Diesel Starting Question

[BobT]

I have a question for you diesel guru types. 

• Allis-Chalmers 190XT Series III with turbo-charger.
• Equipped with an intake manifold preheater for cold starting. Manual recommends using it when temperatures are below 40 degrees F.

• Approximately 900 hours on rebuilt engine.

• Approximately 20 hours on rebuilt injectors.

Until a couple years ago starting my tractor at temperatures above 40 degrees was as easy as setting the throttle to about 1000rpm position, pulling out the fuel shutoff, and pressing the start button. It would usually start right up without difficulty. 

Now, even at temperatures as warm as 60-70 degrees I can crank that starter all day and it will not start at all unless I use the intake manifold heater for about 20-30 seconds. 

I have tried using fuel system cleaners and conditioners with no improvement and I never use starting fluid to get it started.

While cranking it over the smoke is white. Once it starts it runs smooth with a very light white smoke for a few minutes until it begins to warm up and then almost zero exhaust smoke is visible. While running, it has plenty of power with no noticeable crank case blow-by pressure. Under heavy load the exhaust is a light black. 

I do not suspect the fuel pump is losing prime. It is gravity fed from the tank which is located above the level of the pump so the fuel can't drain back toward the tank. Is it possible the fuel pump is getting weak or is slightly out of time? 

Thoughts?

Thank you.

[Powerstroke]

Time to check glow plugs and injectors. 

 

I Know its not a direct comparison, but my truck was having similar issues, the controller for the injectors was not getting enough voltage to the injectors and they weren't operating properly until everything was warmed up, even in normal summertime temps. 

Should be fairly easy on a motor like that to get a multimeter in there and find if all the injectors and glow plugs are getting similar voltages. 

[BobT]

Thanks for the reply Powerstroke.  

This is a 1965 tractor. The injectors are mechanical and were rebuilt earlier this summer. Being mechanical I assume the fuel pressure must exceed some minimum tolerance for them to work and that is partly why I am wondering if low fuel pressure could be the issue. Just not sure though because it runs so good once it starts.

It does not have glow plugs but does have a single intake manifold heater that I can manually operate. I know it works because the manifold gets hot enough I can't touch it. But even using that heater, it doesn't start at temps below freezing like I know it can. I am forced to plug the tractor in, which isn't so bad as long as it is parked near a power source.

[jmd1]

Question for you, have you pulled the intake line off the turbo to make sure it is not plugged up or restricted?  Have you checked the turbo to make sure it is not locked or broken?  Has the injector pump been off?  If so was it timed when replaced?  If you rebuilt the injectors, what was the reason, obvious issues or is there a pump problem that caused injectors to fail?  Sorry for all the questions just running it through my mind.  Jeff

[Surface Tension]

  If the engine isn't cranking over as fast as it should I can see needing the preheater to start in warmer temps.  Check condition of cables, connections, starter and batteries.  

[BobT]

Question for you, have you pulled the intake line off the turbo to make sure it is not plugged up or restricted?  Have you checked the turbo to make sure it is not locked or broken?  Has the injector pump been off?  If so was it timed when replaced?  If you rebuilt the injectors, what was the reason, obvious issues or is there a pump problem that caused injectors to fail?  Sorry for all the questions just running it through my mind.  Jeff

I have done nothing with the turbo but I can hear it spinning as it winds down when I shut off the engine so I believe it is working okay.

The only time the injector pump has been removed to my knowledge was when the engine was rebuilt 900 hours (about 9 years) ago. It worked great after it came back but only started doing this a couple years ago.

I rebuilt the injectors with the hope that it was the source of my trouble. According to the mechanic that did the work, they were in pretty poor condition. Since rebuilding them, the engine certainly runs cleaner, smoother, and with more power but the starting issue still exists.

Not sure about a possible pump problem so that is why I'm asking.

 

  If the engine isn't cranking over as fast as it should I can see needing the preheater to start in warmer temps.  Check condition of cables, connections, starter and batteries.  

Been through everything. Cleaned up the battery posts with my brush cleaner, polished up the battery clamps with same, applied dielectric grease and reinstalled them. I also removed the cable connections from the starter, polished them with emery board, and applied dielectric grease. Discovered that I had one battery beginning to fail so replaced with two new 950CCA batteries. Engine has never turned over better.

[delcecchi]

A naive question, but could it be a compression thing like leaky valves or rings? I know 900 hrs isn't that much but it sort of fits the symptoms.

[BobT]

That thought has come to me as well. I've been watching crankcase pressure ventilation tube for excess blowby but haven't noticed anything at all. This gives me the impression that the rings should be okay. I suppose there could be some on the top end around the valves. A compression test is the only way I know to test for that. Unfortunately, I don't have the equipment necessary to test it. 

Something I haven't tried yet is to add some Seafoam to the crankcase oil and running it prior to changing the oil. I will be changing the oil soon. Anyone try doing this? The product claims it is okay but....

[jmd1]

So thinking through this, we have a cat 924 with a 3116 in it.  Had same issue a while ago.  What we found was we bypassed the fuel filters and ran clear hose to the pump.  No bubbles found while doing this.  Hooked clear line to secondary filter hard start, bubbles in fuel line.  Moved to the primary filter bubbles again.  What it ended up being was a bad fuel filter housing that was sucking air.  It would crank, had to use ether to get it fired off and would continue to run fine after it warmed up.  Cat said they have seen where the housing will contract when cool, once engine warmed up housing would expand enough to stop sucking air.  replaced housing no problem since.  Might be something to look at.

[BobT]

Thanks for the tip. I'll have to get some clear line to see if I'm getting air in the system.