What makes a diesel hard starting?

Neighbor has a mid-80s garden tractor with a 2 cylinder Lombardini diesel. Super hard starting even in 60 degree weather. My Oliver starts in this weather within a second or 2 of cranking.

He asked me to look at it (like I know anything) and found the "thermostart" system had a broken wire on a solenoid valve and the "glowplug" portion of the system was burned out. Fixed the broken wire on the solenoid and got a new glowplug. Tested all that and it glows red and bursts into a little fire. Install in into the manifold thinking I have it solved but it still takes lots and lots of cranking before it finally fires. When it finally gets running there is a large amount of grayish smoke that clears up in just a few seconds. Once it is running the exhaust is very clean. You have to keep the RPMs up for a couple minutes before it will idle. I checked the valve adjustments and they were fine.

Don't know the full history of the machine. The hourmeter only has about 400 hours on it and it works so it is possible it might be correct. I do not have a compression tester for a diesel so can't check that. The injectors have a carbon buildup but they both spray and appear to have a decent pattern. The pump is driven by lobes on the camshaft so I don't think the injection timing can be messed up or even changed without messing up the valve timing too.

I suppose I should look for a compression tester and send the injectors out for testing, cleaning, calibration what have you.

What else would you folks advise? Are some diesels just hard starters while others will light right off?

Some designs of diesels will start harder than others. The smoke and throttle need that you describe sound normal to most diesels. One major factor however is the speed of cranking. Since diesels have no ignition they rely on the heat of an adequate amount of compression to start the fire. If cranking speed is low it takes more cranking to get the pressure up there. If it is too slow, it can crank all day and not get there. A few years ago I had trouble getting my F-350 started one time when there was no electric around to plug into. Awhile later I realized that one battery was weak. A new battery made it crank much faster.

I would check compression and cranking speed, which effects compression,.

Sounds like an AC 920 they were always pretty hard to start don't think they had compression release.Compression release makes a big different on small diesels,release compression
get the cranking speed up and drop the compression release.Also those needed the throttle wide open and then pull it back just as soon as it fires up.

Your Oliver has a direct-injected diesel, correct? Many of the twin Lombardinis are indirect-injected and use glow plugs besides the
thermostart. I don't know which engine you have since Lombardini also makes some direct-injected engines that start fine with no glow plugs.

That said, even some direct-injected diesels start lousy at temps of 50F like many Detroit Diesel two-stroke-cycle diesels.

Again, I don't know which model Lombardini you have and if it is IDI or DI. IDI has to have heat even at 80 degrees F to start.

As already mentioned, compression cranking speed and compression heat are critical for best starting cold. I'd at least check the rocker arm clearance too before tearing it apart.

If it?s an idi you need the glow pugs working right in
any weather . I ran an old international tractor that
would not start in 100 degree heat without glow
plugs also had a 6.5 Chevy that wouldn?t start below
100 degrees without cycling the glow plugs . If it?s
not an idi then compression cranking speed . Also if
it?s getting air in the system or losing prime that will
make either design hard to start

Did you try cycling the glow plugs twice. My New
Holland skid steer needs the glow plugs even in
summer . I switch them on , they cycle and go off,
then I cycle the glow plugs a second time, and it will
fire right up. Perhaps the preheat cycle isn?t long
enough to get the job done.

biggest difference i saw in my kubota, which started hard unless you used the glow plugs was when i installed a new battery, it was like a new tractor.

Sounds more to me like the fuel system is losing its prime. There are check valves that can get stuck and countless connections that can leak and let air in.

Quickest easiest thing to try is a heavy dose of your favorite diesel fuel system cleaner. Stanadyne, Power Service, they're all good.

Low compression/too slow a cranking speed. Gotta get the air hot enough to explode the fuel mist, considering you are efficient in your fuel hygiene.

I had the same problem with my JD4200, come to find out the rubber fuel line had hardened and were sucking air. replace them and
now it starts first crank without heat.

With glowplugs, cranking speed is less of an issue. My 1980 AC 5030 2-cyl turns over slow and starts within 4-5 cranks. Check the wiring on the glowplugs, may not be getting the amps.

Thanks for all the advice! I've been reading through them and considering how they affect what I'm seeing.

I have been wondering about the cranking speed. The starter has been rebuilt or replaced at some point. It has newish looking paint and a label from an auto electric shop. IMO it really doesn't seem to spin it as fast as I would expect. One thing that makes me think that is that even after the engine has been running a while and nice and warm it is still slow to start.

There is no decompression device to allow the starter to spin it up before going to full compression.

Battery is near new and connections have been cleaned within the past couple weeks.

I think this is a direct injection style engine. Based on a couple pictures I found on the Web,the injectors spray right into a "depression" on the top of the piston.

The entire "thermostart" system is working. I've repaired or replaced the bad parts and tested it. Glows bright red and after about 20 seconds, releases fuel and it catches fire.

I did check valve clearances and they were fine.

I think I'm going to experiment with cranking it faster. Not sure if I want to try 24V on the starter or rig up an alternate "starter". Have to scratch my head over that one a bit.

Lombardini engines especially without compression release are never going to crank but so fast and the ones I've been around (on the 920 and a pasquali) never started but so good in cold weather anyway.

Diesel engines rely on adiabatic pressure to reach the ignition point of the fuel. A lot of things tie in to that. Gray smoke on start up indicates you are getting barely enough fuel, and barely enough compression. Add that to needing to run off idle after start up indicates several things.

1. Low compression. Adiabatic pressure is built by compression. If it was rated at 18:1 originally, and is now down to 16:1 that will make a huge difference in starting, and staying running.

2. Crank speed(mentioned already). The faster the piston rises, the better adiabatic heating is generated. You could push the piston up super slow, and generate no pressure as it leaks past the rings.

3. Gray smoke indicates complete combustion of the fuel, with no residual fuel left over. Many old diesels will exhaust a bit of black smoke, which indicates plenty of fuel, and incomplete combustion. There is a fine balance there, because too much fuel can inhibit combustion and cause the combustion event to be extinguished before it gets hot.

Have you tried any starting fluid? Carb Cleaner? Warning, starting fluid for gas engines can damage a diesel. I've used WD-40, which is primarily Kerosene, not that much different that diesel, but it is vaporized in CO2(harmless). Of if you have a propane bottle handy with a hose, you could give it a snort of that when trying to start it.

Warning again, if you use propane, into the intake, and you have the glow system on, you may find parts of your engine in the next zip code.

If the glow system is in top condition, you would look at the fuel delivery, and if that is sorted well, next is compression. Is it using oil? Is the oil becoming contaminated with a lot of fuel? How much crankcase blowby are you getting?

The S series two strokes , for example the 53 series with the 17 to 1 compression ratio were lousy starters .
Rebuilt with N series 21 to 1 injectors and N series injectors that have a diner spray mist . Combined with a large battery(s), heavy cables and a direct ground connection . My 2-53 at freezing temps will start on the 3-4th turn .

If it is indirect injection with glow plugs . It won t start unless the glow plugs are red hot prior to cranking .
We have some dimwits at work that jump into the Kubota 1140 s and start cranking . After 10-15 seconds the engine starts in a cloud of smoke . Or the driver goes back to the foreman whining that the Kubota won t start.
Depending on the temperature. 5-10 seconds of preheat and the engine starts in the first turn.
A new battery won t help if the battery is too small or there are high resistance connections . Just polishing connections is no guarantee of low connection connections . The cable could be rotten inside the clamp , corroded through mid cable . Or the cable attachment point at the chassis or at the starter could have high resistance .
Unless the connections are checked with a voltmeter while cranking . It is guess work and random replacement of part$.
Then again I have yet in 18 years or so . I have yet to have anyone report back with the results of a voltmeter year while cranking .

Traditional Farmer has mentioned twice that the Lombardini 2 cyl used in the AC 920 and the Simplicity 7790 (model I am working on) are noted hard starters. That jives with other Google results I have found.

The comment about possibly not having enough fuel for starting may have some beaing. The owners manual and experience from others shows that the fuel control must be wide open while starting.

I have not tried any starting aids. I'm not a fan of ether, but might try some of the other suggestions.

I know I need to get a compression test. Despite it not having many hours on the meter, the history is unknown and it is very possible that the cylinders and rings are worn. I'll have to look at what it will take. The engine is air cooled so there is a really long reach through the head to get to where a tester would have to seal against.

All the adjusting screws on the injector pump still have wire and lead seal crimps on them. Leads me to think that nobody has messed with those. Not to say that it might not need adjusting, but that's above my pay grade.

Again, thanks to all for the advice. It is helpful to get different minds with different experiences passing out things to consider.

If it has glow plugs, then probably need to use them for at least 30 seconds. Old drill on VW Rabbit Diesel, Ford Escort Diesel, IHC 350D has a full minute of glow plugs before using starter. Mercedes owners
had the Memory Minute- heater switch and think about Gotlieb Daimler and Rudolph diesel, Mercedes fuel pump- and maybe weiner schnitzel. then turn over engine. For some Mercedes cars in real cold weather-get a
hait dryer, stick in aircleaner intake and set it on Fry/dry after shower for 5 minutes before trying starter, remove hair dryer after started. A few diesel had a glow plug or ignitor in intake manifolds that
would start a teaspoon of fuel on fire in manifold as starter turned. English Standard or the Austin made Nuffield(?) - fuel line from bypass/return at pump was one thing to check, dry holding cup from a
prior failure to start or setting too long. Ether NOT recommended for those systems- explodes intake manifold. squirt of WD40 or a teaspoon of lamp oil or kerosene was the recommended emergency try to get hot
air into cylinder without explosion. John Deere Combine had a propane injector using small bottle for winter starts, some diesel needing help would get a propane torch burning in aircleaner, then shut off
flame, crack open valve again for couple seconds just before using starter- 2 person drill at times depending on engine, starter button location. Maybe check Garden Tractor site? for Pasquali starting drill?
RN

Go to simpletractors people there with experience with those motors

(quoted from post at 10:12:22 05/20/19)
If it is indirect injection with glow plugs . It won t start unless the glow plugs are red hot prior to cranking .
We have some dimwits at work that jump into the Kubota 1140 s and start cranking . After 10-15 seconds the engine starts in a cloud of smoke . Or the driver goes back to the foreman whining that the Kubota won t start.
Depending on the temperature. 5-10 seconds of preheat and the engine starts in the first turn.
A new battery won t help if the battery is too small or there are high resistance connections . Just polishing connections is no guarantee of low connection connections . The cable could be rotten inside the clamp , corroded through mid cable . Or the cable attachment point at the chassis or at the starter could have high resistance .
Unless the connections are checked with a voltmeter while cranking . It is guess work and random replacement of part$.
Then again I have yet in 18 years or so . I have yet to have anyone report back with the results of a voltmeter year while cranking .

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B&D It is probably because few have a meter and fewer have the jumpers with alligator clips to go with them.

. Less than $30 at Habour Freight . Cheaper than guessing and throwing random parts on the machine . Cheaper than than not getting the work completed by the tractor .
An extra degree or two of advance in the injection timing may help . If it is an emissions engine the timing will be retarded and cause hard starting .
No one ever installed a too large of battery, cables and starter on a diesel .

......Unless the connections are checked with a voltmeter while cranking . It is guess work and random replacement of part$.
Then again I have yet in 18 years or so . I have yet to have anyone report back with the results of a voltmeter year while cranking .

Click to expand...

I'll check those next time I'm working on it. I know there is going to be some voltage drop through the cables and connections, but how much is too much?

....... An extra degree or two of advance in the injection timing may help . If it is an emissions engine the timing will be retarded and cause hard starting .......

Click to expand...

From the information I have, the pump is a plunger type and actuated by 2 additional lobes on the camshaft. Seems like the timing could not be altered without also changing the valve timing.