MAN TGA fuel filter replacment

[renesis]

Hi, I have a MAN TGA running on D2066 Bosch common-rail fuel system.

I have just replaced the fuel filter, and it is difficult to start the truck on the first crank. The truck will start on the 2nd crank though. Once the truck is started, there is no problem with the fuel system, ie, under all conditions there is sufficient fuel pressure.

I have checked the following
1) Fuel lines from Fuel Tank to Primer Pump to Gear Pump to Fuel Filter Housing and to Hi-Pressure Pump. No leaks discovered whatsoever.
2) If starting is hard, a few pushes of the Primer Pump will generate enough fuel pressure to allow starting of the truck.
3) When I remove the fuel filter cover, there is air in the filter housing. I have bled the fuel system as indicated in the service manual, but why is there still air in the fuel filter housing?

Prior to replacement of the fuel filter, the truck starts on the 1st crank.

In the Mercedes Actros, the fuel filter housing is of a similar design, yet I have never encountered such problems.

Any advice will be greatly appreciate
Thanks and best regards

[cactikid]

wrong filter or seal leaking,if it only happened after filter was changed it points to that area.

[renesis]

Hi Thanks for your information.
I have tried using back the original fuel filter and seal as well, same case.
Even tried using 3 new pc of the fuel filter and seal, but to no avail.

[MITROSCAT]

my friend.try to see if there's a return valve for diesel and it doesn't hold presser.maybe there's a broken spring.

[renesis]

Thank you for your reply.
i have dismantled the entire fuel filter housing to check and clean it up, but could not find any return check valve which can maintain the pressure.
Even cleaning up the primer hand pump does not help.
The fuel return line from the filter housing to the fuel tank has a built in check valve but that is working fine.

[xboxin]

the friend who put this post is absolutely right
filter seal leaking or wrong, only if it Happened filter was changed after it That points to the area.

[renesis]

Yes it could just be a fuel filter seal. But i have tried to use the original seal and result is the same.
I will try again.

Is there a special bleeding tool to use?

[cactikid]

if the primer hand pump is on top of filter i have known a few of these to go as in over a period of time air gets in and does not start on first but does on second crank,new filter housing needed.

[Poptest]

Is it possible that the low pressure lines to the CR pump have been put back the wrong way? ...... damaged or missing copper gaskets on the fuel fittings to the filter and/or pump?

[renesis]

if the primer hand pump is on top of filter i have known a few of these to go as in over a period of time air gets in and does not start on first but does on second crank,new filter housing needed.

On a few of my other trucks, ie, Actros, the fuel water separator has a hand pump ontop of the filter, and if air goes in over a period of time,yes the housing needs to be replaced.
Especially for Racor type water separators...

but for this MAN TGA..... No water separator is installed.

[renesis]

Is it possible that the low pressure lines to the CR pump have been put back the wrong way? ...... damaged or missing copper gaskets on the fuel fittings to the filter and/or pump?

Thanks for your reply. Thr low pressure lines to the CR gear pump is straight from the primer pump. The Fuel is then fed to the filter housing which has a pressure sensor and a heating element. Fuel is then fed to the CR pump (hi-pressure) side then to the fuel rail.

Am i missing out something?

[MITROSCAT]

take a 20 litre can and start directly to the fuel rail.or see your Racor type if u have to put washer with seals or bronze washers to the racor

[Poptest]

Thanks for your reply. Thr low pressure lines to the CR gear pump is straight from the primer pump. The Fuel is then fed to the filter housing which has a pressure sensor and a heating element. Fuel is then fed to the CR pump (hi-pressure) side then to the fuel rail.

Am i missing out something?

You have a suction leak. Primer pump could be faulty. Put a temporary transparent hose between priming pump and CR gear pump to check for presence of air bubbles.

[dimitar22]

Thanks for your reply. Thr low pressure lines to the CR gear pump is straight from the primer pump. The Fuel is then fed to the filter housing which has a pressure sensor and a heating element. Fuel is then fed to the CR pump (hi-pressure) side then to the fuel rail.

Am i missing out something?


This is the most common problem when replacing fuel filter on MAN tga common rail.

I have this kind of problem verry offten.

In service literature you will find no breather or kloged breather holle. I dont know what this means or where to find that holle.

Try to blead out the fuel system by priming on the hand pump with opened return hose from high presure pump until you see clean fuel with no air in it.

If this does not work take the truck for 1-2 hour drive, leave the truck over night the next morning starts without problem.

Tested by me few times.

[renesis]

I have since solved this problem. There is no suction leak.

As what Dimitar has said, there is no breathe hole, nor bleeding nipple available.
Using the hand primer pump will only purge the air outside of the filter, but the air in the fuel filter does not escape.

Tilt the entire housing sideways, and bleed the air through the fuel pressure sensor while pumping in more fuel from the fuel outlet connector.
Then turn the housing over and bleed the air through the water drain plug while pumping in more fuel from the fuel inlet connector.

This removes most of the air in the housing already, and vehicle starts like a spark.
Thanks to all who contributed.

[Poptest]

Thank you too renesis and dimitar. We all learned from this problem.