Glow plugs?
- Thread starter Maximus
- Start date
mjmason1
New Member
Definitely no glow plugs. Just push the switches and she starts. I don't know what an intake heater is.
cwiert
Active Member
Neither.
- Oct 6, 2006
- 12,153
- Boat Info
- 1996 450DA
- Engines
- 3116 Caterpillars
the 3116 uses a unit injection system that uses a fuel gallery charged with fuel to supply individual injectors. As a result the engine starts easily and quickly. If you are not getting prompt starts, it is more than likely because the engine cranking speed is too slow. The cause is usually electrical and can range from low voltage due to weak batteries to lose or corroded battery terminals.
cwiert
Active Member
Hi Frank,
Since you brought up slow starts, I have a follow up question. My port engine takes longer to start than my stbd. About 3 secs for the port, and half that for stbd. All batteries are new.
However, I can "fix" that slow start by giving the engines a little throttle before pressing the start button. For example, if I put the throttle at 15-20%, the port will start immediately.
I'll be turning 1000 hours with my next trip, and I've already scheduled a diesel pro to come check it out in the next month or so for routine maintenance issues. Based on what I just told you, is there anything specifically I should have him look at?
- Oct 6, 2006
- 12,153
- Boat Info
- 1996 450DA
- Engines
- 3116 Caterpillars
No, and I don't think there is anything wring with the engine exhibiting that starting difference, but you can discuss t he following with your diesel guy.
I think it is just a difference in the internal governor and its spring pressure. To get a Caterpillar to start, you have to spin the starter enough for the fuel pump to build enough fuel pressure to compress the governor spring and open the governor which controls idle rpms. By setting the throttle at some point above idle you are manually compressing the governor spring so the fuel pump doesn't have to. I start my engines this way all the time just to save wear and tear on the starter motor and ring gear.
I think it is just a difference in the internal governor and its spring pressure. To get a Caterpillar to start, you have to spin the starter enough for the fuel pump to build enough fuel pressure to compress the governor spring and open the governor which controls idle rpms. By setting the throttle at some point above idle you are manually compressing the governor spring so the fuel pump doesn't have to. I start my engines this way all the time just to save wear and tear on the starter motor and ring gear.
cwiert
Active Member
Thanks!
And, there are several little check valves in the injection assembly that tend to get gummed up and sticky; these will contribute to such a situation. They are very small and plastic. They are also very easy and cheap to change. If they are sticking your return fuel pressure will fluctuate at the pump frequency.
Xplicitlnck
Well-Known Member
Ok now you got my mind going. (I know little to nothing about diesels) my assumption was all diesels had glow plugs. The glow plug was the "ignition or heat source" and the fuel was ignited by the heat and compression. Now your telling me some diesels don't have glow plugs so please school me on how these engines turn please
cwiert
Active Member
Found this on the ol interwebs: explainthatstuff.com
Diesel engines are similar, but simpler. First, air is allowed into the cylinder and the piston compresses it—but much more than in a gasoline engine. In a gasoline engine, the fuel-air mixture is compressed to about a tenth of its original volume. But in a diesel engine, the air is compressed by anything from 14 to 25 times. If you've ever pumped up a bicycle tire, you'll have felt the pump getting hotter in your hands the longer you used it. That's because compressing a gas generates heat. Imagine, then, how much heat is generated by forcing air into 14-25 times less space than it normally takes up. So much heat, as it happens, that the air gets really hot—usually at least 500°C (1000°F) and sometimes very much hotter. Once the air is compressed, a mist of fuel is sprayed into the cylinder typically (in a modern engine) by an electronic fuel-injection system, which works a bit like a sophisticated aerosol can. (The amount of fuel injected varies, depending on how much power the driver wants the engine to produce.) The air is so hot that the fuel instantly ignites and explodes without any need for a spark plug. This controlled explosion makes the piston push back out of the cylinder, producing the power that drives the vehicle or machine in which the engine is mounted. When the piston goes back into the cylinder, the exhaust gases are pushed out through an exhaust valve and, the process repeats itself—hundreds or thousands of times a minute!
Diesel engines are similar, but simpler. First, air is allowed into the cylinder and the piston compresses it—but much more than in a gasoline engine. In a gasoline engine, the fuel-air mixture is compressed to about a tenth of its original volume. But in a diesel engine, the air is compressed by anything from 14 to 25 times. If you've ever pumped up a bicycle tire, you'll have felt the pump getting hotter in your hands the longer you used it. That's because compressing a gas generates heat. Imagine, then, how much heat is generated by forcing air into 14-25 times less space than it normally takes up. So much heat, as it happens, that the air gets really hot—usually at least 500°C (1000°F) and sometimes very much hotter. Once the air is compressed, a mist of fuel is sprayed into the cylinder typically (in a modern engine) by an electronic fuel-injection system, which works a bit like a sophisticated aerosol can. (The amount of fuel injected varies, depending on how much power the driver wants the engine to produce.) The air is so hot that the fuel instantly ignites and explodes without any need for a spark plug. This controlled explosion makes the piston push back out of the cylinder, producing the power that drives the vehicle or machine in which the engine is mounted. When the piston goes back into the cylinder, the exhaust gases are pushed out through an exhaust valve and, the process repeats itself—hundreds or thousands of times a minute!
Xplicitlnck
Well-Known Member
Now that's interesting. Thank you very much for the explanation!
Steve195
Member
- Jan 15, 2016
- 314
- Boat Info
- 2017 Sweetwater 2286 WB Tri-toon
- Engines
- Yamaha 150 Outboard
I love how many of us do little things like this to make sure our boats last longer and are as trouble free as possible.
I watch my slip neighbor crank up his boat, immediately throw it in gear and head out. It's only about a 30 second no wake zone, and then he's at full throttle getting on plane. I start mine, let it idle in the slip for a minute or two, watch the temp come up, then slowly head out until I'm almost at full operating temp, then I take off. I just know that type of treatment has to be easier on my engine that my neighbors "pedal to the metal" approach.
Xplicitlnck
Well-Known Member
Drive it like you stole it!
Tell me about it, and I'm the one this year that had to haul out for a new drive after blowing one up. Meanwhile, one of our neighbors had an idle issue he wanted me to hear. He started it cold and immediately revved it to 4k rpm in neutral. We fixed his idle issue with a new fuel filter and he's had no problems since. Maybe I should run ours harder.
