gonawol83

I have been having a problem with my 90 T/A. Car has no low end and hesitates or bogs when given gas. I have replaced the fuel pump twice, the sending unit, filter, tune up, checked for vaccum leaks and put on a fully adjustable pressure regulator and still cannot get the pressure past 26lbs. I know it should be aroud 40lbs but can't figure out what the problem is. Now the car will stall occasionally when put into gear. could it be possible to have 2 bad pumps in a row or is it something else? Car runs better at higher speeds but idles a bit rough. Any help would be greatly appreciated. Car has a 5.0 TPI motor with only about 60,000 miles.

gonawol83

So far no luck yet on figuring out problem. Car idles better some days than others but still no change in pressure. I notice delay in the throttle response while in park meaning that I can press pedal quickly and motor delays reving for a second and it also revs rough most of time. I don't know if its from low pressure or if the problem is causing the low pressure. I am not good with fuel injection and need some help to figure this out. Please! I am about to give up on this. I've had third gens in the past but all were carburated.

irocman79

iTrader: (5)

i don't know about your fuel pressure problem but have you checked the resistance of your injectors. how are you checking your fuel pressure. you have your adjustable fuel regulator adjusted correctly. are you checking it with engine off correct. correct way to check fuel pressure is to hook fuel pressure gauge to fuel rail remove built up pressure with check valve on pressure gauge turn ignition key to prime fuel pump should read 45 to 47 start car fuel pressure should go down 3 to 5 psi.

ninetyone

iTrader: (2)

The correct way to check your fuel pressure is to first remove your gas cap. Next, take your fuel pressure gauge and hook it up to your schrader valve on your fuel rail but, First, remove the fuel pressure regulator vacume hose from your intake manifold. Plug the hose with a small screw. Next, turn on your car. The hose being disconnected and plugged will resemble your car's fuel pressure at WOT. Set your fuel pressure between 40 and 45 psi for a stock tpi car.

ninetyone

iTrader: (2)

The correct way to check your fuel pressure is to first remove your gas cap. Next, take your fuel pressure gauge and hook it up to your schrader valve on your fuel rail but, First, remove the fuel pressure regulator vacume hose from your intake manifold. Plug the hose with a small screw. Next, turn on your car. The hose being disconnected and plugged will resemble your car's fuel pressure at WOT. Set your fuel pressure between 40 and 45 psi for a stock tpi car.

ninetyone

iTrader: (2)

Really sounds like a bad fuel injector. Ohm your injectors. They should all be pretty close for example. 0.017 ohms or so. If you find one that is say 0.003 , then it is the bad one. Car will sputter, lack power and sometimes stall out on you. Also, check your IAT sensor. They can cause a rough idle if they go bad too. Do you have any codes ? Check engine light on ?

ninetyone

iTrader: (2)

OH and when checking the fuel pressure, Yes, you do have to start the car to get a proper reading.

gonawol83

thanks for the info guys i really do appreciate the help. I have checked the injectors and they all seem to check out fine although i probably will replace anyway. I have went over everything as far as sensors and so far everything seems to be good the only thing i am questioning is if I am getting enough voltage to the pump. I am going to check that next because the car is not trippin any codes. I also ordered a new diaphram for the new pressure regulator i put in thinking maybe i got a bad one. Sorry for delay in responding I had to go out of town for a bit. If anyone has any other ideas please let me know. Thanks.

86White_T/A305

im also having this problem..except i have a holley stealth ram on my car now.I never had issues with fuel pressure before my hsr swap but i have no mounted an underhood fuel pressure guage..and inside i have a vacuum guage. im getting around 12-15inches of vacuum on idle and only 15psi of fuel pressure.ive change the fuel filter,regulator to and ajustable..and its cranked down and still no change in pressure.my injectors all read fine..hot or cold.no fuel leaks anywhere to be seen,installed a aftermarket 255lph fuel pump,new fuel pump relay.

my last step is to replace the injectors and then maybe the check valve in the tank.my fuel pressure doesnt hold anything when you turn the key off.

HCR13

iTrader: (5)

@gona:
I think I'd look more into the fuel pump voltage. It is odd that after 2 pumps it still has the same symptoms. Sometimes the grounds go bad on the fuel pump wiring...

90HSR406

I have similar problems as 86White_T/A305 only my hsr is on a 400 without an adjustable regulator. and i have my 3rd 255 lph pump installed currently. none lasting longer than 6 mos. my diagnosis process led me to the same conclusion, i don't know whats wrong. at least i know im not the only one.

86White_T/A305

well i just posted on the alternative intake board about my underperforming 383 hsr and i found y problem last night and now all is well.the cheap 255lph pump i bought came with some cheap rubber foam type of hose and it kept shredding apart.I replaced it with efi high pressure fuel line hose and steel claps and that was my issue all along..aswell as my crappy holley regulator.now the car burns 3rd like no tomorrow and holds 50psi of fuel pressure for hrs after i prime it...im a very happy man now

oh and the car starts up within a half crank too.all i can suggest guys..check every single connection in your fuel system..leave no stone unturned..thats how i found my simple..stupid problem that had me pulling hair for 3 months cursing the idea of doing my 383..now it has the value i paid for.

John 89 Formula

Gonawol, when you replaced the fuel pump did you also replace the pulsator coupling?
sounds like it may have a torn diaphram.

rian1000

have you checked your tank to make sure your lines arent plugged up with rust and stuff? i just went through a pressure problem and my problem was actually the inside of my fuel tank.