What Am I Waiting For?

[Utah Dually]

This might be a dumb question, but when I turn the key on the "Wait To Start" light comes on. Just what is the system doing? What am I waiting on to happen?Since this is my first diesel every once in a while I jump in the truck, put the key in and start it like a gas motor. Am I hurting anything because I am old and forgetful?

[Wild and Free]

There is an intake heater that is warming up the air inside the intake manifold so that the engine will start better, if it is warm enough it hurts nothing to just start but when it gets colder it will start a wee bit harder due to not having warm air to pull into the cylinders to aid in combustion.

[Mopar1973Man]

If the outside temps are below +60*F and this is first start you should wait for the light. But if the engine is fully warmed up no need to wait just hit the key and go.All the WAIT TO START does it the ECM boots up and detect the manifold temperature if the IAT teemparture is below +60*F then the grid heaters are active for a pre-set amount of time. Then the light goes out after the time. If the IAT temperature is above +60*F then the light only comes on as a bulb check and go back off. How can you tell the grid heater pull the battery voltage way down where the bulb check doesn't.

[rancherman]

nice sterile way of helping to start a cold engine! ^^^^I have a couple of 'antiques' around here that use an actual fireball inside the intake. It's a drawn out process of holding a button in..(which heats a white hot element)..... then pushing another button (which releases a set amount of liquid diesel) poof! you have about 1 second to start cranking.. It actually works pretty good!My 903 cummins has a little porthole to veiw the fireball (to see if it's working or not).

[Utah Dually]

Thank you everyone. This is the best diesel site on the web....

[ISX]

Being your first diesel, I'll fill you in on some more you might not understand. All fuels (diesel/gasoline) have what is known as flash points and autoignition points. A flash point is the temperature where the fuel is able to ignite by an open flame (or spark). It is mainly due to the vapor given off by the fuel, which is why gasoline vapor will ignite if you light it in some form. Gasoline engines actually take in this vapor, which is fed from the fumes of the constantly replenished bowl in the carburetor. As long as there is fuel, there will be vapors coming off it. The same goes for propane, it is the vapor you are burning, not the liquid. In propanes instance, it is boiling into a gas and you are burning that gas. The flash point of Gasoline is -45*F. The flash point of diesel is 144*F. So as long as gasoline is over -45, it is giving off ignitable fumes, which does mean that under that temp, it becomes hard to start (so in alaska or something they have to use block heaters on their gas engines sometimes). Once the engine is warmed up, some of that heat gets absorbed by the fuel so then it isn't really an issue. But this means that if diesel was warmed up to 144, it would ignite if you put a flame to it. The other thing was autoignition temperature. This is the temperature where the fuel will just blow up due to heat alone (no outside source of ignition such as an open flame or spark). Gasolines autoignition temp is actually 536*F and diesel is 410*F. This means without a spark plug, you would have to heat the gasoline up to 536 before it would blow up. Diesels only need to reach 410*. Maybe you are seeing the connection between terms. Gasoline engines rely on the fuels flash point to set it off with a spark plug. Diesels however, have no spark plug and rely solely on the heat produced during the compression stroke. When the piston goes up really fast, the air is compressed and it gets VERY hot in the process. Hot enough to get over 410F and ignite the diesel when it shoots in. But, therein lies the problem. On colddd days, the heat from compression sometimes doesn't get the fuel to that 410* point, so it doesn't ignite. A combination of things contribute to this. On a 0*F morning, the oil is thick, the engine is cold and contracted so things are tighter (more friction), and this contributes to a slower cranking speed. The piston and cylinder walls are also freezing. The heat produced by compression is absorbed by the piston and cylinder walls, further hindering the ability to reach the 410* point. Eventually the heat generated from cranking the engine absorbs into the pistons/cylinder walls enough that the 410* point is eventually able to be reached, and the engine starts. So, the diesel world has created methods to help the engine out on these cold days, mostly by heating the air. You must recall that on these cold days, the engine is sucking in that same 0* air and trying to get it over 410*. So if you heat that incoming air, then it has a much better chance of reaching 410* quicker. The cummins engine does this with a grid heater which gets very hot (500*F). When you turn the key on, it is turning the grid heaters on, you are waiting for them to get hot. They are electrical so just like an electric space heater, they take a little but to warm up. The wait to start light is telling you they are on and warming up. The colder it gets the longer they run. After you start the truck, they continue to cycle on and off for a few minutes to keep the incoming air nice and toasty until the engine gets warm enough to heat the air on it's own. When I mention 410F I mean the fuel has to get to that temp, so the air has to be even hotter. I have a calculation somewhere that determines the temp it gets based on RPM. I think it was around 700-900F idling.If you don't use the grid heater (lets say you unplug them), then you won't really notice anything until it gets under 20-30*, then you will start noticing it takes a few more cranks than usual. At 0* it will probably take 5 seconds of cranking, possibly more, to start. A worn out engine will take longer since the compression isn't as high as it used to be. If you look on youtube you will see guys at 20F (usually in power strokes and duramaxs ) who spend 30 seconds starting their trucks and then revving the crap out of them to keep them running. Those are worn out like no other. The trick is to ALWAYS use the grid heaters any time the engine is under 30*, unless you have just driven it and the engine is already warm so I am talking the BLOCK itself. Then let it idle for 30 seconds, then slowly take off, be nice to it until the engine temp has got to at least 140F, then do whatever you want. Idling tends to just make the engine run longer at a colder temperature since idling doesn't really produce much heat. That is why you let it idle for 30 seconds on those cold days and then slowly take off. Mike (mopar1973man) has things to remedy this. Here is a video I made of the grid heaters in action.

http://www.youtube.com/watch?feature=player_embedded&v=i5CZJcyyZeg

Does that help? I can write more if you want

[flagmanruss]

Since this is your first diesel... these grid heaters in the intake make it unwise to use any starting fluid. They could ignite in the intake... potentially catastrophic results. Once the engine starts, you'll notice the ammeter showing discharge for a few minutes... that's the draw of the grid heaters doing that. Once the heaters shut off, the alternator will recharge the batteries.My old John Deere does not have grid heaters & it's common to cold start with ether/starting fluid.