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Walbro at 40 psi, 25% LTFT's

This is a discussion on Walbro at 40 psi, 25% LTFT's within the General Help forums, part of the LSx Technical Help Section category; I have been trying to find out why my Long Term Fuel Trims are at 25%, I checked all around ...

  1. #1
    Member mike171562's Avatar
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    Walbro at 40 psi, 25% LTFT's

    I have been trying to find out why my Long Term Fuel Trims are at 25%, I checked all around for vacuum leaks, but could not find any.

    I checked my Fuel pressure today and its
    at 30Psi with the key turned on, When I start the motor it goes to 40psi and stays there , is this too low? and could this be why my LTFT's are so high?

    The pump is only about 6 months old.

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    Moderator Firebirdjones's Avatar
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    Yep, you have a weak fuel pump, or the fuel filter is so clogged that it's killing fuel pressure. Should be about 55-58 psi with key on or idling.

    If the filter is old, try that first. Otherwise it's time for a new pump.

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    Member mike171562's Avatar
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    So the low fuel pressure is probably whats causing the high LTFTs?

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    Moderator Firebirdjones's Avatar
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    Yep, the computer is trying to compensate by adding fuel. Either way, that fuel pressure is way below spec and needs addressed. Once it's up to normal, I'd log it again and see how your fuel trims react. I'm betting they'll come back to normal plus or minus 5.

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    Veteran 0rion's Avatar
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    yeah...you're leaned out. I can't believe the car even starts on that low of pressure. Normally it takes quite a bit of pressure to open the poppets on the injectors. How many miles on the filter? You could also have a kink or hole in the supply hose to the pump.....that's fairly common too. That accordian style hose will get a hole in it or split and cause low pressure. Have you watched to see if the pressure is bleeding down? Turn the key to run and let it prime then watch the gauge and see if it's dropping. That split hose will do that too.
    If it ends up being the hose don't just throw regular R9 fuel hose in the tank......you should use R10 submersible hose. THe R9 will soften over time and create problems.

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    Member mike171562's Avatar
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    thanks for the information, I took a look at the pump when i got home today and the hose that runs from the pump was disconnected at the top, it was close enough to still have gas pumped through it, but was barely on there. I'm not sure what kind of hose it was, but it was the piece of hose I got with the pump. It was running fine, not cutting out or hesitating at all. I tightened it up with two clamps and put it back together, fuel trims are back down to +-5. Thank god I did the access door, I knew some shit like this would happen.

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    Veteran 0rion's Avatar
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    glad you got it working right and it's times like this the access door makes life easier. I didn't do the door when I did mine.....and I had to drop the tank a second time. I'm sure walbro supplies the correct hose for in tank....it's when people run up to the parts store and just throw regular fuel line in there that it becomes a problem. Over time that stuff will weaken and start to break down when it's submersed in fuel.

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