Cat 3116 fuel injectors/filters

[Hathwaydc1]

Hey everyone,
My family and I are (were) headed out on the road today for our first trip in our bus and have had some mechanical trouble. Taking the bus to the doc tomorrow but want to know what y’all think the problem could be.

Having trouble with acceleration, particularly under a load (like going up a hill) and blowing black smoke. Sometimes after making it up a hill I can all of a sudden no longer accelerate.

It’s been sitting for about a year (I would let it idle every few weeks and drive it a little in a parking lot). My first guess was bad fuel, gunky filter, etc. . Changed the fuel filter and put in new diesel with additive and immediately noticed a difference. A few miles (moments, seconds?) after though it’s up to the same tricks. I let the bus idle for a few hours and would rev the engine slowly and it seemed like gunk (black smoke, engine chugging) was clearing but I’ve never gotten full acceleration back.

Could this be fuel injectors or something else?

It does shift up in gears so I don’t think it’s the transmission. And I have air acceleration so I’m wondering if there’s a slow leak or bad connection possibly...

Anything you guys can think of?

[alpine44]

Originally Posted by Hathwaydc1

Hey everyone,
My family and I are (were) headed out on the road today for our first trip in our bus and have had some mechanical trouble. Taking the bus to the doc tomorrow but want to know what y’all think the problem could be.

Having trouble with acceleration, particularly under a load (like going up a hill) and blowing black smoke. Sometimes after making it up a hill I can all of a sudden no longer accelerate.

It’s been sitting for about a year (I would let it idle every few weeks and drive it a little in a parking lot). My first guess was bad fuel, gunky filter, etc. . Changed the fuel filter and put in new diesel with additive and immediately noticed a difference. A few miles (moments, seconds?) after though it’s up to the same tricks. I let the bus idle for a few hours and would rev the engine slowly and it seemed like gunk (black smoke, engine chugging) was clearing but I’ve never gotten full acceleration back.

Could this be fuel injectors or something else?

It does shift up in gears so I don’t think it’s the transmission. And I have air acceleration so I’m wondering if there’s a slow leak or bad connection possibly...

Anything you guys can think of?

Black smokes means too much fuel for the air in the cylinders. Unless someone messed with the pump/governor/ECU it is typically caused by low boost due to leaks in the intake system past the turbo or severe restriction before the turbo.

Other possible issues mentioned here

Does your engine have mechanical unit injectors or a HEUI system?

[Hathwaydc1]

Thanks.

I’ll have to go look at the manual, but I’m assuming it’s mechanical injection.

When you say severe air restriction before the turbo, could that be the air intake filter? (I know very little about all this).

[alpine44]

Originally Posted by Hathwaydc1

Thanks.

I’ll have to go look at the manual, but I’m assuming it’s mechanical injection.

When you say severe air restriction before the turbo, could that be the air intake filter? (I know very little about all this).

Yes, either an ancient, clogged air filter or maybe a rodent nest in the filter box.

[Hathwaydc1]

Ok, more fun stuff to look at.
Thank you again.

The thing I should have also mentioned, was that the engine idles clean (for the most part). Would that still happen with clogged air filter? I guess more acceleration = more fuel and more air, so maybe?

[alpine44]

Originally Posted by Hathwaydc1

Ok, more fun stuff to look at.
Thank you again.

The thing I should have also mentioned, was that the engine idles clean (for the most part). Would that still happen with clogged air filter? I guess more acceleration = more fuel and more air, so maybe?

Lots of clean air is paramount for the health and performance of a diesel engine. Checking the intake system for leaks and/or restrictions is easy and should be part of regular inspection and preventive maintenance. That should include a close look a the exhaust piping between engine and turbo. Any leak there will also compromise the amount of fresh air the engine gets.

Yes, you get acceleration through burning more fuel, which needs more air. If that air is not there, the engine will smoke (black) instead of delivering the desired power.

When people "roll coal" they are spewing chemical energy out of the exhaust that could have been converted to acceleration by proper combustion. In this case they have crammed all the air that will fit into the cylinders and then added fuel beyond what the engine can possibly burn. A slight dark haze at full pedal will give you a little more power at the expense of higher exhaust gas temperature and lower fuel economy, but billowing clouds are just stupid.

White smoke that smells like raw diesel fuel is also unconverted chemical energy but the cause is either bad atomization from worn out pump/nozzles or low compression in one or several cylinders. It is great for keeping mosquitoes down though.

White steam that smells like antifreeze is really bad news. Coolant is getting into the cylinders, typically through the head gaskets. Fixing that is expensive and if not fixed early, even more expensive.