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sprinkles08
sprinkles08, ASE Certified Technician
Category: Car
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Experience:  ASE Master and Advanced level certified. Factory trained with 14 years dealership experience
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Nissan sentra 1.8L: I have Nissan Sentra 1.8L . When engine

Resolved Question:

I have Nissan Sentra 1.8L . When engine is cold, engine starts immediately with one or two cranking revolutions. With engine full hot, starting is the same. When engine is between full hot and cold ie; (cooling down about 30/40 minutes), engine will not start after several cranking revolutions. If I then try starting a second time, engine will start normally .

I'm afraid this is causing much undue wear on starter motor.
Please advise what may be going on.
Submitted: 10 months ago.
Category: Car
Expert:  sprinkles08 replied 10 months ago.

Hello and welcome to JustAnswer!

 

It sounds like you may have a vapor lock issue due to a weak check valve in the fuel pump.

 

When you park the car with the engine hot the high underhood heat will cause the fuel in the rail to elevate in pressure, often the fuel will actually boil.

 

There is a check valve in the fuel pump to prevent fuel from draining back to the tank while the pump isn't running. High pressure in the rail during a hot soak can cause the check valve to open partially and fuel is forcefully pushed back to the tank.

 

This leaves pressurized vapor in the rail rather than liquid fuel so it causes a hard start after the engine has reached operating temperature, the car is parked and you try to restart it while it has been sitting for a bit but is still hot.

Customer: replied 10 months ago.

I'm somewhat confused by your answer in last paragraph ie; "so it causes a hard start after the engine has reached operating temperature,"


 


As my inquiry indicated, when engine is at operating temperature, the engine will start with one or two cranks. Since changing check valve requires removal of gas tank which is very expensive, I need to be sure the check valve is the correct answer. Is there any way to verify it is the check valve before I start repairs?

Expert:  sprinkles08 replied 10 months ago.

The quote should have included the entire sentence: '...causes a hard start after the engine has reached operating temperature, the car is parked and you try to restart it while it has been sitting for a bit but is still hot.'

 

To verify that the check valve is causing the issue you would need to install a T hose before the fuel rail and then pinch off the delivery side of the fuel system to prevent fuel from being pushed backward and then see if the problem goes away. If it goes away when the delivery side of the system is pinched off then you know it's a check valve issue.

sprinkles08, ASE Certified Technician
Category: Car
Satisfied Customers: 16473
Experience: ASE Master and Advanced level certified. Factory trained with 14 years dealership experience
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