How do you know when you have a bad injector and how do you figure
out which one it is?
Gordon

On Sat, 25 Apr 2009 07:52:32 -0700, Gordon wrote:

How do you know when you have a bad injector and how do you figure
out which one it is?
Gordon

A bad injector will usually cause a miss, or rough running. A field
check is to run the engine at idle and loosen one injector pipe
connection at a time. Loosening the connection on a good injector will
cause the engine to miss or run rough. Loosening the connection on a
bad injector will change nothing.

However.... Injectors can be set at the wrong opening pressure or have
a defective spray pattern that may not show up using the above check
and can only be found by removing the injectors and having them tested
at a shop that specializes in repairing fuel system components.


Cheers,

Bruce in Bangkok
(bruceinbangkokatgmaildotcom)

"Gordon" wrote in message
m...
How do you know when you have a bad injector and how do you figure out
which one it is?
Gordon


Remove the spark plug wire one cylinder at a time. The spark plug wire
removed on the cylinder with the bad injector will not cause an additional
miss.

Wilbur Hubbard

Gordon wrote in
m:

How do you know when you have a bad injector and how do you figure
out which one it is?
Gordon


YouTube is your friend!
http://www.youtube.com/results?
search_type=&search_query=diesel+injector+testing& aq=5&oq=diesel+injec

How NOT to test injectors:
http://www.youtube.com/watch?v=_gUB81VfK40

Bad spray pattern from crap in the injector will make one cylinder knock
really loud. There's ALWAYS one injector that knocks louder than the
rest and that's just "normal". Same thing is true if the metering
circuit doesn't close right, bad springs, etc. That cylinder pulls lots
harder than the others from the supercharge of fuel.

A clogged injector simply has no fuel spray so the cylinder either never
fires at all and the engine goes on "humping" past the dead cylinder's
compression stroke never having a power stroke or the engine runs like
crap because that cylinder isn't pulling its share of the load,
virtually putting the engine in idle when it's the bad cylinder's turn
to fire.

Testing is pretty easy. All this runs on very high pressure, but very
tiny amounts of fuel. With the engine running under load, underway,
simply take an appropriately sized wrench and crack open the fuel
supply fitting to each injector, one at a time, while listening to the
results as you add yet another cylinder that isn't firing. When you
come to the one that's not firing or is overfiring, when you crack its
fuel line the engine runs the same....or that awful knocking from too
much fuel stops. When you open the good injectors, adding to the
problem, the engine runs much worse, now that it has two cylinders dead
instead of just one.....

When you think you've got it, shut her down and swap that injector with
a spare I just KNOW you have in your spares locker, right? You DO have
a calibrated torque wrench and know how to use it so you can set the
torque on the nuts correctly, right? No? Get one. Harbor Freight's
cheap Chinese torque wrenches are amazingly close to correct....closer
than the Snap-On ones we tested for lots more money.

If that fixes it, you found it. If nothing changes, you'll know we have
injector pump problems you can't fix at sea.

BTW, Harbor Freight also has fuel injector testers, the kind you attach
to the injector then pump by hand so you can see the spray pattern of
fuel coming out of them....very handy for testing injectors.

What make/model of engine are we testing, anyways?? Doxfords wouldn't
use this kind of test:
http://www.youtube.com/results?searc...y=doxford&aq=f



--
-----
Larry
You can tell there's very intelligent life in the Universe
because none of them have ever tried to contact us.....

Gordon wrote in
m:

How do you know when you have a bad injector and how do you figure
out which one it is?
Gordon


Here's a video of about the same tester I use:
http://www.youtube.com/watch?v=6NSydOqjIY8&NR=1

It's not rocket science....just make sure all the air bubbles are out of
it.

--
-----
Larry
You can tell there's very intelligent life in the Universe
because none of them have ever tried to contact us.....

"Wilbur Hubbard" wrote in
anews.com:

"Gordon" wrote in message
m...
How do you know when you have a bad injector and how do you figure
out
which one it is?
Gordon


Remove the spark plug wire one cylinder at a time. The spark plug wire
removed on the cylinder with the bad injector will not cause an
additional miss.

Wilbur Hubbard




Wilbur, or whatever name you're using today.....How many diesel engines
have you ever actually touched?



--
-----
Larry
You can tell there's very intelligent life in the Universe
because none of them have ever tried to contact us.....

I picked up a used W40 for parts. It was in a Tartan 37 and when he
saw a light sheen of oil on the cooling fresh water, he decided to re
engine. No smoke, no water in the oil, smooth running. Installation of a
new Yanmar only cost him 18k!
The W40 came with a new panel, spare alternator, upper end gasket
kit, impellers, oil filters and a good spare injector. When I saw the
spare injector, I realized I didn't know how to test to replace the bad one.
What make/model of engine are we testing, anyways?? Doxfords wouldn't
use this kind of test:
http://www.youtube.com/results?searc...y=doxford&aq=f

"Larry" wrote in message
...
"Wilbur Hubbard" wrote in
anews.com:

"Gordon" wrote in message
m...
How do you know when you have a bad injector and how do you figure
out
which one it is?
Gordon


Remove the spark plug wire one cylinder at a time. The spark plug wire
removed on the cylinder with the bad injector will not cause an
additional miss.

Wilbur Hubbard




Wilbur, or whatever name you're using today.....How many diesel engines
have you ever actually touched?

http://www.indianindustry.com/engineparts/2815.html

Diesel engine spark plugs! Gotcha, Larry.

Wilbur Hubbard

On Sat, 25 Apr 2009 15:30:21 -0700, Gordon wrote:

I picked up a used W40 for parts. It was in a Tartan 37 and when he
saw a light sheen of oil on the cooling fresh water, he decided to re
engine. No smoke, no water in the oil, smooth running. Installation of a
new Yanmar only cost him 18k!
The W40 came with a new panel, spare alternator, upper end gasket
kit, impellers, oil filters and a good spare injector. When I saw the
spare injector, I realized I didn't know how to test to replace the bad one.
What make/model of engine are we testing, anyways?? Doxfords wouldn't
use this kind of test:
http://www.youtube.com/results?searc...y=doxford&aq=f


If you are installing a used engine, and assuming it has a
conventional Bosh or CAV type fuel system, I would suggest that you
take off the injector pump and all the injectors and have them tested
and calibrated. My experience is that every time I have done this the
shop made some repairs to either the pump or the injectors - in other
words there was something wrong that wasn't noticeable by listening
to the engine run.


Cheers,

Bruce in Bangkok
(bruceinbangkokatgmaildotcom)

"Bruce in Bangkok" wrote:

If you are installing a used engine, and assuming it has a
conventional Bosh or CAV type fuel system, I would suggest that you
take off the injector pump and all the injectors and have them
tested
and calibrated. My experience is that every time I have done this
the
shop made some repairs to either the pump or the injectors - in
other
words there was something wrong that wasn't noticeable by listening
to the engine run.

SFWIW, my next door neighbor's SIL operated a diesel injector/pump
repair shop.

At least every 2nd year, would make a visit with my Yanmar parts in
hand at the start of the season.

They usually found something.

BTW, Yanmar uses a totally unique system.

Lew