1993tpik1500

Will a bad pressure regulator stop pressure from building?I have a 1987 tpi 350 and can only get 28 psi fuel pressure at the rail. I tried everything, engine running same, clamped off return line same, today put brand new oem pump and filter in, same 28 psi. doesnt change when revved, vacuum line unplugged, running, not running. 28 psi builds instantly when key first on and holds when key is off for at least an hour. I am sick of just throwing parts at this and need some help. thanks

red rock

iTrader: (2)

Sounds to me like a bad regulator, if your going to replace it, maybe think about getting an adjustable one.

keykey

If you clamp the return line you should get FULL pressure (max pressure pump can deliver).

I received a new regulator that was bad so my pressure was ok while pump was running, but bled off too quickly after pump stopped. I tried clamping the return line while diagnosing this, and i got 100 PSI. So even if you remove the regulator completely, when clamping return line fully you would get max possible pump pressure.
I have a new Carter pump and AC Delco filter on the car.

Did you check the hoses inside the tank when replacing pump? Maybe the suction hose has a hole or something?

1993tpik1500

brand new Whalbro 255lp pump, new rubber line in the tank, new Delco filter. Still only get 28 psi at the port on the rail, even with return line clamped. doesnt matter if the engine is running or not, doesnt matter if vacuum line is on or not. Gauge doesnt even move when throttle is gunned.

keykey

Does it hold pressure with return line clamped after pump is stopped? Are you 100% positive that you are clamping the line completely shut? I tried 3 different hose clampers before i got it pinched completely so it built pressure. Are you using the fuel pump test terminal or are you doing Key On Engine Off?
If you have a wiring diagram, try removing the FP relay and using a jumper cable, jumper battery power to the fuel pump power wire to eliminate the possibility of low voltage to fuel pump because of faulty relay/bad connection.

1993tpik1500

Yes its holds the 28 psi for at least an hour with the line clamped or unclamped. Positive line is completely clamped, using a pair of rubber line/hose clamping pliers. Tried it both ways with key on/ engine off, and with straight battery power to the pump. The more I think about it, the more im thinking restricted feed line. because if full pump pressure was getting to the regulator, psi would be more than 28 pounds and if it was only regulating it to them 28 pounds then blocking return line would have to spike the pressure gauge or its blowing the fuel right through the injectors, but they dont leak off any fuel when the system is pressurized for the hour between pump being turned off and back on again. Anyone ever get a bad filter?

rusty vango

yes it is possible to get a bad filter .personally I only use wix filters. but anyway I would inspect the feed line end to end you may find your problem there

Bob88GTA

iTrader: (2)

Just a guess here but.......28 psi seems to be the only reading you ever get. Have you checked to see if the GAUGE is even any good. IT may be bad and you may have all kinds of pressure. Just my 2 cents.

1993tpik1500

Havent had any spare time in the last couple months to mess with this, but this AM I woke up thinking maybe I have feed line going to return and return line going to feed. couldnt get lines undone from pump, so I cut the rubber hoses and spliced them back together. Cant just run out to the garage and chech though, car is 20 miles away. Anybody have thoughts on that theory? Gauge works correctly on other vehicles, so I rule that out.