Volvo 850 1996 / Tranmission or PNP or what? Topic is solved

[BeerDeer]

One very common problem is failed or failing check valve at the fuel pump. When this happens, after you turn the Carr off the fuel pressure leaks down over time. Then it takes a few turns of the key to get the fuel pressure back up, and it starts.

Here's one easy way to test for bad check valve at the fuel pump:
1 let car sit overnight
2 turn key to position II until all dash lights illuminate but do NOT crank the starter
3 wait 2-3 seconds until fuel pump stops running
4 repeat steps 2-3 again
5 repeat steps 2-3 again
6 repeat steps 2-3 again
7 now can the starter, does it start more quickly now?

If it doesn't start any better after priming the fuel pressure then look elsewhere, but this is one way to check.

You can also monitor fuel pressure at the rail and see if it leaks down when you turn off the car, how quickly it creeps back up during steps 2-6, etc.

It can be difficult to hear the fuel pump in position II. Easier to hear if someone else turns the key and you are back near the pump, especially easier if the cover is removed in the trunk/cargo area.

This does not sound like a fuel pump relay problem, but you can always jumper it to test that.

This does not sound like a problem with the new spark plugs.

If this were my car I would not try to troubleshoot any minor startup problems until the cam seals and the PCV were fixed.

Thank you for your help. I did the fuel pump test today and could hear the buzzing sound for about 3 seconds, so I assume the fuel pump is working fine. I’ll perform additional tests tomorrow to confirm.

However, guess what? The car randomly experienced rough idling, misfires, and other symptoms again—just as I suspected. I opened the rotor cap, and it was the same as before: a lot of oil and condensation inside. (Attached is a picture I took a week ago, and it looked exactly the same today.)

My PCV kit and seals arrived today, and I’ll be replacing them soon. It seems that the root cause of all these issues is the oil and condensation leaking into the rotor cap. Hopefully, fixing the PCV system and seals will finally resolve this.

I cleaned the rotor cap, reinstalled it, and all the issues are gone. The car is back on the road and running smoothly!

[erikv11]

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It seems that the root cause of all these issues is the oil and condensation leaking into the rotor cap.
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Yes!

100% agree, no need to mess with anything else until that's fixed.

[BeerDeer]

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It seems that the root cause of all these issues is the oil and condensation leaking into the rotor cap.
...

Yes!

100% agree, no need to mess with anything else until that's fixed.

I'm making new thread and booking this as closed as I serviced almost everything this week.