I have an 03 gmc 2500 I just got new injectors ,cups and all new lines installed and I have a fass lift pump .now I have a knock that comes and goes sometimes it's pretty loud and others you can hardly hear it.it seems to be quieter when the air temp outside is cold and it gets louder when hot I took it to a shop to have it scaned everything looked good but the fuel pressure was high out of spec ..can that cause a knock it's driving me crazy I don't want to cause any damage by driving it and I don't want to have to pull the injectors again has anyone on here experience this ..I need help !!!
lb7 knocking
- Thread starter barrett
- Start date
Yes high rail will cause a knock. What's your lift pump pressure? Try running it with the pump off.
Also check the connection to the fpr. Make sure it's connected and nothing is broken.
What's desired and actual rail pressure?
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Also check the connection to the fpr. Make sure it's connected and nothing is broken.
What's desired and actual rail pressure?
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I have a new cp3 with a new fpr. I think the lift pump was 15psi and the rail I can remember I have a print out at home
If I run it with pump off will the fuel go threw the filters I red somewhere if the pump stops working the fuel will bypass the filters
The FASS should still flow through the filters with it off. It also has a adjustment for its regulator on the side. You'll have to look at the manual.
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8-10 is all you want for supply pressure, 12 and up can cause rail pressure issues unless you adjust the rail valve current table for it. If rail pressure goes to high at idle, it can definately make the engine noisy.
My lbz surged for a day or so at idle after the Fass and then she figured it out. But lb7s are not as smart for say. Contact Fass and ask how to turn it down
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I would call Fass and ask about lowering the pressure. Find out how and if u can. Then find a shop with the tools to.monitor pressure with it running. Basicly the tool to hook on the quick connect on front of engine
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Check your supply pressure 1st. If it's more than 10, turn it down. If it's 10 or less, than I would be looking elsewhere.
