Updated July 31, 2006
Idle Speed Too Low
An idle speed below about 650 rpm could contribute to the engine stopping at idle. If the engine easily re-starts, a simple idle speed adjustment will most likely take care of the problem.
The fuel filter should always be changed whenever any engine running problem develops. A plugged filter can cause any number of symptoms. Filters are relatively easy to change, and are one of the least expensive components in the injection system.
Air in Injection System
The fuel level in your tank should never be allowed to get too low if you're driving on anything other than level roads. Operating off-road or at odd vehicle angles could allow the fuel pick-up in the tank to momentarily suck air. After a few minutes of running, the air in the fuel line will make it's way to the injection pump and the engine will stop.
Air leaks in the fuel system have been adequately covered elsewhere in this troubleshooting guide and should be reviewed if your diesel exhibits stalling or unexplained quitting.
A faulty electrical supply or injection pump shut-off solenoid can produce unexplained stalling or quitting. If the problem is intermittent, you could rig a temporary bypass that will power the solenoid independent to the ignition switch and original wiring.
Fuel Lift & Injection Pump
When the EPA forced the petroleum industry to provide low sulfur diesel fuel for on-road applications, diesel injection system companies began to see more lubrication related injection pump failures. Many injection pumps began to behave erratically and would cause many symptoms including stalling and quitting. A low lubricity fuel can cause many of the internal injection pump components to stick and in some cases fail. The internal governor, fuel metering and advance mechanisms to name but a few. Adding a lubricity additive might help an otherwise OK pump to operate more reliably. Most major brands of fuel treatments also include a fuel lubricity enhancer. It might be a good idea to run one of these for a few tanks of fuel to see if there is an improvement.
Driving in 90 degree or warmer summer heat may contribute to engine stalling at low rpm's with worn injection pumps. In these situations, the extreme heat will open up the close tolerances in the fuel pressure portion of the injection pump and allow the fuel pressure to drop below what is required to keep the engine running at low throttle settings. You can test for this problem by mixing new motor oil with diesel fuel at a concentration approaching 10%. This will increase the fuel viscosity and will allow a worn injection pump to generate the required fuel pressures even in the extreme heat. If increasing fuel viscosity helps in these situations, a new injection pump should be installed after all other possible contributors have been ruled out.
If this problem appeared suddenly, you should consider fuel quality as a possible contributor.
1994-mid year 1996 DS4 Injection Pump
These electronic injection pumps have seen many updates and modifications since being first introduced. The optical sensor in these pumps have been a source of stalling. The pumps that incorporate the latest modifications have a blue label on the side of the pump and a green tag under one of the top cover screws.