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I have a yanmar 3GMD. It started making a "popping' noise a…

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I have a yanmar 3GMD...
I have a yanmar 3GMD. It started making a "popping' noise a few days ago. It is obvious at startup, about 30 seconds after starting and when you rev up it disappears in general engine thrumming. I had the injectors serviced and they replaced one of the three nozzles. It seems to start more easily and the white smoke that was there (not much but some) seems to be gone. But the popping is still there...
Submitted: 1 month ago.Category: Boat
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Customer reply replied 1 month ago
Here are the things we have done already: Removed mix elbow and checked it for obstruction (none). Re-bled all fuel lines, eliminating one fuel leak. Checked valve adjustment (all within spec). Rebuilt the injectors, replacing one nozzle. Popping noise starts about 20-30 seconds after startup, then when RPMs are higher, it smooths out into the overall engine noise. There was a BIT of white smoke before, and now, after replacing the injectors, there does not really seem to be any, so there has been an improvement.
Answered in 7 hours by:
5/26/2018
Marine Mechanic: Jason, Marine Mechanic replied 30 days ago
Jason
Jason, Marine Mechanic
Category: Boat
Satisfied Customers: 17,492
Experience: Degree in Marine Technology. Gas and diesel marine mechanic.
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Good morning, my name is ***** ***** am I speaking with? I read what you wrote. Have you tried running it off of a portable fuel tank filled with brand new diesel fuel in order to make sure that the fuel itself was not the cause of the problem?

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Customer reply replied 30 days ago
My name is ***** ***** I have not tried running off a clean tank but everyone tells me diesel fuel does not go bad. As I said it it a YANMAR 3GMD, a marine diesel engine. That sounds like a solution for a gasoline engine. The fuel is a mix of fuel from September and fuel from yesterday. I cleaned the fuel tanks in September. I do not think that is it. I really need advice from someone who is a DIESEL MECHANIC.
Customer reply replied 30 days ago
Also, I replaced both fuel filters, the racor and the one on the tank right before I left on this trip. There are twenty gallons in the tank now and I will be filling up the tank shortly with 20 more gallons of fresh fuel, so if it is bad it will get diluted. But, again, I have asked other people this question before and they all tell me diesel fuel from September should not be a problem.
Marine Mechanic: Jason, Marine Mechanic replied 30 days ago

HI Mary. I service both gas and diesel engines. Diesel fuel absolutely goes bad. It can get water in it just like any other fuel tank can. On top of that, algae can form in diesel fuel, and you can get algae blooms in diesel fuel no differently than you would see an algae bloom in a swimming pool or pond. Because of that you should be running an all purpose diesel fuel biocide with every fill up. Click this link for a picture, this is what a bad diesel fuel sample would look like - http://www.boatcoachbob.com/wp-content/uploads/2013/01/dieselbacterie.jpg If you look at the picture, you will see bacteria and sludge at the bottom. Followed by water. Followed by a biomass, the biomass is your algae that forms in diesel fuel. Then finally you have some actual diesel fuel. I would not recommend filling the tank up. If there is water, algae, bacteria in your fuel tank filling it up will not dilute those items. If anything, adding fresh diesel fuel to a tank with algae in it simply gives the algae more food to feed off of. Instead what you want to do is look in the yellow pages or on google and find a company in your area that does what they call "Fuel Polishing". Fuel polishing is a filtration method of getting all of the water, bacteria, and algae out of the fuel tank. Click this link, this article explains the process - https://www.powerandmotoryacht.com/maintenance/what-you-need-know-about-fuel-polishing-systems-your-boat After you get the fuel polished that should take care of it. However, going forward, you will want to start using a biocide with every fillup to prevent algae from forming in your fuel. Click this link, this is just an example of the product - https://powerservice.com/psp_product/bio-kleen-diesel-fuel-biocide/ You can get diesel biocide at any autoparts store, as diesel trucks also use the biocide in their fuel tanks as well. Does that all make sense to you. I think that should do it but I work for tips so I do want to make sure you are happy with my service before you go. If you had a further or more specific question on the issue by all means feel free to ask. If not, Just in case you do not understand the way the website works (and some folks do not). You do have to put forth a positive rating in order for it to credit me for helping you. When ratings are not done, the website simply keeps your deposit and they will not credit me. The ratings box is located at the top of the screen. To rate, you must select the star you wish and also confirm it. Please let me know if you run into any problems or errors when trying to do it. If you do have a problem, or if you can not see the ratings box which is at the top of the screen. Please reply back "I rate Jason's service _______" and fill in the blank.

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Thank you
Jason

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Customer reply replied 30 days ago
I understand about biocides and I use it all the time. The fuel in the bowl of my racor primary filter is clear
Marine Mechanic: Jason, Marine Mechanic replied 30 days ago

I explained what needs to be done and what we would do in the shop. Did you have any further questions for me on the issue?

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Customer reply replied 30 days ago
No. There is nothing but clear diesel in the bowl of the Racor and I have always used biocide. Sounds like there is nothing new here.
Marine Mechanic: Jason, Marine Mechanic replied 30 days ago

Okay lets compression test the engine next and see what it has for compression. Is that something you can do?

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Customer reply replied 30 days ago
When the problem first started, we checked the valve adjustment and used the hand crank to turn over the engine. We were not able together to move it past compression for cylinders 2 and 3. Cylinder 1 we could barely move pushing it as hard as we could together. Other than that, we don't have the equipment. When we told the mechanics that, they said OK, and they did some troubleshooting and diagnosed it as dirty injectors. They checked valve adjustment and upped the idle and things were fine until the next stop. Since the injectors were overdue, I focused on that when I got to the next stop.
Marine Mechanic: Jason, Marine Mechanic replied 30 days ago

Diesel engines are pretty simple. You need compression and fuel, and that is it. Since the compression is untestable there simply isn't anything else you can do on your own other than hooking the engine up to a portable fuel tank full of brand new diesel fuel.

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