94' 8.3 Mech. Losing power

[Wayne Tull]

After driving for several hours on rolling hills I noticed a slight loss of power that slowly continued until I was in fourth at two thousand RPM.

Temp. engine and Trans. remained normal.

Have not used exhaust brake.

Did not notice a change in exhaust color or content.

As performance continued to degrade it seemed to run better at 1500 RPM until the latter stages.

Stopped at rest stop to look things over. Did visual on turbo connections did not  identify any problems. 30 min. stop.

Started traveling again all was OK for about an hour or less and started to repeat.  Thought maybe it started when climbing grade.

Stopped at a rest stop to eat. 60 min. Stop

Started traveling again for about an hour until stopping for the day.  No grade changes no problem.

I'm thinking sticking waste gate.   What do you think?

[Dick Simonis]

Simplest thing first....I would suspect fuel filter(s) and/or air filter.

Good luck.

Dick

[Dave Atherton]

Wayne, your problem sounds like fuel problem rather than sticking wastegate on turbo.
First I would check the fuel filter, last change, possible loosen up, fuel transfer pump
and return fuel to tank. I would suggest first take loose the return line going back to fuel tank
and connect a clear plastic hose and let run into container with engine running. Run at
Idle, half speed and hold at full speed. What you are looking for is air bubbles ( return fuel
cannot have any air ). This will tell you if there is a restriction, low transfer pump pressure,
Fuel filter needs changing. Dave Atherton Retired Cat Mechanic

[Wayne Tull]

I did first think fuel filter until it would recover from being turned off for 20 min. or so, but you still feel fuel related?

[Dave Atherton]

Wayne, way you reported on post it very much is a fuel related problem. Shut down for while
Fuel settles down and will go again for short time, little or no smoke. Going back to turbo
charger in 1994 you can disconnect little hose that goes to your waste gate and run down the road,
( test for power and wastegate ). What your doing your wastegate is now full closed and you
Will provide you max power because wastegate  will not open and dump turbo exhaust ( note:
Your engine is different than the electronic engines and you have a governor that will prevent
Over RPM. This should put back into the fuel related problem. Dave Atherton Retired Cat Mechanic

[Wayne Tull]

Not at home, so going with replacing primary fuel filter and drain water separator see where that gets me.  Wasn't stuck on the waste gate, just didn't understand interment fuel filter.  Thank you Dave, appreciate your help.

[Gerald Farris]

Wayne,
There is a much higher chance that the secondary fuel filter is your problem vs the primary filter.

Gerald

[Wayne Tull]

Replacing the Primary fuel filter corrected the power loss problem.   When I emptied out the primary filter there was a fair amount of junk that came out with the fuel.  Looks like my fuel tank is pretty dirty and will be doing this again.  Will also change the Secondary filter as well.

Again thanks for getting me on the right track.

[Dave Atherton]

Wayne, if the secondary fuel filter does not correct problem than you have low fuel pressure
or fuel metering orfice with dirt. You might have to go like I posted and clear plastic hose on
return fuel line and run into container and check for air bubbles at engine different rpms.
If air bubbles present let Dave know and will help you at that point with your 8.3
Dave Atherton Retired Mechanic or go to Ask Dave on BAC technical section on Forum.

[Gerald Farris]

Wayne,
If you are getting large amounts of a dark material in your primary filter, you probably have a microbial growth (diesel algae) in your fuel tank. If so, I would use a biocide fuel additive to kill it. Several filter changes may be required after treatment before the clogging stops.

If you have any water in your fuel tank from contaminated fuel or storing the coach in a humid area without a full tank of fuel, the microbes grow on the layer between the fuel and water. So if the microbe problem gets too bad to control with a biocide, you may need to completely drain the tank, or use a fuel polishing service if you are in a area where it is available like a large maritime installation.   

Gerald