Duramax Won’t Start: Fixing Duramax Diesel Starting Problems
Don't always expect the problem to be major. Sometimes the issue may be something very minor. You can never tell with these modern motors. They are very finely tuned and leave very little room for error. Keep an open mind when it comes to starting failures.
One source for this problem could be a loss of prime. This happens when the fuel leaks back into the tank. That return is due to being parked the wrong way up a hill. Not every problem will be major and sometimes you just have to buy a new filter cap to solve it.
To learn more possible sources and solutions to this problem, just continue to read our article. It explores the topic so you have the best information to help you solve your Duramax problem. Take a few minutes to see if this information helps you solve your starting issues.
Duramax Starting Problems 101
Common Duramax Diesel Starting Problems
Let’s start with the transmission. Not a Duramax motor but it is a Duramax-related problem. The Allison 1000 has been attached to the Duramax from 2001 to 2019. When the transmission gets damaged you are in for expensive repairs.
Non-transmission issues are as follows:
Turbo Inlet Manifold
Head Gasket Failure
Injector Harness Chafing
Water Pump Failure
Overheating
EGR Valve Problems
Glow Plug Failure
Fuel Pressure Relief Valve
Suspension/Steering Problems
Bent Rods
Lack of a Factory Lift Pump
Since there are about 6 different versions of this engine, you may say some all or none of these issues that other owners may experience. It is impossible to provide any explanations for all 11 of these problems but one stands out.
The head gasket can be a severe issue for the LLY Duramax and not the other versions. This problem is caused by the large factory turbocharger and a poor cooling system. Also, aftermarket modifications can contribute to this common problem.
2004-2007 Duramax Turns Over But Won't Start
The most likely problem will be with the Prime. These motors can lose their prime for a variety of reasons. One option is to replace the bleeder screw on the primer. It is a black color and plastic screw so you should not miss it.
The prime leaks out through this screw and the only repair are to replace it. Another prime issue would be the filter cap. This can leak and one owner replaced his and the no start problem went away.
Or you can replace the fuel filter. The new set of O-rings should seal the fuel line better at that point. Look for a leak as that seems to be the consensus that causes this issue.
Before and after replacing those parts try to re-prime the fuel line to see if that gets you going again.
Duramax Just Stopped Running
When it comes to starting, running and then nothing, check the fuel lines first. The fuel filter may be clogged or the O-rings have worn out or there is another problem along that line.
Some people have suggested that the WIF sensor may have cracked and that is a good possibility. Given how parts are made these days, cracking seems to be par for the course.
Another possibility is that water got into the fuel and froze. This blockage will cut the fuel supply and stop the motor from running. A fuel de-icer treatment may be all you need to clear up this clog.
Another p[art to check would be the injection pump. It could have gone bad at that exact moment. This part pulls fuel directly from the tank and if it fails, then your engine may not run until it is fixed.
Will Duramax Start With One Battery?
Usually, this motor has two batteries attached to it. The primary one, it seems, is the one that is directly connected to the starter. This battery provides the power needed for the starter to turn over and get the engine running.
The second battery is connected to a junction box but its main duty is for charging and also powering what devices are connected to the fuse box under the hood.
So yes, the Duramax will start with just one battery and it seems to run well without the second one as well. Some owners relocate the second battery to keep it hidden from the elements. This is a good idea if you live in a cold or rainy state.
Some owners use Duramax van parts to mount the second battery to the frame. Others look to the truck’s bed instead.
Will a Duramax Start Without Oil Pressure?
According to our research, it seems that the Duramax s designed to run on low oil pressure. Many owners have reported starting the engine with very low oil pressure. They did some maintenance work and the pressure returned to normal.
One of those maintenance work was replacing a new Mann filter with an AC Delco option and the pressure returned to normal. You can idle well and have the oil pressure down to 15 LB, according to GM.
Also according to GM, the engine is designed to run when there is high oil pressure. The company tried to make the engine as sound as possible. If you hear a knock when you start the engine, do not be surprised if you started it with no oil in the crankcase. 30 lb pressure should not cause a knock.
Will a Duramax Start Without Glow Plugs?
As you are aware, diesel engines do not have spark plugs. That is because diesel fuel ignites differently than regular gas does. If you have a diesel engine, you have glow plugs to help start the motor.
The glow plugs are best when you are cold starting your vehicle. Since Duramax is a diesel engine, there will be glow plugs inside warming the cylinders.
The last we looked, every diesel engine had glow plugs and how they are used during the day is up to the technology used to design the engine. That technology allows for the engine to start if the glow plugs fail.
However, the on board computer may over-ride that technology and keep the engine from running when the glow plug fails or is missing. Glow plugs are essential for cold weather areas.
Duramax Won't Start After a Battery Change
One reason for this problem is that you probably need to reset the Passlock system. To do this reset you turn the key to on but do not start the engine. Then start the engine and release the key to on.
See what the security telltale is and wait for 10 minutes until that security light turns off. Turn the key to off and wait five seconds. Repeat these steps two more times and the vehicle is ready to relearn the Passlock.
This problem should only arise if you have a remote start installed. Another way to reset the system is to take the battery cables off both batteries. Touch together only one set of cables for 10 seconds. This should reset your vehicle.
Do not do this for both sets of cables. Your vehicle should start again.
Duramax Won't Start After Running Out Of Fuel
This may be due to the engine or fuel line failing to prime again. It is a common problem that many owners have experienced. If you have an injector return line pop off, then you will lose a lot of fuel and run out of gas very quickly.
The way to re-prime the system is to turn your key to on, then go under the hood and turn the fuel filter back 1/4 turn. Then wait for the filter or system to re-prime before tightening the filter back up again. The engine should start after that.
Another possibility is that air got into the system and you would have to leave the bleeder valve open to rid the line of the air. You do this while pumping and cranking at the same time. Make sure to have all fuel coming out of that valve. That lets you know the air is gone.
Duramax Won't Start After a Fuel Filter Change
This one can be a bit tricky. After changing the fuel filter, the truck may start and run for about 15 minutes or so. After that time, it may shut down and not restart. The go-to solution would be to re-prime the fuel line and see if that clears up the problem.
If the fuel system will not hold prime, then you need to check to see if the filter head is cracked or not. The line may be letting air in at some location. This leak can stop your engine from running or starting.
Or you simply forgot to put a little diesel fuel on the upper seal. That seal may have twisted and caused the problem. Another place to look would be the O-ring on the fuel filter. It needs lubing from diesel fuel as well to sit properly in its spot.
How To Start Duramax That Ran Out Of Fuel
This situation simply calls for a re-priming of the line. You will need to open the bleeder valve and start pumping the prime button. Keep pushing the prime button until all fuel comes out of the valve and then tighten the valve back up.
Then you just have to try to start the engine. You may have to repeat the process several times before the fuel system is fully primed and your vehicle starts.
Make sure not to crank the engine until you bleed all the air out of the system. Be careful not to overheat the starter when doing this.
2006 Duramax Starts But Will Not Stay Running
If you have just completed a filter change, you may have air in the system. You would have to bleed the system. However, in this case, it may not be the air’s fault.
Sometimes it is an electrical problem and you will need to start by checking your fuses. Then move on to all your electrical connections including the battery. Check for loose connections, wires, and any corrosion.
When everything shuts down at the same time, then it should be a loose connection only. Start there and do the fuel system if it is needed. Sometimes the BCM plug is loose and all you need to do is unplug it and plug it back in again.
How Cold Will a Duramax Start?
This will depend. We have read accounts where the Duramax will not start at -9 degrees F and others where it will start, without plugging it in, at -25 and sometimes at -40 degrees F.
Your results may differ and sometimes the issue may not be the starter but the glow plugs. If the glow plugs are failing or wearing out, then you need to replace them and get back to cold-weather starting.
The key is not to leave your vehicle unplugged when it gets too cold. At those low temperatures, you may also have a problem with the diesel fuel gelling and not making it through the fuel line.
How To Start a Duramax in Cold Weather
One thing NOT to do is use ether or some other car starting aid you can buy at different auto parts locations. You can destroy your motor and possibly hurt yourself.
To start the vehicle you may only have to turn the key to on and wait for the glow plug light to go out. Then turn the key off and back on again and wait one more time. Then the engine should start like normal.
Also, watch out for the type of diesel you buy. The wrong blend can ruin your day and keep any attempt to start your vehicle unsuccessful.
Duramax Cold Start Procedure
You can cold weather prep your fuel but that seems to be more important for older diesel engines rather than the more modern options. The key to cold weather starting is to just do it like you always do. Wait for the glow plug light to go out and then start your engine.
In all of the examples we read, the owners never said anything about any process they went through. They all said that they forget to plug the truck in but it started the next morning with no trouble.
The problem you may have is the diesel fuel gelling on you. You may have to add some de-icer to get it flowing before you start your motor.
Duramax Cold Start Check Engine Light
This light may come on when after starting the engine in extremely cold temperatures and driving at about 60 mph or higher. In those conditions, the fuel can gel or freeze up and not flow smoothly.
When this happens the engine may be reduced to 2000 rpm and not go any higher. To diagnose this problem is to attach a code reader to see what code was triggered. Once you get that information you should know how to fix the problem.
Also, you may have a transmission problem as some people could not get into gear even with a re-start. This is a dealer-only fix.
Duramax Will Only Start With Ether
This is a possibility but it is a highly discouraged activity. Using ether, even if it works, is risky. While some people can only start their vehicle with this motor aid, it is not something you should do long term.
You can damage the motor if you do it too often or you may hurt yourself. The risk is too great. If you ignore this advice, disconnect the glow plugs first. That will be a safer way to use this fluid but only for a couple of starts.
If you are in this position, take the vehicle to your dealer or a good mechanic.
Duramax Won't Start Even With Ether
This may be an issue with the CP3 unit or the injectors. If you have replaced other parts in the fuel system, this may be your next part to check. If those are not the source, check your starter. It may be bad and you will need to replace it.
Not everything will be fuel-related when it comes to non-starting issues. It is just the first thing people think of when presented with this problem. If it isn’t the problem check your batteries and electrical system.
When they go bad, the power is not there to start the motor.
Some Final Words
It is frustrating when your engine will not start. It is even more frustrating when you have an engine with technological upgrades. These days it is harder to find the problem than it was 40 years ago.
If the above information does not solve your problem then you need to go to a good mechanic or a dealer. They may have a good idea to try. Just avoid using ether.
