Chevy/GMC 6.2L and 6.5L Discussion of Chevy and GMC Trucks with 6.2L and 6.5L Diesel Engines

PO1218 and slight miss

Old 01-13-2015, 11:17 PM
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Default PO1218 and slight miss

I just bought a 1996 3500HD shop truck with a 5 speed.

While driving home with it I noticed a dead spot in the throttle sometimes, accompanied by grey smoke. At idle it has a slight miss about 80% of the time.

Today I did a few needed things- all new AC delco GP's, new matched batteries.

GP circuit is working fine, charging system is good, no funky wiring.

Pump looks to have a new PMD on it, Stana-dyne.

According to limited maint records, the pump was off in the last 30k for a no start condition. sounded like a mechanic throwing owners money at a problem. seems true judging by the shiny pump and the paint seals on the PMD plug / pump mount bolts.

I tested lift pump by opening water drains on T valve and filter top while trucks running. no hesitation, So im ruling lift pump good.

IM going to do a filter tomorrow, but I dont think it needs it.

TO recap,
  1. Finally got it to spit a code, PO1218 "injection pump timing calibration circuit"
  2. Doesn't start immediately with two hot batteries and a gear reduction starter
  3. Has a slight miss at idle, and stumbles at about 1350 rpms with white/grey smoke, clears up past that. Doesnt always act up, about 15% of the time it runs pretty good.
  4. No blowby to speak of
  5. no coolant loss

The code points to the PMD resistor right? how could it go bad? I took a look at the resistor and its clean and shiny, no corrosion or funk.
Old 01-14-2015, 12:47 AM
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undiagnosed air leak, fuel restriction, fuel starvation, most likely.....
You lift pump test only confirms the circuit is working and the lift pump is working. It does not confirm that the lift pump is providing sufficient fuel volume and pressure on demand. Could be a cloggged or partially restricted fuel strainer..

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:

-- 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).

ANYTHING that disturbs the OS tranquility can set spooky IP timing related DTC's,
17, 18, 19, 34, 35, 36, and any number of APP dtcs.....

Check out this diagnostic list..
6.5L Diagnostics

This is often caused by a bad PMD (Pump Mounted Driver or Fuel Control Solenoid Driver); however it is unusual to have multiple failures of the PMD. A bad Fuel control Solenoid (part of the injection pump) can cause the same symptoms and codes. A bad EGR, EGR vent, wastegate control, and transmission solenoid are on the same quad driver circuit and can cause intermittent stalling.

If you have a no start condition, disconnect the encoder (optical) sensor and crank the engine for 15-20 seconds. If it starts then the problem is with the optical sensor.

The encoder sensor has to be able to see through the fuel inside the pump, if there is any air in the fuel it can cause trouble codes to set. Dirty fuel, SVO, no fuel supply pressure (air in system) or dyed fuel can all cause a problem with the encoder sensor "reading" the windows in the cam disk. There are 8 windows in the low resolution circuit and 512 windows in the high resolution circuit. In on minute at idle the high resolution circuit needs to read about 180,000 windows, in order to not set a code.

Note; multiple codes can set for just one fault, as if the other codes wanted to come to the party. On an OBD2 system use the Tech 2 scan tool to determine which code set first and under what condition, A DTC17 (370) can trip a DTC18 (P0251), a DTC18 can trip a 19 (P0335) and a DTC19 can trip a DTC35 (P1216) or DTC36 (P1217)
DTC17 (P0370) high resolution circuit fault can be caused by aeration in the fuel from a plugged fuel filter or low fuel supply pump pressure.
DTC18 (P0251) Pump cam reference error
DTC19 (P0335) crankshaft position reference error
DTC34 (P0216) injection timing stepper motor, watch the stepper motor and make sure it retracts when activating TDC learn.
DTC35 (P1216) fuel solenoid response time too short, less than 1.2 ms or less than .75ms on later years.
DTC36 (P1217) fuel solenoid response time too long, more that 2.5 ms, can be caused by a weak fuel control solenoid.

Bottom line.. Smallest amount of undiagnosed air can send the PCM chasing its ***, along with your cash if your not thorough... all Im sayin'
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airspeed181 (01-19-2015)
Old 01-20-2015, 12:06 PM
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I would just clear the code and see if it returns.
Old 02-12-2015, 11:01 AM
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any update or resolution?

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