[Diy_efi] RE: 94 fuel pressure

[RogeranCarol]

Clayton;

You didn't indicate a specific engine, so hopefully the following info, 
which is mostly GM based is helpful.
The GM based TBI system for the 5.0 and 5.7L engines through '95 used a 
low pressure pump mounted in the fuel tank that was nominally rated at 
18psi. The throttle body regulated this pressure to 9-13 psi.
Some GM performance models offered a "cross Flow Injection" (CFI) system 
that had two TBI units, and it too used the 18psi pump regulated to 9-13 
psi. Additionally, some, if not all, 7.4L-equipped GM models through '95 
used TBI with a high pressure pump regulated between 26 and 32psi; I 
don't know what the pump pressure is before regulation.
The tuned port injection systems (TPI) used by GM through '95, and 
probably latter, used an in-tank, high pressure pump regulated to 35psi 
with a vacuum modulator that increased pressure between 5 and 10 psi 
upon acceleration.
As an aside, my '88 Jeep Cherokee 4.0l inline six used an in-tank pump 
capable of 70 psi, but regulated to 34psi plus 5psi upon acceleration. 
It's interesting to note that this pump, when used to fuel my 5.7L Chevy 
caused the engine to run lean! The engine would run rich at idle and 
immediately go lean off idle; pressure but no volume?? I changed out the 
pump to the specified TBI pump and now the engine runs rich and will not 
go into closed loop--oh well, that's my problem that I need help with.

Regards
Roger 


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