Archive for June, 2009

Fuel Filter

June 30th, 2009

Yeeks, I’m pretty sure the fuel filter hasn’t been replaced in 30 years.    It had a Volvo part # on it…though if the firefighters in Kungsbakka did replace it it would have likely been a Volvo part as well.     I performed an autopsy…




Finished Intake system

June 27th, 2009

Trog’s air intake and filtration system is a somewhat flawed design.    The plastic air filter box sits right above the carburetors.    After Trog is turned off, there is a little bit of gas remaining in the carbs.   This gas evaporates and soaks the air filter.    In the event of a fire or backfire this is ready fuel (to quickly light the plastic air filter box).     When the Swedish military renovated their fleet of TGBs they added a new metal air filter box further upstream in the intake system and just used the old air filter box as a manifold to feed the carbs.

I have been wanting to make the same mod to Trog, but have had trouble finding a suitable air filter box.   I finally found one off a mid 90s Jeep Wrangler with a 6 cylinder engine, same as Trog, so it should be sized appropriately.    Plus, this means that air filters are easy to come by.   Most auto parts stores don’t stock the correct filter for the old filterbox.


The air path goes thru the new filter box behind the passenger and up thru a stainless tube to an intake box.   A vent plate finishes the outside.   I believe the vents will alllow enough air in (their combined area is almost the same as the diameter of the intake hose).    If not, I will replace the vent plate with something with larger orifices.


The old route was thru a bit of flexible tubing with an intake just in front of the radiator.   This took up some room in the engine tunnel and I found it somewhat untidy looking, as well as possibly prone to water intake.


Replaced Vacuum system hoses

June 27th, 2009

The 30 year old vacuum hoses were showing some significant signs of deterioration so I decided to pull them and replace with new.     Trog uses a vacuum based system for locking the differentials, engaging front wheel drive and the power take off (PTO).   It’s a bit of a mess with hoses having to run up into the front cabin to be switched via manual valves.    Volvo was a bit sloppy with this system.  Where a nice neat manifold would minimize mess, they went with a series of T’s.

The front wheel drive actuator is controlled by a 12v solenoid.

FWD is engaged when any of the following are true:

  • FWD switch enabled in the main cabin
  • Gearbox put in low
  • Hard braking (there is a pressure sensor on the brake line)


Most of the old hoses.    They were replaced by Gates fuel line.   The fuel line is rated for vacuum service and won’t degrade quickly with oils or gasoline vapors that will creep into the vacuum system.   The vacuum system is “powered” by a port on the intake manifold of the engine.    After then engine is turned off, residual fuel in the carburators evaporates and makes it’s way into the vacuum system (not much, but over time, enough).     That gas can also degrade the membranes of the vacuum actuators (and brake servos), so I intend to put a charcoal filter  inline with the intake manifold hose.

It took almost 25′ of 3/8″ Gates 27004 hose and 25′ of 1/4″ Gates 27002 hose to do the system.

I still need to redo the hosing for the vents on the various gearboxes.    To prevent stuff from getting into the gearbox vents, Volvo has run a network of 1/8″ish hose connecting them.   The output uncermoniously dumps into an interior panel stiffener box tube.

In the future, I want to replace most of this tangle of hoses, at least the ones that lead to the manual switches in the main cabin, with  solenoid activated valves

I believe Skinner 3000 series valves should work, specifically 3133BJA7LNC4 RR T1J1 C1  12 VDC


The common manifold eliminates a lot of redundant hose.   It is a little unclear whether the valve seating on this are appropriate for vacuum on the common side.   Also, I’m not sure if the Cv of the valves are sufficient to move enough air to engage the actuators in a short enough amount of time.

Trog, Uncategorized

Flipout Flaps Finally Finished

June 8th, 2009

With gas springs, gaskets, latching locks and bamboo inner faces installed.