New Holland L785 Hard Starting

[Jake7824]

I purchased a NH L785 Skidloader about 18 months ago. Good machine. Not perfect but does everything i need. Has over 4000 hrs. In the last 6 months we have redone the valve cover gasket, glow plugs, battery, starter, fuel filters, put a push button for the intake heater. I think im forgetting something but we also put a check valve in the fuel line to stop any potential back flow on the machine.

The reason for that is that no matter the time of year it could be July or December the machine is hard starting. We have to crank and crank and crank. Once it starts we can come back an hour later and it will fire right up. It does smoke when we turn the key. Its white/blue smoke. One of the opinions i have gotten is low compression. All the cylinders are equal but no one can confirm this is the actual issue. I wondered about the injection pump as well. Once its running it seems to run well.

Just wondered if anyone had any ideas. It seemed to be a sudden and drastic decline rather than gradual.

 

[mrbb]

well I think I would start with doing a compression test
I would also , maybe check condition of fuel, since you said issue seems to have started recently, maybe you have bad fuel

 

[Jake7824]

well I think I would start with doing a compression test
I would also , maybe check condition of fuel, since you said issue seems to have started recently, maybe you have bad fuel

I think the fuel is good. Its filtered in and out of the barrel and we have run multiple tanks through it. I spose its been going on 6 months.

When the compression test was run they just said it was lower, I didn't get a solid answer as to how low or low enough to for sure be the issue.

 

[mrbb]

I think the fuel is good. Its filtered in and out of the barrel and we have run multiple tanks through it. I spose its been going on 6 months.

When the compression test was run they just said it was lower, I didn't get a solid answer as to how low or low enough to for sure be the issue.

well if they said it was LOW< then you need to find out HOW low, low on all cylinders or just ????


as low compression can cause both starting and running issues!

and as for fuel
, how is fuel filter on machine?? when was it replaced last?

 

[Kenskip1]

Compression low? According to who? Try this stunt. With the engine hot and running simply remove the oil fill cap. Is there excessive amout of blo/buy? If so then you may have low compression and worn rings.

 

[Rayhat]

I don’t think it’s a fuel issue, unless it is bad fuel as suggested above, but if you want to rule it out, get a fresh jug of fuel like a gallon container and rig a line up after the filter. It’s messy and a pain because you have to bleed the pump, but if the problem persists it’s probably not a fuel issue. Compression I believe is an extremely important part of a diesel system. I don’t know much about it.

 

[foton]

lets say that you have some blow by but are unsure as to how bad, harbor freight has diesel compression gauges that come with a few adapters pretty cheap , I have heard that people have had fairly good luck with them. And this will tell you exactly what the pressure is in each cylinder and then you can compare it to the manfs. listed acceptable compression requirements. I would try to use the glow plug holes to test from .

 

[st0ck1ng]

My L785 does NOT have glow plugs or an air intake heater. That said, it starts right up except in the coldest temps.

In addition to compression:
Weak battery?
Weak starter?
Fuel system maintaining prime?
Engine timing off?
- any of these can contribute to slow starting

For your question, "I" would try a quick shot of ether (make sure glow plugs/intake heater disconnected) if low compression OR significant system prime issue it "should" fire then die rather quickly
- if fuel prime is minor could sputter for a few moments, then smooth out

If battery/starter/timing, it "should" keep running

My $0.02

Good luck

 

[Kenskip1]

st0ck1ng​

Sir in his first paragraph he mentioned the following, replaced, glow plugs, battery, starter, fuel filters,

So after thinking about this I have come up with another brillant idea. From your description the injection pump may be loosing the prime ..So here is what I have thought of. With the engine stone cold loosen one or two fuel lines going to the injectors. After letting it set overnight have someone watch the loosened fuel line for signs of fuel leaking while cranking.If no fuel is leaking then we may suspect a fuel deliverry problem.

 

[Jake7824]

Talked with the dealer again. The mechanic that worked on it was out but they thought compression was around 140. Really low. Normal sounds like its around 250 to 290. Will definitely crack the fuel lines to make sure thats not an additional issue but sounding like compression is the main culprit.

 

[Kenskip1]

"Once its running it seems to run well.". This is why I suspect a fuel delivery problem. As I mentioned, the next time you have it running and at operating temperature simply remove the oil fill cap and see if there is oil fumes pooring out. I would like to have the mechanic verify his findings A new set of rings will cost a group of $$$. Was this a dealers mechanic? I may be wrong here but I would like you to get a second opinion. If this is a dealers mechanic he may be working for the boss so to speak. Suppose they put in a set of rings and everything else and it is still difficult to start.Do you trust your dealer? I hope that I am wrong however I am sticking to my guns. Good luck Jake, Ken

 

[st0ck1ng]

st0ck1ng​

Sir in his first paragraph he mentioned the following, replaced, glow plugs, battery, starter, fuel filters,

So after thinking about this I have come up with another brillant idea. From your description the injection pump may be loosing the prime ..So here is what I have thought of. With the engine stone cold loosen one or two fuel lines going to the injectors. After letting it set overnight have someone watch the loosened fuel line for signs of fuel leaking while cranking.If no fuel is leaking then we may suspect a fuel deliverry problem.

Yes, but how many times have we replaced failed equipment with new, just to find out it was faulty also, been there, done that, have several t-shirts.

If in doubt recheck what's been done.

Wasn't trying to be a PITA.

 

[foton]

I could not find the required compression psi for that perkins 4.2032 engine but as a rule 350 psi is the low end of compression required for a diesel to cold start, so you need to figure out what yours really is. 140 aint it.

 

[Kenskip1]

There is a possible solution.If the injector pump is loosing prime then how about hooking a 12 volt pump and sending the fuel directly to the injector pump. as he mentioned that when it starts it runs well.This solution may save him a boat load of $$$ When he turns on the switch the electric pump comes on and sends fuel to the injecctor pump. This stunt has been used a few times. I hope this helps, Ken

 

[Kenskip1]

Normal compression readings for the Perkins 4.2032 engine typically range from 350 to 450 psi (pounds per square inch). It's important to ensure that all cylinders have similar readings, as significant discrepancies may indicate issues such as worn piston rings or valve problems. Regular checks can help maintain engine performance and longevity.

This was generated by AI.

 

[Jake7824]

All cylinders were equal according to the dealer.

Also when attempt to start it I have white/blueish smoke instantly. Not saying its not a fuel issue as it could just be low on fuel but we did put a check valve in the fuel system so the fuel wouldn't drain back into the tank. Maybe not far enough into the system as it was before the first filter.

12v pump is something I will try.

 

[Kenskip1]

Jake, the white smoke is fuel that has vaporized however not enough to support combustion.
I want to state that I could be totally off base on this topic. All I have is experiance dealing with similar problems. BTW, the blueish smoke that you see could be engine oil. Ken

 

[Kenskip1]

For a Perkins 4.203 (which the 4.2032 is a variant of), expect readings around
300-500 PSI, with all cylinders within 10% of each other, but some owners report closer to 30-35 bar (approx. 435-507 PSI), tied to its 17:1 to 19.3:1 compression ratio, indicating healthy engines usually fall in the higher end of that range.

Key Compression Points for the Perkins 4.203/4.2032:

• Target Range: Aim for readings in the 300-500 PSI (or 20-35 bar) range for good health, with a good spread (less than 10% variance) between cylinders.
• Compression Ratio: The engine's physical compression ratio is high (around 17:1 to 19.3:1), so expect high PSI readings when testing.
• Service Manual (Ideal): While specific service manual figures aren't in the snippets, expect the service manual to specify a target PSI, with low readings (e.g., below 250 PSI) indicating issues.
• Normal Range: Generally 300 to 400 PSI (which is roughly 30-35 bar).
• Minimum Acceptable: Values above 300 PSI are generally considered fine for older diesel engines.
• Variance: All cylinders should be within 10% of each other to indicate good engine balance and health

 

[JWD]

May seem obvious but make sure your air filter isn't plugged up. I had that happen to mine once after pushing up burn piles it got plugged up with fine dust and ash and was very hard to start.

I also ran out of fuel one time and had allot of trouble getting the injection pump primed. I used a small 12v pump like mentioned above and it made short work of getting the air purged out of the system.

 

[Jake7824]

Just thought id update everyone. I plan to try to 12v pump. Haven't had a chance yet. Does anyone have a suggestion on pump? Psi? Easiest place to put pump i think will before the lift pump. It's the on fuel hose on the machine.