Quote:
Originally Posted by Rufton
Don't follow why spider specified for OEM application would require a restricted return line.
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Quote:
Originally Posted by speedygonzales
they can NOT achieve that pressure.
The unit from the build could not achieve 45 pounds. Now first remember the OEM spec is 60 to 66 pounds.
So I first changed the FPR no change. Then changed the fuel pump, no change.
So I surmised the only thing it could be was the central fuel block. I ordered a new injector unit and returned the old one for credit. The pressure now was higher but still not spec. New one was still only 48 pounds.
MP spec was 55 to 62 pounds. But these units still could not get there. So an easy mod to the return line and it runs 100 percent better.
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In short the original spec (using the old poppet style injectors) for fuel pressure is NOT 58 PSI it is 60 to 66 PSI. I have the GM shop manual.
Second, the replacement MP unit has a lower spec. It is 55 to 62. I checked with Standard. (Standard is the manufacturer contracted by GM). This lower spec for the replacement MP unit is not printed anywhere.
Third, 2 different units purchased 1 1/2 years apart could NOT obtain the 55 pounds minimum. Once I brought pressure up to spec, it ran much better. (for those that did not read, I first changed the FPR then I changed the pump).
For those that did change to the new style injectors, even if you think it runs ok, check the fuel pressure. I an willing to bet that it does not get to 55 PSI minimum and if the pressure of your unit is upped to spec, it will run even better.
That is why I upped the pressure.