That's exactly what it should do. When it is down below 30 degrees, the amount of heat from the block heater is not sufficient to raise the temperature of the entire engine much above 80 degrees or so. But, that is all you need. Think about starting the engine in 80 degree weather. You don't want to spend any more electric than that.

Now, if the block heater is not working, you will know it when the temp gets down below 20 degrees. If it cranks for ten seconds and starts with a cloud of smoke and runs rough for 15 seconds or so, then the block heater is not working. If is starts like it's 80 degrees outside, it's working fine.

As a young boy I grew up in a large logging community. My father owned the only Service Station in 20 miles of the largest town. We serviced about a 100 Log Trucks, it was common to see a can of ether or starting fluid in a Diesel Log Truck. Loggers kept alot of it in there service trucks to start there Logging Skidders. We used it to some degree, but not much. My father always told me that too much could "lock up" the engine or "blow it up", besides being "harmful" to you. We normally just used our Block Heaters in our Ford F-250's at our shop. I've seen too much Ether blown into the air intakes, and the engines start "violently". The Block Heaters are the safer way to start a "Cold" Diesel engine. If that's not helping you've got more problems, such as the "glow plugs". I've had my 300 SDL for 2 years and have never blown any starting fluid or ether into it and I sure don't plan on it.

Years ago I saw some guys use charcoal in a pan to heat up the engine enough to start it, yes, it was a diesel, a semi with a Cat engine. The charcoal was started and let burn to white edges and then they slid it under the truck. Well, it did start, and no one got hurt! But, I was amazed.

DS
87 300 D

But you must have a BRAIN to do it in a safe manner.

There are too many DANGEROUS FOOLS in the world for me to ever suggest doing this.

I watched one try to use this procedure on a Mack, near the Mackinaw bridge, he let it warm for an hour, then got out a can of ETHER, started spraying the intake, some dripped down to the charcoal, the blast threw him ten feet, and burned his snow suit and face mask.

Some people are DANGEROUS FOOLS, soon to be DEAD FOOLS.

Agreed. WD-40 is IMO useless as a lubricant, but well known among big diesel folk as starting fluid. Even works with Wankel (aka: rotary) engines where regular starting fluid will destroy them.

Using starting fluid of any kind in a glow-plug or heated intake engine is risky without disabling the glow-plugs and overdoses can cause bigger problems, even in big diesels it can cause stretched head bolts etc.

__________________

Gone to the dark side

- Jeff

whunter;all,

it's been said for eons in the US Army that: "NOTHING can be made idiot-PROOF because idiots are so ingenious."

over the years, i've found that to be TRUE! = promiscious use of ether in engines of all kinds is one of those.

yours, tn46

My '77 U1000 Mog has the ether injection option. No glow plugs in the OM352.963 engine. Of course the little cartridge cans to put in it are probably impossible to find now.

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1986 300 SDL - rolling parts car and test bed.
1987 300 SDL - semi daily driver.
1977 U1000 Unimog
2007 Ram 2500 6.7l

Go to your local Penske truck service center. The original cans may be hard to find, but heavy trucks use this system and an upgrade is surely available!

I had a CAT with ether injection also, called a "cold start aid". The trick is that the ether only goes in in a controlled shot, not as long as you want to hold the button etc., and was disabled if the engine was on. That of course was a non glow-plug direct-injection 10.4L engine, big difference w/o glow-plugs.

Oh, and I agree on "idiot-proof". In my too many years of Engineering, I preferred the term "idiot resistant".

__________________

Gone to the dark side

- Jeff

Would it be safer to wait another minute for the glow plugs to cool off (from red hot) after you hear the glow plug relay click off before cranking the engine?

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85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

I have been told by several folks that the chemical make up of WD40 has changed and it is no longer flamable and will not help a diesel start.

My powerstroke truck sat for over a week in sub zero weather a month or so ago.

I plugged in the block heater a while and tried to start it - nothing. After replacing the fuel filter (I suspected it was frozen) pouring fresh diesel into the filter housing with the new filter - charging the batteries, etc.... it would crank and smoke, but not start.

wd40 had no effect...

In desperation, I sprayed about a 1 second burst of ether into the air filter housing AFTER waiting for the glow plug relay to shut off (and a minute or so after that) and the engine started - it did rev up over 2500 rpm even with that little amount of ether.


So - certainly it is a last resort and must be used with care.

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95 E300 Diesel 265k and counting

room, my neighbors 1985 300d didnt get the heat from the block heater because of a broken ac cord,near zero degrees,i took 2 five gallon buckets and filled with hot water from the house water heater,poured slowly over the valve cover,kept the water comming for 4 total buckets,cranked the engine and got a start.
larry perkins lou ky

wd40 is not a cold start aid. It is a way to start the car if you have a need to bleed and for some reason your prime pump does not work correctly. You have to spray it directly into the intake and keep spraying it. if the engine is sound it will run on the wd 40 until the fuel lines bleed themselves and take over as long as you keep spraying.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Thanks for clearing that up for me - and for making the point about priming - as I'll be needing to do just that once I finally put my 606 back together again after replacing all the fuel lines, rebuilding the fuel pump, and replacing the delivery valve seals, and having the injectors rebuilt....
You probably just saved my new starter a lot of un necessary cranking!
Thanks a million!

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95 E300 Diesel 265k and counting

My pleasure.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.