How Long Before Your Perkins 4.108 Starts?

[Hampus]

Originally Posted by GordMay

5 - 15 seconds maximum.
5 - 10 seconds usual.

It's OK then. Thanks Gord!

[SkiprJohn]

As with most diesels - if your battery is not spinning your engine fast enough at start it may take a while longer to get it going.
Experiment with the preheat feature a bit to see if it really is working properly. My Mercedes engine has glow plugs but some have a preheater on the air intake side to warm the air. I can't remember how my Perkins was set up but it always started very quickly once the preheater was used.
Short bursts is better than 15 seconds straight.
Good luck.
JohnL

[Mike Sibley]

When starting the Perkins 4.108, make sure the throttle is full open when starting. It should then start up reasonably quickly. Also, make sure that the shut off knob (used to stop engine) is pushed in all the way. If it is still difficult to start, you may have a mechanical problem.

In a previous boat, I had a Yanmar that became difficult to start. It turned out to be a cracked head, due to overheating. The engine was raw water cooled and the internal chambers in the engine had become clogged. The resulting heat buildup resulted in a small crack in the head. The engine became difficult to start, but would run fine once started.

Good luck.

[CSY Man]

Old fashioned injectors (atomizers) in the 4-108:

They need to be overhauled every 400 hours as per the service manual.

The engine will run with more than double that on the injectors but don't expect stellar starting performance and no-smoke.

As for starting with full throttle, then bring it back when the engine fires...?

The excess fuel may wash oil of the cylinder walls and cause premature wear. I try to start with minimum throttle, but after I adjusted my idle down to 600 warm to avoid any shock on the tranny, it takes a little bit of throttle to get it going.

Thought of a high pressure pump overhaul a few years ago, in case that was the problem, but the engine seems to run fine, 30 years old, but with a 1985 overhaul, so no HP overhaul needed yet...The 4-108 seems bullet proof in my book. Would get another one in a heart-beat..Rock solid.

[Mike Sibley]

The service manual for my 4.108 indicates that one should "place the throttle in the fully open position and engage the starter motor." You can download a free copy of the manual at http://users.firenet.uk.com/stewartbray/perkins4108.pdf. Yes, you do reduce RPM once the motor starts.

Also, I believe the normal idle speed is not 500 or 600, but more like 1,000, or maybe even 1200. Problems result if the engine is run at too low an idle.

[Maddog]

Originally Posted by Mike Sibley

The service manual for my 4.108 indicates that one should "place the throttle in the fully open position and engage the starter motor." You can download a free copy of the manual at http://users.firenet.uk.com/stewartbray/perkins4108.pdf. Yes, you do reduce RPM once the motor starts.

Also, I believe the normal idle speed is not 500 or 600, but more like 1,000, or maybe even 1200. Problems result if the engine is run at too low an idle.

I just replaced the fuel injector pump on my 4-107 and the tech had it benched tesetd and adjusted for right around 600 rmp at low idle. 1200 seems high to me. I share my research afetr a bit.

[CSY Man]

The service manual for my 4.108 indicates that one should "place the throttle in the fully open position and engage the starter motor."

Hmm, never seen that in my manual, but will look again...Perhaps different versions of the 4-108?

[bobfnbw]

Before she hosed out on me, the engine always started within a few seconds. Even after sitting for a while. I used half throttle.

[MikeNZ]

My experience with cranking times is that it depends mostly on ambient air temperature. In our (NZ) summer (18-25 degrees) my 4-108 starts almost before I press the starter. In the winter, however, when it's say 5-10 degrees C, and the engine has stood for while and is really cold, the crank time goes up to around 5-10 seconds. My 4-108 was rebuilt last year and is a pretty good 'standard' to use. BTW I don't use any pre-heat, and have the throttle half open. Maybe the temps in Sweden are similar to mine?