86 tpi 305 Put new afpr and pressure regulator in and checked pressure. I had 42 psi key on and the same with engine running. I followed these instructions(((((A: The correct way to adjust your fuel pressure is with the vaccum line of the fuel regulator disconnected. The instructions with many adjustable fuel regulators don't tell you to do this, but it is essential! You must remove and plug the vaccum line going to the regulator or you will be getting false readings, similar to adjusting the timing on vacuum advance distributor. What you are attempting to do is set the maximum fuel pressure. At idle, fuel pressure is reduced due to high vacuum, so the presence of the vacuum line is detremental to fuel pressure. Repeat the process until you have the desired reading.)))))) AND my pressure read 52psi and the needle vibrated. I had the bolt backed all the way out and it still read 52 PSI. I tightened the bolt a little bit and it still was at 52PSI. I got mad because it did not want to adjust so I hooked the vacum line back up and it went back to 42psi. So I drove it and it lost power, when I steped on the gas it was like the engine lost power sometimes. Then it died twice and would not start. I checked fuel pressure key on and it only goes to 20psi. With it cranking it still only goes to 20psi. It holds the fuel pressure ok. My only idea is to replace the fuel filter (mine is 1 year old with 2000 miles on it). What else can I do or check? Why did I only get the 52psi reading with the vacum hose removed?

 

If the system cannot develop over 20 PSIG, there are only a few potential causes:

1. The pump itself may be incapable of building that pressure;
2. The filter may be clooged;
3. The regulator may be leaking internally.

Since you have established that the pump can develop 52 PSIG with the engine running, the pump itself is not a likely cause. It is possible that the pump voltage is too low with KOEO to develop adequate pressure. Electric fuel pumps are very voltage sensitive. It's worth looking at the fuel pump relay and wiring, or measuring voltage at the pump with KOEO to determine it that is a problem.

The second possibility is the filter, but again, you have been able to develop 53 PSIG with the engine running, so that is not a likely cause.

The last item is the pressure regulator. If there is any damage to the valve disc/seat, the pump may not be able to develop adequate volume to create the necessary pressure with KOEO. Since you are apparently having other anomalous actions from the regulator, I'd suggest starting there first. Does the regulator say "Holley" on it anywhere? That is tantamount to the K-Mart of fuel system components, and can only be expected to provide a similar level of satisfaction and quality.

Finally, through some experimentation, I think you'll find that 52 PSIG is more than adequate pressure. Most factory fuel pumps aren't intended to operate at over 48 PSIG, and the TPI systems seldom require pressure higher than that on even highly modified engines. The more acceptable method is to install larger injctors if flow is inadequate at anything over 48 PSIG.

 

Thanks! Ill have a chance to check the voltage at the pump KOEO wednesday. The afpr is a BBK. I ruined a previous pressure regulator by tightening the bolt too much, it bent the regulator rod and made the spring crooked. I was a lot more carefull this time. Is it possible that I damaged the part of the fuel rail where the pressure regulator mounts?


Oh, and since I changed the fuel pump the gas gauge allways reads full. I think the float must have caught on something when I pit it back in because it worked fine before.

 

OOOOPS!!!! HAHAHA, your car will loose power, stall out and have low fuel pressure when you run out of gas. Put some gas in and it runs..... DUHHH

 

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Vader, you don't like the holley afpr? which would you suggest? only cause im buying one shortly and i had intended on getting the holley cause i read on here that it was the easiest to adjust and all.