Bad fuel pump or fuel pressure regulator?

#1
Lean fuel pressure problem. Weird thing is, it only does it once in while. I could drive the hell out of the car say for a few hours... stuck in traffic... You know the drill. Then all of a sudden step on the gas and the air fuel gauge drop off the map and the fuel pressure gauge goes 60.. 50..40..30..and then intake back fires. Weird right? Won't do it all the time! Just once in a while. BL at idle is about 130-135 and always has been for the last 10 years. I'm using the extender chip with 55lbs injecters set at 45psi. I'm using translator with base maf set at 0 no change,maf wot throttle set to 6% rich, spark base 2 degrees advance and spark wot 6 degrees retarded. Any body have thoughts on this problem. It's has to be the pump right? Or fuel pressure regulator. Any of your guys or gals thoughts would be appreciated! Summer is coming to an end fast lol.
 
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Anthony P

Active Member
#2
just a checklist of ideas to work through as I think and type...

what fuel pressure regualtor? adjustable like accufab or Bosch 237 to get 45 psi? If Accufab-like unit, would think that diaphragm or spring issue would be all the time. How about vacuum connection at regulator? Leaks? leaks when underhood temps rise and heat soak everything including the lines?

What is fuel tank level when this happens? Is there debris in the tank that gets sloshed around by fuel at the sock? Condition of sock?

Fuel pump hanger electrical connections? Is that Walbro pump one of those part # F20000169 units that were recalled in 2008?

Is something amiss with the fuel pump hot wire kit or relay that only happens when it get hot? like relay drops out when it's hot.

a fuel filter problem would present all the time...

if fuel tank level is low, pump can get warm when not immersed in fuel.

how long does it take for fuel pressure to bleed down once the engine is shut off? should hold static fuel pressure for at least 20 minutes. if not, check fuel pressure reg. or check valve in pump.
 
#3
just a checklist of ideas to work through as I think and type...

what fuel pressure regualtor? adjustable like accufab or Bosch 237 to get 45 psi? If Accufab-like unit, would think that diaphragm or spring issue would be all the time. How about vacuum connection at regulator? Leaks? leaks when underhood temps rise and heat soak everything including the lines?

What is fuel tank level when this happens? Is there debris in the tank that gets sloshed around by fuel at the sock? Condition of sock?

Fuel pump hanger electrical connections? Is that Walbro pump one of those part # F20000169 units that were recalled in 2008?

Is something amiss with the fuel pump hot wire kit or relay that only happens when it get hot? like relay drops out when it's hot.

a fuel filter problem would present all the time...

if fuel tank level is low, pump can get warm when not immersed in fuel.

how long does it take for fuel pressure to bleed down once the engine is shut off? should hold static fuel pressure for at least 20 minutes. if not, check fuel pressure reg. or check valve in pump.
 
#4
Its s a bosch style regulator.
Doesn't matter where the fuel level is when it happens.
Hot wire pump relay is new last week.
Static pressure is about 20 mins.

Thanks for the feed back! makes me think back and check 3 times on things.

I want to add car was parked for 4 years with a 1/4 tank in it.
I drained it out and put some 94 octane in there,I WANT TO BLAME BAD FUEL REALLY bad ...but i just don't think i can,there is no way im picking up bad fuel still.
Im going to drop the tank this weekend and see if there is any debris in there.

Thanks for the input!
 

Anthony P

Active Member
#5
maybe some condensation in the tank from storage at 1/4. when you drop the tank, check for surface rust that formed in the areas not in contact with fuel.

wonder if you have a "jellyfish" blob of jellied fuel in the tank. fuel today with its 10% ethanol content becomes a real problem if left untreated and unused for a few months. Shelf life of E10 fuel is about 100 days. ethanol attracts and absorbs water. interesting read is found here.

curious to learn what you find in the tank. with it sitting for 4 years, change the fuel filter too.

EDIT ADD: when you drained the tank before adding the fresh gas, did you drain the tank by jumping out the fuel pump connector (black) at the wire loom by the a/c compressor and removing fuel via the removed schrader valve in the fuel rail? stuff may still be in the tank.
 
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