Hard Starting? Losing Coolant?
There are two main ways Volvo injector cups fail- Fuel airation and Coolant airation
When the combustion gas gets in the fuel, the injector is not sealing against the injector cup allowing combustion gas to come up past that sealing point and get into the fuel gallery.
The most common symptom is hard starting or extended crank time. Other symptoms can include low fuel pressure and low power
The injector often needs to be replaced because the sealing surface is damaged.
A quick indicator of air in the fuel system is to look in the fuel tank for bubbles at the return line.
The more accurate test is to fit a clear fuel line on the in line to the head and inspect for bubbles to rule out the fuel system before the head. Then fit a clear fuel line on the return line coming out of the head. If you see bubbles after the head and not before you have confirmed faulty injector cups.
The second way injector cups fail is from coolant airation which becomes pressurising- pushing coolant out the over flow of the surge tank.
Performing a combustion gas in the coolant test is a good starting point for diagnosing this. You can also fit a clear line from the head to the surge tank and check for bubbles
Some common misdiagnosis that should be ruled out first where possible are- a crack in the surge tank can stop coolant returning from the overflow compartment to the main compartment
- a faulty radiator cap will allow coolant to be pushed out the overflow.
- a faulty egr cooler can allow combustion gas in the coolant.
- a faulty air compressor can allow compressed air in the coolant causing pressurising
- a lot less common but still possible is a blown head gasket or cracked head, allowing combustion gas in the coolant