M925 difficult starting when cold

[Bushwacka]

M925 is slow to start in cold weather. Cummins 250. When turning over, the exhaust stack belches blue-white smoke. Engine turns over 3-6 times with up to 3-4 attempts to start before it finally starts.

Could I have seepage back into the cylinders after turning off ignition or a cracked injector?

The longer the truck sits, the more turns it takes on the starter before it starts. Once started, the engine is smoothe and responsive with no exhaust smoke. Restarts after initial start are instant.

Ideas for how to diagnose slow starting?

 

[Farmallmilitary]

All of the cummins 250's are very cold blooded. Mine most likely there is nothing wrong with the truck because in even 50 degree weather it still has to turn over some along with belching out white smoke. good luck.

 

[commandojeff]

It's the nature of the beast. At least you got it started! Get a block heater if you are worried about it.

 

[Bushwacka]

Appreciate the perspectives and experience with the Cummins 250.
Perhaps that is why it has the ether injection system
As long as you guys see it as normal, a quick shot of ether should resolve it.
Thx!!!

 

[Scarecrow1]

I know mine has a mind of it's own. It seems to start great until it puts up a fight then it's ether time. I won't try cranking it more than a couple of short cycles for fear of burning up a good starter. Ether is what it needs to beat the cold. I just put my batteries back in after having them charged today it's in the high 50's and it busted off on the first turn as usual. . I haven't cranked it in a week because of some well meaning curious kids playing with the switches in my absence. I am putting it on a RV storage yard tomorrow to end this potential future problems . Just read the post on starting with ether and you will be okay.

 

[rrrr]

It's the nature of the beast. At least you got it started! Get a block heater if you are worried about it.

Put a block heater in mine, makes all the difference. Do a search its in the 5 ton forum or 5 ton mod forum.

 

[commandojeff]

Put a block heater in mine, makes all the difference. Do a search its in the 5 ton forum or 5 ton mod forum.

I looked into the block heater and I saw that you got one. I was interested but I don't really use the truck at all during the winter. I started it a month ago on a warm day and all was good. The only reason I would want to have the block heater is to have the truck ready if I needed it for any reason during the cold weather. I see it as an upgrade in the future. As of yet, I am just working on getting most of the fluids changed and the back axle seals changed. The maintenance comes first right now, seeing as my cash is limited. Looking forward to warm weather, that's for sure.

 

[Triple C]

M925 is slow to start in cold weather. Cummins 250. When turning over, the exhaust stack belches blue-white smoke. Engine turns over 3-6 times with up to 3-4 attempts to start before it finally starts.

Could I have seepage back into the cylinders after turning off ignition or a cracked injector?

The longer the truck sits, the more turns it takes on the starter before it starts. Once started, the engine is smoothe and responsive with no exhaust smoke. Restarts after initial start are instant.

Ideas for how to diagnose slow starting?

That would be fast for my 925. In cold weather it takes about 30 seconds of cranking before it fires off. I don't start getting smoke for about 15 seconds and then it takes about another 15 seconds to light off and that's WITH the block heater. It wouldn't start at all in cold weather before, (though I am only using two batteries.)

 

[jonesal]

Mine was that way in cold weather, took about 30 seconds before it would light off. I installed a block heater and no matter how cold, it starts with a single crank. It really, really does help. I like that it is much easier on the starter.

Al Jones
'84 M023

 

[CUCVFAN]

That would be fast for my 925. In cold weather it takes about 30 seconds of cranking before it fires off. I don't start getting smoke for about 15 seconds and then it takes about another 15 seconds to light off and that's WITH the block heater. It wouldn't start at all in cold weather before, (though I am only using two batteries.)

Four batteries makes a HUGE difference in cranking speed when cold. With these monsters, cranking speed is what you need.

Also, are you giving it any throttle when cranking? I've found some of them like it and some don't. The cold start instructions say give it some throttle, but I've seen them start right up without it.

 

[Bushwacka]

Four batteries makes a HUGE difference in cranking speed when cold. With these monsters, cranking speed is what you need.

Also, are you giving it any throttle when cranking? I've found some of them like it and some don't. The cold start instructions say give it some throttle, but I've seen them start right up without it.

Will try the block heater. Pleased to know it is just my Cummins 250 being a slow starter. Which is best-magnetic 300 watt heater or coolant bolt-on?

Also, was giving no throttle, then tried full throttle. Same result....no fire
Thanks

 

[jonesal]

I have four new Interstate 6TL batteries - and those are always plugged into a battery minder (in the winter only). When cold, I use about half throttle for 30 seocnds (no block heater) and then it starts. When using the block heater, I use just a smidge of throttle and it lights immediately. The engine is a 2008 build so not very many miles on it.

 

[Bushwacka]

Four batteries makes a HUGE difference in cranking speed when cold. With these monsters, cranking speed is what you need.

Also, are you giving it any throttle when cranking? I've found some of them like it and some don't. The cold start instructions say give it some throttle, but I've seen them start right up without it.

Thanks for the block heater info. I just want to be sure that the NHC250 Cummins does NOT have a glow plug and I missed the obvious........

Thanks

 

[CUCVFAN]

There is no glowplug in the M939 trucks. The M809 trucks, which use the same basic engine, have a glowplug and primer pump to use for cold starts. But, for M939 trucks there are neither, hence the ether start feature.

The block heater does work wonders too. A couple of hours of heat and no ether is usually required.

 

[73m819]

If it takes 15 seconds BEFORE smoke shows, and takes longer the longer the truck sits, realy sounds like you are loosing your prime, allowing the fuel to drain back to the tank, even a little loss of prime WILL give you starting fits
You SHOULD be getting smoke as soon as you try to start, may not start due to cold but smoke should be there.

Check to MAKE SURE ALL the fittings are tight, the top fuel filter o ring is seated right, ALL the suctions lines are good, the filter bleed valves are fully seated, again it does not take much to cause proplems.

 

[Csm Davis]

There is no glowplug in the M939 trucks. The M809 trucks, which use the same basic engine, have a glowplug and primer pump to use for cold starts. But, for M939 trucks there are neither, hence the ether start feature.

The block heater does work wonders too. A couple of hours of heat and no ether is usually required.

Actually CUCVFAN there is a primer pump it is just under the hood instead of in the cab. Try the primer pump then start it you will be able to tell if you are losing prime.

 

[CUCVFAN]

Well, yes, but it is not practical to be used for starting, like the M809 trucks. Priming after a fuel filter change, yes, but you need soldier B to pump it if you want it to behave like the M809 trucks, and even then, it won't be spraying fuel past a glow plug.

He could certainly pump it to see if he gets smoke sooner than 15 seconds, though.

 

[goldneagle]

If it takes 15 seconds BEFORE smoke shows, and takes longer the longer the truck sits, realy sounds like you are loosing your prime, allowing the fuel to drain back to the tank, even a little loss of prime WILL give you starting fits
You SHOULD be getting smoke as soon as you try to start, may not start due to cold but smoke should be there.

Check to MAKE SURE ALL the fittings are tight, the top fuel filter o ring is seated right, ALL the suctions lines are good, the filter bleed valves are fully seated, again it does not take much to cause proplems.

He could also have cracked fuel lines. We have discussed this before. Have to pressurizer the tank and see if there is signs of escaping fuel. As mentioned the lines look normal until you pressurize them.

 

[Bushwacka]

He could also have cracked fuel lines. We have discussed this before. Have to pressurizer the tank and see if there is signs of escaping fuel. As mentioned the lines look normal until you pressurize them.

Thanks guys. Great insights.
Tried hand held ether injection sprayed into engine intake
Seemed to make no difference in starting....took several attempts. 6-10 revolutions
Will go back and prime the pump (handle) a coupla times , then see if cranking time reduces and if I get smoke on first crank

 

[Csm Davis]

Yeah about that pumping the primer a couple times you should pump it until it becomes firm to push an and that will probably take about 50 or 60 bumps on a light prime loss.