Fuel pressure issue connected to ac fan speed?

[cetme1]

My 87 GN started showing fuel pressure dropping with the engine running so I put in a new pump. When I first start the car the pressure is low, just like the old pump. So I put in a new filter, didn't help. Put in a new hotwire kit, still didn't help. Rebuilt regulator, but still having issues.

Today I notice that with the AC on the pressure rises to about 38-41 in idle, line on Which is good. I thought maybe it was just the extra RPM's with AC on, so I turned off AC and revved engine, but the pressure stayed low. Then I turned on the AC fan speed to high and up goes the fuel pressure? Tried it with ac off and vent on and it rises as well.
So what is the connection to fuel pressure and fan speed? I can't figure this one out. Any ideas?

 

[87geeinn]

I don't think there is a connection between fan speed and your fuel pressure. What I think you're seeing is minor fluctuations due to the changes in the level of vacuum being applied, which is normal. Any measurements in fuel pressure should be made at idle with the vacuum source removed (i.e., static). It doesn't take much in the way of changes to idle speed RPMs and IAC counts to affect your fuel pressure when there is a vacuum 'signal' being applied to the regulator.

Additionally, you may want to consider what gauge you are using. Is it liquid filled? Have you made a back to back comparison with another gauge? A liquid filled gauge will tend to read erratically because the fluid will heat up and skew the readings. Ironically, some of the cheaper gauges I have used have been the most reliable and accurate. I've also had a gauge get stuck for no apparent reason and ended up throwing that fucker in the garbage. As a side note, I've come to reason that gauge quality of the years has gone to shit. I bought some fancy Autometer gauges but have noticed they read low....consistently.

 

[usetaboost]

Check power at your pump while the car is running.