I'm trying to determine if I have installed the proper fuel pump for this car. I am getting a flooding condition, and am wondering if the pump is putting out too much pressure (pumping too much gas into the engine).
If I measure the fuel pressure at the tank with the return line plugged, what should it be?
When I prime the pump with the engine off the needle on the gage pegs at 100 PSI then drops to 60 PSI and stays there. Does it need this high of pressure to maintain 40 to 45 PSI at the rail?
Check your pressure at the fuel rail. The regulator should hold it at 43.5 psi primed pressure. The ECM will turn off the pump at 1.8 seconds or when 43.5 psi is reached, whichever comes first. The regulator should continue to give you the correct pressure. Excess will go back to the tank via the return line when running. Normal idle fuel pressure will be somewhere from about 38 to 40 psi.
A flooding condition might be a stuck injector or cold start injector.
I have replaced the injectors and the fuel pressure regulator, and temporarily deleted the cold start injector. Fuel rail primes to 45 PSI and then drops to and maintains 35 PSI.
FYI...this all may sound familiar to some of you, as I am trying to figure out why my car is flooding out on another post titled " V6 runs like there is water in the fuel".
With this new posting I am intending to deal only with the fuel pump question. If this is not proper forum proceedure, please forgive me.
The pressure shouldn't leak down except minimally if the engine isn't started. What injectors did you use as replacements? Fiero ECM's can't always control MulTec injectors efficiently. Whatever you used, they should be 15 lb/hr at 43.5 psi with a duty cycle of 80%. If the flooding (rich) condition is while running, one trouble area could be the Coolant Temperature Sensor that's located in the lower intake manifold just below the thermostat housing. That wouldn't cause your pressure drop if not started, though.
I don't see a problem with separating multiple problems out into their own thread. That way the title will attract persons who wish to respond to that particular issue and not have to sort through questions and answers about other problems or to see if someone else has already answered a question.
Is 60 PSI at the tank ok? I called on the stats of the fuel pumps that Auto Zone sells, and they have a maximum pressure range of around 95 PSI. The system should be able to handle 60 PSI, right?
I am not sure about the injector information, so this picture is what came with the injectors. Are these good injectors? Also I've replaced the coolant temperature sensor, and the pressure regulator was a standard one (exact replacement) purchased at Auto Zone.
Fuses are in a box next to your left knee. Feel around for a tab on each side that you can depress and pivot the fuses down so you can see them easily. INJ1 and INJ2 are the injector fuses.
I looked at their site and it doesn't have a lot of information plus many links on their site are dead or under construction. There is no search function to find OST Part number 1401. What I saw was mostly for smaller import engines and the ones for GM, BMW, etc were rated at a minimum of 17# which is too much for a stock 2.8.
Originally posted by fierofool: Check your pressure at the fuel rail. The regulator should hold it at 43.5 psi primed pressure. The ECM will turn off the pump at 1.8 seconds or when 43.5 psi is reached, whichever comes first. The regulator should continue to give you the correct pressure. Excess will go back to the tank via the return line when running. Normal idle fuel pressure will be somewhere from about 38 to 40 psi.
A flooding condition might be a stuck injector or cold start injector.
ECM does not know Fuel Pressure. ECM does run pump for ~2 sec if key not turn to start engine or stalls. (OP switch will run FP after stopping engine and oil pressure >4 psi.)
Note that V6 does have Vacuum adjusted Fuel Regulator. Fuel Pressure will change a bit depending on Vacuum. Is why you get Two numbers... Engine on = w/o starting or vac line is disconnected. Edit to add> or 12v connected to ALDL pin G
------------------ Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should. (Jurassic Park)
As always, you come through with the corrected information. I don't know what I was thinking. There's no sensor to report fuel pressure.
But, that raises a question. When the setpoint fuel pressure is reached, why won't the pump and relay cycle again if you keep turning the ignition off and back on?
Originally posted by fierofool: But, that raises a question. When the setpoint fuel pressure is reached, why won't the pump and relay cycle again if you keep turning the ignition off and back on?
on/off/on depends on time off and/or ECM programing. Most OBD1 ECM... Off time needs to be off long enough so ECM sees key is off. ECM Power Supply section have Capacitors that need to drain etc. I think ECM should "reset" after 10-20 sec max and then ECM thinks you try to start car in the morning. You might not hear pump priming because of other issues.
Old ECM standby power goes only to memory alive. ECM doesn't keep track of time off that I know of. (Seconds running is a value of ECM's Data Stream.)
This is you have not run the engine... OP switch will keep power to pump in cool/cold weather and engine still cold for 1 - 45 sec. 1 - 2 minutes if engine is very cold.
Ok, so I have determined that I don't have a problem with losing pressure at the gas tank. The question remains however;is 60 PSI at the tank ok? If so, why am I losing pressure at the rail when I have replaced the injectors, the pressure regulator, and eliminated the cold start injector? What else is there to consider?
Not that I am an expert at all just learning by posting and working on my family cars. I don't beleive your tank should be positive pressure that's what the evap emissions is suppose help do is relieve the pressure, but that might be newer vehicle only. Did you pinch the return line to see if the pressure stays high?
If you put a gauge directly to pump or fuel return is block... 60+ psi is likely Max Pressure. Fuel Reg is on the engine.
flows goes from pump to fuel rail and injectors then regulator out to fuel return.
If you switched evap/vent and return line... Evap line at tank is often very small opening. Evap line is not made to a return line.
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Originally posted by LornesGT: Not that I am an expert at all just learning by posting and working on my family cars. I don't beleive your tank should be positive pressure that's what the evap emissions is suppose help do is relieve the pressure, but that might be newer vehicle only. Did you pinch the return line to see if the pressure stays high?
In many modern cars the fuel pump is usually electric and located inside the fuel tank. The pump creates positive pressure in the fuel lines, pushing the gasoline to the engine.
2. EVAP system does nothing to fuel pressure. Not even new cars. Many new cars have moved regulator to the tank to avoid heating fuel to reduce fuel evaporation.
Today I hooked up the fuel gauge to the rail and took the car for a spin. The fuel gauge was at about 36 PSI while idling, and varied only one to two PSI while reving. As soon as I was under way and put the the peddle down, the PSI dropped to zero and I stalled. PSI recovered to 36 as I let the car idle. The process repeated itself multiple times on the way home.
Does this mean that I need a new pump? I put a new pump in three years ago, and have only traveled approximately 40 miles since then.
Problem fixed!!!! Thank you everyone for your suggestions.
I replaced the fuel pump and eliminated the pulsator. I replaced the pulsator with a piece of fuel immersable hose as suggested on other forums. I suspected that the pulsator was the problem, but replaced the pump at the same time to cover my bases. Anyway, the car runs great now.
