The vacuum line is on the fuel pressure regulator & on the 97 its located close to the fuel rail Schrader valve.
The Actron likely erases the codes, but probably doesn't wipe the KAM = Keep Alive Memory, where the fuel trim tables & cold & warm idle strategy reside, like a battery disconnect does.
Good idea to repost the codes you have.

 

Tested the fuel pressure again last night with a full tank. With three key-on's (power on cycles) the gauge went up to 36 psi. With the engine running it dropped to 30 and stayed there. I did not know how/where to do the vacuum hose on/off test and will do that tonight.

My understanding is, the regulator will pull the pressure down, which appears to be happening. I also read most likely the pump either works or it does not. So, do we have a bad regulator, bad pump or what?

Replacing that pump means pulling off the bed and that will be a major job. Getting those six rusted bolts out will be a pain in a half. Want to be darn sure that's the problem before I do that, obviously.

I still have not had anyone tell me if running at 30 PSI is enough to trigger these three codes I keep getting.

P0136, P1131 & P1151

Still others are saying this is all because of vacuum leaks. I have checked and rechecked and found no leaks, no bad hoses, nothing. I sprayed carb cleaner all around the intake manifold gasket last night and no change in RPM's at all.

I can try doing a smoke test if I can rig up a DIY smoker. Push smoke in via the intake cleaner snout and see where it may come out.

There must be a way to test overall vacuum pressure off the intake manifold.

Feels like I'm going to two directions here and running out of time on this 10 day temp plate.

Don't get me wrong, I appreciate the help. After over a month of most every night, every weekend working on this truck I'm getting very frustrated.

 

On your 97 at idle, 25-35 psi with the pressure regulator vacuum hose connected is normal.
If it took that many key on/off cycles to get the fuel pressure up that high, then something seems to be amiss with the pressure regulator, fuel pump, or fuel lines, seeing as how you say the filter has been recently replaced. Wimpy pump, clogged up in tank pump pick up screen, line restriction, crimped fuel line, leaking fuel pressure regulator diaphragm ect, belong on your suspect list & is why I suggested a volume over time test.
Did the 20 psi reading you posted earlier come about after only one key cycle????
How long will it hold the 35 psi reading????
When you disconnect the FPR vacuum hose, is it wet inside with fuel, or does it reek inside of fuel????

 

No, I said it was 28 to 30 psi and you said that was way low. Had to be at least 35 psi, you said.

All the articles I found recently on doing the fuel pressure test say to do three key-on cycles to see if the pump is able to build up more pressure each time.

Mine does that well in to 36 psi (on the 3rd try) and holds it there until I start. Then it drops to 30.

The first time I did the test I only did one key-on and it went to 20 after a few seconds.

 

Lets review #10 & #11 posts.
In #10, you posted that the fuel pressure with the key on was around 20. I assumed this was a KOEO test.
In #11, I replied that the 20 psi pressure was low & KOEO psi should be 35-45.
In #13 I listed the KOEO & KOER pressures with the FPR vacuum line connected & disconnected.
If the KOEO pressure rises to only 20 psi on the first turn of the switch, it suggests to me that the pump, or voltage to it might be wimpy.
Since we need the specified Volume of fuel at the minimum specified psi, I thought it would be a good idea to perform a fuel pump volume over time test & to perform the psi/ vacuum line removal psi tests on the pressure regulator & a psi leak down test over time & do a visual & sniff test on the interior of the regulator vacuum line to see if its diaphragm might be leaking. So that's the line of thinking on my test suggestions. Sorry if we've had a interpretation disconnect along the way.

 

No problem.

Can you please answer my question, though.

Will running at 30 psi, in and of itself, cause a lean condition on those three O2 sensors?

Have you had this happen or know that it can happen?

 

We may be able to answer the 30 psi question after you complete the KOER FPR vacuum line disconnect fuel pressure reading & fuel delivery rate over time tests.
You seem to be fixated on a one problem cause & I'm thinking with the miles on this puppy & not knowing where it is on all past & present due scheduled maintenance items history, you could have more than one problem confusing things. So imo you need to begin with & make sure the basics are right. That 20psi KOEO reading suggests that something with fuel pressure is at least borderline.
If you find that the KOER vacuum line removal fuel pressure test is ok (be sure to plug the vacuum line so it doesn't act like a gross vacuum leak & further confuse things), fuel pressure bleed off time after engine shut down & delivery rate are ok, then you can say the 30 psi fuel pressure is fine & it is, as long as those other things are ok too. Then you can begin to look at fuel injector & O2 sensor problems. For instance if fuel pressure bleed down time is short, it would suggest an injector with a runny nose, or maybe a FPR with a leaky diaphragm (ie the vacuum line visual & sniff test for raw fuel in there), or the codes might suggest corrupt O2 sensor feedback(they've lived 2 lifetimes at this mileage if they've never been replaced). Lean codes on one cyl bank might suggest O2 sensor problems, dirty injector/s, manifold leak, ect, ect, so a good bit more testing needs to be done to try & isolate whats going on.
Your scantool, fuel pressure & vacuum gauges can help quickly perform some enlightening tests, so keep us posted on your trouble shooting progress with Numbers.

 

I did the fuel pressure tests all over and here are the results:

First key-on = 10 psi, 2nd = 20 psi, 3rd = 40 psi
Running/idle = 30 psi
Vacuum off = 40 psi
Key off = 32 psi and stayed there for well over 10 minutes until I let out the fuel

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I have long suspected this was electrical. Earlier in the week I tested the connector for the O2 sensor after the cat. The voltage and ground was correct as was the heater resistance.

This morning I did the same tests for the passenger side O2 sensor before the cat. Made sure Fuse #20 was OK. That supplys juice to these O2 sensors. The pin at 10:00 on the female side of the 4-pin O2 sensors is the ground through the PCM. Monitoring the voltage between there and the positive at the 2:00 position should be 12 vdc and it is not. Measuring to chassis/battery ground from there should be close to 0 ohms with the key on and it is not. Therefore, the O2 sensor's heater is not getting a ground and cannot be working correctly.

I did not check the driver side O2 sensor as I'd need to get under the truck and I had my office duds on but I suspect it will best the same.

When I took the truck out last night (battery disconnected for 30 minutes prior) I got the P1131 and P1151 codes to show up in less than 2 miles. They may have been there before but I did not look at the screen until then. No way the system had time to compute any kind of emissions data. Has to be the fact that the O2 sensors are not getting to the PCM.

I located a good diagram on the web this morning and can now trace back from the 4-pin female connectors of the two O2 sensors and find out where the break is.

 

OK, good feedback on the fuel pressure test. Sounds like the FPR is ok, just that the fuel pump is wimpy, so it'll likely need replacing soon. If your having start problems, go to KOEO several times to build fuel pressure before cranking the engine for a start, until you get around to replacing the fuel pump.
To see if maybe you have a injector with a runny nose, leave the pressure gauge attached for say 30-45 minutes & see what it measures. Also review the old spark plugs deposits, to narrow down the hunt for cylinders with injectors that might have problems.
On the P1131 & P1151 lean codes, look for a upstream vacuum leak that would affect both cyl banks. Maybe consider rigging & performing a propane sniffer test around suspect vacuum lines, the PCV valve, its hoses & grommets, the intake manifold gaskets, listening for a change in idle speed or quality.
Seeing as how you like turning your own wrenches, it might be a good time to consider investing in the low cost ELM scantool discussed here.
https://www.ford-trucks.com/forums/1...-scantool.html
Running freeware FORScan that's tweaked for Fords, or the like software, to the viewing device of your choice & have it aid in your trouble shoot, as it can read & display things like the O2, MAF, TPS, IAT, ect, ect sensors PID to the computer, while you monitor things from the drivers seat, or your favorite lounge chair perch like I do & watch it perform & display all the trouble shooting tests & measurements. Makes trouble shooting Way more accurate, faster & fun to do.
Its a danged good low cost investment for our electronic tool box.
You might check your local library for the schematics your interested in. Some have membership in Mitchel On Demand, ect, & can down load or print what you want for pennys.

 

Have you performed the fuel pump volume over time test yet?? If so post the numbers.

 

I really need to find this code issue pronto. Only have a few more days on this temp plate.

I'm going to work on the electrical problem since I can actually verify there is an issue there. No ground on the O2 sensor as explain in my post from this morning.

 

Ok, well disconnect the O2 sensor & check its internal connections. If ok, then disconnect the computer firewall electrical connector, look for the same color code wire there & perform a end to end continuity test on each of the suspect O2 sensors wires from the O2 connector back to the firewall computer connector.
The ELM scantool can do all this for you while you sit in your Lazyboy or Stratolounger!!! lol If not previously replaced, at 180K the O2's are ready for retirement, sorta like me!!! Let us know what you find.

 

Found the ground lead from the PCM cable bundle fully corroded to the point it was not making contact with the chassis at the firewall. Replaced the lug and wire with new. Cleaned up the threaded hole and installed a new 6mm bolt to secure the new ground. Checked with meter to negative on battery. 0 ohms. Checked with pin #25 on PCM cable. 0 ohms. Ground is good.

Had the battery disconnected for the ground fix. Reconnected and went for a drive. After a few miles P1131 & P1151 were there but no engine light yet. After 8 miles P0136 was there and so was the engine light. So frustrating!

My Actron CP9575 scanner offers "live data" but it is not showing anything for the fuel trim or the O2 sensors at all. Tested on my Toyota and they are there so scanner is working correctly.





Called Actron and they refused to tell me what this means. Told me to ask Ford. Nice folks over there at Actron.

What does this mean? Defective computer, bad O2 sensors?

What is meant by FUEL SYS 1 Open2 in this second picture, at the bottom? I found this description in an article on using scanners but it does not go in to detail

"Fuel System 1 Status and Fuel System 2 Status should be in closed-loop (CL). If the PCM is not able to achieve CL, the fuel trim data may not be accurate."

 

Diagram of PCM where the three O2 sensors connect and the chassis ground comes in.

 

Bad O2 sensors, wiring, or engine, body grounds, or some combination there-of maybe.