At what RPM Do You Start a Diesel ?

[squarpeg]

I just bought a boat with a old diesel perkins 4-108 in it. I have not owned a diesel before. There is a single lever shift on it. The speed in neutral can be adjusted by pulling out the shift lever. If I leave the shifter clicked in the standard neutral position the engine runs at about 1,000 RPM. ....... Question: am I supposed to start it at that throttle speed? or am I supposed to bump it up like on an outboard where you start at a higher RPM ( throttle to start position) and then back her down to an idle once the engine is running ?

Thanks

[goboatingnow]

Give it about 10- 20 % throttle to start I like to start at about 1000 -1100 Rpms from cold. ( this on a big engine) starting on idle is more of a challenge for a cold diesel. However this isn't true for modern electronically controlled diesels. They should be started at idle .

The Perkins will definitely require the throttle to be advanced for starting.

Dave

[O.C.Diver]

What RPM do you start diesel at?

Engines start at "0" RPM.

Generally you want to start the engine at the lowest RPM that the engine runs smoothly with all the cylinders firing. Best to start with zero throttle and move up as necessary.

Ted

[daddle]

The diesels I've used are started with the fuel control, or speed control, in the idle position. The typical injection pump and governor is designed to supply more fuel, perhaps max fuel, at startup.

[goboatingnow]

Originally Posted by daddle

The diesels I've used are started with the fuel control, or speed control, in the idle position. The typical injection pump and governor is designed to supply more fuel, perhaps max fuel, at startup.

Err no it not

Dave.

[four winds]

I have the same question. Clicked here to find the answer and found three answers. I love this forum.

Please continue.

[atoll]

older diesels definitely like a bit of throttel,i agree with dave(goboating)

[Sabbatical II]

Originally Posted by O.C.Diver

What RPM do you start diesel at?

Engines start at "0" RPM.

Generally you want to start the engine at the lowest RPM that the engine runs smoothly with all the cylinders firing. Best to start with zero throttle and move up as necessary.

Ted

As a qualified but no longer practicing diesel mechanic, I like this answer best. Initially start the engine with minimal throttle until you can be sure it has full oil presure (the warning light goes out if you don't have a guage) and you can be sure that all cylinders are firing. This should only be a few seconds but if you wait another ten seconds or so, particularly if it's turbocharged, you can be pretty sure that the oil is circulating right through the motor before bumping it up to about 1000 RPM or so. I would wait a further few minutes after that before moving off so that the oil is getting warm before you are loading the engine.

Greg

[goboatingnow]

Actually Greg many Perkins manuals for the older engines required full throttle starting in cold conditions. With a reduction to fast idle on firing. Diesels benefit from being brought up to temperature as fast as possible( preferably loaded) long slow idles at startup are the worst way to handle diesels . This is the same advice given by many engine companies. Never was a diesel mechanic myself merely was involved in designing them! . All engines are normally designed to handle a start on normal full operating throttle, think generators etc. In fact in industrial applications ( an area that Perkins are strong) this is the norm. With modern ECU engines this is now handled electro- mechanically

Dave

[RTB]

OK, not a Perkins.

The Yanmar manual says;

Warm engine
Move the speed control lever to the MEDIUM SPEED position.

Cold engine
Move the speed control lever to the HIGH SPEED position. Injection timing is retarded when starting with the lever in the HIGH SPEED position.

I have had little luck starting my older engine with lower throttle settings, especially in the winter.

[goboatingnow]

Originally Posted by RTB

OK, not a Perkins.

The Yanmar manual says;

Warm engine
Move the speed control lever to the MEDIUM SPEED position.

Cold engine
Move the speed control lever to the HIGH SPEED position. Injection timing is retarded when starting with the lever in the HIGH SPEED position.

I have had little luck starting my older engine with lower throttle settings, especially in the winter.

I was just about to quote yanmar and nanni all of which give full throttle cold starts. Sorry Greg.

Dave

[four winds]

On my 3gm30fv with 1800 hours, in cold weather, I have had better starting with the throttle open quite a bit. When warm or warm weather it fires right up regardless of throttle position.

I might try wide open starting in cold weather next time to see if it fires up fast.

[Seahunter]

The 4108 idles at about 800RPM. Download a copy of the service manual and operating manual for the Perkins 4108 and read it (there are lots of copies floating around the internet). Try Endeavour Manuals
ALL Perkins engines are set up to start in first position. ALL Perkins engines should start within a full turn of the crank without messing with the throttle. The "first position" is "all off" and transmission in "neutral". If the 4108 doesn't start right away, it is usually a fuel issue; "pumping" the throttle does nothing as it a mechanical driven fuel pump. You might as well wave at it for it to have any effect. If they sit too long (more than month between starts) the fuel leaks back out of the lift pump (the manual shows how to prime). This can be remedied by adding an electric lift pump and sending it back to the tank through a Racor or similar fuel filter stack. It solves the problem with poor lift pump issues and polishes your fuel at the same time. Perkins employs fuel starve to stop with a fuel shut-down switch and solenoid attached to the injector pump. There is an idle adjustment on the 4108, but read the manual first. High RPM starts on diesels are not a good idea and can cause internal damage; high idle while operating can cause transmission problems when shifting (as per the manual).
Anyways good luck and if all fails find a Perkins mechanic; I heard they're all working at CAT now.

[daddle]

Originally Posted by goboatingnow

Err no it not

Whatever you tried to say ... my Bosch fuel injection manual says, I don't make this stuff up: "...when the engine is cranked the plunger will travel through a complete delivery stroke ... giving ... maximum delivery quantity ... Thus the maximum delivery quantity [of fuel] is made available when the engine is cranked."

A nearby graph indicates the starting fuel supplied may be as much as twice the full power amount.

[Source: Diesel Fuel Injection Pumps, Bosch, 1995]

Now as far as the speed at starting, perhaps some engines won't happily idle until warmed up. These may need the speed control adjusted slightly to boost the idle for smooth initial running. Probably most common with tired engines, worn engines with sticky governors, low compression, and the like.

And Bosch calls it an engine-speed control lever.

[Seahunter]

Originally Posted by daddle

Now as far as the speed at starting, perhaps some engines won't happily idle until warmed up. These may need the speed control adjusted slightly to boost the idle for smooth initial running. Probably most common with tired engines, worn engines with sticky governors, low compression, and the like.

And Bosch calls it an engine-speed control lever.

This might be true of German designed engines built in Taiwan with "Botched" electronics, but Perkins engines were designed and built by the Queens carriage makers and were deliberated over in the minutiae of detail including thread count on each metric screw over a thermos of tea. Perkins engines are complicated only in their all mechanical way of dealing with everything. In the end they managed to put together a fairly simple and dependable way of oiling the bilge while sipping fuel over great distances.