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Fuel Pressure Confusion by TurboGN
Started on: 10-05-2021 10:36 PM
Replies: 2 (61 views)
Last post by: TurboGN on 10-07-2021 09:57 PM
TurboGN
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Report this Post10-05-2021 10:36 PM Click Here to See the Profile for TurboGNSend a Private Message to TurboGNEdit/Delete MessageReply w/QuoteDirect Link to This Post
I'm really confused on the way my L32 3800 SC fuel system is set up. I'm going to try and take a look underneath the car tomorrow to check everything out but it's really strange. As I understand it, the L32 has no fuel return line (I have checked and there is only a supply fuel line to the injector rails) and keeps the fuel pressure at 52 psi and the PCM adjusts the injector pulse width as boost rises. On this beast KOEO the fuel pressure is only 45 psi for a second and drops to 35 psi and then slowly drops to 25 psi, then the pressure drops to only 10 psi over the next 1 to 2 minutes. At idle it is running at 44 psi and rises with boost as I imagine a L67 would do.

Wouldn't this mean that I am running lean at idle and light throttle, and then running super rich under boost as not only the PCM is adjusting IPW but fuel pressure is rising with boost?
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olejoedad
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Report this Post10-06-2021 07:42 AM Click Here to See the Profile for olejoedadClick Here to Email olejoedadSend a Private Message to olejoedadEdit/Delete MessageReply w/QuoteDirect Link to This Post
The 'return' line is actually a bleed line for excess pressure.
It could be built in to the pump and live in the fuel tank, or it could be fabricated a Series 2 FPR and some plumbing bits and be remotely mounted on the firewall.

Locate the vacuum line leading to the FPR and follow to it's termination.
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Report this Post10-07-2021 09:57 PM Click Here to See the Profile for TurboGNSend a Private Message to TurboGNEdit/Delete MessageReply w/QuoteDirect Link to This Post
I finally looked under the car and found it has an adjustable FPR with vacuum line and a return line. It seemed to be set to low so I cranked it up from 44psi at idle to 55psi. The idle seemed to smooth out a bit and now at full boost I'm at 10 instead of the previous 6.
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