I got a Crane AFPR installed and I attached a Hypertech Fuel Pressure Guage to the Shrader Valve... I installed a new pressure regulator (that thingy with the diaphram)...

After I installed it all and adjusted my pressure it was fine, at idle my fuel pressure would sit at around 42 psi solid...that was two days ago... now my pressure guage is jumping all over the place at idle!! I mean the needle is really jumping back and forth between 40 and 50 psi, almost like it's quivering it's jumping that fast....you can almost time it to the injectors firing...

What could be the possible cause for this?

PS: It seems to me that my car is running rich..... she idles fine and drives fine but if I'm standing beside her while she's idling I get a nice smell of gas on my clothes (can't remember her doing that before!)

 

Back in January I installed my freshened up injectors, Crane AFPR, and screwed my Hypertech fuel guage onto my Shrader Valve....... I fired up the car and adjusted my fuel pressure with my guage (approx. 44 psi)... the needle held steady.... everything was fine and I left my car alone...

Then in March I went back to my car and did a few small things, the pressure guage was working fine.... before I was ready to leave I disconnected my battery and in the process of doing that I accidently dropped my vise grips across my battery terminals... at the time I never thought anything about it...

Last Saturday I went back to get my car...never paid any attention to the fuel pressure guage as I was a little anxious to get her out on the road.. As I was driving home I noticed my CD Receiver was not working... never thought much about it....

Yesterday evening I sat in my car and I also noticed that my dome lights weren't working... after closer inspection I noticed a few other electrical things were not working...

After checking all the fuses in the fuse block (they were all fine) I found a 20 AMP fuse blown... this fuse was off by itself in it's own separate holder...I replaced the fuse and sure enough all of my "non-working" electrical devices were now working...

It was only then that as I had the engine running I noticed my guage bouncing all over the place....

After looking in the Chilton electrical section I see that the Fuel Pump Relay is connected indirectly to what they have labelled as "Fuel Pump AutoFuse 20 AMP" ... coincident maybe???

I can take this fuse that blown out altogether and the car will still start, idle fine, run fine...

Do ya think I fudged something in the Fuel Pump Relay???

If I put my hand on the rubber fuel line going to the guage I can feel the erratic surges.. almost like a pulse timed to the engine...

 

I'd get a vacuum gauge.

First...set the fuel pressure @ idle with the vacuum disconnected from the FPR.

Then...check engine vacuum at idle with the vacuum still disconnected from the FPR. If the vacuum is jumping around you have other issues.

If the vacuum is steady and normal...14inHg or whatever for a stock cam/engine combo...but your fuel pressure still jumps around, you have fuel issues.

If vacuum steady/normal and fuel pressure steady, reconnect the vacuum to the FPR and observe vacuum and fuel pressure. If one or the other is now fluctuating, your regulator is suspect.

Report back with findings.

 

The problem was not with the fuel pump, it was not with the Fuel Pump Relay, it wasn't with the Fuel Regulator, or the AFPR...

The problem was with one lousy 20 AMP fuse....the fuse which I never knew existed....it's called the Fuel Pump AutoFuse - 20 AMP. It is located in it's own separate holder, clipped to the fender right by the battery.

I called a friend of a friend who is a mechanic at a :hail: GM Dealership (don't know why never thought of him before). Told him my problem, he pointed me to the fuse and sure enough it was blown... when I fired the car I looked at the fuel pressure guage and it was once again solid!!!

My new found mechanic buddy :hail: :hail: said that when I dropped my vise grips across the battery terminals I must have almost blown that 20 AMP fuse, weakened it to the point where it was causing the Fuel Pump Relay to not work properly because of improper current through the fuse. When I went and put power directly across the fuse in a "tap .. tap" fashion by jumping the two wires in the plug it finished it off....

Popped in a new 20 AMP fuse and I am set once again!!!

Another good thing came from all this is that I noticed that someone did a **** poor job on the wires going into the Fuel Pump Relay plug...looks like a hack job... I have this on my "to-do" list to fix up properly before I put my car back on the road!

Thanks to all that replied!!!