truck listed above and it stalls when driving

Good evening,

I would start by confirming the compression to be sure the valve timing is correct.

https://www.2carpros.com/articles/car-cranks-but-wont-start

https://www.2carpros.com/articles/how-to-test-engine-compression

Do you have a noid light to see if the ECM is commanding the injectors to fire? try spraying some starter fluid into the air filter and see if it starts and stalls.

Did you verify the spark to the plugs?

https://www.2carpros.com/articles/how-to-test-an-ignition-system

Roy

Clearly fuel pressure is okay, but was this taken during the stall or are you taking this pressure reading when it is just idling? Plus this doesn't eliminate injectors but we can get there if all this checks out.

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

So let's just tape the pressure gauge to the windshield and drive it and make sure the pressure is correct.

The fact that it does not restart when hot points to a spark or fuel issue. So let's rule out fuel first.

Next, since you have that scan tool, can you monitor the MAF while driving and then see what it does when it stalls? Clearly once the engine is shut off the air flow will drop but I am just curious what it is doing leading up to the stall. What happens if you unplug the MAF after it stalls? Does it restart?

Let's start with this and go from there. Thanks

Yes, the pressure was taken while driving but it did not stall when I had the gauge hooked up. it wasn’t until after I pulled it off when it was warm enough did it stall. I will see if my work has a compression tester and if not I will rent one tomorrow. I do not have a noid light. Should I be checking my spark after the stall or while it is running? Also my fuel filter was changed 3,000 miles ago. I will try pulling the MAF after the stall.

Check for spark while cranking.

Let us know about the noid.

Roy

My MAF varied from 9.5 (GM/S) to 5.8 before it stalled. It took about 3 minutes from it to stall and the whole time my engine was idling at 1,200 RPM's and gradually dropped to 850 before it stalled. The MAF (V) stayed around 1. Have to get the compression tester tomorrow when the parts store is open. No results with the starting fluid. One thing I forgot to mention is my coolant gauge is reading noticeably lower then before but when I had everything apart I did spray a lot of stuff out of the cooling fins. Only bring It up because I read it’s possible to have a faulty coolant sensor which could cause crank no start.

Also tried pulling the MAF off after the stall and it still would not start.

So those MAF readings are not out of line based on the number but the key is to know if it is reading correctly based on the RPM. So let's just prove that out because I am concerned of how it is changing.

Take a look at this attachment. Basically if you don't have a graph feature on the tool then you can do it as they show. Just idle the truck and note the RPM and MAF reading g/s. Then raise it slowly to around 2,500 RPM's and note the MAF reading at about 4-5 intervals.

Then let us know the compression. Also, do you have spark when it stalls and won't restart? We may have a crank sensor issue.

Can you give us the fuel pressure reading while running especially when the engine shuts off? I want to see if the fuel pump is dropping out.

Roy

Cylinder 1 compression ~150psi.
Cylinder 6 compression ~160psi (this cylinder had the largest ring gap of all of the cylinders when I checked them). Fuel pressure sat at 50psi. Had a check engine code come on the scan tool: MAF sensor out of range. Unplugged my sensor while the engine was running and nothing happened. I’m sure the sensor is bad but I don’t like being a parts changer. Going to research the procedure for checking a 6 wire MAF plug. Have not checked for spark yet after the stall.

Fuel pressure is way too low.

Fuel Presure
Key on, engine off .................... 414-448 kPa (60-65 psi)
Engine running .................... 414-448 kPa (60-65 psi)

You need to replace the fuel pump to get the pressure correct.

https://www.2carpros.com/articles/how-to-replace-an-electric-fuel-pump

Roy

Wrench, Fuel Tank Lock Ring
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SPECIAL TOOL(S)

REMOVAL
1. Remove the fuel tank.
2. Clean the area around the fuel pump mounting flange.



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3. Using the special tool, remove the fuel tank pump assembly locking retainer ring.
4. Remove the fuel pump assembly.

CAUTION: The fuel pump assembly must be removed and handled carefully to avoid damage to the float arm and filter.


5. Remove and discard the fuel pump mounting gasket.

Removal

Warning:
Do not smoke or carry lighted tobacco or open flame of any type when working on or near any fuel-related component. Highly flammable mixtures are always present and may be ignited, resulting in possible personal injury.
fuel in the fuel system remains under high pressure even when the engine is not running. Before repairing or disconnecting any of the fuel lines or fuel system components, the fuel system pressure must be relieved to prevent accidental spraying of fuel, causing personal injury or a fire hazard.


1. Relieve the system pressure.



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2. Disconnect the fill pipe main hose.
Loosen the fill pipe main hose clamp.
Disconnect the fill pipe main hose from the main fill tube.

3. Drain the fuel tank.



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4. Remove the four bolts (two each side) and remove the skid plate, if equipped.
5. Support the fuel tank.



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6. Remove the bolts and pivot the fuel tank support straps away from the fuel tank.



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7. Disconnect the fuel pump connector.
Lower the fuel tank slightly.
Disconnect the fuel pump connector.



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8. Disconnect the fuel supply and return line push-connect fittings, the vapor tube and fill tube vent hose fittings at the fuel pump.



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9. Disconnect the vapor line fitting at the rear of the fuel tank.
10. Lower the fuel tank.

INSTALLATION
1. To install, reverse the removal procedure.

New update:
Fuel pressure tester fitting was stripped out and leaking fuel while I tested. Changed fitting 61-62 psi all the way through and after stall.
Cleaned IAC.
MAF data from scan tool showed MAF kind of erratic. I am going through frame by frame and at one point the rpm was at 2219 and the MAF gm/s was at 16.99 and a few frames before it read 14.23 at the same rpm.
While at 2192 rpm the gm/s was at 15.06 and a few frames later it read 13.89. I think I can upload the data but I will have to check.
Tested my no. 6 spark plug and didn’t see any spark, pulled the plug and had it on my window with a grounding cable from my battery attached.
pulled my MAF connector wires while the engine is idling and nothing happens.(didn’t looks at the scan tool when I did this).
Once the engine is idling it takes the approx the same amount of time for it to stall and in the last part before it stalls if revved it will sputter and choke.
Also noticed it smells strongly of fuel after start up.

Did you graph the crank sensor to watch the pattern?

I know you are checking the mass air flow but that will not cause a no spark issue.

Roy

Also tested my MAF according to this website: https://easyautodiagnostics.com/ford/4.9L-5.0L-5.8L/maf-sensor-tests-2
And everything passed when tested at start up.

Okay, I would look in another direction as I suggested.

Roy

Alright I looked through all of the monitors on the scan tool and couldn’t find anything labeled CPS. Does it have another name that it goes by that you know of?

Engine speed sensor.

You should have it somewhere that will read engine speed.

Roy

The Crankshaft Position (CKP) sensor is a magnetic transducer mounted on the engine block adjacent to a pulse wheel located on the crankshaft. By monitoring the crankshaft mounted pulse wheel, the CKP is the primary sensor for ignition information to the powertrain control module (PCM). The trigger wheel has a total of 35 teeth spaced 10 degrees apart with one empty space for a missing tooth. The 6.8L ten cylinder pulse wheel has 39 teeth spaced 9 degrees apart and one 9 degree empty space for a missing tooth. By monitoring the trigger wheel, the CKP indicates crankshaft position and speed information to the PCM. By monitoring the missing tooth, the CKP is also able to identify piston travel in order to synchronize the ignition system and provide a way of tracking the angular position of the crankshaft relative to fixed reference (Figure 25).

The crankshaft position (CKP) sensor (Figure 54) is a magnetic transducer mounted on the engine block adjacent to a pulse wheel located on the crankshaft. By monitoring the crankshaft mounted pulse wheel, the CKP is the primary sensor for ignition information to the PCM. The pulse wheel has a total of 35 teeth spaced 10 degrees apart with one empty space for a missing tooth. The 6.8L ten cylinder pulse wheel has 39 teeth spaced 9 degrees apart and one 9 degree empty space for a missing tooth. By monitoring the pulse wheel, the CKP sensor signal indicates crankshaft position and speed information to the PCM. By monitoring the missing tooth, the CKP sensor is also able to identify piston travel in order to synchronize the ignition system and provide a way of tracking the angular position of the crankshaft relative to a fixed reference (Figure 54) for the CKP sensor configuration. The PCM also uses the CKP signal to determine if a misfire has occurred by measuring rapid decelerations between teeth.

I have vehicle speed sensor (mph) monitor but nothing labeled engine speed sensor or CKP. Would you recommend troubleshooting the sensor/wiring to the sensor?

I attached the wiring for you to view.

Check for the reference voltage to the sensor.

https://www.2carpros.com/articles/how-to-check-wiring

Roy

I have not checked my sensor to computer yet but I got reference same reference voltage on both connectors and the same ohm value on each connector as well. This means that there is a short if I’m not mistaken... Checked the camshaft position sensor as well and got 1 Ohm in one pin with 98ohms on the other.

You should have resistance between the 2 wires. The resistance comes from the ECM.

It is voltage that counts. When toy test for voltage use the connector. Red lead in one terminal and black on the other and tell me the voltage.

Roy

Last night when the engine was warm with ignition on I was getting 5v on both by grounding one test lead and testing the terminals. Today when I haven't cranked the truck over yet I am getting 1.5v on both terminals. When I test the terminals without grounding a test lead I get no voltage reading.

Okay, did you test it the way I suggested? I need that reading.

If you do not have the reference voltage at the connector, that comes directly from the ECM.

Roy

Oh yes I did forgot to mention. It was 0v on both terminals.

I do not think you understand.

Do not put the black lead to a body ground.

Put the red lead in one terminal and the black lead in the other terminal and give me the reading.

Roy

Yes, with the ignition on I checked my multimeter reading with one test lead in one terminal and the other test lead in the other terminal. The CKP was not connected. The reading was 0V DC.

Okay, that indicates a short circuit with the wires. If you had ghost voltage or voltage all over the place, that would indicate an open circuit.

You should read 5 volts with that check.

Roy

When I pulled my engine apart that CKP wire ran between my pulley mounts and the block. May have routed it wrong when it was reinstalled and it got sandwiched. Going to pull that mount because that's probably where my issue is, but I will keep updating. Thank you very much for your unwavering help.

You are welcome.

Always glad to help.

Roy

Yep I found it. Is it okay to solder CKP wires?

Yes, solder and shrink wrap.

Good find.

Roy

So far no issues. Thanks again.

Glad to hear.

You are welcome.

Roy