Hello all! I am a newbie to this site and diesels....so here goes. Recently bought a 1994 Chevy 3500 flatbed 4x4 with the 6.5 TD. Initially I had some battery and alternator issues, I got those worked by replacing the alt and 2 new batteries. So I decided to change the oil, after the oil change I started the truck up fine, idle was fine. The truck died, ever since the truck had a rough start up, it will turn over and over and over then it will hit. The initial idle is rough for 1-2 seconds the idle is smooth. It seems to have a little bit of power loss since the oil change as well. Once the truck is started its fine, the dying has just stopped, once it's up to temp I can shut the truck off and it's still hard to start. I have replaced the fuel pump and pmd with no changes. Any help would be greatly appreciated.

 

Hopefully one of the Chevy guys will chime in

 

Faulty OPS?
Fuel pressure check?
Air leaks?
Glow plugs all working?
Clean grounds? Good cables and battery connections?

 

i went and got the codes checked today and this is what was found.
1. DTC 27, PEDAL POSITION 2 IN RANGE FAULT.
2. DTC 26 PEDAL POSITION 2 LOW INPUT
3. DTC 45 EGR VENT OUTPUT FAILED
4. DTC 44 EGR PULSE WIDTH OUTPUT FAILED
5. DTC 87 HIGH RATIO.
Does any of these make sense of my initial posting? What are the fixes for these codes.

 

sounds like a fuel issue to me, none of the codes make sense. make sure your lift pump is working correctly, the OPS controls it and will cause the same issues.

 

Most likely faulty OPS making the lift pump inop after the engine is running..
Anytime you replace the lift pump, proper maint and/or repair procedure MANDATES that you drop, clean and inspect the fuel tank and sender, as well as replace the fuel strainer and OPS. Its a good idea to check all the grounds also to ensure proper voltage is reaching the lift pump.
But because the diesel's lift pump is located most conveniently outside the fuel tank, most all pro's and DIYrs conveniently skip the hard part (dropping the tank) until a few more lift pumps and/or OPS quickly die only to then biotch 'bout s'itty parts and what not when in fact its just half assed mechanics who are most often to blame for not following the proper procedures. Much like jumping around troubleshooting, or as is so often the case, they skip straight to the end of the lengthy and labor intensive diagnostic process in there rush to a sure misdiagnosis...

Inop/faulty lift pump will expose air leaks that otherwise wouldnt exist. For the purpose of this discussion think of airleaks, fuel starvation, fuel restriction, contaminated fuel as one and the same. Any one of those conditions can cause the PCM to scramble and set seemingly random DTCs.
1. PCM DEFAULTS TO "BACKUP FUEL" so loss of power and limited/poor performance is par for this course.
2. Once PCM defaults, it runs a continuous diagnostic loop looking for the problem, trying to determine if its safe t continue, while simultaneously trying to maintain limited operation aka limp mode as per driver demands.
3. While performing the continuous diagnostic loop and limpin' down the road, PCM is expecting signals, pulses, and/or VARIABLE values that are present during NORMAL [Open] Mode however in "Backup Fuel," the PCM defaults to a preset FIX'd set of values that should fall outside the expected NORM will set cooresponding DTCs. If the vehicle is operated in "Backup Fuel" for any length of time, its not unusual to find a grocery list of seemingly random DTCS.
4. If the PCM feels threatened and/or suspects catastrophic engine damage is imminent, and/or the condition is severe enough the PCM can take a time out ie engine just dies.

Wheres your PMD..<sarcasm

The PCM's little known "Fuel Cutoff Mode" is a forgotten safety feature buried deep within the PCM's proprietary emissions programming so it was never made public knowledge, not even to the factory authorized service centers and techs charged with its care..

Wheres your PMD..<sarcasm

GM took steps to protect these most expensive injection pumps, if even from ourselves..
The IP only form of lubrication is the fuel, so any interrruption of the fuel supply albeit fuel contamination (microorganisms and/or fungis for ex), fuel restriction(s) (clogged filter, clogged strainer, kinked or crushed fuel line or hoses for ex), fuel starvation (weak/inop/faulty LP for ex) and/or air (system breach) that is detected ie disrupts the PCM's most important Optical Sensor [encoder] signals can be interpretted as your running out of fuel and if allowed to continue to run these expensive IPs at normal engine speed until the very last drop would most likely cause severe internal damage to the IP..


Perform "Fuel Pump Relay Circuit Diagnostics" (attached) but NOTE on '94 models, the DLC's "Fuel Pump Test Terminal" is "G," not "F" as is indicated for the '95 models.
Suggest you also go through the "Fuel Supply System Checks," specifically the lift pumps flow and pressure checks plus the supply [suction] line check.

If simply going through the motions, dont bother.. You must be thorough leaving no rock unturned and avoid skipping 'round. BEST TO FOLLOW PROPER PROCEDURES.

Good Luck.

 

Link to DB2 and DS4 GM 6.5L Turbo Diesel Engine TRAINING MANUALS
EXCELLENT 6.5 REFERENCE MATERIAL

Fuel Contamination Inspection and Cleaning
Note: This procedure checks for the presence of water and gasoline in diesel fuel that may cause injection pump and nozzle damage.
1. Remove the fuel filter element and inspect it:
• If water, gasoline or fungi/bacteria are not present, end the inspection.
• If water or fungi/bacteria are present, go to step 2.
• If gasoline is present, go to step 3.
2. Clean water from the fuel system in these steps:
A. Disconnect the batteries.
B. Drain the fuel tank.
C. Remove the fuel tank.
D. Remove the fuel pick-up/sending unit.
E. Inspect the fuel tank and fuel pick-up/sending unit for rust, fungi or bacteria:
• If no rust is present, clean the inside of the fuel tank and fuel pick-up/sending unit with hot water, then dry them with compressed air.
• If rust is present, replace the parts.
F. Disconnect the ends of the following lines:
• Lift pump suction
• Lift pump pressure
• Fuel filter outlet
• Fuel filter drain
• Fuel return
G. Inspect each of the lines and replace any rusted pipes.
H. Dry the inside of each line with low-pressure air.
I. Clean the inside of the fuel filter housing and dry it with compressed air.
J. Disconnect the electrical connector for the fuel shut-off solenoid in the injection pump.
K. Install a new fuel filter element.
L. Install the fuel pick-up/sending unit and fuel tank (add clean diesel fuel to 1/4 full).
M. Connect the following lines:
• Lift pump suction (both ends)
• Lift pump pressure (both ends)
• Fuel filter drain
• Fuel return (at injection pump)
N. Connect the fuel filter outlet and the fuel return line at the pick-up/sending unit to hoses that flow to metal containers.
O. Connect the batteries and crank the engine until clean fuel flows from the fuel filter outlet into a metal container (see Figure 7-59):
• Allow a maximum of 15 seconds cranking time, followed by 1 minute of cranking motor cooling time.
P. Connect the hose from the fuel filter outlet to the injection pump inlet.
Q. Open each injection line at its nozzle end and crank the engine until clean fuel flows from it:
• Use two wrenches when loosening the injection line fittings.
• Allow a maximum of 15 seconds cranking time, followed by 1 minute of cranking motor cooling time.
R. Tighten each injection line fitting at its nozzle:
• Use two wrenches when tightening the injection line fittings.
S. Remove the electrical connector for the fast idle/cold advance temperature switch and jumper its wiring harness terminals with an insulated wire.
T. Connect the electrical connector for the fuel shut-off solenoid in the injection pump.
U. Start and run the engine for 15 minutes while fuel flows from the fuel return line into a metal container (see Figure 7-60).
V. Stop the engine.
W. Connect the fuel return hose to the fuel pick-up/sending unit.
X. Remove the jumper wire and install the electrical connector for the fast idle/cold advance temperature
switch.
Y. Clean the engine of fuel spillage.
Z. Fill the fuel tank and add a biocide, if needed.
3. Clean gasoline from the fuel system in these steps:
A. Determine a procedure:
• If the engine runs, follow steps B, C, J and K.
• If the engine does not run, begin at step C.
B. Drain the fuel tank.
C. Fill the fuel tank.
D. Disconnect the electrical connector for the fuel shut-off solenoid in the injection pump.
E. Remove the fuel filter outlet and connect it to a hose that flows to a metal container.
F. Crank the engine until clean fuel flows from the fuel filter outlet into a metal container:
• Allow a maximum of 15 seconds cranking time, followed by 1 minute of cranking motor cooling time
G. Connect the hose from the fuel filter outlet to the injection pump inlet.
H. Remove the electrical connector for the fast idle/cold advance temperature switch and jumper its terminals with an insulated wire.
I. Connect the electrical connector for the fuel shut-off solenoid in the injection pump.
J. Start and run the engine for 15 minutes.
K. Stop the engine.
L. Remove the jumper wire and install the electrical connector for the fast idle/cold advance temperature switch.
M. Clean the engine of fuel spillage.




Fuel-Specific Gravity Check
Note: The hydrometer fuel quality tester provides a general indication of fuel quality and should not be considered scientifically accurate.
1. Drain the fuel filter housing by doing these things:
• Stop the engine.
• Place a container under the drain valve exit hose at the left front side of the engine.
• Open the drain valve.
• Start the engine and operate it at operating speed until clear fuel appears at the drain valve exit hose.
• Fill a 1 -liter (0.946-quart) container with a sample of clean fuel.
• Close the drain valve and stop the engine.
• Bring the fuel sample to 60° F (16° C).
2. Obtain a fuel quality hydrometer (special tool J 34352).
3. Fill the hydrometer with the fuel sample by doing these things:
• Squeeze the hydrometer bulb.
• Submerse the hydrometer tip into the sample.
• Release the bulb, allowing fuel to enter the glass tube until it floats the glass bulb inside the tube.
• Gently spin the hydrometer to relieve the surface tension of the fuel sample.
4. Read the scale on the glass bulb at the point where the top of the fuel sample contacts it (see Figure 7-61):
• If the top of the fuel sample is in the yellow part of the glass bulb scale (above the green part), suspect the presence of gasoline in the fuel.
• If the top of the fuel sample is in the green part of the glass bulb scale, the fuel has high quality (approximate cetane rating of 46 to 50).
• If the top of the fuel sample is in the yellow part of the glass bulb scale (below the green part), the fuel has moderate quality (approximate cetane rating of 41 to 45).
• If the top of the fuel sample is in the red part of the glass bulb scale, the fuel has low quality (approximate cetane rating of 38 to 40).



cont............

 

FUEL SUPPLY SYSTEM CHECKS
If the fuel supply system is not delivering enough fuel, or air is being drawn into the fuel injection system, driveability could be greatly effected or a "Cranks But Will Not Run" symptom could exist. If other diagnostics indicates, or if the fuel supply system is suspected of not delivering enough fuel or drawing air, it should be tested as follows:

!!Important!!!!
-- Air leaks or restrictions on the suction side of the fuel pump will seriously affect pump output.
-- Make sure there is sufficient fuel in the tank.
-- Check for leaks at ALL fuel connections from the fuel tank to the injection pump.
-- Tighten any loose connections.
-- With engine running, check all hoses and lines for flattening or kinks that would restrict fuel flow.



Lift Pump Flow Check
1. Disconnect the electrical connector for the engine shutoff solenoid at the injection pump.
2. Disconnect the pipe at the lift pump outlet fitting.
3. Install a hose at the lift pump outlet fitting and place a 1 liter/quart container at the hose to collect fuel.
4. Crank the engine and measure the amount of fuel :
-- If more than .24 ltrs (1/2 pint) in 15 seconds, refer to "Lift Pump Pressure Check" in this section.
-- If less than .24 ltrs (1/2 pint) in 15 seconds, refer to "Lift Pump Suction Line Check" in this section.



Lift Pump Suction Line Check
1. Remove the fuel tank cap and repeat the "Lift Pump Flow Check."
-- If more than .24 ltrs (1/2 pint) in 15 seconds, replace the defective fuel cap and refer to the "Lift Pump Pressure Check."
-- If less than .24 ltrs (1/2 pint) in 15 seconds, go to the next step.
2. Separate the lift pump suction line from the fuel sender.
3. Connect the suction line to a source of clean fuel, using an additional hose.
4. Repeat "Lift Pump Flow Check."
-- If flow is more than .24 ltrs (1/2 pint) in 15 seconds, remove the fuel sender and check it for restrictions.
-- If flow is less than .24 ltrs (1/2 pint) in 15 seconds, go to step 5.
5. Check lift pump suction line for restriction:
-- If restriction exist, repair it and recheck the lift pump flow.
-- If no restriction exist, replace the lift pump and recheck lift pump flow.
6. Attach the lift pump suction line to the fuel sender.



Lift Pump Pressure Test
1. Install a tee adaptor at the injection pump fuel inlet connection.
2. Connect a pressure gauge with a dial indication of 0 to 103kPa (0 to 15 psi) to the tee adaptor.
3. Run engine and measure fuel pressure.
-- If pressure is at least 3 psi or 27 kPa go to step 4.
-- If pressure is less than 3 psi or 27kPa, refer to Chart A-5 in SECTION 3 (Fuel Pump Relay Circuit Diagnosis) before replacing lift pump.
4. Remove pressure gauge and tee adaptor.
5. Connect outlet pipe at the lift pump outlet fitting.
6. Clean any fuel spillage.
7. Run the engine to check for fuel leakage.



Fuel System Air Leak Test
1. Install a transparent hose between the fuel manager/filter outlet and injection pump fuel inlet.
2. Start and idle the engine, observing the fuel for air bubbles.
-- If air bubbles are not present, stop the engine and go to step 6.
-- If air bubbles are present, stop the engine and go to step 3.
3. Check the lift pump suction line for air leakage:
-- Disconnect fuel pipe from the fuel sender and plug it.
-- Disconnect the fuel pipe from the lift pump, and install a hand held vacuum pump with gauge.
-- Apply vacuum to the fuel pipe and observe the gauge reading:
--- If vacuum does not drop, connect fuel pipe and go to step 4.
--- If vacuum drops, repair the air leak in the suction line and install the suction line pipe and hose.
4. Check the fuel sender for air leakage:
-- Remove the fuel tank.
Remove the fuel sender from the fuel tank, remove strainer and plug the bottom of the pickup tube.
-- Apply a vacuum to the upper end of the pickup tube, and observe the gauge reading.
--- If vacuum does not drop, install the fuel sender and fuel tank.
--- If vacuum drops, replace the fuel sender, install the fuel tank, connect the fuel pipe and go to step 5.
5. Start and run the engine, observing the fuel for air bubbles:
-- If air bubbles are present, stop engine and recheck steps 3 and 4.
-- If air bubbles are not present, stop the engine and go to step 6.
6. Remove the transparent hose and connect the hose of the fuel manager/filter outlet to the injection pump inlet fitting.
7. Disconnect the return hose from the injection pump.
8. Install a transparent hose between the injection pump and the hose of the return line.
9. Start and run the engine, observing the fuel for air bubbles:
NOTICE: It is OK to see a small stream of air bubbles on snap acceleration
-- If air bubbles are not present, go to step 10.
-- If air bubbles are present, replace the injection pump.
10. Stop the engine.
11. Remove the transparent hose and attach the fuel return hose at the injection pump.
12. Clean any fuel spillage.
13. Run engine and check for fuel leaks.

Following any "Fuel Supply System Check(s)" outlined aboved or otherwise, or any routine maint procedure(s) eg fuel filter change, or any repair(s) eg lift pump replacement and normal engine operation has been restored.. The last step of the process is to check for, make note of, and CLEAR DTC(s).



Hope all that helps. Good Luck..