87350IROC

iTrader: (2)

My car recently started running really rich. It is an '87 350 TPI. I am getting BLM's around 108-110 at idle. The oxygen sensor is reading ~800mV consistently, not up and down like normal. The injector duty cycle is ~2%. The injectors are ford 24's and the tune is set up for 24's. I am getting black smoke out the exhaust.

I did a fuel pressure test while the car was idling with the vacuum line connected and got a steady 23psi. When I shut down the engine the pressure immediately went to zero. So I figured the cold start injector or main injectors were leaking or stuck open. So I pulled the fuel rail out of the intake manifold and primed the fuel pump. I got ~10psi and then it immediately went down to zero. There was no gas coming out of any injector.

Next I pinched the fuel return line and primed the motor. Went up to ~10psi then right down to zero.

Next I primed the motor, and when it reached 10psi, I pinched the fuel supply line. This time the pressure held at ~10psi until I unpinched the supply line. I think this means the check valve in the fuel pump is bad, or maybe the pump itself is bad.

However if the fuel pump was bad and not supplying enough pressure, why would me car be running so darn rich? I'm out of ideas.

Also.
Every runner and intake manifold port is lined with fuel. Also my spark plugs are sooty and smell like fuel.

So I'd really appreciate any ideas.

Thanks,

John

Quick_Trans_Am

iTrader: (2)

That almost sounds like a cracked regulator diaphragm. If you pull the vacuum line off the regulator do you see/smell fuel in the line?

87350IROC

iTrader: (2)

Well I primed the fuel pump a few times with the vacuum line disconnected and didn't see any fuel coming out. Also the fuel rail holds pressure if I pinch fuel supply line closed after the pressure builds.

Its kind of hard to tell if it smells because I was messing around with the fuel lines all day today so the whole motor smells like gas. But I did not notice a particular gassy smell to the vacuum line.

Quick_Trans_Am

iTrader: (2)

Well if memory serves, and you blocked the supply line after the pump shut off, then that would tell me your injectors and regulator are not leaking. 10psi after priming though... that's just not good. Have you tested the resistance across your injectors? If the resistances are all the same I would say the fuel pump could be the culprit. Still doesn't explain why it's running rich though :/

87350IROC

iTrader: (2)

Quick,

Thanks for the reply. I checked the injectors they came back with 16 ohms, so I think they are okay. I came to the same conclusion as you, bad fuel pump. I was hoping someone could create a rational argument for why the pump is causing a rich condition .

Also, I jumped the fuel pump so it ran constantly. And the rail got up to 18-20psi and stayed there. When I turned off the pump the pressure goes right to zero.

Quick_Trans_Am

iTrader: (2)

I'll flip through my book and see what it says, I know there's a diagnostic chart in there for issues like this. I'll get back to ya some time tomorrow.

91brandon

check the fuel seperator between the fuel pump and the main line in the tank the rubber inside the seperator goes bad and is really hard to tell.