A few general diesel engine questions. - PeachParts Mercedes-Benz Forum

lorainfurniture · #1 01-07-2017, 11:37 AM

Vehicle in question is my 08' Mitsubishi Fuso. It is direct injection, with that stupid DPF filter. About 120k miles.

I find that the truck at this point in its life will not Crank very well, if at all when the temps reach below 15 degrees. This was never an issue up until this year. If I leave the truck plugged in (block heater), it will usually start reliably.

What typically happens that would require the truck to be plugged in now in order to start? Batteries are new, less than 2 months old.

Second question is regarding the product "Diesel 911". Is that something that should be used sparingly, or is it something that I should add regularly to the tank durning the winter months?

The truck is a delivery truck, so it is used almost daily. It has been somewhat regularly maintained since I bought it new, oil changes are regular, usually every 7 thousand miles. (interval via owners manual says every 10 k miles.

Any input is appreciated.

Jeremy5848 · #2 01-07-2017, 12:15 PM

One of the factors in engine cranking is oil viscosity. A synthetic oil (5W-40, for example) will allow the engine to crank more easily in cold temperatures than a 15W-40 Dino oil. Products such as Diesel 911 are useful in preventing fuel gelling but that is unlikely at 20°F except in biodiesel. Diesel 911 will not harm the engine but will have a negative effect on your pocketbook. Use it if it makes you feel better.

Jeremy

Diseasel300 · #3 01-07-2017, 12:16 PM

Checked the glow plugs? If you have one or more out, you could have difficulty starting the engine. Keeping it plugged in will retain enough warmth in the block for you to start. Diesels require heat, compression, and fuel to operate properly. Normally the heat comes from compression/ignition, though to start you need a heat source. If your glow plugs are malfunctioning (120K is enough to warrant a check), it will cause poor starting in cold weather, and as the engine ages will cause poor starting in more temperate weather as the compression reduces due to internal wear. I wouldn't think 120K is enough for the compression to be down far enough to cause your issue.

Other things that could potentially be an issue (though I'd somewhat doubt it) are injection issues, low compression, gelled fuel, etc.

I'm under the impression that Diesel 911 is for "emergencies" when the fuel has gelled or the vehicle will otherwise not start. You can get anti-gel additives that have a cetane boost component that help in the winter months. They help the fuel from turning to wax.

I personally don't run additives in my vehicles unless there's a specific reason, though I know some people who do run the D911 additive in every tank and their vehicles are fine.

Alec300SD · #4 01-07-2017, 12:27 PM

Quote:

Originally Posted by lorainfurniture

Vehicle in question is my 08' Mitsubishi Fuso. It is direct injection, with that stupid DPF filter. About 120k miles.

I find that the truck at this point in its life will not Crank very well, if at all when the temps reach below 15 degrees. This was never an issue up until this year. If I leave the truck plugged in (block heater), it will usually start reliably.

What typically happens that would require the truck to be plugged in now in order to start? Batteries are new, less than 2 months old.

Second question is regarding the product "Diesel 911". Is that something that should be used sparingly, or is it something that I should add regularly to the tank durning the winter months?

The truck is a delivery truck, so it is used almost daily. It has been somewhat regularly maintained since I bought it new, oil changes are regular, usually every 7 thousand miles. (interval via owners manual says every 10 k miles.

Any input is appreciated.

First question: In cold weather glow plugs need to be healthy, engine needs to spin fast when cranking, higher cetane fuel helps, a warmed up engine helps, and you need good compression.

Compression is probably fine with your low mileage.
Engine can spin faster with good battery.
Clean starter circuit electrical connections can help.
Lighter viscosity synthetic engine oil can be used.
You are already plugging in the block heater.
Cetane boosters can be used.
Glow plugs may need replacing...or longer glow times (double or even triple glow).

Second question: Power Service Diesel 911 (red bottle) is designed as an emergency de-icing product when water has frozen in your fuel filter and the fuel is not gelled.
Carry a bottle for emergency use but don't use it every day.
Anytime, but especially in the winter you can use the white bottle of Power Service Diesel fuel supplement to boost your cetane and prevent gelling of your fuel. Available at Walmart and other vendors.

t walgamuth · #5 01-07-2017, 01:05 PM

Its driect injection so glow plugs are unlikely. I'd suggest thinner oil and checking all your connections to the battery and starter.

And really no harm plugging it in. If you plug it in an hour before its needed it will probably start fine and its cheaper than plugging in all night.

t walgamuth · #6 01-07-2017, 01:05 PM

Also 10K oil changes might be too long.

dude99 · #7 01-07-2017, 01:12 PM

Starters also get weaker over time. It could be time for a new one.

Diseasel300 · #8 01-07-2017, 01:39 PM

Quote:

Originally Posted by t walgamuth

Its driect injection so glow plugs are unlikely.

LOTS of direct-injection diesel engines have glow plugs. Some have grid-heaters in the intake snorkel. They are both there to provide heat.

kerry · #9 01-07-2017, 02:48 PM

My 99 Fuso has glow plugs. You should check them. My glow plug light only comes on in very cold weather. Does yours come on? However, there was a recall on Fuso's of some years, to install a 'cold weather kit'. You should ask your dealer if yours is recalled. It's not cheap. I was talking to the dealer I use and he says the kit costs $20k. He also says that if the kit is not installed, the EGR? system freezes up, overpressurizes the crankcase, blows out the turbo and then blows all the oil out the turbo seals, seizing the engine. He had one truck which had two engine replacements as a result of the problem. That truck was a 2012. Don't know if the problem extends back to 2008.

lorainfurniture · #10 01-07-2017, 05:52 PM

Quote:

Originally Posted by t walgamuth

Also 10K oil changes might be too long.

I always thought the same, I change the oil every spring and fall regardless of mileage. I barely put 15k miles per year so it works out to roughly 7500 mile intervals. I think this spring it will be due for a synthetic upgrade, and I'll check glow plugs.

To answer re: the glow plug light: yes, it does turn on only during cold temperatures. It cycles for 10 ish seconds then shuts down. Last time I did a double glow, but when I cranked, the engine was slow to turn.

Once started, it runs like a top, no smoke, very smooth idle. Power has been consistent since it was new. I typically never shut it off during the day when temps get this low, to avoid hard starts and possibility getting stuck.

To check glow plugs, I simply would ohm them out? Amp draw test? Visual check?

Also, I find that the truck won't start unless plugged in for a minimum of 2 hours. I don't have too much of an issue leaving it plugged in overnight, when the truck doesn't start I have lots of employees sitting around getting paid, and angry customers. It's not worth the few extra bucks in electricity.

My concern is that it never needed to be plugged in before. Oil is always changed at same dealer (I assume they are using the same oil). Maybe the starter is starting to wear. During the summer months this truck gets started 10 times a day.

97 SL320 · #11 01-07-2017, 07:44 PM

A " Glow plug " has about zero effect on cranking ability. ( I will give that if the cranking system is weak, a good set of glow plugs will help the engine start to fire. )

To quote the OP

" Vehicle in question is my 08' Mitsubishi Fuso. It is direct injection, with that stupid DPF filter. About 120k miles. "

" I find that the truck at this point in its life will not Crank very well, if at all when the temps reach below 15 degrees. This was never an issue up until this year. If I leave the truck plugged in (block heater), it will usually start reliably. "

Very, very few direct injected engines have in combustion chamber glow plugs so I doubt the engine in question has them. ( A Deutz 100% oil cooled F3L1011 / F4L1011 has in chamber glow plugs but even then only by special order. )

Direct injected engines with some sort of starting assist have an intake air heater. ( Some older tractor engines have what is called a flame plug that uses diesel fuel to internally heat the intake air. )

Given our OP lives in the salt belt, I'd remove and clean every high current battery connection between the battery and starter. This is including the entire high current ground path. I've seen trucks that ground the battery to the frame then have a strap between the engine / starter and frame.

Look for external loads on the cranking system. ( Like a hydraulic pump engaged / AC compressor engaged. )

If none of this helps, the starter may be getting weak. Starters generally have 4 brushes, I've seen a single brush fail or even one of the 4 field windings open up leaving you with a starter that has only 1/2 power.

Have a look at the engine fan while cranking, if the fan isn't turning, the starter drive is slipping. ( starter drives use a one way clutch so the engine doesn't overspeed the starter motor once it fires. )

kerry · #12 01-07-2017, 08:07 PM

Good point. There are two batteries in my Fuso. Are both batteries good in yours and are all connections clean on both of them. I modified mine with a marine battery switch so I can use one or both batteries.

I have noticed however, that my Fuso does seem to crank slower than I would like. Not sure if that is the starter or what. I did replace my starter a few years ago. It's had what I would call a lazy starter or a slow crank for a few years now. I typically don't drive it in cold temperatures though since its a camper. It's never failed to start. I don't think the actual energizing of the glow plugs stops when the light goes out so you can glow it longer without doing a second glow. I have a cigarette lighter voltmeter in mine and can tell the length of the glow cycle by watching the voltage.

Diseasel300 · #13 01-07-2017, 11:34 PM

So it's the cranking itself that's slow, not just the ignition from the cranking process.

A few things can cause a slow crank - weak starter, weak batteries, poor electrical connections, thick oil.

Since plugging in the block seems to help speed up the cranking process, I'd lean heavily towards the oil being too thick for the conditions. Perhaps you have a different brand of oil than you've had in the past? The temperature of the block is the only thing changing by plugging the truck in, so that largely rules out the electrical system, including the glow plugs.

Could be worth changing the oil and putting in a wider temp range or synthetic oil and seeing if it helps.

BillGrissom · #14 01-08-2017, 01:43 AM

Aren't all diesels "direct injection"? Mine do have a pre-chamber, but that doesn't affect the basic compression-ignition operation, just makes it quieter (relative term). With the electronic-controlled injection of the newer "common-rail" designs, they were able to get rid of the pre-chamber. I don't think big semi-truck engines ever used pre-chambers.

Answer is just like our older engines, need good compression, good glow plugs (if have), and a strong battery and starter. Keep cranking until the engine takes over, which can be slow on a very cold morning.

97 SL320 · #15 01-08-2017, 08:03 AM

For a diesel, " direct injection " is where the injector nozzle sprays fuel against the piston. In this case generally there is a " mushroom " in the middle of a bowl in the piston, this is to promote swirl in the chamber. In other cases there is a stainless steel disc that is bolted to the piston top, this is to protect the piston from flame erosion.

"Pre chamber ", " Pre cup " or " Indirect Injection " ( IDI , this term is also used to describe early Ford Tk diesels ) is where a sub chamber in the cylinder head contains the injector and glow plug. Fuel is injected , lit off by the glow plug then the rich burning mixture makes it's way to the cylinder where it continues to burn. ( More oxygen is in here. )

Having a glow plug is absolutely necessary because too much heat of compression is lost into the head casting. Having a physically intact glow plug ( even if it isn't electrically functioning ) is also vital to a running engine, the glow plug continues to retain heat as a hot spot making it easier to light off fuel.

Pre chambers are used to reduce noise / vibration because they smooth out the combustion process. A mechanical injection system instantly sprays fuel making for a big bang.

Modern electronic diesel controls can puff the injectors smoothing out the combustion process eliminating the need for a pre chamber. Rather than one big spray, the spray is modulated over time to get things going then the bulk of fuel injected. Another benefit is that we now can have engine braking by injection a bit of fuel very early so the engine is fighting against it's self.