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I have a gmc duramax with lb7 was running great until a week ago when i pulled into the driveway and died.

duramax wont rev up

It would not start back up. Did some research and i desided the cp3 pump was bad so i replaced it with a new one. Now it still wont start unless i use strating fluid and it will not idle. It also losses prime after i start it. I have checked the lines and they are not clogged, there is not leaks, and no air in lines. My oil pressure gage has also stopped working since i changed the cp3 pump. Any ideas on what could be wrong? Started with starting fluid and i keep my foot on gas to keep it running for 30min and it still wont idle.

The air should be out of the lines. Fuel filter housing thing where the filter screws on can I bad and won't hold prime u can get a rebuild kit cheap or just a while new one.

I'd look at your fuel filter housing, they are a common issue. Also I would change all the rubber lines on the motor, they get pretty dry rotted and cracked.

duramax wont rev up

I got some BAD fuel a couple weeks ago, truck wouldn't start. Drained the tank and put new filters on now its back to normal I hope. Ok now i have tried pumping the prime and it pumps just fine and pumps up til i cant pump it no more but in 10min of just sitting not running not trying to start it it loses prime and i cant find where the pressure is going.

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You could have an injector stuck open and you can't maintain the min fuel pressure to keep the ficm working. Those would be your injectors that are stuck open. Not trying to be an asshole but do you have enough fuel in the tank? Reason I ask is because my fuel gauge quit working a long time ago and I keep track of fuel level with my trip odometer.

Girlfriend accidently reset it without knowing. Clueless to me, my truck died and had the exact same symptoms. However, there was enough fuel to prime and turn over for a second as well as hearing the lift pump return fuel to the tank.

Easy fix. Where did you get your cp3 from? Is it an LB7 cp3? Rebuild the fuel filter head, cheap and easy to rule out. Do you have a way to log fuel rail psi while cranking? So this issue started out of the blue and since it quit running you have put a new cp3, regulator, and injectors in it? Do I have that sequence correct or did it quit running after you put the new injectors in?

And how do you know that there is no fuel coming from the injection pump? You dont have enough fuel presure to keep the truck running at idle so you have an injector stuck open the fprv is sending the fuel back to the tank or your sucking air at the filter head. I even bought a computer to hook up to my truck to tell me what codes its flashing and all it is saying is glow plugs and air intake heater would those cause it to not start plus my dash board is still not showing any oil pressure.

Try plugging the fuel rail with a race plug i had my releif valve not seat after doing a shim job and it made the truck not run right then i messed with it again and tried to shim it solid and it lost fuel pressure and died wouldn't start till i finally fanageled the valve in place till my plug came in?

I used the XDP one. Had the same conditions as you with the loosing prime and not starting. Bottle test!!!! Are my post invisable :roflmao:.

As stated search the bottle test and attempt that, but before you spend any more time do two simple things: Check for leaks at the hard lines Rebuild your fuel filter head. Do not: Buy any more parts before you diagnose the problem.If you have a Duramax 6.

Over the years these trucks have been really good performers, but they do have some common problems that we see over and over again. The original injectors that came in these trucks had all sorts of issues with cracking. The symptoms are constant smoke at idle and gaining fuel in the oil. Unfortunately the best thing to do if you have this problem is to replace the whole set at once. Injector replacement on the LB7 truck is rather labor intensive and just changing one is usually not worth the risk for the labor costs.

The new injectors available from us and others are updated and do not have the cracking issue. Fuel Filter Housing Oring Leaks — The Duramax fuel system does not have any sort of low pressure fuel pump pushing fuel to the engine from the tank. The injection pump sucks all the fuel from the tank.

While we are seeing more and more rusted out fuel lines causing the engines to suck air, nine times out of ten the issues are in the fuel filter head. Under the primer button there are some orings that fail on a regular basis. This can produce long cranks and hard starts. Glow Plug System Issues — Nearly half of the check engine lights that come in for the Duramax pickups are for glow plugs.

The glow plugs burn out over time and can be a real nuisance to remove from the aluminum heads sometimes. Not only does the threaded metal part of the glow plug seize in the head, but the tips of the glow plugs sometimes bulb making it really difficult to get them out.

Also the metal strips that connect the glow plugs together on each side corrode and break causing issues.

Lastly we replace a fair amount of glow plug controllers as well. You will usually get a diagnostic trouble code for the cooler when they go bad. Head Gaskets — As these truck reach themiles we are seeing more and more head gasket issues. The Duramax has a multi-layer steel head gasket. When they have issues, they do not typically smoke out the exhaust or get coolant into the cylinders.

What happens is the head lifts a little during the compression stroke. This allows the layers of the gasket to separate which lets combustion pressure into the coolant system. The pressure will cause the coolant to be pushed out the coolant overflow.

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You can check for a head gasket issue by squeezing the top radiator hose when the engine is running and right after you shut it off. You should be able to squeeze the hose very easily. If it is rock hard, you have a head gasket issue. We recommend using ARP head studs for a high clamp load along with one of our head gasket kits to fix it. It is extremely important to have the heads surfaced flat before putting the truck back together.

This one is fairly common and unfortunately a huge pain in the butt to change. Water will seep from the underside of the pump. Be prepared though because you will have to remove the dampner pulley to get the pump off. The pulleys are pressed onto the crank and you will need a really good puller to get it off.For example, did you know the injection pump on the LML version is prone to coming apart and wrecking the entire high-pressure fuel system when it does?

Perhaps the most devastating of all Duramax failures is a broken factory crankshaft. The failure is most common in higher horsepower engines, but can still occur in moderately modified and even stock power plants.

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The crankshaft usually breaks near the number one rod journal due to a combination of excessive rpm and the large external counterweight. A factory firing order that beats up the front area of the crankshaft has also been blamed for imposing undue stress on the crank. The billet Callies crankshaft available through Wagler Competition Products is machined from triple heat treated V steel and features reduced rod journal widths for improved strength which calls for narrower rods.

For a more budget-friendly option, a properly balanced Compstar forged crankshaft also made by Callies has shown great results in the sub-1,hp arena. In an effort to reduce crankshaft fatigue on the front of the crankshaft, alternate fire camshafts are employed. By changing the firing order of the engine from stock tothe hard hit at the front of the crankshaft is eliminated and the overall load is more evenly distributed across the crankshaft.

Unlike the ultra-durable CP3 that came before it, the CP4. Any time water, rust or debris infiltrates the CP4. Unfortunately, the latter scenario plays out more often than seizures do. Typically, the roller lifter or bucket that rides on the CP4. When a CP4. Second, always change the fuel filter at or before the recommended service interval.

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This means that not only does the CP4. For utmost peace of mind, the CP4. Various aftermarket kits come with everything you need to complete the conversion, mechanically note that a few ECM tweaks will be required, too. On top of being known to last hundreds of thousands of miles without any major issues, the CP3 flows roughly percent more fuel volume than the CP4. However, because better than one in four diesel-powered GM trucks is graced with an electronic power-adder, and the fact that this is an enthusiast site, all of you should take note.

So what causes the rods to shrink? In a word, torque. Thanks to a This stress is directly imposed on the pistons, the rods and the crank—but the rods are the weakest link in LB7 and LLY engines. Luckily, the rods found in these two engines are forged steel, which is to say that they bend long before they think about breaking. Other than dialing back the tuning or scrapping your performance plans altogether to save the factory connecting rods, aftermarket units are in order.

In addition to its competition-ready rods rated for 2,plus hpWagler also offers As-Forged units, which are the most budget-friendly Duramax rods in the diesel industry. Low-quality castings from its suppliers and a reduced amount of meat present in the wrist pin area thanks to the use of wrist pin bushings are to blame for factory piston failure.

In most cases, the cast-aluminum piston cracks along the center line of the wrist pin, as shown above. For many all-out, competition-type builds, forged pistons from Diamond Racing are known to get the call.Hey guys, So I have been meaning to post this thread about an year and half now.

But the issue is SO intermittent, I have been reluctant to do so. But the issue is SO intermittent, I have been reluctant to do so because when it doesn't happen, I tell myself "the issue has been fixed" Smooth, fast and actually I think it still feels like it has 15, miles! When this happens, it just happens to randomly. I have Gold prefferred Bumper to bumper warranty till or K miles. When I got back into the highway, as I was rowing through gears, it won't let me rev past Just out of the blue, this issue started.

I have no idea when this rev limiter thing will trigger. I can have the rev limit occur on my way to grocery store. Then 2 days can go by and It won't happen, 2 months can go by, it won't happen or heck even 6 months will go by and this will not occur once I think 6 months was the longest gap. Sometimes it happens twice a day then it may not happen for next 6 months. It can be 1 hour or 6 months. When it happens, I can still drive the car as long as I row throw the gears and keep it below RPM.

I really don't know what's the problem. Has this happen to anyone here?

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I took the Z for service in past, but they were giving me the eyes, thinking I'm crazy. They spent hours looking for a code or to replicate the issue -- nope no luck.

However they said, if it occurs again, come straight to the dealer. We want to see it. I said,"fine". I went straight to the dealer. Had the tech drive the car and he finally saw what I meant. As I type this, my Z is in the Nissan dealer. All day today they tried replicating the issue first but of course he couldn't get to replicate it as it's VERY random and even I have no idea what triggers it.

Tech called Nissan Tech line and they were confused as well. They NIssan first suggested a faulty oil temp sensor which is telling ecu the oil temp is high but in reality it isn't. I personally think it might be a buggy old ECU as my car is one of the earliest built car.

5 Fatal Flaws of the Duramax—and How to Fix Them

Tech wants to call Nissan tech tomm or try to replicate the issue again so that there's a solution to this and I told them I really want this fixed as I bought the car before for exact thing.

I have tried that. What do you guys think is the issue? Has this happened to anyone? What should I tell the tech tomm to look specifically? You help, comment, suggestion is highly appreciated. Then click here!Sign In with Edmunds.

Howdy, Stranger! It looks like you're new here. If you want to get involved, click one of these buttons! Sign in or Register. On Edmunds. Visit Edmunds How-To Guides. Service Centers in. Browse Forums by:. What Edmunds Says Pros. Got a lease deal in hand? Give us the details and we'll tell you if it's a good one.

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Evaluate my deal. Did you get a great deal? Meet your fellow owners in our Owners Clubs. July We just went through a battle with Ford on warranty of the fuel system on an 06 F The biodiesel gummed up the injection pump and they basically had to disassemble the entire fuel system and clean it. When the smoke cleared in the battle, the dealer finally warrantied the repairs. Now, it hasn't been determined that the cause of the problems were biodiesel, poor filtering from the fuel company or some other contaminates in the fuel system.

But since the vehicle was running biodiesel from the time we received it, we can't imagine that it was any other contaminates. On the other hand, we have several 05 F's, that are running B without any problems at all. Also, be aware that if you are in an area with low temps in the winter, biodiesel gels at relatively high temps. B gels at considerable higher temps than diesel, while B20's gel point is much closer to diesel's gel point.

The biggest thing with biodiesel, as was pointed out, is to make sure the filtering system of where you are getting it and of the vehicle's is sufficient. I have had some serious issues with my new duramax and the exhaust. I put miles on it before going on a road trip pulling my 14, lb fifth wheel.

It left us on the side o the road twice and is still 2 states away as GM engineers try to figure out why 12 codes keep coming up and the computer is in permanent fail mode. Also the exhaust filter will not regenerate. August Do you have access to a scanner?

If so, what values does it show for the baro sensor? What altitude are you at? You need to make sure that the BARO sensor is showing the correct values. Causes for it to go out of range are broken wires, disconnected connector or a bad sensor.

It should show 5V, does it? I have my injectors, pump, fuel filter and fuel lines replaced. Try the new stepped filter from the dealer also.If you have a Duramax 6. Over the years these trucks have been really good performers, but they do have some common problems that we see over and over again. The original injectors that came in these trucks had all sorts of issues with cracking.

The symptoms are constant smoke at idle and gaining fuel in the oil. Unfortunately the best thing to do if you have this problem is to replace the whole set at once. Injector replacement on the LB7 truck is rather labor intensive and just changing one is usually not worth the risk for the labor costs.

Fuel Filter Housing Oring Leaks — The Duramax fuel system does not have any sort of low pressure fuel pump pushing fuel to the engine from the tank. The injection pump sucks all the fuel from the tank. While we are seeing more and more rusted out fuel lines causing the engines to suck air, nine times out of ten the issues are in the fuel filter head.

Under the primer button there are some orings that fail on a regular basis. This can produce long cranks and hard starts. Glow Plug System Issues — Nearly half of the check engine lights that come in for the Duramax pickups are for glow plugs.

The glow plugs burn out over time and can be a real nuisance to remove from the aluminum heads sometimes. Not only does the threaded metal part of the glow plug seize in the head, but the tips of the glow plugs sometimes bulb making it really difficult to get them out. Also the metal strips that connect the glow plugs together on each side corrode and break causing issues.

Lastly we replace a fair amount of glow plug controllers as well. You will usually get a diagnostic trouble code for the cooler when they go bad. Head Gaskets — As these truck reach themiles we are seeing more and more head gasket issues.

The Duramax has a multi-layer steel head gasket. When they have issues, they do not typically smoke out the exhaust or get coolant into the cylinders. What happens is the head lifts a little during the compression stroke.

duramax wont rev up

This allows the layers of the gasket to separate which lets combustion pressure into the coolant system. The pressure will cause the coolant to be pushed out the coolant overflow. You can check for a head gasket issue by squeezing the top radiator hose when the engine is running and right after you shut it off. You should be able to squeeze the hose very easily.

If it is rock hard, you have a head gasket issue. It is extremely important to have the heads surfaced flat before putting the truck back together. This one is fairly common and unfortunately a huge pain in the butt to change.

Water will seep from the underside of the pump. Be prepared though because you will have to remove the dampner pulley to get the pump off. The pulleys are pressed onto the crank and you will need a really good puller to get it off.

Allison Transmission - The Allison transmission behind the LB7 Duramax to be honest is nothing to brag about in stock form.Remember Me? Page 1 of 2 1 2 Last Jump to page: Results 1 to 10 of Thread: Duramax "rev limiter".

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Thread Tools Show Printable Version. Duramax "rev limiter" On a recent trip, I was in tow-haul mode and stepped on the petal pretty hard to get around a slow moving truck and the engine appeared to die.

No check engine light, all gauges were normal - just wouldn't go over 2, rpm. I pulled to side of road, checked everything out the best I could.

duramax wont rev up

I found that from turning the ignition off, I could reset whatever was limiting the rpm's. All was well, but was more sensitive to this problem during remainder of trip.

LB7 6.6 Duramax Common Issues, Problems, and Fixes

I figured some sort of a faulty rev limiter. Chevy dealer informed me that the fuel filter should be replaced every 15, miles if towing a lot. I had 41, on mine and he said I was lucky not to have come in on the hook. Since this is my first diesel, now I know better!

The filter was starving the fuel flow. Also, Chevy found that my air filter was not for a diesel engine. A gas engine filter the local oil change company put on will not handle the volume of air being pulled in by the turbo. I was not aware they had put on the wrong filter. Best to stay with GM parts, spend the extra money and stay off the side of the road!!! GM built that feature into the Duramax to protect it from damage.

It allows you to limp to a service facility--not very fast, but you will get there.

5 Fatal Flaws of the Duramax—and How to Fix Them

A good forum for new GM diesel owners is Dieselplace. Like this site, it is an excellent source of information. By the way, from test results on that forum it was determined that the OEM air filter was about as good as you could get for flow and efficiency. Towing or not, 15K on the fuel filter is the interval. Make sure you're using the latest generation of fuel filters and not the older superceded filter.

Remember to change the fuel filter because it does stop lots of junk and water from getting into the injectors. I have the drive information center on my duramax and it tells me how much the filter has been used. I always change mine at 10k and even have installed a pre-filter and change it at 20K miles.


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