Fuel pressure"apparently"dies when revving about 4.5k

[GSntncT]

Whether at regular driving, low boost, or high boost, I completely lean out, no matter how much fuel I add to the safc or MAFT. I've had my battery, and alternator checked, and both check ok-however I'm running at like 11.7 volts.:thumbdown: Is it possible this low voltage is causing the voltage to not get to the fuel pump? Or could it be something bigger? Help!

 

[NOSLO2PT0]

YES!! You should see 12.5V or more with the car turned OFF. With the car running it should be in the mid-hi 13's voltage wise. Are you running the stock fuel pump? Check the voltage back at the pump. I bet you are barely seeing 10V back there, due to the long length of 22 ga. wire that's used in the stock harness.

You may have a bad voltage regulator in the alternator (most are internal) or your charging system isn't up to snuff. In ANY case, i'd buy a new battery. 11.7V volts isn't enough. Surprised your car starts with that. i've got one of the small dyna-batt batteries. I know my car won't start at anything less than 11.8V, but it's also got a LOT less CCA's then your normal battery.

Stick a new battery in the car, take it out for a spin, and see what happens. Then go rewire your fuel pump.

 

[GSntncT]

Originally posted by NOSLO2PT0
YES!! You should see 12.5V or more with the car turned OFF. With the car running it should be in the mid-hi 13's voltage wise. Are you running the stock fuel pump? Check the voltage back at the pump. I bet you are barely seeing 10V back there, due to the long length of 22 ga. wire that's used in the stock harness.

You may have a bad voltage regulator in the alternator (most are internal) or your charging system isn't up to snuff. In ANY case, i'd buy a new battery. 11.7V volts isn't enough. Surprised your car starts with that. i've got one of the small dyna-batt batteries. I know my car won't start at anything less than 11.8V, but it's also got a LOT less CCA's then your normal battery.

Stick a new battery in the car, take it out for a spin, and see what happens. Then go rewire your fuel pump.

Ok, yesterday I bought a new optima battery with virtually no change. I have the walbro 190 pump-not rewired tho(doh!) with the engine off, I barely hit 10v, with it on, my alt. belt sqeals like crazy for a few min, then it levels off sometimes at 13.8, then it oscillates, sometimes as low as 10.9 volts. I'll rewire the pump, tighten the belt again, then take her out. But where do I look if my fuel pressure still drops off at 4.5k?

BTW, thanks for your help.

 

[NOSLO2PT0]

Originally posted by GSntncT
I barely hit 10v, with it on, my alt. belt sqeals like crazy for a few min, then it levels off sometimes at 13.8, then it oscillates, sometimes as low as 10.9 volts. I'll rewire the pump, tighten the belt again, then take her out. But where do I look if my fuel pressure still drops off at 4.5k?

BTW, thanks for your help.

You should see at least 13V at the pump with the car ON. AS for the fuel pressure problem, go buy an AFPR and an electrical fuel pressure gauge, mount it in the car and view that way.