Fuel pressure sudden drop!
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Instructor
Joined: Jun 2015
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Fuel pressure sudden drop!
Car is vette c6 ls3 m6 d1sc @11 psi 710 rwhp , fuel system : is stock intank pump + bosch 044 with feed -8 an and return -6 an that start with 2.5 boost switch with regulator and siemens 60lb with stock ls3 fuel rail, i did research more than 2 months but i didnt get anyone with same my issue , the issue is the fuel pressure is 50-52 psi at idle and crusing , but at WOT its jump to 70 psi in 1-2 seconds then suddenly drop to 52 psi while my rpm and boost still climbing! Sound like it connect and disconnect , i did change the bosc pump harness with relay because before they get wire supply from stock pump relay and make it separated to avoid load on pump relay also i change my alternator with bigger 220 amp because i had drop in voltage before . That mean everything i fixed it but still it drop !!!!
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Thread Starter
Instructor
Joined: Jun 2015
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Issue solved 👍👍 , i went to experience mechanic and he told me , even you put biggest fuel pump in the world or biggest injectors they will not solve the issue ! So if u want to solve it you should remove the fuel tank and open your oem intank pump and there is regulator and regulator hose , block it by pulg or something fit with hole then pressure will raise and no drop , after that adjust the fuel pressure in idle by adjusting the regulator that locate in return line . 👍👍
Le Mans Master
Joined: Apr 2011
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From: Montreal
St. Jude Donor '13
Originally Posted by Bojwayes
Issue solved 👍👍 , i went to experience mechanic and he told me , even you put biggest fuel pump in the world or biggest injectors they will not solve the issue ! So if u want to solve it you should remove the fuel tank and open your oem intank pump and there is regulator and regulator hose , block it by pulg or something fit with hole then pressure will raise and no drop , after that adjust the fuel pressure in idle by adjusting the regulator that locate in return line . 👍👍
Le Mans Master
Joined: Apr 2011
Posts: 7,821
Likes: 412
From: Montreal
St. Jude Donor '13
Originally Posted by Bojwayes
I did it and its fixed the issue 👍
Drifting
Joined: Aug 2009
Posts: 1,263
Likes: 115
Issue solved 👍👍 , i went to experience mechanic and he told me , even you put biggest fuel pump in the world or biggest injectors they will not solve the issue ! So if u want to solve it you should remove the fuel tank and open your oem intank pump and there is regulator and regulator hose , block it by pulg or something fit with hole then pressure will raise and no drop , after that adjust the fuel pressure in idle by adjusting the regulator that locate in return line . 👍👍
Thread Starter
Instructor
Joined: Jun 2015
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Interesting you said mechanic. The tuner who fixed my car was a mechanic as well. After trouble shooting he suspected the intank pump. He replaced it and while the tank was out I took advantage and did a return line with aftermarket regulator up front. My issue was solved. Your fix is beyond my understanding but I by no means am a mechanic. I have a c5z but I'm sure the systems aren't that much different from a c6. Enjoy, now go add meth.
Racer
Joined: Jul 2014
Posts: 315
Likes: 8
From: Puerto Rico
For my 2005 I am to replace the fuel pump for the same issue, where can I find the upper crossover lines and connectors that are mentioned here? I would like to replace them while the tanks are down. Please let me know
Thanks
Thanks
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Instructor
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Last edited by Bojwayes; Jun 23, 2016 at 11:51 PM.
Race Director
Joined: May 2004
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From: Raleigh, NC
St. Jude Donor '15
57 psi at idle seems high to me if its a FI car. Say you're at 9psi vacuum at idle and go up to 11psi boost. That means if it's a boost referenced regulator you'll be running 78psi at the pump at 11psi boost. Can your pump keep up at that pressure?