Injector cups, or sleeves, seal each injector to the cylinder head and separate fuel and combustion from the coolant, and a failed cup can let coolant and fuel mix.
What it does
On many diesels the injector seats in a cup pressed into the head, which seals combustion and fuel from the surrounding coolant passages. When a cup cracks or its seal fails, coolant can enter the cylinder or fuel can reach the coolant.
Signs it is failing
- Coolant loss or coolant in the cylinder
- Fuel in the coolant or a fuel smell
- Rough running or a misfire
- White smoke and hard starting
Replacement and what to know
A failed injector cup is replaced, which is a precision job requiring the injector to come out and the cup to be resealed or re-installed correctly. Because symptoms overlap with injector and gasket problems, proper diagnosis is important.
Frequently asked questions
What does an injector cup do?
It seals the injector to the head and separates fuel and combustion from the coolant passages.
What happens when a cup fails?
Coolant can enter the cylinder or fuel can reach the coolant, causing white smoke, coolant loss, or contaminated coolant.
Is it a hard repair?
It is precision work, since the injector must come out and the cup resealed or replaced correctly.
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