Delphi HDF924 Fuel Filter Arrow Direction Explained (31390-H1970)
We’ve had a wave of calls and emails about the flow-direction arrows printed on newer batches of the Delphi HDF924 fuel filter (also known as 31390-H1970). Some customers have understandably thought the flow direction is wrong. Because this is a popular filter used across a range of Hyundai, Kia and Ssangyong vehicles (including models like the Hyundai Terracan), we wanted to clear it up properly.
The short answer: focus on what the arrows are indicating
It’s a bit of a mind game at first. The key is to ignore the change in how the arrows are drawn and focus on what they are actually telling you:
- An arrow pointing into a tube indicates the inlet (fuel entering the filter).
- An arrow pointing away from a tube indicates the outlet (fuel leaving the filter).
Old vs new arrows (why it looks confusing)
Pictured below is the older arrow style vs the newer arrow style. Although the arrows look different between batches, the meaning is the same.
On the LEFT (old): one arrow points into a tube (inlet) and one arrow points away from a tube (outlet).
On the RIGHT (new): one arrow points into a tube (inlet) and one arrow points away from a tube (outlet).
So which port is inlet and which is outlet on HDF924?
When you interpret the arrows correctly:
- The top tube is still the inlet.
- The middle tube is still the outlet.
So even though the printed arrow direction may appear “reversed” at a glance compared to an older filter, the fuel flow through the filter remains the same.
Buying the correct Delphi HDF924 / 31390-H1970 filter
If you need the correct filter for your vehicle, you can view the product here:
Delphi Fuel Filter HDF924 (31390-H1970)
Related vehicle filter categories
If you’re servicing a Hyundai, Kia or Ssangyong, you can browse filters by brand here:
Quick fitment note
Always confirm fitment for your exact model, year and engine. If you’re unsure, reach out to Sydney Filters and we’ll help you match the correct filter and installation direction.
FAQ: Delphi HDF924 arrows
Are the arrows printed the wrong way on some HDF924 filters?
Usually not. Some batches use a different arrow style that can look confusing. Use the inlet/outlet meaning: arrow into the tube = inlet, arrow away = outlet.
What happens if a fuel filter is installed backwards?
In some systems it can restrict flow, cause poor performance, or create starting issues. If you suspect it was installed incorrectly, double-check the inlet/outlet ports and refit.
Which vehicles commonly use Delphi HDF924 / 31390-H1970?
This filter is commonly used across certain Hyundai, Kia and Ssangyong applications. Always confirm via your specific vehicle details.
