Bleeding a Perkins 4108 ( and other engines I guess)

[pcatterall]

When I first bled my 4108 I followed the book. After the filters there are 3 ( I think) points to bleed then the injectors. I did the job as per the manual and annotated the manual correctly for my model and even put a blob of paint on each of the screws.
It was a difficult job, upside down, mirrors, torch etc. Next time I did it I noticed that one bleed point didn't seem to 'do anything' so I started to by pass that and the engine still started. Next time I was at sea and it was very difficult to get at the second bleed point so I left it out and the engine still started. Next time I went straight to the injectors and the engine started no probs.
I recall on field work in various hell holes we always used to bleed reluctant gennys just at the injectors.
Question..... is it always essential to work through the bleed points or does it just mean less cranking with the injectors out. I didn't notice that it took less cranking whether I had bled each point or not.
perhaps the advice may be " try it just using the injectors and if it doesn't start PDQ then go through the completer process.
Advice please.

 

[TradewindSailor]

It rather depends where the air is. The 4107 and 4108 tend to be a little difficult to start if there is any air in the fuel lines in my experience.

The first bleed is at the primary filter, the second at the fuel injector pump, and the third would be cracking off any of the feed lines at the injectors if memory serves ....... I haven't played with a Perkins for 7 years.

I have always bled my Perkins with the aid of an in-line electric fuel pump providing the pressure, and opened each bleed in sequence as once I was able to get to that side of the engine all were in easy reach ....... and I didn't want to enter that particular space again if I didn't have to .... I would only start the engine if I was in the cockpit.

 

[neil1967]

Recently fitted an electric pump to my 4108 in series with the mechanical pump. Had the injectors out for a service over the winter (and they needed them, it's made quite a difference), and was not looking forward to the bleeding - I've struggled in the past. With the electric pump it was a doddle. Turn pump on, bleed at the engin mounted filter - fair amount of air, bleed on pump, just fuel, so bleed each injector in turn, some air, then start engine - ok, it took 3 cranks, but after an injector change, I was pleasantly surprised.

Neil

 

[nigelmercier]

Last time I changed the fuel filters I totally emptied the inlet pipe as I was fitting a new pre-filter housing. When done, I filled the secondary filter with fuel, and started the engine. No bleeding. This was exactly the same procedure as done by a VP engineer when he changed the timing belt.

 

[ghostlymoron]

Maybe you should get some of this http://www.asap-supplies.com/marine/fuel-treatments/soltron-fuel-treatment-enzyme-314101 then the filters wouldn't block up in the first place?

 

[AndrewB]

The first bleed is at the primary filter, the second at the fuel injector pump, and the third would be cracking off any of the feed lines at the injectors if memory serves ........

Yes. It's the fuel injector pump that is the most critical. If the batteries were in good order, I could usually get the engine to start by cranking a while once it had been bled here and at one of the injectors, I chose no 2. Mind you, the only time this was necessary was if I'd accidentally emptied one of the fuel tanks.