Tbi running lean and rich..

[MrobsMan]

So my tbi 350 was running a bit lean and has been having a little missfire here and there so I decided to try the vortec pump and it ran rich with the vortec pump which makes me think my fuel pressure regulator has **** the bed. What’s y’all’s thoughts. I put a new stock Delphi pump back in it and it’s running better but still seems a little off. I’m thinking the regulator has gone bad since it ran lean with the stock pump and rich with the vortec pump. Any thoughts?

 

[Nad_Yvalhosert]

It would be easier to diagnose if you'd have checked fuel pressure during those try-agnostic sessions. But since GM, in its infinite wisdom, chose not to equip us with a test port...
Since you loaded up the parts cannon once, throw one at it and see what it does.

 

[RichLo]

Your TBI regulator wont be able to bring Vortec pressure (around 60psi) down to 12-15psi. You were definitely way above recommended fuel pressure with that pump.

Yes, we will need actual fuel pressure to give you better advice. There are ways of bumping your fuel pressure up for free in a TBI if the regulator spring is weak.

 

[Schurkey]

Guys put high-pressure fuel pumps in TBI vehicles all the time.

The regulator (IN GOOD CONDITION) is perfectly capable of dropping the pressure of an OEM higher-pressure pump. You might have problems with an aftermarket high-volume, high-pressure pump if the return plumbing is overloaded.

My own '88 K1500 has a EP241 higher-pressure pump, might not be as high as the Vortec pump, though.

Would be worthwhile verifying fuel pressure, and assuring that the regulator is in good condition. I've heard of TBI regulator springs rusting to pieces, although I've never actually seen it.

Connect a scan tool, verify all sensors and computer outputs.

How old are the usual tune-up items--cap, rotor, plug wires, plugs, fuel and air filters, initial ignition timing checked, electronic spark advance checked, EGR verified, etc?

 

[Scooterwrench]

Sounds like a regulator problem,fix the regulator problem,no more problem!

I just rebuilt the TBI on my truck and the regulator diaphragm was starting to de-laminate. I chaulk it up to the 10% corn liquor.

 

[tsr2185]

Guys put high-pressure fuel pumps in TBI vehicles all the time.

The regulator (IN GOOD CONDITION) is perfectly capable of dropping the pressure of an OEM higher-pressure pump. You might have problems with an aftermarket high-volume, high-pressure pump if the return plumbing is overloaded.

My own '88 K1500 has a EP241 higher-pressure pump, might not be as high as the Vortec pump, though.

Would be worthwhile verifying fuel pressure, and assuring that the regulator is in good condition. I've heard of TBI regulator springs rusting to pieces, although I've never actually seen it.

Connect a scan tool, verify all sensors and computer outputs.

How old are the usual tune-up items--cap, rotor, plug wires, plugs, fuel and air filters, initial ignition timing checked, electronic spark advance checked, EGR verified, etc?

Sorry for the ignorance, but how do you verify ESC and EGR?

 

[Erik the Awful]

Your TBI regulator wont be able to bring Vortec pressure (around 60psi) down to 12-15psi. You were definitely way above recommended fuel pressure with that pump.

I'll also testify that this is dead wrong. I've put a Vortec pump in two TBI trucks so far and the stock regulator had no problem with it.

 

[Schurkey]

Sorry for the ignorance, but how do you verify ESC and EGR?

1. Any ESC or EGR codes stored?
2. ESC: Disconnect the one-wire timing connector. Start engine. Timing should be "0" or close (some guys add a few degrees to the base timing, but the official spec is "0".) Shut off engine, re-connect one-wire timing connector. Disconnect battery cable for ten seconds to clear the code. Reconnect battery cable. Engine running. Verify timing advance to "about" 12--15 degrees. Tap the cylinder head or intake manifold with a small hammer. You should hear the idle speed slow due to timing retard from knock sensor activity. If you had a timing light connected, you'd see the timing retard as well. Put the hammer away. With that timing light connected, rev the engine. Timing should advance.
3. EGR: Engine running. Reach under the EGR valve with two fingers. Lift the diaphragm. Engine should run rough, maybe stall. Let go of diaphragm. Engine should smooth out again like normal. Remove vacuum hose from EGR valve. Connect a vacuum pump--or a clean section of vacuum hose--and suck on the hose with those same two fingers feeling (not pulling) on the diaphragm. The diaphragm should rise as you suck on the hose, and stay "up" as long as you don't deliberately release the vacuum. If the diaphragm doesn't rise, or doesn't stay up (and you have trouble getting a vacuum) the diaphragm is torn and the EGR valve is "done". Verify that the EGR Valve Solenoid is connected, and working. One vacuum hose from throttle body to solenoid, one vacuum hose from solenoid to EGR valve, and one empty nipple as a "vent" that "should" have a foam filter on it, but won't because the foam rotted away twenty years ago. Disconnect the vacuum hose at the EGR valve, put a vacuum gauge on the hose. Start a previously-warmed-up engine. There'll be no vacuum at idle. Open the throttle some, watch for vacuum on the gauge. Should have near-manifold-vacuum level vacuum at the EGR hose.