941 not cranking with glow plugs update

wlf89

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i got the new breaker put in and it isnt tripping no more but it still wont crank when 50 outside or below after being heated 2mins. it tries to but wont quite do it. when its about 60 or hotter about 30secs of glow plug and it will crank right up. i took all the battery connections from battery to starter and all the grounds off and cleaned them up but didnt seem to make no difference. it sounds like the engine is spinning fast enough.
any ideas why it might not be cranking like it should?

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Fri, Jan 6, 2017 7:30 AM

catdozer876

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Check for water in your diesel fuel, cleaned your fuel screen, check for free flow of diesel from the tank and changed your main fuel filters. I have had algae cause a problem very similar to what you are describing. It just was not getting enough fuel to start after sitting over the course of just one winter. When you do change your filters try dumping out the fuel from the fuel filters into a clean bucket and see if the fuel is discolored or smells different than fresh diesel.

Also sometimes if it is really cold I have had luck with cranking the diesel with the fuel in the off position for about 10 seconds. Then wait about 30 seconds, then apply the glow plugs for same duration as you would normally for the conditions, then give it a little bit of fuel, not too much and then crank it. You have effectively heated the engine a little and it can make a big difference in starting in the cold. Also if you give it too much fuel when trying to start it can make it much harder to start form a few tractors I have had. Keep us posted. Have you checked to see if all of your glow plugs are working?

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Fri, Jan 6, 2017 8:36 AM

Old Magnet

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Reply to catdozer876:

Check for water in your diesel fuel, cleaned your fuel screen, check for free flow of diesel from the tank and changed your main fuel filters. I have had algae cause a problem very similar to what you are describing. It just was not getting enough fuel to start after sitting over the course of just one winter. When you do change your filters try dumping out the fuel from the fuel filters into a clean bucket and see if the fuel is discolored or smells different than fresh diesel.

Also sometimes if it is really cold I have had luck with cranking the diesel with the fuel in the off position for about 10 seconds. Then wait about 30 seconds, then apply the glow plugs for same duration as you would normally for the conditions, then give it a little bit of fuel, not too much and then crank it. You have effectively heated the engine a little and it can make a big difference in starting in the cold. Also if you give it too much fuel when trying to start it can make it much harder to start form a few tractors I have had. Keep us posted. Have you checked to see if all of your glow plugs are working?

What's the status and specification of the batteries you are using?

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Fri, Jan 6, 2017 10:32 AM

wlf89

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Reply to Old Magnet:

What's the status and specification of the batteries you are using?

just going from memory here old magnet but i think the specs below are correct for the batteries i put in it about 2yrs ago. and it was checking somewhere around 24.8volts to the starter.

Battery Electrolyte Composition:Acid
Battery End Type:Top Post
Battery Purpose😖tarting Lighting Instrumentation
BCI Group Size:27
CA at 32 degrees F:1035
CCA at 0 degrees F:840
Freight Class:65
Polarity:Left Positive
Reserve Capacity:140
Terminal Type😄IN
Volts:12

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Fri, Jan 6, 2017 11:43 PM

cojhl2

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Reply to wlf89:

just going from memory here old magnet but i think the specs below are correct for the batteries i put in it about 2yrs ago. and it was checking somewhere around 24.8volts to the starter.

Battery Electrolyte Composition:Acid
Battery End Type:Top Post
Battery Purpose😖tarting Lighting Instrumentation
BCI Group Size:27
CA at 32 degrees F:1035
CCA at 0 degrees F:840
Freight Class:65
Polarity:Left Positive
Reserve Capacity:140
Terminal Type😄IN
Volts:12

Even though you have the trip fixed, are you sure the glow plugs are not burned out?

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Sat, Jan 7, 2017 12:01 AM

wlf89

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Reply to cojhl2:

Even though you have the trip fixed, are you sure the glow plugs are not burned out?

all 4 plugs are working

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Sat, Jan 7, 2017 12:36 AM

Old Magnet

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Those batteries should be adequate if they are in good condition. I'd note your voltage reading. Batteries in good shape should produce 2.2v per cell = 26.4v for the two 12v batteries.

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Sat, Jan 7, 2017 1:56 AM

wlf89

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[quote="Garlic Pete"]but if all four glow plugs are working for sure, you have good batteries and the voltage you describe, it sure seems that you just need more heat to get that thing started when its cold. Two minutes at the temperatures you describe is way more time on the glow plugs than I'd expect. That time to me would be more expected at freezing or below.

i'm afraid you may be seeing the effects of a worn engine. If the compression is low because of worn rings or valves not sealing well, it won't make anywhere near as much heat upon cranking. I don't remember you posting any information about blowby. If there is enough wear to cause this starting difficulty, I'd expect you to see a fair amount of blowby when it is running.

If the blowby isn't bad, I'm confused. When you are cranking with it below 50 degrees and the fuel on, are you getting a lot of white smoke? I think in your other thread we pretty much ruled out a fuel supply problem.

catdozer876's suggestion to crank it a bit with the fuel off would really help build some heat, even if internal wear is part of the problem.

You mention that you have 24.8 volts at the starter, but you might want to measure volts at the glow plugs with them energized. Even though you cleaned all the connections, maybe you've got a voltage drop somewhere which means your glow plugs aren't making the heat they should.

Pete.[/quote]

the engine only has about 50hrs on it since i rebuilt it, but i didnt do any head work and am wondering if that is my problem,although they seemed to be sealing good when i inspected them when rebuilding the engine.

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Sat, Jan 7, 2017 3:06 AM

mrsmackpaul

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Reply to Old Magnet:

Those batteries should be adequate if they are in good condition. I'd note your voltage reading. Batteries in good shape should produce 2.2v per cell = 26.4v for the two 12v batteries.

Old Magnet maybe onto something here as the cranking speed when the motor is cold is critical as it generates the heat and faster it cranks the more heat
Even in my mild climate and our very mild winter motors can wind over at what appears normal speed but still not fire straight up and the problem is its just not making the speed to make the heat
So maybe it is as simple as Old Magnets suggestion

Paul

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Sat, Jan 7, 2017 3:25 AM

Deas Plant.

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Reply to mrsmackpaul:

Old Magnet maybe onto something here as the cranking speed when the motor is cold is critical as it generates the heat and faster it cranks the more heat
Even in my mild climate and our very mild winter motors can wind over at what appears normal speed but still not fire straight up and the problem is its just not making the speed to make the heat
So maybe it is as simple as Old Magnets suggestion

Paul

Hi, wlf89.
I would have expected a better figure than 24.8 volts from a good pair of 12 volt batteries connected in series, like somewhere North of 26 Volts. A quick test would be to add another good 12 volt battery to the mix, using booster cables to connect it to ONE battery at a time in the machine and then cranking.

If this makes more difference when connected to one battery than to the other, you may have a weak battery in the machine. If you notice the same change in response from connecting to either battery in the machine, then both machine batteries may be weak.

Some years ago, the starter failed on a Cat D5B that I was operating. It barely managed to start the engine to get the machine on the float/lowboy. I called the boss and told him about it and he arranged for his pet auto-electrician to go the new job to investigate. When we went to start the dozer, the starter was even worse, so the 'sparky' took another 12 volt battery out of his van and used booster cables to connect it directly to the starter cables to give 36 volts to the starter when the key was turned. The engine lit up very nicely, thank you. I took the dozer off the float so that it could leave and the 'sparky took the starter out while the engine was still running. I worked the dozer through the day without shutting the engine down and the 'sparky' had the re-built starter back there to put in again at the end of the day. Food for thought?

Just my 0.02.

You have a wonderful day. Best wishes. Deas Plant.

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Sat, Jan 7, 2017 4:27 AM

rmyram

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was the 24.8 volts at the starter when you were cranking the engine? i was always taught 2.1 volts per cell which would equate to 25.2 volts for two 12v batteries in series. I'm not going to quibble, 24.8 volts at the starter when everything is at rest is slightly low and will generate low cranking speeds.

garlic pete may be onto something as well. i have seen and even have a diesel that displays similar characteristics. the valves may be sealing well, but was the valve protrusion checked when the engine was rebuilt. valve recession in diesel engines can significantly alter the compression ratio making it hard to start, especially if the valves and seats were ground during the rebuild.

My old 4020 JD which does not have glow plugs had a complete engine overhaul, but the owner did not check the valve protrusion, they had the head checked for cracks and leaks, then they had valves and seats ground. valve protrusion was just on the edge of acceptable towards the maximum side of the spec, one or two may have been above the maximum spec. it is a cold starting tractor at anything other than warm engine temps. i am opposed to using the ether bunny to get it going so i installed a webasto diesel fired engine heater. at -20 celsius it takes less than 20 minutes for the engine to reach operating temperature, the old diesel fires right up like it was after lunch an a warm summer day plowing.

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Sat, Jan 7, 2017 5:01 AM

941 not cranking with glow plugs update

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