Perkins 4108 Injectors

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neil1967

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The Perkins manual states that the injectors on the 4108 should be inspected every 700 hours. Since I have only had the yacht for a year I don't know when they were last done, and the engine has now done approx 4500 hours. Whilst it starts and runs fine above idle and there is no smoke in the exhaust, at idle it is 'lumpy'. Given that I probably should inspect the injectors, it seems sensible to replace them at the same time - a set of 4 nozzles is around £70. I have seen dire warnings about not playing with injectors, but the sites selling nozzles imply that changing them and refitting the injectors is no more difficult than changing a spark plug. I would be grateful for any advice/experiences.

Neil
 
neil1967 said:
The Perkins manual states that the injectors on the 4108 should be inspected every 700 hours. Since I have only had the yacht for a year I don't know when they were last done, and the engine has now done approx 4500 hours. Whilst it starts and runs fine above idle and there is no smoke in the exhaust, at idle it is 'lumpy'. Given that I probably should inspect the injectors, it seems sensible to replace them at the same time - a set of 4 nozzles is around £70. I have seen dire warnings about not playing with injectors, but the sites selling nozzles imply that changing them and refitting the injectors is no more difficult than changing a spark plug. I would be grateful for any advice/experiences.

Neil
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Lumpy, what is the idle speed, 900 is about right.
i would leave the injectors alone, how often do you check a diesel car
 
My injectors came out easily when they had to be serviced last year. Although the engine did not appear to smoke, I was getting a sooty deposit on the transom.
 
Forte is the best cleaner to use, tried many but this brand had the best result on a elderly BMC Commander, local garage may stock Forte about £10 for a bottle, dose as per label, best to apply before filling tank. Forgot Goggle for local suppliers from Forte site.
 
""sites selling nozzles imply that changing them and refitting the injectors is no more difficult than changing a spark plug. I would be grateful for any advice/experiences.""

Apples and Oranges I think- swapping out injectors straight forward (if they don't stick/have stripped hold down threads/snapped hp pipes/leaky seals/unobtainable seals/leaky water jacketty things:eek:)

Nozzles however are only part of an injector, they need to be set up/lapped on calibrating rigs to ensure even performance and spray patterns.

Not recommended for us mere mortals

Nick

ps- a non smoky, under-load Perky? Leave well alone!
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NickRobinson said:
""sites selling nozzles imply that changing them and refitting the injectors is no more difficult than changing a spark plug. I would be grateful for any advice/experiences.""

Apples and Oranges I think- swapping out injectors straight forward (if they don't stick/have stripped hold down threads/snapped hp pipes/leaky seals/unobtainable seals/leaky water jacketty things:eek:)

Nozzles however are only part of an injector, they need to be set up/lapped on calibrating rigs to ensure even performance and spray patterns.

Not recommended for us mere mortals

Nick

ps- a non smoky, under-load Perky? Leave well alone!
N
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Disagree. I changed mine a couple of months ago and it only involved unscrewing the lower part of the injector then fitting the new nozzles but being scrupulously clean when doing it.
No issues at all since. There is nothing you can lap, no other seals to worry about, its just a straight swap.
 
Ianj99

Did you notice any improvement in the engine once you had changed the injectors - was there a specific problem you were trying to solve, or was it a preventative change?

Neil
 
ianj99 said:
Disagree. I changed mine a couple of months ago and it only involved unscrewing the lower part of the injector then fitting the new nozzles but being scrupulously clean when doing it.
No issues at all since. There is nothing you can lap, no other seals to worry about, its just a straight swap.
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I may be out of date, but have a look at pages B13 and N10 of the Perky manual where it states otherwise.

http://www.bluemoment.com/manuals/Perkins-4.107_4.108_4.99-WorkshopManual.pdf

drfack.jpg


Nick
 
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Pretty brave to do it if all ok but I did mine over the winter but on a mercedes om636. I couldn't get anybody to service them as the local injector specialist said the bodies where too corroded to service. Thankfully I managed to buy a second set of injectors which I serviced and then fitted. I bought a pop tester from ebay with some shims for about £120. I tested them and found the opening pressure was quite good on two but low on another and high on another. Then cleaned the outside of the injector, then took it apart and cleaned the parts in brake cleaning fluid keeping all the parts together and in the same order. I then reassembled and fitted. I needed sealing washers to seal the bottom of the injector. One leaked around the body and had to be taken out and cleaned again. In the injectors there are no seals and you are fitting metal to metal to achieve a high pressure seal 115psi on mine.

The engine runs much more smoothly and revs more quickly. The hull around the exhaust seems cleaner to. So fingers crossed.

I must say I do believe in servicing stuff before it breaks or becomes unreliable but accept that sometimes I do unter the words 'why the hot place opposite to heaven did I start doing this job'. good luck with it.
 
Like I said earlier LEAVE THEM ALONE!

Lots of well documented trials where the failure rates on injectors fitted to high hours engines were compared. Half were serviced and half allowed to run til they failed in service. Most if not all found that it was better NOT to service them. I was involved in a trial with the Midland bus company and the results were clear.

Finally if you change the nozzle you have to adjust he spring at the top. This controls the 'break' pressure. Correct and matched break pressures have significant affects on power output and engine emmissions. Mind you the 4 108 is a tough old lump.
 
neil1967 said:
Ianj99

Did you notice any improvement in the engine once you had changed the injectors - was there a specific problem you were trying to solve, or was it a preventative change?

Neil
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It was just a preventative measure - the engine runs as smoothly and quietly as you can expect the trusty 4108 to do.

To the OMG brigade, here's quote from the sellers: http://www.parts4engines.com/index.php?main_page=product_info&cPath=39&products_id=457

The nozzle is the only wearing part of the injector and with new injectors becoming prohibitively expensive, the alternative option of reconditioning your existing injectors by fitting a new set of nozzles is a realistic and cost effective option. The only tools you will need are a bench vice and a 22mm ring spanner!
To finish the job off properly, you are going to need to replace the injector sealing copper washer, so we include a set of four with the kit. there are no scare stories.

Man on the moon, OMG!!, You want to climb Everest, OMG, You're going to the North Pole, OMG. The OMG lot would still be living in caves, too scared to take the slightest risk.

What's the worst that can happen with a diy nozzle change - the engine runs a bit rough, but we're talking about a 4108, not a Rolls Royce . Get real.


Ian
 
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Rather than OMG please could you explain why. My perspective on changing just the nozzle and doing nothing else on an old engine is that it has to be better to have a new nozzle than the old poor spraying nozzle and the only real risk is ending up with an injector body that is not sealed and leaking fuel. But as long as everything is super clean the risk is minimised. The lack of a torque wrench is a little concerning but as long as they are not done up stupid tight it is likely to be done up tight enough. Or could a new nozzle be so out of range that it will not open? Could this damage the pump? Etc
 
But what's the point of changing nozzle if it ok?
Taking the injector to a specialist and having them tested for pressure setting and spray patern would make far more sense and you would know for sure if there was any problem.
 
stav said:
Rather than OMG please could you explain why. My perspective on changing just the nozzle and doing nothing else on an old engine is that it has to be better to have a new nozzle than the old poor spraying nozzle and the only real risk is ending up with an injector body that is not sealed and leaking fuel. But as long as everything is super clean the risk is minimised. The lack of a torque wrench is a little concerning but as long as they are not done up stupid tight it is likely to be done up tight enough. Or could a new nozzle be so out of range that it will not open? Could this damage the pump? Etc
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I think[/B] the manufacturing tolerances on injectors would be so close that a random set of components assembled onto a top section with a spring that had been previously adjusted correctly would most likely not be too far off the correct setting.

So the pump should be safe too.
 
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