Pressure Drop In The Diesel Filter

[Vishnugs]

Hello mates, I own a 2006 model Toyota Innova (Minivan based on Hilux platform) with 2.5 D D4D engine. The car has covered 130K KM and is in good condition. I have one problem with starting which is not reproducible at the dealership and hence haven't been able to fix it even after 3 repeated visits.

The car cranks 4-5 times before starting "if and only if" driven continuously for 250+ km / 4-5 hrs on highway. After even one long drive this problem starts and persists until I bleed the diesel filter and manually prime it. Once primed and if not driven on highway, it goes perfect for several thiusand km without this issue.

Some more observations:

- The fuel lines were cleaned recently and the tank aawell but did not solve the problem.

- The diesel filter was suspected and replaced.

- The injectors are in perfect condition

- The car starts and runs absolutely normal until it is taken for extended drive.

- There are no fault codes reported with regard to any pressure drop in the fuel lines

- Whenever this problem occurs, the priming lever will be loose, meaning there is pressure drop and can be pumped couple of times.

- Been having this problem for 20K KM, it neither seems to have got worse or better.

- Even when this problem persists, after the long crank start, the engine runs absolutely fine and power and performance is as good as new.

- The problem remains similar in both cold and warm starts after the long run.

- The vehicle had a history of clogged EGR valve and though this was fixed, once it a while the CEL comes up with this error code.

I have been having suspects on diesel filter enclosure or fuel lines or vaccum drop but haven't really been able to do a through test myself. In general it starts and runs perfectly when taken to service center.

Is diesel pump a suspect, I hope not as it would be too complex and expensive. Can you suggest all the other suspects before going to the diesel pump. Also do you recommend any fuel additives that I should try to clean?

Appreciate your support.