Hi, I have a 1987 with a 4.9 that will barely idle. What is the fuel pressure suppose to be? My haynes manual is confusing on that. Due to the 2 pumps. I would like to know the pressure it is suppose to have at the fuel rail?

 

You should have 55-60psi at the fuel rail engine running and vacuum removed from the FPR.

 

Was that the case right from the start of the FI engines in '87? I've never been clear on whether the pressure was initially a more typcial ~40PSI and then raised later, or if it was always the higher value you indicate, right from '87 through to the end in '96.

 

The 4.9 has always been that high.

 

Okay, thanks for the data-point. I think what has confused me is that the FPR and injectors are spec'd differently with a break point of 1990 I think. But it may have been some miniscule change, not a significant one.

 

Thank you for the replys