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Chris (aka-Moose)
Chris (aka-Moose), Auto Technician
Category: Toyota
Satisfied Customers: 901
Experience:  16 years of experience
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2007 5.7 tundra not starting. Have a p0171 and P0174.

Customer Question

2007 5.7 tundra not starting. Have a p0171 and P0174. Replaced plugs and air filter. Tested fuel pressure. It's at 40 lbs. still no start. Bypassed air induction pumps. Tested them with 12volt and they run. Still no start.
Submitted: 1 year ago.
Category: Toyota
Expert:  Jared D replied 1 year ago.

Have you checked the Mass air flow sensor? A bad fuel pump can cause the p0171 and p0174, but if you are getting 40lbs cranking that sounds normal.

If you have a scan tool you can check the signal from the MAF, if not try unplugging the connector on the MAF and see if it will run. Sometimes it will start but run poorly with the MAF unplugged if it is faulty.

Expert:  Jared D replied 1 year ago.

You can also check the signal from the MAF with a multi-meter:

Check the Blue(L)/White wire at the mass air flow sensor for 12 volts and the Green/White and Brown wires for grounds.

The Blue(L)/Yellow wire is the signal wire; the voltage should increase as the airflow into the engine increases. Confirm that the voltage signal is getting to the ECM at connector D74 pin 74.

Customer: replied 1 year ago.
Replaced the mass airflow sensor as well.
Expert:  Jared D replied 1 year ago.

Can you test for spark or injector pulse?

Customer: replied 1 year ago.
I have not
Expert:  Jared D replied 1 year ago.

That will be the next thing to check to see where to go from here. The spark can be tested by pulling one of the ignition coils and cranking the engine to see if the spark will jump from the coil boot to the block.

The injector pulse can be checked with a noid light. It is a small light that plugs into the injector connector. It will flash while cranking if you have injector pulse.

Customer: replied 1 year ago.
I do have spark
Expert:  Jared D replied 1 year ago.

Ok. Now you'll need to check for injector pulse. You could also use a multi-meter to check for injector pulse but some multi-meters won't see the voltage pulse because it is so quick. You can usually borrow a noid light set at most parts stores with a deposit.

Customer: replied 1 year ago.
Tested injectors with noid light. All working.
Expert:  Jared D replied 1 year ago.

So you have spark and you have fuel, it should run unless the fuel pressure is dropping during cranking. If you spray starting fluid in the intake duct while cranking will the engine fire?

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