> Main > Diesel Index > 2nd Gen Trouble > Star Center Diagnostics

Diagnostic tips from the Star Center News

Note: See also TSB 18-06-98 - Hard starting diagnosis.

If a customer brings a Ram truck equipped with a Cummins Diesel engine in with a hard start complaint, there are a number of possible causes.

1)    Low fuel supply pressure or air getting in the fuel For basic fuel supply system diagnostics; please reference TSB 14-07-96.

2)    Loss of fuel system prime If there is a leak in the fuel return portion of the fuel system, gravity will pull the fuel down to the fuel tank. A leak will allow air to enter the system, thus displacing the fuel and siphoning the fuel out of the injection pump. A common cause of this problem is a 5/16" rubber hose, which is connected to a steel line at the rear of the injection pump. Inspect this hose for cracking, leaking, or a dry-rotted appearance. Note: This hose is very hard to see and reach. It is located behind the fuel filter.

3)    Incorrect cold starting procedure In ambient temperatures below 60F, the throttle should be at least partially depressed after engaging the starter. If the engine will not start, full throttle should be applied. Do not exceed a maximum cranking time of 30 seconds at a time. Starting at temperatures above 60F is affected by low idle speed. Lower idle speeds increase the need to depress the throttle to start the engine. Please reference the decal on the drivers side visor, and/or the appropriate Owners Manual. The procedures outlined in the 1997 Owners Manual are preferred if different from earlier manuals.

4)     Injection pump timing Injection pump timing has a minor effect on starting. Retarded (late) injection pump timing has more of an effect on starting and excessive white smoke complaints in severe cold weather (below 20F ambient temperature).

5)    Intake manifold heaters not functioning. Verify proper pre-heat cycling of the heater grids. This also will be more noticeable in severe cold weather. Please reference the appropriate service manual or heater grid diagnostics.

6)    Fuel heater The fuel heaters purpose is to prevent fuel 'gelling' or waxing which will clog the fuel filter and stop fuel flow. #2 diesel fuel typically starts to jell at about 10-20 F above zero. For a died out and/or no-start complaint in cold weather; remove the fuel filter and inspect for solid wax plugging the element. If wax is present, verify proper fuel heater operation per the appropriate service manual.


Last Update: March 7, 2008