Flames in tbi!

[f85gtron]

Ok. Back on topic. 
I checked the ecm coolant sensor. It showed 3100 ohms at 70°f.  That's good, right? The spray pattern is even and no drips.  Key on prime also no drips.
I'll do a compression test maybe this weekend and report results.
Any other suggestions?
Could timing be too advanced?  8° on number 1 for duke, right?

[Fierofool]

The GM Temperature sensor chart shows 3400 Ohms at 70* F.  But at 90 degrees, it drops to 2150, so 3100 should be close enough. 

Looking at some manuals, there is exhaust gas ported directly through the EGR valve pintle seal and into the intake.  Since the exhaust manifold is on the opposite side of the head, there has to be a direct port from probably the number 2 and 3 cylinder exhaust valves, over to the intake.  A diagram of the L4 head appears to support this, as it shows a port that's definitely not one of the fuel intake ports to the head. 

If that EGR valve is stuck open, and you have a misadjusted or burned exhaust valve on one of those cylinders, it may be possible to ignite fuel vapors through that passage.  Just a theory on that. 

[f85gtron]

Compression:
I performed a compression test.
Dry. Didn't do a wet, I was satisfied with the dry.
#1@120, #2@115, #3@140, #4@120.  The only suspect would be #3. The rest seem close to normal.
Fuel:
Fuel pressure stayed at 12# running and didn't fluctuate much during revving. 
Key on runs pressure up quickly, but falls quickly.  No change when return is clamped. Also, tbi is dry during test, no leaks from injector.

I haven't checked the egr yet.

The fuel pressure leaks down so fast, i find it suspect, but stays up when running, so I don't know what to think.

Any thoughts?

[Fierofool]

Could it be that the fuel pump is holding the pressure up when the engine's running?  Leakdown as you described could be a bad regulator, or is it possible that the check valve in the filter is bad and letting pressure bleed backwards through the filter?

There are warnings about removing the screws for the regulator diaphragm cover due to the heavy spring underneath.  Also about fuel spray if the pressure isn't relieved before opening up the regulator. 

[f85gtron]

I rebuilt the tbi complete with new regulator. That doesn't mean I didn't screw it up though.
Here's a video of it's behavior.

[f85gtron]

Question:
On the v6, the pressure rises when the fuel is goosed. Shouldn't the tbi do the same?  I did notice it's not vacuum controlled at all. Just a spring, so I guess I shouldn't expect it to. I just would like someone's experience on that part.

Observation:
I hooked up tuner pro to see what the ecm sees and it had a value of 195.7° for the coolant temp. It is about 60° in the garage and I don't think anyone else was driving it...  That leads me to believe that the coolant temp sensor needs replaced. So I guess the 3100 ohm value wasn't good enough for gm.  Oh well. Back to the drawing board.

[TopNotch]

Question:
On the v6, the pressure rises when the fuel is goosed.

Goosed? Pressing the accelerator? The only reason I can think of for that to happen is that the alternator turns faster, making more power for the fuel pump. All things considered, the pressure should otherwise go down.

[f85gtron]

On the v6, there's a vacuum on the spring side that holds the regulator back.  The more vacuum (idle), the less fuel pressure. As the throttle is goosed, vacuum drops and the spring does it's thing. The pressure then rises during that event to feed the injectors.
I don't see anything like that on the duke. It's a low pressure system and I'm not used to it.
The false hot coolant sensor reading explains the extended cranking to start and crappy cold characteristics. It's always in closed loop instead of open in the beginning, which means no choke, no cold crank fueling, and ecm calc based on a cold o2 sensor that would be far from accurate for a few seconds at least.
I still have to cap off the egr to test. I agree that the exhaust side is the only way that the intake could have ignited while running.

[Fierofool]

What TopNotch said was what I was thinking, too.  Most V6's run at about 38-40 psi at road speed.  In absence of a vacuum function, the Duke regulator has to be an equalizing pressure type regulator where the pressure drops on one side will cause the valve to open to try to attain equal pressure on each side of the diaphragm.  I used this type regulator extensively in water pressure control on golf courses.  Whe n pressure dropped downstream due to increased demand, the spring pushed the valve open to equalize demand and supply side pressures.  Very efficient with miniscule lag time.

[f85gtron]

So it's normal then?... to run at 12# with minimal fluctuation?  Sounds like you're saying yes. From what you're describing, sounds like it's good to go.

[Fierofool]

I don't know for sure, Ron, but that's the way an equalizing valve works.  Think of the pressure regulator on your home water system.  It works the same way.  Water pressure drops at the faucet due to demand and the valve opens up to try to equalize the pressures on the up and downstream sides.  The thing I don't understand is how the injector pulse widgh is actually increased, unless it's through signals from the throttle position sensor.  The pulse width would need to be increased as speed increases, essentially the same as opening the faucet more. 

Our V6's have an over-pressure return line, but does the L4?  The pump needs fuel moving through it any time it's running in order to keep it cool so it would need a return bypass line. 

I didn't have time to fully read this, but maybe it will help.  Headed out the door.

https://www.hemmings.com/magazine/hcc/2011/08/Half-Breed/3702631.html

[Raydar]

Does your car have the little tin "deflector" under the throttle body, in the intake manifold?
Many people have speculated regarding it's intended purpose. Some suggesting that, whatever it is, it restricts air flow.
Perhaps it's there to divert EGR gases away from the throttle body opening. (Assuming it's missing.)

[TopNotch]

Our V6's have an over-pressure return line, but does the L4?

Yes.

[f85gtron]

I think it's there. I have to look again. I forgot about that deflector.
Yes, the 4 banger has a fuel return line too. 
The pulse width of the injector calc is derived from several variables. Mostly from the map vs rpm vs fuel. It's a 3d table that if load (map), and rpm, then fuel specified.
The tps only is used for pump shot (acceleration enrichment), entering wot (power enrichment), decel derichment, and delta movements to change spark at diverting rates if using rpm derivative spark.

[GTRS Fiero]

Any update?