wires from my battery down to the tank sitting on the ground and applied 12 volts to the positive terminal and grounded the negaticve side and verified the pump was indeed putting out fuel. This is a good way to know for sure before you reinstall the tank. Also I took the inlet off of my intake and squirted fuel directly into it and verified the engine would run which it did. Just a few things I learned thru trial and error troubleshooting weather my pump or regulator was bad.

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    Junior Member crashandburn_01's Avatar
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    if it ran it's not the wrong polarity on the wiring check press with gauge should be 45-50 psi with one key on cycle and should maintain if it doesnt reach 45 or the pressure drops pinch off the rubber line on the return and see if pressure spikes, if it does, the regulator is bad, if not it's on the supply side, prob a pinched metal line or clogged filter also if you didn't use screw clamps on the hose for your pump, it could be leaking at the fittings in the tank, also will cause low/falling pressure, the spring clamps or zip ties they usually supply with the pumps are junk.

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    Rice Hungry GottaHaveLS1's Avatar
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    Quote Originally Posted by crashandburn_01 View Post
    if it ran it's not the wrong polarity on the wiring check press with gauge should be 45-50 psi with one key on cycle and should maintain if it doesnt reach 45 or the pressure drops pinch off the rubber line on the return and see if pressure spikes, if it does, the regulator is bad, if not it's on the supply side, prob a pinched metal line or clogged filter also if you didn't use screw clamps on the hose for your pump, it could be leaking at the fittings in the tank, also will cause low/falling pressure, the spring clamps or zip ties they usually supply with the pumps are junk.
    i'll try that. btw, where is the "regulator" and what exactly does it do?

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    Junior Member crashandburn_01's Avatar
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    the regulator bypasses unused fuel back to the tank from the fuel rail, the pump can put out well over 100 psi but the regulator keeps it around 45-50 at key on and higher under load. this also keeps cold fuel cycling through the system and helps the pump last longer than a non return style. it lookes like a small cylinder with a line coming out of it on the fuel rail, it also has a vacume line attached to it pinch off the fuel line comming out of the valve at a rubber section and see if it affects the pressure reading. dont pinch off the supply line to the rail or it wont help you do need a gauge to do this you can get a test kit at local parts stores, worth the money

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    The Bandit Wesman's Avatar
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    Quote Originally Posted by GottaHaveLS1 View Post
    i'll try that. btw, where is the "regulator" and what exactly does it do?
    Its located on the rail crossover and has a vacuum line attached to it. The pressure regulator works off engine vacuum, the more vacuum applied to the FPR, the lower the fuel pressure. So if you were to pull the vacuum line off the FPR and cap it off, you would be recieving 100% of fuel pressure that the pump is putting out. That is an easy way to check if the regulator is bad, just pull and cap the vacuum line and if the car runs fine, the problem is the FPR.

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    Rice Hungry GottaHaveLS1's Avatar
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    thanks, how much does a regulator cost if i need a new one? i'm going to take apart my fuel pump assembly tomorrow and see if theres anything i can fix. i replaced the fuel filter about 3K miles ago, but for $12 i'll just replace it again.

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    Rice Hungry GottaHaveLS1's Avatar
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    Quote Originally Posted by Wesman View Post
    Its located on the rail crossover and has a vacuum line attached to it. The pressure regulator works off engine vacuum, the more vacuum applied to the FPR, the lower the fuel pressure. So if you were to pull the vacuum line off the FPR and cap it off, you would be recieving 100% of fuel pressure that the pump is putting out. That is an easy way to check if the regulator is bad, just pull and cap the vacuum line and if the car runs fine, the problem is the FPR.
    i'll have to try that out at some point i guess. This morning my car would not start since last friday so i can't run this test if the car doesn't start right? I must have wired the fuel pump correctly because i did start it up and drive it. that's why i was so confident that it was the hose that split or popped off becuase i drove it a a little while after swapping the pump. would a bad FPR make the car not start?

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    The Bandit Wesman's Avatar
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    Quote Originally Posted by GottaHaveLS1 View Post
    i'll have to try that out at some point i guess. This morning my car would not start since last friday so i can't run this test if the car doesn't start right? I must have wired the fuel pump correctly because i did start it up and drive it. that's why i was so confident that it was the hose that split or popped off becuase i drove it a a little while after swapping the pump. would a bad FPR make the car not start?
    Yes, because the car requires more fuel on startup than it would require during warm idle. Its basically like running the choke on a carburated engine. So if the FPR is restricting fuel pressure down to the minimum amount for some reason, it could prevent the engine from starting.

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    Rice Hungry GottaHaveLS1's Avatar
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    Quote Originally Posted by Wesman View Post
    Yes, because the car requires more fuel on startup than it would require during warm idle. Its basically like running the choke on a carburated engine. So if the FPR is restricting fuel pressure down to the minimum amount for some reason, it could prevent the engine from starting.
    hmmm so is there a way i can test the FPR without starting the car?... cuz i can't. btw, how much is a new FPR?

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