Hey, today I did a compression test on my 93 FD, When cranking the psi, the very first pulse/jump was always low but 4 or 5 cranks after were consistent. Does the first pulse affect the readings?
First pulse was always around 30-50. While the next 4-5 cranks were 90+.

 

The rpm is very key when doing this test. The first few pulses might be low as the starter gets up to speed.
If you are seeing THREE consistent pulses once the car is turning over at full speed then your good. You need to see three to coincide with the three rotor faces.
90psi is on the low end of the spectrum I’m sorry to say. Not horrible but on the low end. Hope this help!

 

On my junkyard engine I consistently get 90-95 psi on the front (95 to 100 psi rear), been like for years. As long as you can start the car and drive it, you can always add boost to compensate..... think of it as a boost friendly 8:1 or 7.5:1 engine....

I wouldn't worry about it until hot starting becomes an issue.