NEED HELP: understanding fuel pressure
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Tuned
Joined: Feb 2003
Posts: 426
Likes: 4
NEED HELP: understanding fuel pressure
My '87 EFI 300 is showing fuel pressure of 55 lbs. with the key off. Key on, running, it is around 45-47 lbs. According to a couple of manuals, this is too high for this truck. How will too-high pressure affect running?
Thanks,
Thanks,
Junior User
Joined: Apr 2004
Posts: 81
Likes: 0
From: oregon
It stays high when off due to a check valve in the pump, it is lower when running because some of the pressure is being "used". Check a haynes or chilton for actual pressure. Although that doesn't sound that high. Chryslers run 50 psi, VWs run 60 psi and I think Ford runs about 40psi. Also it could be your regulator if you deem it too high.
Senior User
Joined: Feb 2004
Posts: 116
Likes: 0
From: Northwest
Your fuel pressure is ok. When the truck is running, and the vacume line is disconnected from the regulator...... you should see somewhere between 55 and 60 psi.
The 300 is different from all other EFI Fords. It uses smaller injectors and ups the fuel pressure to compensate.
Most stock fords run 19lb injectors at 39psi
The 300 uses 14 lb injectors at about 55psi
The 300 is different from all other EFI Fords. It uses smaller injectors and ups the fuel pressure to compensate.
Most stock fords run 19lb injectors at 39psi
The 300 uses 14 lb injectors at about 55psi
Junior User
Joined: Apr 2004
Posts: 81
Likes: 0
From: oregon
14lb injectors are tiny, my neon that I turboed with my home made kit came with 19lb running at 50psi with the stock injectors and I upgraded to 30lb ford motorsport injectors for the turbo. I know it was a dodge but they were bosch style injectors so they fit. Also my 2.0 neon motor was 122 cubes and 4 cylinders so each 19lb injector was feeding 30.5 cubes and the efi ford 6 is a 4.9 at 300 cubes and 6 cylinders so each 14lb injector is feeding 50cubes at about the same psi as my dodge was. They must be long duration and I woukld assume a good way to increase fuel into the efi 300 is with 19lb injectors and a K&N kit.
