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Discussion Starter · #1 · (Edited)
https://youtu.be/sNEgNCOoGnk

I had the classic check valve issue with the fuel pump, had the pump assembly replaced by my indie. Since then, the car often has a problem restarting when the engine is hot. It cranks up quickly (ie, not low pressure like before), but it doesn't settle back to an idle, it just shuts back off quickly. If you "catch" it after it starts and give it a little gas, it will then settle to an idle fine. See video. Any ideas?

Pulled the check engine code with VIDA and it's: P242100 - Evaporative Emissions Control System Vent Valve Stuck Open. I have not had a chance to run the diagnostics on it but am guessing it's likely related.
 

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Discussion Starter · #2 ·
The fuel tank leak test diagnostic did not find any issues. I cleared the existing codes and am going to see if anything reappears, but would still appreciate advice on this. There was nothing obvious in the stored codes, although there was a weird smattering of 10-15 different minor electrical faults with stuff like door locks, parking brake motors, windows, etc.
 

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Discussion Starter · #4 ·
Just ordered a Bosch sensor for $40 to be safe. Car has not done this in a few days now since I cleared all the codes.
 

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Discussion Starter · #5 ·
Update. The car was doing this about 75% of the time. Replaced the rail fuel pressure sensor and it has not happened once in ten days now. Fingers crossed, but it seems to have fixed it!
 

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This sounds like what might happen when the EVAP vent valve is stuck open. Every time the engine is started up, the ECM runs a short EVAP Test to see if the fuel tank and its hoses have any air leaks. It does this by sealing off the fuel tank for a few seconds (including closing the EVAP Vent Valve), having the EVAP pump build up pressure in the tank enclosure, and using the EVAP Pressure Sensor to measure the rise in tank pressure. If the EVAP valve is stuck open, the EVAP test will fail.

The important question is, would the engine be getting unmetered air during the EVAP Test??? If the EVAP Purge Valve is not closing during the EVAP test, then yes, the engine would be getting unmetered air, which makes the air/fuel mixture go lean, and this can stall the engine.

The EVAP Test is omitted from the startup sequence when the fuel tank is > 85% full. So, here's a simple test: Fill the tank full. Does this startup stall like it has?
If not, then this points a the EVAP Test, and the solenoid valves operated during it, as the root cause.

Giving the engine a squirt of gas right after startup would prevent stalling, since it ups the metered airflow drowning out the impact of the smaller EVAP system air leak.

If it's an EVAP system problem, the best solution is to use VIDA diagnostic testing of each solenoid valve.
 

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18 months after replacing the fuel pressure sensor, this has never happened again.
Fuel Pressure have always been a sparatic replacement on Volvo's
 
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