Uneven engine operation.

[Jason]

Watched the video, sounds/looks like an intermittent miss to me. The engine shakes more than it should, especially at idle. Have you tried cracking one injector line at a time to see if you can narrow it down to a certain cylinder that isn't firing correctly? Could have an injector nozzle hanging up. I'd also run a piece of clear hose for the fuel return from the pump/injectors and see if you're getting any air bubbles. You can have air pushed into the injection pump from a fualty injector which will really screw up how it runs... Ask me how I know! If you don't see any air, but can narrow it down to a particular cylinder, I'd do a leak down test of that cylinder, and depending on your findings, I'd swap injectors from one cylinder to another and see if you mis-fire follows the injector.

Jason

[samvear]

Thank you Jason for your input. I am very glad for your help.
I will answer your questions

Have you tried cracking one injector line at a time to see if you can narrow it down to a certain cylinder that isn't firing correctly?

Yes, I did. Result: at the moment of releasing the nut of each nozzle, the engine runs on five cylinders. It starts shaking even harder.
Unable to identify a cylinder that is not performing well.

I'd also run a piece of clear hose for the fuel return from the pump/injectors and see if you're getting any air bubbles.

I did. There is no air in the return pipe.
All injectors were tested on the stand. The high pressure pump is also tuned.

[Jason]

Do you have access to another known good injection pump? I think at this point I would swap it for another pne and try it.

Jason

[samvear]

Originally Posted by Jason

Do you have access to another known good injection pump? I think at this point I would swap it for another pne and try it.

Unfortunately, in this situation, it is not possible to install another fuel pump.
Do you still think it's the pump?
In the same way, the motor worked with the previous pump. before pump repair. Repair of the pump did not give any result.

[Jason]

Well if it's not the pump it would have to be a mechanical problem with the engine, however the miss sounds to be intermittent. If there was a cylinder down on compression due to a ring issue or valve not sealing, the low compression would cause poor running consistently which typically will diminish as rpm increases as there is less time for the engine to loose compression. Have you done a leak down test? Another possible way to help with diagnosis would be to pull the injectors and inspect the tips of the nozzles. If there is a cylinder that is struggling to fire correctly the nozzle will be either moist with fuel or carbon'd up more than the other nozzles. Something to look at anyway. If you still can't narrow it down to a particular cylinder via injector inspection or a leak down test, I would suspect the pump and try swapping with another one.

Jason

[samvear]

Thanks for helping!!! Thanks to your advice, it is easier for me to endure the war. You give advice. I check them. It takes away from the war.
v8volvo - this applies to you too.

Originally Posted by Jason

Have you done a leak down test?

Yes. I did a test. The difference between the cylinders is 0.5 kgf / cm2
IMG_20220616_182709.jpgIMG_20220616_182735.jpg (Instrument readings are not correct)

Another possible way to help with diagnosis would be to pull the injectors and inspect the tips of the nozzles

That's the difficulty, that soot on nozzles and washers is the same. Even after a long trip.

If you still can't narrow it down to a particular cylinder via injector inspection or a leak down test, I would suspect the pump and try swapping with another one.

It may be necessary to do so


I have a question:
what if the engine has a different degree of compression in the cylinders? If anyone cylinder protrudes from the block less than the others. A leak test won't show this.
Can I try to reduce the thickness of the washers under the injectors?

[Jason]

There is no adjustment for injector height, just the heat shield. But you would be able to detect difference in compression via a compression test.

Jason

[Jimarilo]

My recent 940s 1995 purchase runs like this ......lumpy on warm tick over. Cold and hot start works perfectly

I changed the fuel filter and clogged air filter but still lumpy

Will investigate further after I change the cam belt

Is the crank bolt 27mm and the torque setting 300 lbs ??

I don't have the tool for locking the crank pulley, but will figure something out. Also need to find a bigger torque wrench lol

[ngoma]

Originally Posted by Jimarilo

My recent 940s 1995 purchase runs like this ......lumpy on warm tick over. Cold and hot start works perfectly

Too little info to make a diagnosis, if that's what you are looking for. What is the history? Did it come on immediately one day? Have you checked the IP timing? Valve clearances? What is the power? Smoke? How many mileage?

Originally Posted by Jimarilo

Is the crank bolt 27mm and the torque setting 300 lbs ??

I don't have the tool for locking the crank pulley, but will figure something out. Also need to find a bigger torque wrench lol

More like 350 lb-ft. You may be a mechanical genius but most "figure something out" with a monster torque wrench solutions don't work out successfully in the end.

Forum members have made satisfactory facsimilies of the Volvo special tools, you can search here and find them. Involves welding and fabbing skills.

[Jimarilo]

Originally Posted by ngoma

Too little info to make a diagnosis, if that's what you are looking for. What is the history? Did it come on immediately one day? Have you checked the IP timing? Valve clearances? What is the power? Smoke? How many mileage?


More like 350 lb-ft. You may be a mechanical genius but most "figure something out" with a monster torque wrench solutions don't work out successfully in the end.

Forum members have made satisfactory facsimilies of the Volvo special tools, you can search here and find them. Involves welding and fabbing skills.

Indeed, I am starting to think this engine is more trouble than it's worth. A nice merc 300 straight 6 would be a lot less trouble. Just changing the rocker cover gasket is a bleeding nightmare to change, especially if the nuts on the injector side are rusty and seized. It is probably just a matter of time before it starts leaking again on the exhaust side

I took the cambelt cover off to have a look at the belt as I am still in contemplation mode regarding the belt change, as I need so many specialist tools before attempting the replacement. So with the slack on the adjusting pulley side, I slackened the adjuster bolt and let the adjuster take up any slack, which it did. What a difference that made, no stuttering when pulling away or when changing up the box and a little less lumpy on tick over.

The air intake pipe that goes over the rocker cover has evidence of oil in it so suggests the engine is breathing heavy and at 165K I am thinking it is in need of a rebuild ......but is it worth it ??