knkreb
12-08-2006, 10:12 PM
So, with cold weather upon us, we wait for the children to say "I want snow." If you are like me, cold weather is for the birds. Actually, birds hate it too, that’s why they fly south. But I digress into our thread about now-its-cold-and-my-truck-doesn’t-work-right thread.
If you have had some issues with not being able to start up like you used to, (say like in warm weather) it’s because sometimes diesels are a bit cranky in cold weather. No pun intended, but it takes a lot more to get a diesel engine started in cold weather.
Diesel engines differ from gasoline engines because they have no spark plugs. Diesel engines work off of heat of compression. This is where the old lady from they Wendy’s commercial comes out and says on that cold winter morning "So where’s the heat?" Heat of compression comes from taking air and compressing it to 21 times it’s current pressure and viola you’ve got heat. Well, almost. It’s winter remember. Heat is a hard thing to come by in most places. Even compressing air that much itsn’t enough to get diesel fuel to ignite. Oh, yeah, fuel, that’s right. We’ve got to have fuel in there somewhere. Once the piston is at the top of the cylinder, the fuel is injected into the cylinder, and BANG, you got power baby.
So what if you don’t have enough heat to get that diesel fuel lit? Well, there are a few things that goes on inside there to help out. First off, is our friend the glow plug. For a full run down a the glow plug, read up on it (http://www.dieselplace.com/forum/showthread.php?t=39182). In short, it’s a little pencil like heater in the head of the engine. This heater glows red hot, so that when fuel is injected into the cylinder, it ignites, even if the heat of compression isn’t enough to get it started by itself.
So what can go wrong you say? Well, glad you asked, let’s look at some of the finer points of this engineering marvel we call the diesel engine.
Glow plug system. If our glow plug system is not working properly, then we can expected hard to no starting depending upon the conditions that you are attempting to start a cold engine.
What goes wrong with the glow plug system? There are many points of failure that can hinder it’s proper operation. So following is a list:
Bad connection to glow plug relay itself. Bad connections do not allow full current to flow to the glow plugs themselves. Make sure ALL connections are clean and tight. Visual checks don’t count. Best way to check them is to remove, clean, and reinstall.
Chaffed wiring. After x amount of miles of vibration and travelling there can be electrical wiring that gets chaffed through. Check your connections and make sure that all wires are safe do not have the insulation compromised from any metal or heat damage.
Spade (flag) terminal on the glow plug not making contact. Glow plugs are near the hottest part of the engine, and they tend to oxidize. Oxidation can cause poor connection/continuity for current flow.
Failed glow plug itself. This is by far the most popular failure of all. Glow plugs are wearing parts. They do fail. Exposed to extreme heat, and nearly a dead short electrically speaking. They don’t last forever.
Are there different kinds of glow plugs? There are different styles and some heat quicker, or last longer. There are some differences. Do a little reading and research, and see what you think before purchasing.
How do I know if a glow plug has failed? Ohm it out. Resistance should be less than 1 ohm. You can test with a test light, however, that will not clearly tell the electrical integrity of glow plug itself, or how well it works. Digital volt ohm meters are relatively inexpensive, and a good investment not only for testing these, but helping to shock yourself while doing other household chores.
Failed glow plug relay. If the relay fails, then it must be replaced. Sometimes these will throw a DTC code to let you know that it has failed. If it fails, it will not power the glow plugs.
Failed Engine coolant temperature sensor. This is the sensor that tells the computer (ECM or PCM) just how cold it is, and how long the glow plugs need to be on before starting the engine. If this sensor fails or is out of spec, then glow time (wait to start time) is shortened. You can experiment by pulling the plug to this sensor, which will cause the computer to think that it is –40°. You’ll get a pretty good glow time at that temperature.
Best thing to do is check out all the above. Consider it routine maintenance.
What else can go wrong? Well, some other rather simple things.
Weak batteries. As the temperature gets colder, the amount of cranking amperage that is available from our batteries begins to diminish. Of course when you need it the most, is when it starts to fade. You don’t need nearly as much cranking time in the summer, as you might in the winter.
Weak batteries also contribute to the next thing on the list.
Slow cranking speed. You engine has got to turn a minimum of 100 rpm to get it to start. Slow cranking speed will not develop enough heat or fuel pressure to start the engine.
What causes slow cranking speed? Weak batteries, weak starter, or bad battery cables.
Battery cables. What can go wrong with battery cables you ask? Well, it’s more the connection on the end of the cable that you’ll have an issue with. Side post connections are not the best means of delivering high current demands to the engine’s starter and glow plug system. Oxidation of these terminals will hinder the electrical current flow. Sometimes also, acid can wick it’s way from the connection end up the cable itself. This oxidation will deteriorate current flow through the cable as well.
Check over all engine power and ground connections. As said before, visual check doesn’t count. It has to be a remove, clean and reinstall. Many times you’ll discover that the connector on the end does not have good contact with the cable itself after removing it from the post connection.
Fuel issues.
Fuel gelling. With lower outdoor ambient temperatures, comes the chance of fuel gelling. Fuel will "gel" or thicken up to the point where it won’t flow through the filter at differing temperatures. There is a fixed temperature that it will gel at, however, it has to do more with what "mix" you are running. Most fuel stations are running a winter time mix of #1 diesel and #2 diesel. #1 has a much lower gel point. It also has less energy per gallong than it’s #2 counterpart.
Is there any thing I can do about improving my chances of not gelling my fuel? Yes, you can put additives in the tank. Additives that are designed for DIESEL SERVICE is what you want. Please don’t just put something for a gas engine in your tank. You have a very expensive, precise fuel delivery system. It’s not something you just want to add "anything" to your tank.
I’m running alternative fuels, so I do I have to worry about fuel gel issues? Yes. If you are running Biodiesel (from a pump, or home brew method) the gel point is much higher, as in it can gel at warmer temperatures than winter mix diesel. Do your research on these areas to see what’s available and specific gel points for biodiesel products. There is a section of dieselplace.com that has alternative fuel discussion.
Does my fuel system have any way of heating the fuel? Yes, there is a fuel "warmer" in the fuel filter bowl.
Injectors
Good injectors will start engines well. If your injectors are of an unknown age, then they may be suspect.
How long are injectors good for? Well, GM says about 100,000 miles average. If you are over that, you’ve got two options. Either have them tested at a local fuel shop, or purchase new ones.
Are there better grades of injectors? There are different injectors, with very different price tags. Some promise the world. Do your research before purchasing a set of injectors. Injectors along will not provide extra horsepower alone. That’s a whole ‘nother thread to itself.
Compression
The stock 6.5 engine comes with 21:1 compression ratio engine. This is a very high compression ratio, designed for easy starting in colder weather. If you engine is worn, your compression may be failing. Thus, getting more difficult to start.
Modification to engine compression
If you have modified your engine to an 18:1 compression ratio, then you’ll have less heat available in the cylinder. This translates to more cranking before it gets started.
How do you know if your engine is 18:1? This is a serious modification. This is not just a bolt-on thing. You’ve got to rebuild the engine practically speaking to change the compression ratio.
Why does it sound like my engine will wake the dead on cold starting? The ECM has changed the timing of injection to get things going. It sounds very loud on startup, but then tends to subside. It depends on how cold it is as to how loud it will sound during the starting and warming up period.
These are just some of a few things to consider when you come across the winter time blues when the truck won’t start.
If you have had some issues with not being able to start up like you used to, (say like in warm weather) it’s because sometimes diesels are a bit cranky in cold weather. No pun intended, but it takes a lot more to get a diesel engine started in cold weather.
Diesel engines differ from gasoline engines because they have no spark plugs. Diesel engines work off of heat of compression. This is where the old lady from they Wendy’s commercial comes out and says on that cold winter morning "So where’s the heat?" Heat of compression comes from taking air and compressing it to 21 times it’s current pressure and viola you’ve got heat. Well, almost. It’s winter remember. Heat is a hard thing to come by in most places. Even compressing air that much itsn’t enough to get diesel fuel to ignite. Oh, yeah, fuel, that’s right. We’ve got to have fuel in there somewhere. Once the piston is at the top of the cylinder, the fuel is injected into the cylinder, and BANG, you got power baby.
So what if you don’t have enough heat to get that diesel fuel lit? Well, there are a few things that goes on inside there to help out. First off, is our friend the glow plug. For a full run down a the glow plug, read up on it (http://www.dieselplace.com/forum/showthread.php?t=39182). In short, it’s a little pencil like heater in the head of the engine. This heater glows red hot, so that when fuel is injected into the cylinder, it ignites, even if the heat of compression isn’t enough to get it started by itself.
So what can go wrong you say? Well, glad you asked, let’s look at some of the finer points of this engineering marvel we call the diesel engine.
Glow plug system. If our glow plug system is not working properly, then we can expected hard to no starting depending upon the conditions that you are attempting to start a cold engine.
What goes wrong with the glow plug system? There are many points of failure that can hinder it’s proper operation. So following is a list:
Bad connection to glow plug relay itself. Bad connections do not allow full current to flow to the glow plugs themselves. Make sure ALL connections are clean and tight. Visual checks don’t count. Best way to check them is to remove, clean, and reinstall.
Chaffed wiring. After x amount of miles of vibration and travelling there can be electrical wiring that gets chaffed through. Check your connections and make sure that all wires are safe do not have the insulation compromised from any metal or heat damage.
Spade (flag) terminal on the glow plug not making contact. Glow plugs are near the hottest part of the engine, and they tend to oxidize. Oxidation can cause poor connection/continuity for current flow.
Failed glow plug itself. This is by far the most popular failure of all. Glow plugs are wearing parts. They do fail. Exposed to extreme heat, and nearly a dead short electrically speaking. They don’t last forever.
Are there different kinds of glow plugs? There are different styles and some heat quicker, or last longer. There are some differences. Do a little reading and research, and see what you think before purchasing.
How do I know if a glow plug has failed? Ohm it out. Resistance should be less than 1 ohm. You can test with a test light, however, that will not clearly tell the electrical integrity of glow plug itself, or how well it works. Digital volt ohm meters are relatively inexpensive, and a good investment not only for testing these, but helping to shock yourself while doing other household chores.
Failed glow plug relay. If the relay fails, then it must be replaced. Sometimes these will throw a DTC code to let you know that it has failed. If it fails, it will not power the glow plugs.
Failed Engine coolant temperature sensor. This is the sensor that tells the computer (ECM or PCM) just how cold it is, and how long the glow plugs need to be on before starting the engine. If this sensor fails or is out of spec, then glow time (wait to start time) is shortened. You can experiment by pulling the plug to this sensor, which will cause the computer to think that it is –40°. You’ll get a pretty good glow time at that temperature.
Best thing to do is check out all the above. Consider it routine maintenance.
What else can go wrong? Well, some other rather simple things.
Weak batteries. As the temperature gets colder, the amount of cranking amperage that is available from our batteries begins to diminish. Of course when you need it the most, is when it starts to fade. You don’t need nearly as much cranking time in the summer, as you might in the winter.
Weak batteries also contribute to the next thing on the list.
Slow cranking speed. You engine has got to turn a minimum of 100 rpm to get it to start. Slow cranking speed will not develop enough heat or fuel pressure to start the engine.
What causes slow cranking speed? Weak batteries, weak starter, or bad battery cables.
Battery cables. What can go wrong with battery cables you ask? Well, it’s more the connection on the end of the cable that you’ll have an issue with. Side post connections are not the best means of delivering high current demands to the engine’s starter and glow plug system. Oxidation of these terminals will hinder the electrical current flow. Sometimes also, acid can wick it’s way from the connection end up the cable itself. This oxidation will deteriorate current flow through the cable as well.
Check over all engine power and ground connections. As said before, visual check doesn’t count. It has to be a remove, clean and reinstall. Many times you’ll discover that the connector on the end does not have good contact with the cable itself after removing it from the post connection.
Fuel issues.
Fuel gelling. With lower outdoor ambient temperatures, comes the chance of fuel gelling. Fuel will "gel" or thicken up to the point where it won’t flow through the filter at differing temperatures. There is a fixed temperature that it will gel at, however, it has to do more with what "mix" you are running. Most fuel stations are running a winter time mix of #1 diesel and #2 diesel. #1 has a much lower gel point. It also has less energy per gallong than it’s #2 counterpart.
Is there any thing I can do about improving my chances of not gelling my fuel? Yes, you can put additives in the tank. Additives that are designed for DIESEL SERVICE is what you want. Please don’t just put something for a gas engine in your tank. You have a very expensive, precise fuel delivery system. It’s not something you just want to add "anything" to your tank.
I’m running alternative fuels, so I do I have to worry about fuel gel issues? Yes. If you are running Biodiesel (from a pump, or home brew method) the gel point is much higher, as in it can gel at warmer temperatures than winter mix diesel. Do your research on these areas to see what’s available and specific gel points for biodiesel products. There is a section of dieselplace.com that has alternative fuel discussion.
Does my fuel system have any way of heating the fuel? Yes, there is a fuel "warmer" in the fuel filter bowl.
Injectors
Good injectors will start engines well. If your injectors are of an unknown age, then they may be suspect.
How long are injectors good for? Well, GM says about 100,000 miles average. If you are over that, you’ve got two options. Either have them tested at a local fuel shop, or purchase new ones.
Are there better grades of injectors? There are different injectors, with very different price tags. Some promise the world. Do your research before purchasing a set of injectors. Injectors along will not provide extra horsepower alone. That’s a whole ‘nother thread to itself.
Compression
The stock 6.5 engine comes with 21:1 compression ratio engine. This is a very high compression ratio, designed for easy starting in colder weather. If you engine is worn, your compression may be failing. Thus, getting more difficult to start.
Modification to engine compression
If you have modified your engine to an 18:1 compression ratio, then you’ll have less heat available in the cylinder. This translates to more cranking before it gets started.
How do you know if your engine is 18:1? This is a serious modification. This is not just a bolt-on thing. You’ve got to rebuild the engine practically speaking to change the compression ratio.
Why does it sound like my engine will wake the dead on cold starting? The ECM has changed the timing of injection to get things going. It sounds very loud on startup, but then tends to subside. It depends on how cold it is as to how loud it will sound during the starting and warming up period.
These are just some of a few things to consider when you come across the winter time blues when the truck won’t start.