Perkins 4-108 preheater

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mel80

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Hi.


I have a Perkins 4-108 with a preheater in the air intake. This preheater seems to have stopped working entirely. The electrical connections seem fine (12.5V between the live terminal and the engine block), but the heating coil doesn't heating up. I've taken the heater out, but I can't get inside it to check the connections. Does anyone have any suggestions as to what might be wrong, or know of where I could get a replacement part?

Thanks
 
the manual says

if the starting aid does not work, first check that fuel reaches it by unscrewing the fuel inlet connection

then, to check if the starting aid itself is working, *do not* take it off the engine, but take off the air filter cap and observe the starting aid while it is being operated: it should become red hot

also, "to prevent damage, it is essential that the thermostart is never operated dry (...) whenever necessary, air should be bled from the thermostart fuel pipe before the device is operated"

cheers

add: you do not say where do you keep your boat, but the thermostart is hardly necessary, except perhaps when temperatures are quite low...
 
Thankyou both for the replies. I checked (and bled) the fuel line. No problems there, so it looks like I need to get a new one.

I've only had the boat for a few weeks, but so far the heater has been essential to starting the engine. That said, it has been a bit chilly up here (Fife) recently.

Any ideas for a bodge if I can't get the part quickly (I may need to move the boat soon)? I was thinking along the lines of putting hot air (from a blowtorch on a low setting) directly into the air intake. Anyone think of why this would be a bad idea (aside from the obvious issue of having a naked flame next to the engine)?
 
Flames are good, we had a Baudouin once that would only respond if we burned about 4ft of used meter paper under the intakes: a blowtorch would be safer.
We sold a Leyland truck that had always needed every possible device and incantation, plus a steep hill, to get going. the new owner was pleased with it: "Just need to spin it quick enough" he said, pointing to a huge battery.
 
Good advice! I've just spoken to the local MF dealer, and they have the part in stock. I'll get it this afternoon. Thanks again for all the helpful replies.
 
As fisherman's post says, getting the engine spinning fast enough is most of the battle.

My previous boat had a 4.108 and after years of using 2/3 throttle and a minute of heat (or more), I found by having a dedicated starting battery with short, good quality starter cables it started with virtually no throttle and no heat (other than December months) with barely any cranking and (wonders) no smoke!
What a revelation!
Pre heat became a thing of the past even with an engine that was (by that time) plenty more than 10 years old.

Cheers
 
I often give a sqirt of Easy Start .... a mist not a direct fluid job to the air-intake ... to get started. Many will tell you it's death to an engine ... sorry but my 4-99 was started on the stuff for years and only died after water got in ...

The pre-heat is available via Lucas dealers in most towns ...

Instructions mention about not running it dry ... actually thats a cop-out as mine on the 4-107 at present often doesn't have fuel at it and still engine starts from the heat ....

It's a crude but effective starting aid. Easy-start if all else fails ... but go easy on it - just a short squirt - no heaping great lung-fulls !!!!
 
On this subject. I have a Thermostart on my 4-108 also. While the heating element does work and it appears that the fuel connection is also working, there are no wires to it to activate it. I am in the process of putting that wiring in, BUT...before I do that I want to know how the thing works?

I know that fuel is sprayed in over the hot element and heated up before being drawn down the intake manifold.

And I know that the heater is activated by a selonoid for 15 to 20 seconds before trying to start.

What I dont know is how does the fuel shut off after the engine is started as the fuel pipe is connected to the return line with no valve that I can see unless there is one inside the fuel filter that closes off that line when the fuel pressure comes up after starting.

Anyone know how this operates?
 
[ QUOTE ]
On this subject. I have a Thermostart on my 4-108 also. While the heating element does work and it appears that the fuel connection is also working, there are no wires to it to activate it. I am in the process of putting that wiring in, BUT...before I do that I want to know how the thing works?

I know that fuel is sprayed in over the hot element and heated up before being drawn down the intake manifold.

And I know that the heater is activated by a selonoid for 15 to 20 seconds before trying to start.

What I dont know is how does the fuel shut off after the engine is started as the fuel pipe is connected to the return line with no valve that I can see unless there is one inside the fuel filter that closes off that line when the fuel pressure comes up after starting.

Anyone know how this operates?

[/ QUOTE ]

Ok ... first the diesel is not sprayed out on to it ... it "dribbles minisculely" onto it.
Second ... the ampage needed is quite high and a reasonable +ve wire is needed ... (negative is via the engine block). I use one piece out of standard domestic 13A flex ...
Third .. the fuel is controlled by the Heat-plug itself ... untill it heats up nothing flows through it as it has a heat controlled probably Bi-metal strip.

Basically I have a small supply above it with no valve or other control. The electric supply is by a push to make non-locking button that has electrical supply when systems are switched on ready to start engine ...

Simple. Nothing fancy about it all ..... pm me if I can help more ...
 
[ QUOTE ]
What I dont know is how does the fuel shut off after the engine is started as the fuel pipe is connected to the return line with no valve that I can see unless there is one inside the fuel filter that closes off that line when the fuel pressure comes up after starting. Anyone know how this operates?

[/ QUOTE ]

When the element is hot, it lifts a small valve to permit the fuel to enter - and as it cools the valve closes.

I discovered this when we had a series of engine 'run-aways' (luckily only up to aout 3,000 rpm when idling!). The cause was that the engine off/on/heat/start switch was faulty, and sticking in the 'heat' position after starting. Scary! Had to stop the engine by blocking the air intake - then we discovered the fault.
 
[ QUOTE ]
Had to stop the engine by blocking the air intake - then we discovered the fault.

[/ QUOTE ]

Jim,

how did you do with the "mushroom" metal dome covering the air intake ? have you permanently taken it off, or found a way of quickly removing it ?

or perhaps simply put a cloth all around it ?


thanks
 
[ QUOTE ]
Ours was a stiff push fit, so easily removable except for the breather pipe connection. I cut that for speed (got an oily face as a result!) then just jammed my palm over the inlet.

[/ QUOTE ]


I see, I think mine has a jubilee clip around, I will check if I can remove it without the dome tumbling away

thanks Jim

rr
 
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