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The following is a check list of items. A listing for diagnostics, and checkout of common failing items that should be checked for troubleshooting, and before purchasing a vehicle.
When posting, give us the results of the questions below. Links are provided for more clear information (blue underlined text). The more information we have, the more accurate the diagnosis.

Proper troubleshooting and diagnostics
PLEASE, do not just begin reading the forum, and think that just because everyone else had "this failure" I must too. Take the time to properly diagnose before changing parts. If you would like to familiarize yourself with many of the different common issues that are found with the 6.5, read up on the FAQ's.

A word to the wise: If you are a guest reading through the forum, please register and login. Start a thread with the issues you are having and we may help you to verify the issues root cause. If you do not complete a proper diagnosis then you may be spending money on parts you do not need. Please post all of the completed diagnostic steps, rather than just the symptoms without checking. Many of these failures have multiple causes.

Failing to do your homework on the item, and parts changing will create a situation where you have too many variables and may become more difficult to diagnose. Giving advice to someone to just change a part because "it worked for me" without outlining that there should be some diagnostics done does nothing but confound the situation.

This forum is filled with knowledgeable people who dedicate their time to helping to pinpoint the issue. There is a wealth of knowledge housed here within the FAQ's, and if you do a forum search, and the Diagnostic checklist. Use them to the fullest.

Feel free to copy and paste this to the Check List as you begin on the issues you are having. For organizational purposes, please create a new for your vehicle so you don't interrupt someone else’s thread. It just becomes too confusing for all those involved. Please don’t forget to specify exactly what the vehicle is doing.

So to summarize. Do your homework below COMPLETELY. Don't just take for granted something is okay because it isn't always. Register if you are a guest, and post to verify diagnosis before purchasing parts.

The Diagnostic Checklist:
Please fill out to best of your knowledge.​

1. Describe the problem you are having in detail:

2. Year of truck/engine.
3. Odometer reading (indicate miles or kilometers).
4. Indicate the model number on the Injection pump (starts DS4 or DB2......).
5. Indicate if you know if it’s a 1500, 2500, 2500HD, 3500, 3500HD.
6. Do you have an EGR on the engine? (An F or an S engine code 8th VIN digit)
7. Air Filter condition (visual check).
8. Fuel filter condition (freshly changed, mileage since changed).
9. Location of PMD/FSD? (ex. on pump/remote over intake, behind bumper).
9a. If remote mounted, describe wiring harness (homemade or purchased from which vendor).
9b. Indicate the location and condition of the FSD/IP grounding wire.
10. Outside Temperature (C or F). _ °

11. Service Engine Light while running?- on/off/intermittent
11a. Service Engine light does glow during start/cranking/bulb check: Yes/No
12.Have you scanned for engine codes? Yes/No
12a. List exact results on engine codes.

13. Condition of Battery terminals (removed, cleaned and tightened).
14. Known condition and age of Batteries.
14a. Are batteries a matched set of same age?
15. Condition of Major Grounds (removed, cleaned and tightened)
15a Have the batteries been individually load tested?

16. Does engine crank, or "turn over"?
16a. Does engine start and run?
17. If engine does not start- Crack injector line: do you have fuel? Yes/No
18. Does your Wait To Start light come on?
18a.Number of seconds WTS light is lit.
19. Engine Cranking speed (if you have an accurate tachometer).

20. Are you experiencing Stalling?
20a. Describe the event (upon startup only, down the road, hit a bump, etc...)
20b. Do you notice loss of dash or instruments?
21. Check turbo inlet and air filter for obstructions.
22. In a no-hot start, pour a bottle of room-temp water on the injection pump. Does it start now?
23. Lift pump test - Describe results.

24. Upon cold start, does the radiator hose get hard quickly? Yes/No
25. Upon cold start, do you have excessive white smoke? Yes/No
26. Do you have excessive cranking time before the engine starts? Yes/No
27. Have you used the block heater? Does it affect engine starting? (only try for starting problems).
28. Are all glow plugs in proper working order?

29. During hard acceleration, do you have excessive black smoke? Yes/No
30. Do you have any unusual exhaust smoke issues?
31. Turbo check out - Pass/Fail
32. Indicate fuel that you are using: Bio-Diesel, #2 Diesel, SVO/WVO, other
32a. If running Veggie Oil fuel setup, indicate details of your conversion (homemade or packaged system).
33. Are you using any fuel additives? If so, please list.
34. Upon unscrewing fuel cap, do you have a large vacuum formed in the tank? Yes/No
35. Do you have any service history available that might pertain to the problem you are having?
36. Please indicate any modifications to the vehicle that might help us diagnose better.

3,220 Posts
Answer key

Model year will reveal any subtle differences in the engine system and how it operates. Indicating this will help tremendously in troubleshooting.

5. Indicating the chassis series will help us to understand the minor differences between vehicles. Some engines differ (EGR's etc). There were a few early years that had different injection pumps based on heavy duty chassis or not. These pumps are not interchangeable, unless you change the PCM PROM.

6. EGR's are a pain in the rear. You can check within your engine's VIN and see if you have an EGR or not.

7. Air filter condition. Unlike gassers, Diesels require huge amounts of air, even at idle. Diesel air filters get dirty faster. DO NOT rely upon the filter indicator to tell you if it's dirty or not. That is an unreliable system. Open up and look inside to see the filter itself. If the engine is starving for air, it will not produce the power it should.

8. Diesel fuel filters dirty much faster than gasoline engines. If the condition is unknown, now would be a good time to check\replace it. New filters are beige\white - dirty filters are brown\black. You may be unpleasantly surprised at what you find. Time passage is not really a great indicator of filter usage. Now a week is pretty new, but several months, depending upon driving habits can be a few hundred or a few thousand miles.

8a. Fueling up a "discount" fuel station or a diesel truck/bus stop can be an indicator of fresher, better fuel, as opposed to some dirty cruddy stuff. If you care about your fuel system, it may be better to consider fueling at one of the truck depots whenever possible.

9. Location of PMD - this can indicate a greater chance of failure - mounted on the Injection Pump as being the most failure-prone area - mounted on the intake manifold is next - outside the engine bay in ambient temperature is best - if outside, did you water-proof the module\heat sink assembly with RTV?

9a. Wiring harness for remote mount FSD/PMD - if you made the wiring harness yourself, indicate details of its construction - or if you purchased it from one of the site vendors.

9b. Indicate the location of the original FSD grounding wire - can create problems with FSD\IP operation = intermittent run, difficult start, stalling, no run, etc - this short black ground wire MUST be attached to the top of the Injection Pump, regardless of information listed in vendor instruction procedures.

10. Ambient condition: Diesel ignition source is heat of compression, augmented by the glow plug system at START. Lack of heat due to extreme cold may prevent fuel from igniting, aka, not able to start. Please indicate outdoor temperature. Many of us list in °F. However, some of our Canadian friends can help us understand °C too......

11. Service Engine Soon light - or the small engine icon - please indicate if your light is on, off, or has been on for any period of time (brief, or long periods) This will help to pin down exactly where to start looking. There are two different types of computer systems. First is OBD-I, and codes can be retrieved with a paper clip. OBD-II needs a code reader. Codes can sometimes be read at some auto parts stores too.

11a. Service engine light should glow with the rest of the bulbs during the cranking/bulb check period. If you don't have an SES light glow, you may have bulb problem, or someone may have removed it to cover their problem up before you bought it...

12/12a. Don't assume your check engine light is not on, is an indicator of a no-code condtion. Retrieve and indicate any stored engine codes if you have them. OBD-I is very easy. Both OBD-I and II are available in a DTC lookup tool you can find on the internet. If you do not understand how to retrieve codes off a pre-96 (OBD-I) vehicle - check out www.kennedydiesel.com under tech tips for the 6.5. OBD-II as said, you need a reader. This information is essential for correct diagnostics. Codes are not the "end all" answer either. They only indicate what information does not appear to be in spec to the computer. You must understand what causes those conditions before replacing parts. Post results and we can point you in the right direction. For a better understanding of how to interpret codes see this article.

13. Battery terminal connections are a known source of failure. They can result in engine mis-firing, stalling, poor starting, etc. Double check the cable connections, particularly the passenger-side positive terminal, with two cables on the same terminal. Engine Grounds are also of great importance. Without proper grounding, you've not got a complete circuit. Don't believe it? See this thread.

16. Does the engine crank or 'turn over' - great place to start would be the battery connections. These are a known trouble spot, especially with side post connections, particularly the positive terminal on the passenger-side battery. Once that's checked, you may have to move onto more serious things, such as the starter motor. Start with the easy stuff - no pun intended.

16a. Does the engine start and run? There are several conditions that cause a "no-start" to occur. There are three things you need to start and run - air, fuel, and heat. You have to discover why you have a no-start condition. All three things have been causes in the past on the forum. No air from an air filter failure (blocking all air to turbo). No fuel due to fuel system problem(s). No heat, due to lack of compression, no glow plugs, extreme cold ambient with other factors.

18. Do you have a Wait to Start light? This will indicate two things. If you have a WTS light for a period of time, that means that computer is getting power. If you do not have a WTS light, that can indicate that either an IGN fuse is blown, the IGN switch is bad, or your Engine Coolant Temperature sensor may be out of tolerance. The engine has two coolant temperature sensors - one in the driver's-side head for the temperature gage in the dash - and the ECT in the t-stat crossover manifold for the PCM (computer). Check also all engine grounds. Engine grounds are critical for PCM operation. Search engine grounds in FAQ's. Duration of the WTS light will indicate to us (based on outdoor temperature) how well the glow plug system may be working.

19. Engine cranking speed. This is difficult to tell "by ear". You need a minimum of 100 rpm to get the engine to start. Less than that will be very difficult, as the Injection Pump cannot build injection pressure. If you have noticed a reduced cranking speed, check out batteries, connections etc.

20. Stalling. This is everyone's favorite reason for coming to DieselPlace. There are MANY reasons for stalling. You'll have to make your way through the rest of the list to be able to pinpoint exact cause of stalling. This can be as simple as: fuel cap, battery connections, poor grounding, lift pump, fuel filter, etc, etc, etc. You'll need to check the rest out.

20a. Description of stalling will help us to understand exactly where the issue may lie. Please indicate as best a possible when/where/how the stalling is happening.

20b. Loss of dash/instruments indicates that either there is a whole loss of power (battery connections) or the Ignition switch is failing. The ignition switch is not in the key lock - the lock actuates a mechanical relay-type switch that applies power to the electrical components - WTS, Ignition, Accessories, gauges, etc.

23. Lift pump test - click on this question in the above post, and it will take you to detailed information on this.

24. This only applies to cold engines. If the radiator hose gets firm before the engine heats up, it may indicate that your t-stat is stuck closed, or you have head-gasket issues, where cylinder compression is leaking into the cooling system, usually accompanied by burnt-scabby stuff in the coolant. This test is done with coolant system full to proper level and radiator cap on tight.

25. Excessive white smoke at cold start up will indicate that you do not have sufficient heat to start the engine. Diesel fuel ignites by heat of compression, not a spark. If there is not enough heat present, white smoke will result. Check out your Glow Plug system and verify proper operation.

26. Excessive cranking time indicates that you may have fuel system issues. This may be an optic sensor problem, lift pump issue, glow plugs, etc.

27. Using the block heater in cool weather may well reveal the fact that your glow plug system is not working properly.

28. One or more non-working glow plugs can create a no-start or hard-start condition. This can be indicated by white smoke at startup, and the engine sounding like it is not running on all cylinders.

29. During hard acceleration, if you are leaving a smoke screen behind your truck, there's a chance you don't have enough air coming into the engine. You will need to check out the turbo system.

30. Indicating if you are having a lot of white smoke or black smoke may help us to pin down exactly what is going on with your engine.

31. Click on the turbo link, and read up on the turbo system for more information.

32. Alternate fuels - this is a growing area. Many people are starting to use different fuels in their engines. Depending upon what you are using, the issue you are having, climate you are driving, fuel may be effecting how the truck runs. Many recently-occurring symptoms can be traced to recent fuel fill-up.

32a. Indicate if your conversion kit is self-engineered, or if it was professionally built from a vendor. You must heat the SVO/WVO, before it comes to the injection pump - the internal temperature sensor in the Injection Pump will react to over-heated fuel. Filtration can also plug up very quickly too.

34. Unscrewing the fuel cap. Diesel caps are vented for both pressure and vacuum. They allow +2"hg pressure or
-2"HG vacuum in the tank - that's ~1psi - as opposed to what you find on a gasoline application . If you have a large vacuum forming in the tank, then your fuel system has to work much harder. Vacuum is less noticeable when the tank is nearly full, and you've just stopped. An empty tank forms same level of vacuum as does a full tank, but has a greater volume to equalize when the cap is removed. Example - 1 gallon empty space above the fuel at 2"hg vs 20 gallons empty space at 2"hg = much more hiss.
35. Please indicate anything that you may have serviced, or had serviced by someone else. Indicating vehicle mileage when a particular service occurred may indicate something to us.
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