I finally picked up a fuel pressure gauge kit yesterday to check pressures. Car had been running terrible again and lean O2 sensor codes 44 and 64 had popped up simultaneously. At first i thought it might be the Idle Air Control Valve as it said in FSM that it could set those codes.

Now that I checked pressure here is what I found. Last night my first readings with key on only 15psi. Started vehicle and had innitially 35psi, this is below the 41-43 range it should be. as the engine ran for a few minutes it dropped and engine sputtered and ran rough with pressuresdropping to 12-15psi and engine died out. Could not get it above 20 at various rpm's. My first thought was that the screen in the regulator was plugged. So since I had a new one I changed it, but screen looked ok and it seem to hold vaccuum and left new one on. I also ruled out relay as I had intial pressure when I turned key on. Had a problem with a couple injectors leaking after putting rails back on, so took the left side back off and used extra vaseline on o-rings and reassembled and left set 'til this morning to check pressures.

Turned key on this morning and had 15 psi twice before starting. Started and went to 20 psi. remained steady for a couple of minutes than began droping and engine sputtered and died. The fuel filter has about 3000 miles on it, don't feel that is a problem. So that leaves the fuel pump and strainer. It was supposedly a fairly new pump less than 5000 miles high output Granatelli pump. Obviously I am not getting enough pressure to the regulator and volume, so is that where the problem might be now?? Any othe ideas that I am overlooking?? Could the pump have low voltage and cause it to run less pressure? Will a bad relay cause lower current to go to the pump?

Thanks,

Scott

 

What brand fuel filter did you use? As that is the cheapest part I would start there, otherwise it sounds like a bad pump.

 

Pull the fuel filter and blow through it. This will tell you if the filter is resticted. You should be able to blow through it easily, if not it is restricted.(If you can't blow through it, pull it away from your mouth quickly, and to the side to avoid being covered in fuel). Also, where did you buy the pump. Just a general rule of thumb, I ALWAYS use an dealer pump on any GM. I have had to pull "good" pumps out right after the install. Also make sure that your pump is getting full battery voltage. I believe that the pump's power is the grey wire. Also, make sure it has a good ground. If fuel filter, and voltage all check out ok; then it is a fuel pump.

 

The previous owner put on a high volume pump by Granatelli that should have been over 60psi. I am assuming the pump needs a full 12volts. I see disclaimer on replacement pumps to put in new wiring harness. I think the filter was a Puralator around 16-18 $'s. that I bought on the way home in Sept. when I picked the car up. Previous owner said he did not put in new one as they did not have one when they put new injectors in. I had the choice of the higher quality Puralator or a cheaper $8 filter. Of course the injectors they put in were wrong and FIC replaced them for me and ran great up until last week. The gray wire if hot should be at least the 12volts, can check FSM on that probably.

 

There were threads on fuel filters a year or so ago. One of the manufacturers was supplying a filter that was too restrictive. I am thinking it was Puralator, but I can not remember it exactly. Maybe someone else has that info.?

 

I would dump the granatelli and replace with GM. Simple to replace, and not too expensive.

http://cgi.ebay.com/ebaymotors/92-93...Q5fAccessories

 

Was the original a Delphi model, if so I can get that from NAPA.

 

They have the wiring harness also and perhaps a new sock. Will I need the gasket or can I spray some permatex on it for a good seal????

 

Try the cheap fuel filter first before spending the bucks on the pump. Just a suggestion of course. And go with an AC/Delco filter.

 

The fuel filter was a WIX. I got a Delphi pump and sock this morning. When I took the old one loose last night I noticed that all the connections are soldered together. I got the wiring harness but it does not come with the complete harness and pigtale like I thought it would, just the wires inside the tank.

 

UPDATE
Put new filter on and got car started again. Pressure was holding at 35psi. Thinking about pulling pump again and replace pulsator with hose if that might be where I am losing 6 lbs of pressure.