C 2500 Suburban 2WD V8-6.5L DSL Turbo VIN F (1995)
Fuel: Customer Interest
Diesel Engine - Hesitation/White Smoke/Rough Idle
File In Section: 6E - Engine Fuel & Emission
Bulletin No.: 87-63-03
Date: March, 1998
Subject:
Diesel Engine Hesitation, White Smoke, Rough Idle, Lack of Power, Hard or No Start, Stall
(Check for Diesel Fuel Contamination or Poor Fuel Quality)
Models:
1994-98 Chevrolet and GMC C/K, G, P Models
with 6.5L Diesel Engine (VINs P, 5, Y, F - RPOs L49, L56, L57, L65)
Condition
Some owners of the above listed vehicles may comment that their vehicle has a rough idle, lacks power, is difficult or won't start, and may occasionally
stall. In addition, the MIL (Malfunction Indicator Lamp) or WIF (Water in Fuel lamp) may be illuminated and there may be fuel injection pump DTC's
in history.
Do not replace the fuel injection pump for this condition without first eliminating both fuel contamination and fuel quality as sources of the customer's
concern.
Cause
The diesel engine fuel system may be contaminated or fuel quality may be poor. If water, gasoline, or other contaminants are in the diesel engine fuel
supply, or if fuel quality is poor, driveability complaints or injection pump DTC's may be set. The contaminants must be removed and the fuel system
flushed prior to any repairs or diagnostics being performed. In addition, a known good supply of fuel must be used in the vehicle to obtain proper engine
performance.
Correction
If a driveability condition exists, and/or if diesel injection pump DTC's are present when performing an On Board Diagnostics (OBD) system check,
check for fuel system contamination and verify fuel quality prior to any other repairs. Do not replace the fuel injection pump without first eliminating
both fuel contamination and fuel quality as sources of the customer's concern.
Several different types of contamination can occur in diesel fuel. Fungi (mold), water, or gasoline can sometimes be found in a diesel engine fuel supply.
In addition, the customer may use an incorrect fuel grade which can cause driveability or mileage concerns.
Testing for Fuel Contamination
If fungi, water, or gasoline contamination are suspected, the technician should first inspect the fuel filter and/or fuel filter housing as described in the
Engine Controls section of the appropriate Service Manual. For example this procedure is listed in the 1998 C/K Service Manual Book 4, Engine
Controls Section, Page 6-2569.
Water or Fungi (Mold) in the Fuel System
If water or fungi (mold) are detected when inspecting the fuel filter or filter housing, go to the Cleaning Water from the Fuel System procedure listed in
the Engine Controls Section of the appropriate Service Manual. Using the 1998 C/K again as an example, go to 1998 book 4, Engine Controls, Cleaning
Water from the Fuel System on Page 6-2569. This section has the procedure for purging water from the fuel system and describes when to use a bacteria
biocide.
Gasoline in the Fuel System
Gasoline is also sometimes inadvertently mixed in with diesel fuel. This also can lead to numerous driveability conditions, unusually high fuel rates
observed on the Tech 2, fuel injection pump and nozzle damage, and if not eliminated from the fuel system, multiple trips into the dealership for
customers.
If gasoline contamination is detected when checking the fuel filter or filter housing, go to the Cleaning Gasoline from the Fuel System procedure listed in
the Engine Controls section of the appropriate vehicle line service manual. Using the 1998 C/K as an example, this procedure is found in Book 4, Engine
Controls section, Page 6-2570.
What Type of Diesel Fuel Should a Customer Use?
