We have "Lady Charlotte" 1978 45' w/ 8v71 naturals.  I'd like to pull the injectors and send to the injector service.  Can this be done without adult supervision?  We have no injector issues that I'm aware of.

Thanks, Chet

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NO, unless you have been trained on injector change, and setting the racks, you can get into BIG trouble. If you get the adjustments wrong the motor can run wild and scatter pieces and parts all over your bilge. Ask the injector shop if they have a recommendation for a trained mechanic to change them.

If you have no injector issues, why do you want to have them rebuilt?

An injector shop is going to charge some where around $120-180$ ea.. Re-built injectors will be around $110-165$ ea. depending on source.

You might be able to get by cheaper with a local  injector shop but the lower price would indicate that they did not need to do the typical needed rebuild. At a minimum a shop needs to charge at least $75.00 just to replace the tips.

These prices are handing them the injector and receiving the rebuild. You need to add in an extra $12 per injector for new fuel line jumpers.

These injectors are actually the injection pump, fuel control, and timing mechanism all combined in one mechanism. There is a shaft that connects the governor to the individual injectors. This is referred to as the rack. Each injector must be set for timing with a gage pin specific for the injector-engine combination and the injector connector linkage to the rack must be properly set.

Screwing up the timing can result in burnt pistons. If the rack system gets bound up, the engine will run away.

Getting the injectors out is simple as long as you don't pull out the burner tube with it. This is the copper sleeve that the injector sets in that surrounds the injector with coolant. This normally doesn't happen but can happen if you don't understand what too much force will do when pulling a stuck injector.

Properly torquing the injector is mandatory when re-installing so as not to crack the head or have a coolant leak.

To do the injector re-install will take between a day and two days depending on the engine room to do both engines and adjust the rack.

Not trying to scare you but the 2 cycle Detroits and big Cummins injectors are not like changing the pencil injectors in a pickup truck.

If I were you I would have a good Detroit mechanic run the racks on your engines. If there is a need for injector work it will become apparent at  that time. Having the rack adjusted will probably get you where you want to be with only a portion of the cost.

Assuming proper care of the fuel source, injector nozzle wear is a function of gallons of fuel run through the nozzle. It takes a lot of full throttle hours (thousands) to notice any appreciable nozzle wear. A lot of owners equate a rough running Detroit to needing injectors when often all that is needed is a little TLC.

In addition to what Ron just mentioned, I have one comment as to his opening statement.  That is how to determine if an injector is working properly or not without removing it and placing it on a test stand.  On a Detroit Diesel only, I have witnessed many mechanics start the engine, keep it at idle speed and place their bare hands on the exhaust port of each cylinder on the exhaust manifold.  If the port warms up, the injector is functioning well.  If it does not warm up, the injector needs servicing.  Another thing to watch out for is an injector tip flying off the injector onto the top of the piston.  This will cause excessive black smoking and a replacement of the piston head.  I have seen this happen too many times on others, but it never happened on my Detroits.  This is usually caused by water sneeking through the fuel filters.

Any questions, please ask.

Jim Rivas

Ronald Zick said:

If you have no injector issues, why do you want to have them rebuilt?

An injector shop is going to charge some where around $120-180$ ea.. Re-built injectors will be around $110-165$ ea. depending on source.

You might be able to get by cheaper with a local  injector shop but the lower price would indicate that they did not need to do the typical needed rebuild. At a minimum a shop needs to charge at least $75.00 just to replace the tips.

These prices are handing them the injector and receiving the rebuild. You need to add in an extra $12 per injector for new fuel line jumpers.

These injectors are actually the injection pump, fuel control, and timing mechanism all combined in one mechanism. There is a shaft that connects the governor to the individual injectors. This is referred to as the rack. Each injector must be set for timing with a gage pin specific for the injector-engine combination and the injector connector linkage to the rack must be properly set.

Screwing up the timing can result in burnt pistons. If the rack system gets bound up, the engine will run away.

Getting the injectors out is simple as long as you don't pull out the burner tube with it. This is the copper sleeve that the injector sets in that surrounds the injector with coolant. This normally doesn't happen but can happen if you don't understand what too much force will do when pulling a stuck injector.

Properly torquing the injector is mandatory when re-installing so as not to crack the head or have a coolant leak.

To do the injector re-install will take between a day and two days depending on the engine room to do both engines and adjust the rack.

Not trying to scare you but the 2 cycle Detroits and big Cummins injectors are not like changing the pencil injectors in a pickup truck.

If I were you I would have a good Detroit mechanic run the racks on your engines. If there is a need for injector work it will become apparent at  that time. Having the rack adjusted will probably get you where you want to be with only a portion of the cost.

Assuming proper care of the fuel source, injector nozzle wear is a function of gallons of fuel run through the nozzle. It takes a lot of full throttle hours (thousands) to notice any appreciable nozzle wear. A lot of owners equate a rough running Detroit to needing injectors when often all that is needed is a little TLC.

Had to jump in here, not trying to hijack but there are obviously some really experienced DD guys here so I have a few questions that maybe they can help. I have the same 8V71's BTW.

The Starboard engine will not idle unless slightly above zero throttle. To shut it off you don't have to starve it of fuel or air you just zero the throttle and it shuts down. Does this sound like a linkage issue or something else?

As the throttle is opened the same engine exhaust note gets louder and higher pitched which I assume is an exhaust leak but thought I'd throw that out there. Both engines seem to run great and the oil analysis show them in the normal range for particles. I will probably have a DD guy look at them to tweak but was wondering what you smart DD guys thought.

Thanks

Alan     

Alan, Your problem may be a simple adjustment of the low speed governor. You need a DD mechanic to do the adjustment because if it is done incorrectly the motor can run wild. Exhaust that gets louder than normal is usually caused by a lack of, or reduction of, cooling water in it.

Alan, there are a couple of things that can cause this. As Dan mentioned, the governor being out of adjustment is a strong possibility.

One thing you did not mention is the exhaust appearance. Does the engine with the idle problem, smoke more on one bank when it is started? Does it smoke after a warm up? Is there an oil sheen on the water at the exhaust? Do both engines deliver the same rpm at full throttle? I realize this last one might not have been done yet but usually engine internal condition problems develop over a period of time.

Other possibilities:

The rack on the one side of your engine or even on both sides is out of adjustment. This also means individual injectors are not adjusted the same.

You could have a bad injector. This results in the engine firing only on 7cylinders at idle and maybe even full throttle. If you have a worn injector, you will get white smoke at an idle. If the injector tip is blown off then you get the traditional white smoke even at full throttle

You have a cylinder that is dropped out at idle. This can be a scored cylinder resulting in low compression making low speed operation or a bad exhaust valve. This possibility is on the bottom and hopefully not what you have going on as it involves some serious money to resolve. Your oil samples would also indicate that a scored cylinder is very unlikely.

You mentioned a possible exhaust leak. If you actually do have a leak there will be tell tale soot marks at the leak. You do not want to operate the engine very long with an exhaust leak in that it will very rapidly clog the air filters on both engines tight. It will also make a real mess of your engine room and potentially other areas of your boat.

Another problem that develops very rapidly with running an engine with an exhaust leak at the head-manifold interface is that it leads to erosion of the head and manifold surfaces. Detroits use a very high quality stainless steel gasket. These usually do not leak unless the manifold bolts have become loose.

Usually an exhaust leak on a diesel sounds like an airy popping sound. Very distinctive once you hear one.

If you have a Detroit mechanic look at it, he will probably identify the problem within 15 minutes.

Alan Waite said:

Had to jump in here, not trying to hijack but there are obviously some really experienced DD guys here so I have a few questions that maybe they can help. I have the same 8V71's BTW.

The Starboard engine will not idle unless slightly above zero throttle. To shut it off you don't have to starve it of fuel or air you just zero the throttle and it shuts down. Does this sound like a linkage issue or something else?

As the throttle is opened the same engine exhaust note gets louder and higher pitched which I assume is an exhaust leak but thought I'd throw that out there. Both engines seem to run great and the oil analysis show them in the normal range for particles. I will probably have a DD guy look at them to tweak but was wondering what you smart DD guys thought.

Thanks

Alan     

One thing you did not mention is the exhaust appearance. Does the engine with the idle problem, smoke more on one bank when it is started? Does it smoke after a warm up? Is there an oil sheen on the water at the exhaust? Do both engines deliver the same rpm at full throttle? I realize this last one might not have been done yet but usually engine internal condition problems develop over a period of time.

Wow thanks for the tips guys.

Not sure whether that motor smokes more than the left on start up. I will look closely next time and start them separately. I am usually busy doing the myriad of things necessary to cast off and haven't noticed. I do always check to see that water is coming out the side of the hull and the exhausts.There is no smoke or very little after the engines warm up. No oil sheen on the water either. The starboard engine I have only had to 2000 RPM. It gets loud and smokes a bit at higher RPM's and frankly I haven't wanted to push it since they are 43 years old and I don't want the old tub going that fast anyway. The closest thing I can compare the noise to would be a 2 stroke outboard engine that is lifted out of the water while running. Its not as loud but a similar tone only higher pitched and again it is only at RPM's 1700 or so and up.   

I switched from n50's to n60's, the injector replacement was straightforward and cured the fuel sheen on water problem and white smoke during throttle changes problems I'd been having. But setting the racks was over my head, I wound up calling a DD guy to set them up afterwards. They run great.

Hey Chris - what's the difference between n50 & n60?

Chet,
The first two digits or three are cubic centimeters per 1000 strokes.

The letter is a series configuration specified. N and C are similar. N has 5 holes in the injector top. Cs have 7 holes. The purpose was to reduce smoke and used in the latter engines.
There are other series such as S which is old and the Ms were military.

The idea of the bigger injector is to deliver more fuel per stroke. There is a limit to how much you can add and especially the 53 series, do to it's smaller displacement, is limited in how much it can utilize unless you add more air.

Usually bigger injector equals more smoke. It also gets tricky when jumping up on injector size as the timing is affected from the bigger plunger.

This gets into the realm of needing to know what you are doing as it is easy to burn a piston making the boat owner very sad.

You can gain a little bit but it will probably be only 30hp max. on an 8V53.
Yeah I don't think I gained all that much, from rough calc's I think I'm putting out about 310-315 a side now instead of 283 with the n50's. But speaking practically that small gain was a big difference because it allows me to cruise comfortably on plane at 2400-2500, before they would bog down right there when the boat was getting up out of the hole and you had to give it more gas to stay above 2600 or you would fall off plane. I don't like to cruise a 2800 rpm motor at 2600. That and when you hit a wave or something, they would bog down, now they do it much less. I originally up-pitched the props 1/2" for the extra power but then put them back to 23x22 because the motors sounded better.

The new injectors actually cleared up some smoking that I had before. I think that's the key here...for me this was a harmless upgrade as long as I was going to be doing it anyway. If I didn't need injectors already when I bought the boat it wouldn't have made economic sense. But if I had it to do over again, under the circumstances I'd do it again. I did pick up top speed, the boat will do an honest 18+ knots with 1/2 fuel, full water, and all my stuff onboard.
Here is a video of WOT, they sound great, no smoke, and from everything I can tell they like their new injectors.

https://m.youtube.com/watch?v=Pg0f3Dh9l38

I think the n60's are a good upgrade for these motors, and swapping them in was common enough that DD publishes the timing settings for n50, n55, and n60's in the factory manual for the 8v53n's, which tells you they tested them and thought they were ok. I have noticed no ill effects and no extra smoke on mine. I don't know that I would go any bigger than these, the n60's are the largest injector that DD has released factory timing specs for on the 8v53n, so you would be flying blind if you went bigger than that. As with any motor you can grenade it if the timing is off. But I can report you can use n60's with the factory timing specs for them on the 8-53 with no ill side effects.

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