1990 Volvo 760 Turbo: Black smoke when Turbo kicks in

  • Thread starter Thread starter mot12345
  • Start date Start date
M

mot12345

My 1990 Volvo 760 Turbo (Intercooler) has weak accelleration and
billows black smoke when the Turbo kicks in, especially under load up a
steep hill (but also when accellerating by putting the gas pedal down
to the floor on the freeway).

Any ideas on what might be wrong, and how to fix it?

Thanks,
Wolfgang
Santa Barbara, CA
 
My 1990 Volvo 760 Turbo (Intercooler) has weak accelleration and
billows black smoke when the Turbo kicks in, especially under load up a
steep hill (but also when accellerating by putting the gas pedal down
to the floor on the freeway).

Any ideas on what might be wrong, and how to fix it?
Click to expand...

Sounds like you're leaking boost and the injection is injecting too much
fuel for the air that's actually making it into the engine. Check all the
rubber hoses between the turbo and the engine, particularly the couplers
between the metal pipes and the intercooler. Pull them off and poke from
inside with your fingers, I've seen them rip a flap that only opens up under
boost.
 
yep...i agree w/james...porb a broken or cracked turbo hose...check the
big ones 1st...have a friend sit in the car and "punch it" and let
off...see if you see a hose acting up....

ucsb...nice school....great location...how are things in sb county? i
spent 50% of my youth in that area...what are you studying?
 
My 1990 Volvo 760 Turbo (Intercooler) has weak accelleration and
billows black smoke when the Turbo kicks in, especially under load up a
steep hill (but also when accellerating by putting the gas pedal down
to the floor on the freeway).

Any ideas on what might be wrong, and how to fix it?

Thanks,
Wolfgang
Santa Barbara, CA
Click to expand...
I doubt it is a torn turbo hose - those give symptoms of being normal until
a moderate amount of throttle is called for, then the turbo starts spinning
(even when the throttle keeps the boost from getting to the manifold) and
the mixture goes *way* rich (as the others have noted) and the power drops
like a stone... but it doesn't start running right until the engine has
idled down and the turbo has spun down. It produces an odd "fold-back"
throttle feel - just backing off a bit doesn't help; you have to take your
foot off completely for a few seconds to go again. Going up hills is very
difficult.

Our '85 765T did the black smoke and poor power under boost for a couple
years before I stumbled on the problem. The cylinder head temp sensor under
the manifold branch between the #3 and #4 cylinder - not visible without a
mirror - was making intermittent contact. (It started a couple months after
I changed the engine harness, but I didn't make the connection between the
two events.) Try reseating the connector. It has a press-to-release wire
spring latch and can be reached by sticking your arm way back past the
throttle body. It isn't terribly hard to work with once you get your fingers
on it. Ours occasionally has to be reseated still, but it has been over a
year since the last time.

Mike
 
Michael said:
I doubt it is a torn turbo hose - those give symptoms of being normal until
a moderate amount of throttle is called for, then the turbo starts spinning
(even when the throttle keeps the boost from getting to the manifold) and
the mixture goes *way* rich (as the others have noted) and the power drops
like a stone... but it doesn't start running right until the engine has
idled down and the turbo has spun down. It produces an odd "fold-back"
throttle feel - just backing off a bit doesn't help; you have to take your
foot off completely for a few seconds to go again. Going up hills is very
difficult.

Our '85 765T did the black smoke and poor power under boost for a couple
years before I stumbled on the problem. The cylinder head temp sensor under
the manifold branch between the #3 and #4 cylinder - not visible without a
mirror - was making intermittent contact. (It started a couple months after
I changed the engine harness, but I didn't make the connection between the
two events.) Try reseating the connector. It has a press-to-release wire
spring latch and can be reached by sticking your arm way back past the
throttle body. It isn't terribly hard to work with once you get your fingers
on it. Ours occasionally has to be reseated still, but it has been over a
year since the last time.

Mike
Click to expand...

Just how much black smoke and how poorly the engine runs under boost
depends on the size of the hole. My neighbour's 760 turbo had a 1/2"
rip in one of the short hoses at the intercooler, it still made some
power under boost, but also made a huge amount of black smoke. The rip
was on the under side, where oil pooled and was very hard to see.

--
Mike F.
Thornhill (near Toronto), Ont.

Replace tt with t (twice!) and remove parentheses to email me directly.
(But I check the newsgroup more often than this email address.)
 
those turbo hoses cost an arm and a leg....

(if you need to replace them)....
 
~^ beancounter ~^ said:
those turbo hoses cost an arm and a leg....

(if you need to replace them)....
Click to expand...

The standard straight ones aren't too bad, they're easy to get aftermarket.
If you need one of the custom formed ones though... ouch!
 
[email protected] said:
My 1990 Volvo 760 Turbo (Intercooler) has weak accelleration and
billows black smoke when the Turbo kicks in, especially under load up a
steep hill (but also when accellerating by putting the gas pedal down
to the floor on the freeway).

Any ideas on what might be wrong, and how to fix it?

Thanks,
Wolfgang
Santa Barbara, CA
Click to expand...
Pull the hose off of the inlet side of turbo. Feel for looseness of impeller shaft side to side. If it is, the oil seal in turbo is worn and ck oil feed to turbo. Pipe may be clogged not allowing seal to be lubricated
 
You must log in or register to reply here.
Back
Top