On occasion we see Cummins PT
style injectors coming from or being returned by a customer with split injector
cups. In some cases, the damage to the cups can often be difficult to see. The
question then comes up: "How did this happen"?
If a Cummins cup splits, there are 2 ways this can happen.
Water in the fuel:
Water in the fuel can cause a cup to split, although a more common result is
that the tip section of the cup is broken off. What happens is that a
drop of water is superheated in the fuel sac, causing extreme stress in this
area. As a result, either the fuel sac portion of the cup breaks off,
or in some cases the cup splits. We have seen cases where a large
portion of the cup actually breaks off and causes further damage to the
engine. If this is why the injector cup is split and/or damaged there
is usually evidence of water in other parts of the fuel system as well.
Incorrect overhead settings:
This is by far a more common reason for split injector cups. This
normally happens right after new/rebuilt injectors have been installed, or
right after the overhead settings on the engine have been reset.
The solution to the water in fuel
issue is easy. Clean the water out of the fuel system, replace the damaged
injectors and carry on!
The solution to the incorrect
overhead settings is not always that easy. First you need to understand
that this is not usually the fault of the injector, especially if the injector
is a "non top stop" style.
A Top Stop injector has the injector travel set within the injector, and this is
done by the injector rebuilder. Top Stop injectors are normally set in the engine using a "zero lash" setting on the "base circle"
of the camshaft injector lobe. This has become know as the "Inner Base Circle" or IBC method. The Top Stop setting would have to be set considerably short
in order to crack an injector cup. It is however, a simple matter to
measure the injector travel to see if this is why the injector cup cracked.
A Top Stop injector with an incorrect Top Stop setting is not a common scenario.
A Non Top Stop injector has the injector travel set when the injectors are
installed into the engine. There are several methods of doing this:
The first and most common is
by using the "torque" method at maximum cam lift. This involves
torqueing the injector screw to a given value with the injector
plunger at its maximum travel, and bottomed in the cup. This is known
as the "Outer Base Circle" or OBC method. The torque is is the
easiest method of setting an injector, but also the most prone to error! Suppose that the
injector was NOT at its maximum travel, due to problems with the accessory
drive pulley (this is where the marks are located), or due to installer
error. Since the maximum lift portion of the cam is a very small portion
of engine rotation, proper setting of the engine position is very important.
An in-correct torque value can also cause damage to injectors, especially if
this value is too high.
The other method is to
actually set the injector travel from the "Inner Base Circle" or IBC of the camshaft
injector lobe using the
"dial indicator" method. This is the preferred method for setting
these injectors, and this method is also less prone to error, not to mention that it
is a more
accurate method of setting an injector. When using this method, it is
very important to insure that the correct travel value is being used.
Our experience has shown that
installation issues are almost always the cause of split injector cups.
As a double check, it is always a good idea to bar the engine over several turns
(do not use the starter for this) and then double check your settings. If
the engine is very difficult to bar over on the injector down stroke, it could
be that the injectors are set too tight, and this will usually result in damaged
Complete Duramax application information is located
Dodge / Cummins 5.9 application information is located
We have the parts and
equipment to service dual spring injectors such as used by VW TDI
and Landrover. Most TDI injectors are available from
High performance TDI injectors available. Click
here for details!
here to see why setting both springs on these injectors is
Whats New @
We have added a
all our input forms due to the amount of spam we are receiving.
This helps to insure that only real people and not automated web
bots are requesting information! Many pages on this site now have a
printer icon that can be used to display a 'printer friendly'
page. This icon is normally located at the end of the page
We have available from stock most VP44 electronic pumps for Dodge & Cummins
See our online catalog for
Custom designed add on filter kits for both Dodge and Duramax applications. The factory filters on these
applications are lacking at best, and this is both the best and
easiest way to avoid costly injection system repairs.
See our online catalog for
When it comes to fuel additives, we stock only a single
Save 10% on case lots when purchasing Stanadyne Additives!