Open Loop Woes

[SoCalManche]

2 minutes ago, eaglescout526 said:

I might have some IATs from a bunch of 2.5L manifolds I have.

If you have a spare, just throw one my way and the invoice too. Haha

[eaglescout526]

Lol Ill take a look tomorrow unless cruiser still has some already pulled.

[SoCalManche]

14 minutes ago, eaglescout526 said:

Lol Ill take a look tomorrow unless cruiser still has some already pulled.

Just saw that post. My IAT had all year to give break, and instead it happens most likely a hair too late. Ha.

[eaglescout526]

Makes me wonder if I should check mine for filth. But hey at least it’s a quick easy fix. 

[SoCalManche]

So back at the grind;

 

Threw in a "new" IAT and all sensors now running normally as far as what REM is telling me.

 

I've tried three different O2 sensors:

1st O2 sensor wouldn't pull truck out of LEAN and stayed OPEN LOOP.

2nd O2 sensor shifted into RICH, and briefly pulled into CLOSED LOOP, but then shifted back to OPEN LOOP.

3rd O2 sensor same as 2nd.

 

Maybe the exhaust manifold has a hairline crack? 

 

REM isn't able to tell me how O2 sensor is operating beyond the scope of RICH/LEAN because it's a 2.5. 

I've tried backprobing, but I don't get the ~5V readout that's supposed to occur?

Terminal A (yellow wire): Battery voltage

Terminal B (black wire): Ground

Terminal C (orange wire): 0.97V with truck running.

[Ωhm]

What are your Fuel Trim values? ST? LT? Maybe these numbers can help here.

[SoCalManche]

They don't deviate. Both are showing 128. That may provide insight.

[Ωhm]

Sadly, to say NO help here. Those are OPEN LOOP values. Kinda means it major (air leaks, raw fuel). You say REM showed RICH trying to hold CLOSE LOOP (CL). Can you read Fuel Trim (ST) when ECU is in CL. Are numbers going up or going down from 128.

[Ωhm]

You say your running RICH. Make sure no fuel is bleeding out the Fuel Pressure Regulator (FPR) vent when engine is RUNNING.

 

[SoCalManche]

1 hour ago, Ωhm said:

You say your running RICH. Make sure no fuel is bleeding out the Fuel Pressure Regulator (FPR) vent when engine is RUNNING.

 

 

No seepage from that vent. 

 

Just started her up, and she wouldn't even go into RICH this time; she retained LEAN and OPEN LOOP, and sounded like a damn lawnmower while running, also smelled like one honestly. Not the first time to have that happen either. I'm gonna do a couple start ups and see how they differ, if at all. 

[SoCalManche]

Second start-up was normal. Switched to RICH and ST immediately dwindled to 0 within seconds. Of course, once 0, the "CEL" came up and then REM showed shift back to OPEN LOOP.

 

Injector?

[Ωhm]

With ST driving straight to 0, ECU is taking fuel away (less INJ PW time). Faulty injector (leaky or poor spray pattern), raw fuel from somewhere or higher than normal fuel pressure.

[SoCalManche]

2 minutes ago, Ωhm said:

With ST driving straight to 0, ECU is taking fuel away (less INJ PW time). Faulty injector (leaky or poor spray pattern), raw fuel from somewhere or higher than normal fuel pressure.

When prior IAT was pulled, it was coated in fuel. Raw fuel can't really come from anywhere besides the injector, no? Considering that fuel regulator vent was already monitored as being dry during operation.

 

[Ωhm]

Like you mentioned earlier, injector. Also, a plugged fuel return line can cause higher fuel pressure.

[SoCalManche]

20 hours ago, Ωhm said:

Like you mentioned earlier, injector. Also, a plugged fuel return line can cause higher fuel pressure.

 

Went to swap in an injector I had that I knew was functioning last I used it;

 

Before swap: Started truck up again to see how it would start; she retained LEAN/OPEN LOOP condition.

After swap: Started truck up and same occurrence; retained LEAN/OPEN LOOP condition.

 

I then swapped the injector around to see if orientation mattered (been told in the past orientation does NOT matter); as soon as truck started, cycled to CLOSED LOOP and O2 sensor immediately starting pinging back and forth between RICH/LEAN.

 

Can we verify that orientation matters? I've always just thrown injectors in without looking at orientation and it didn't seem to matter - that was always luck?

 

Also, what are ST values supposed to be in idle? She was in the 160-180 range.

[Ωhm]

I would think orientation on the INJ would be keyed somehow so it only goes in one way. My only question would be connecting the connector two different ways would change the current flow through the INJ coil windings (magnetic field). But if this was the case, I would think, the INJ would be keyed.

 

During CLOSED LOOP in a perfect world, Fuel Trim, both ST and LT, would be 128. Your ST 160_180 (more fuel) is well within the ECUs range of authority and is adding a little time to the INJ PW time. This additional time will keep A/F ratio at 14.7_1.

 

 

38 minutes ago, SoCalManche said:

I then swapped the injector around to see if orientation mattered (been told in the past orientation does NOT matter); as soon as truck started, cycled to CLOSED LOOP and O2 sensor immediately starting pinging back and forth between RICH/LEAN.

Hope it stays that way.