a successful learner…… loves learning…… seeks challenges…… values effort…… persists in the face of obstacles
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The design of the valve would normally facilitate that it opens when pressure in the filter builds up - as long as the differential pressure is below a certain threshold as it also seems to be some kind of differential pressure control valve.
The question is whether a malfunction of this valve could explain the starting respectively fuel supply issues?
If it would have been jammed I might have pumped against an air buffer when using the hand pump which would explain why I failed to prime the filter in the first place.
However, it could also be that there was a malfunction of the check valve of the hand priming pump itself.
Or the system sucked air via an un tight hose connection.
Fact is that by changing the fuel filter I eliminated what caused the fuel supply issues; maybe by accident by moving respectively reconnecting parts, or the cause was indeed the fuel filter.
Hence my recommendation for everyone experiencing starting issues is to assess the fuel supply first and
I had a spare fuel filter with me and 5 minutes later the new filter was in.
Tip: when changing filter over use the black plug from the new filter to replace the water sensor to contain the fuel in the filter.
With the new filter it took 20-30 strokes with the hand pump till I felt that squeezing became harder - the sign that the lines and filter is primed and the HP fuel pump won’t run try when attempting to start the engine.
Always prime the system first with the hand pump prior any start attempt after a filter change!
Yep, and the car started now without further issues.
So was it the filter respectively the check valve the cause of the starting issues?
When opening the filter the check valve looked ‘normal’, however it could be that some debris, particles from the seal etc. prevented the check valve to close or to open properly.
The ‘check valve’ is a tricky design; it comprises a stainless steel ball and a spring. It took me a while to recognise that the spring that opens the valve is a thermostatic bi-metal that facilitates that the valve stays open as long as the temperature doesn’t exceed a threshold.
Below the threshold the return fuel from the fuel pump gets partly redirected into the filter, otherwise it is pumped straight back to the tank.
I read a lot of discussions in forums where people complained about their trouble with starting the car.
Recently I made a similar experience; used to an immediately starting engine I found myself surprised when the engine didn’t start after 3 seconds - yes, since 160,000 km it never took longer than a few seconds.
It happened approx. 3 times in a row, and when it happened again and the engine didn't start after approx. 10 sec. I stopped my attempts as I didn’t want to torture the HP fuel pump risking to run it dry for too long if there would have been a fuel supply issue.
I opened the bonnet and tried the hand fuel pump - the rubber bubble close to the filter - to check wether the fuel lines were filled. The difference compared to empty lines respectively an empty fuel filter when squeezing the pump is noticeable.
Yes, I found the lines / fuel filter empty, and also squeezing the hand pump 20 - 30 times didn’t change it. I remembered from occasions when I opened fuel filters to check for debris - and because I’m nosy - that there was a kind of check valve in the filter.
I could hear some clicking noise when squeezing the hand pump, but as this was the only result of my efforts I pondered whether this check valve might have failed causing a pressure loss respectively insufficient priming of the filter.
Safety Note: use gloves and protect your eyes against spilling when working with hazardous liquids! Keep safe distance from heat, fire, electrics! Discharge filter and fuel from the filter according to laws to protect our environment!