The 6.5L No-Start Guide
Where to come when your 6.5L Diesel will not start!
- Remember -
"The PMD / FSD (Pump mounted driver) is by far the #1 cause of 6.5L no-starts (at least 90%). If your truck experienced random stalling like someone shut the key off before ultimately refusing to start again, the PMD is very likely the issue. Typically the random stalls caused by the PMD will become more frequent as the failure worsens. In the beginning stages of failure, the truck can be immediately re-stared while the vehicle is still rolling. As the failure progresses, you will have to wait longer and longer for the vehicle to re-start. To read more about PMD failure and the reccomended cure, our BD Relocation Heat Sync Kit, follow the links below: For those with more in-depth issues, proceed to follow through the no-start guide one step at a time.
This guide is intended to be used by those with basic mechanical skills and common sense. If you lack either, then please leave the process to those so equipped. Always wear safety glasses, and keep clear of rotating components when cranking the engine. Never stand in front of the vehicle while it is being cranked, and never stand in line with the fan. By working on a vehicle, you put yourself in the position of possibly receiving an injury. We cannot list all the possibilities here. The only person who can prevent injuries is you and the method by which this is accomplished is by anticipating and preventing hazardous situations.
- Visual inspection solves a large percentage of problems that would take much longer to diagnose by conventional techniques.
- Spend a minimum 10 minutes in the engine compartment going over everything. Do not rush. Pay very close attention to wiring connectors and grounds.
- There are a number of wires grounded at intake manifold bolts near the rear of the intake. Be sure that these are clean, tight and not broken.
- There is a large round 15-way connector near the back of the intake manifold which joins the injection harness (which contains all the wires to the injection pump) to the main engine harness. Open this connector and ensure that the terminals are in good condition and not corroded as is common in northern trucks. If corrosion is present clean the terminals with a good electrical contact cleaner. Do not spread the terminals by inserting objects into them.
- Pay special attention to any wiring looms where they pass over other objects such as A/C lines. Pick them up and be sure that no wires have rubbed through.
- This no-start guide assumes that the starter will crank the engine over rapidly enough for the engine to start. Diesels rely on the heat of compression to ignite the fuel. If the engine cranks slowly, insufficient heat will be generated and the engine will not start. If everything else is in good condition, a slow cranking 6.5L diesel will start, but if there are other minor issues, a slow crank may compound to create a no-start. Fixing cranking speed issues is beyond the scope of this article, but common suspects are battery connections (very common - start here), poor batteries, and starters.
- This guide also assumes good engine mechanical condition. Most mechanical failures would be accompanied by noise at time of failure and also an uneven sound during cranking. Low compression caused by wear would develop very slowly over time causing successively harder starting. If in doubt about engine mechanical condition perform an engine compression test. Engines with under 350 PSI of compression per cylinder will have difficulty starting. This test will only be necessary in a minority of cases. To run an engine must also breathe. In rare cases the intake system or exhaust system can become completely plugged and the engine will not start. Catalytic converters can plug, neighbor kids can stick objects in the tailpipe, and objects can get sucked into air cleaner ducts! On engines with EGR valves, removing the EGR valve will create enough of an exhaust opening for the engine to run if the catalytic converter is plugged.
- Is there fuel in the tank? I don't care what the fuel gauge says, and forget about banging on the tank. If you don't KNOW there is plenty of fuel in the tank, go buy some more and put it in. In fact, do it anyway! You may save face later!
- What kind of fuel is in the tank? Gasoline will not start a cold 6.5L diesel - the cetane of the fuel is too low. Take a fuel sample and examine it - smell it - is it good diesel fuel? In doubt? Provide the engine an alternate fuel supply or drain the tank and re-fill!
- Do the glow plugs work? The glow plugs must all be receiving power AND not be burned out. Even in warm weather, 6.5L engines need good glow plugs to start well. If in doubt, plug the block heater in for at least 6 hours - this is a partial cover-up for a few bad glow plugs or slightly slow cranking.
- Is fuel getting to the injection pump? This is easy to check. Have a helper crank the engine. While cranking, open the "T" handle valve that drains water from the fuel filter. This valve is located near the oil filler tube and has a hose running toward the ground. Pull the hose up and place the open end in a jar. While the truck is cranking, there should be a generous supply of fuel coming from the hose. If not, the most likely cause is a bad lift pump which is located inside the frame rail underneath the driver's seat area.. Check for voltage to the lift pump with a test light (again while cranking). If voltage is present, replace the pump. If voltage is not present you will need to trace the circuit. If the pump is running, but not delivering fuel, check the following items:
- Plugged fuel filter
- Gelled fuel if weather is cold
- Damaged or crushed fuel lines
- Leaks on the suction side of the pump between the pump and tank (on northern trucks the fuel sending unit often rusts out on top of the tank creating leaks)
- Plugged pickup sock in the tank or damaged pickup unit in the tank.
- If the fuel filter unit has recently been removed, it is possible to connect the lines improperly at the filter.
- Is the fuel return plugged? The injection pump cannot operate with a plugged return system. The injection pump return line is located on the top of the pump and is angled sharply toward the front of the truck. Remove the return line, place a short piece of hose on the fitting on the pump and direct it into a container. Re-attempt to start the truck.
- Turn the ignition on and note if the service engine soon (or check engine) light comes on. If it does, this is a good sign that the computer is receiving power and is functional. If it does not, then you must proceed to check power and ground at the computer. This is beyond the scope of this article. If you have a scan tool, plug it in at this point and determine if you can retrieve data from the computer. This is further confirmation that the computer is in functional condition. If you do not have a scanner you may still proceed with the following tests as presence of the check engine light is sufficient evidence of a live computer and the following tests will provide further verification.
- Disconnect the optical sensor connector from the injection pump. This is the large square black connector directly on top of the injection pump. Again try to start the truck. If the truck starts and runs, this means that the optical sensor is outputting faulty data preventing the truck from starting. By unplugging the sensor, you put the system into backup mode and the computer relies on information from the crankshaft position sensor. In the very unusual case that both sensors were bad, the truck would not start with the optical sensor disconnected.
- The engine shutoff solenoid is a round silver device about an inch in diameter and several inches high that stands at the driver's side front corner of the injection pump. Unplug the solenoid and connect a test light across the two wires in the connector coming from the vehicle (NOT the side coming from the solenoid). Have someone crank the engine. If the test light lights proceed to the next step. If it does not light, then you will need to obtain a wiring diagram and trace the circuit.
- You can also unscrew the solenoid from the injection pump and apply 12 volts to it to verify that the plunger retracts. Failure of this part is rare, however.
- At this point, we will verify if the engine is receiving fuel. Loosen several injection lines at the injectors (19mm or 3/4 inch open end wrench). Keep your hands and eyes back and have someone crank the engine and watch for fuel to squirt from the open lines. There will not be a large quantity of fuel, but there should be a definite squirt. A slight dribble is not acceptable. Tighten the lines and proceed with diagnosis.
- If there is a potential that the truck has been run out of fuel, has been sitting for a very long time, or has had the fuel system open, it may be necessary to bleed the fuel system. If none of these is true of your truck, skip the following procedure.
- First, open the fuel filter water drain valve described earlier and crank the engine until fuel is observed flowing freely from the drain line. Secondly, loosen the injection lines at all 8 injectors. Disable the glow plugs by removing the glow plug wires, disconnecting the relay, or removing the glow plug fuse. Connect a battery charger to the vehicle and place it on a medium to high setting (not "jump" setting). Have someone crank the engine for an extended period - as long as you feel comfortable doing so without doing starter damage - usually 15 to 20 seconds. Wait 10 minutes for the starter to cool and do it again. After repeating the process several times, fuel should begin squirting from some injection lines. Tighten up those that squirt, and repeat until all lines are delivering fuel. Then start the truck after re-enabling the glow plugs.
- Disconnect the PMD (black module on the driver's side of the injection pump about the size of a pack of cards.) Inspect the terminals in the connector for damage. Connect a digital voltmeter set to the DC voltage scale with the black lead connected to a good clean engine ground and the red lead touching the terminal connected to the green wire in the PMD connector. Have your helper crank the engine and record voltage observed. It should be roughly 1.2 volts.
- If this voltage is present, it means that the computer is commanding the PMD and injection pump to deliver fuel - proceed with diagnostics. If the voltage is not present, you have either a wiring or computer issue - obtain a wiring diagram and diagnose.
- The next steps check power and ground at the PMD.
- First, connect your test light to a good clean engine ground. Touch the probe of the test light to the pink wire terminal in the PMD connector. With the ignition on, the light should light. If not, diagnose the circuit.
- Next, connect the CLIP of your test light to one of the positive battery terminals making sure it has a good connection. Touch the probe of the test light to the black wire in position C of the PMD connector (looking closely at one side of the PMD connector you will note that each wire position is lettered). The light should light. If not, there is a wiring or computer problem. Obtain a wiring diagram and diagnose.
- If you started at the beginning, and have reached this point with all tests passing there are only two possibilities left. These are the injection pump itself and the PMD. If you plan to replace the complete injection pump / PMD assembly, you may stop diagnosing after performing the next step. To determine if the issue lies with the PMD itself continue to the end.
- On very rare occassions we find that the injection pump is not being driven by the engine. This can be caused by a timing chain issue, or more commonly be a sheared key on one of several gears (usually due to faulty service practices). To verify that the injection pump is turning, remove the oil filler tube. This will allow you to view the front of the injection pump drive gear. Staying clear of all rotating components, have someone crank the engine and observe gear rotation.
- Those wishing to see if the PMD is outputting control signals to the injection pump, perform the following:
- You will need to access the red wire in position "B" as well as the black wire in position "F" of the PMD connector with the PMD plugged back in. This can be challenging with the intake manifold installed. If the intake manifold is off, you can access the same wires much easier at the back of the injection pump by pulling off the large rubber boot at the very rear of the injection pump. If the intake is still installed, read carefully to understand how to connect to the wire with the PMD plugged in. (This is also a good time to note that an alternative to this test method is to substitute a known good PMD. If you have the means, consider buying one if you plan on owning the truck for many years - especially if you travel with it. Every 6.5L owner should have a spare PMD - it is not a matter of IF the original PMD will fail, it is a matter of when, and you will thank yourself a million times when the extra PMD keeps you from being stranded on a dark, cold, and rainy night.) Back to connecting to the wires. Straighten out a small paper clip and cut it in half. Push one of the pieces of paper clip into the BACK of the PMD connector right alongside each wire (Postions B and F). Push the piece of paper clip gently between the rubber seal and the wire. Wiggle the paper clip and push gently until about an inch of the paper clip is no longer visible. The paper clip is now touching the back of the bare metal terminal connected to the wire. Do this for both wires.Use your ohmmeter on the continuity test setting to ensure that each paper clip is indeed making contact with the respective wire. If you have wire piercing probes they can also be used for a more reliable connection (be sure to repair the wires later). You can also strip sections of the wire and attach short sections of wire as "test leads."
- Now, plug the PMD connection back in. (Yes, it is challenging, but be patient and keep it square and you will get it.) Connect your volt meter to the two wires and set the meter to measure AC volts. Be sure not to let the paper clips short against engine ground or the PMD will be destroyed!
- Crank the engine and observe the voltage. You should observe around 0.8 to 1.0 AC volts - this will vary slightly with cranking speed. If this test fails, but steps 14 and 15 passed, you most likely have a bad PMD. If this test passes, and you have followed this procedure from the beginning, then you most likely need an injection pump.
- For those who came here to test a PMD only: If you have the input signals to the PMD described in steps 14 and 15, and the PMD outputs correctly in step 18, then the PMD is at least capable of starting the truck. This does NOT mean it may not later cause stalling or other issues, but it should bring the engine to life.
This diagnostic procedure is based on years of experience diagnosing and testing the 6.5L diesel and talking with hundreds of owners. There is no possible way we could conceive of every possible failure or combination of failures and partial failures. If you follow through this test and perform the steps EXACTLY as directed there is a 98% or higher probability that you will uncover the issues. Ultimately, any decision you make is your responsibility. This guide is designed as an aid and is provided as a free service to our customers. Accurate Technical Services LLC accepts absolutely no liability for its use or misuse.
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