Yanmar 1GM10 under performing.

[sancho]

Hi

I just don't think I am getting the full performance out of my engine. When my 1GM10 is put to full throttle the engine speeds up to what I would expect to be maximum revs but then backs off and slows down ! is this normal? The engine has been serviced, fuel filters etc, I have checked the exhaust for blockages and found this to be Ok. The engine is 15 years old, is it ready for a new injector? could this be a symptom of out of spec valve clearances or is it the regulator that requires adjustment? is this a DIY job.
What is the effect of a internally rusted exhaust elbow?
The engine starts first time, there is no black smoke and the exhaust is clear under normal running conditions.
Your comments or thoughts would be most appreciated.

 

[ShipsWoofy]

how long does it take to fall back once you have opened it up, how slow does it get?


Have you looked at the silly obvious such as a damaged morse cable / throttle lever before we start stripping it down on here /forums/images/graemlins/grin.gif

 

[sancho]

The morse controls are Ok. I don't have a rev counter so it's difficult to be accurate, but I would say it backs off to around %60 - %70 of it's maximum revs just after it has peaked. I have checked all the usual things and done the searches. I hoped someone else had experienced the same.

 

[Fin]

Had something similar last year and pinned it down to c$%p in the fuel tank.

 

[pampas]

had the simular problem with a brand new 1GM found that the lift pump filter was duff, Installers fitted new pump, problem solved, may be this is you fault,worth looking at before going into the engine.

 

[sancho]

When I changed the engine fuel filter recently the old filter (1year old) looked very clean, is there another filter in the lift pump?

 

[Stemar]

It does sound like fuel starvation. Fisrt suspect is always fuel filters. I presume there's a filter /water separator in the line and that you've changed that?

If it's a diaphrgm type pump, that would be worth a look. A damaged diaphragm might not pump enough to keep the revs up under load. Alternatively, look at the fuel lines - check for kinked or crushed copper pipes, collapsed rubber pipes and rubbish accumulations anywhere.

Sometimes there's an undocumented mesh filter in the fuel tap or the union connecting the tap to the pipe. When the start to get blocked, these have been the cause of untold grief to those who didn't know they were there. A blast of air back up the pipes to the tank (take the filler cap off first) might give a temporay cure, but if the blockage is due to crud, it'll be back unless the crud is got rid off.

 

[jerry_jones]

There is an excellent Yanmar forum at:

http://www.freeboards.net/?mforum=yanmarhelp

Jerry Jones
Marcon Sabre 27
Plymouth, UK

 

[NPMR]

Don't have an answer on the revs but the rusted mixer elbow will need watching.

If it rusts right through, you can get water sprayed into the head of the engine, which can cause very expensive damage. Yanmar recommend examination EVERY 300 hours.

Just a small triumph - the cost of this is now massively reduced as a spare part, after some vigorous campaigning!