Fuel Filter Observations 3500s

Lovel

Lovel

Member
Can anyone tell me if this is normal?

The car is running beautifully, but the other day while travelling along it just cut out dead. On inspection we found the fuel filter was dirty, we changed it out and it restarted, but because the fuel filter has a clear housing now the air bubbles can be seen. After a period of ildling the engine is beginning to falter and eventually the engine died again.

It looks like I'm drawing in air somehow, but perhaps this is nomal behaviour. I rebuilt the fuel pump two years ago, could it be drawing in air or perhaps through the reserve valve?

A little video to show todays runnings. http://youtu.be/59WnUvp9Ho0
 
you do get bubbles in the fuel filter - it's normal. I posted a video of this exact phenomenon a year or two back to get that answer :)

Rich
 
The different chemical components that constitute the fuel have different boiling points, and some are boiling off, as can be seen by the bubbles. The pressure reduction before the mechanical fuel pump will allow the fuel to boil off at a reduced temperature, hence the bubbles you can see rising through the fuel. When there is sufficient vapour before the pump, fuel can no longer be pumped efficiently, and the engine falters and eventually cuts out.

Winter grade fuel is far more volatile in comparison to Summer grades, so will see the car suffer from vapourisation at much lower ambient temperatures. This can happen at temps as low as 5 degrees C, and with the coolant temperature barely warm.

An electric fuel pump mounted at the rear beneath the tank will prevent this problem from occuring, as will the use of a fuel injected engine where the fuel line pressure is typically in the region of 15 times higher, thus preventing the fuel from boiling at the ambient and operating temperatures.

Ron.
 
Well I decided to investigate a bit more, I cut open the opaque AC fuel filter and found a fine thread fibreglass like compacted up. I then drained the fuel tank, removed the sender and found the braiding around the sender had disintegrated and had been sucked up through the system to the filter. The picture shows the replacement I fitted alongside, which I fitted a piece of fuel pipe too just incase the braiding broke up in future. I dismantled the reserve valve and fuel pump just in case the fibre had stuck in any of these components, but all clear, I changed the o-ring out on the valve on the engine bay bulkhead which was easier than I had anticipated, leaving the cable attached to the ferule end on the lever helps matters.
I also took readings from both the sender units for reference.
Replacement sender Empty = 245ohms - Full = 15.5ohms, reads spot on with gauge, I ran some jumper leads to allow me to sit in drivers seat and function it manually.
Original sender (not reading too well on gauge) Empty =239ohms - Full=19.9ohms.



 
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