slow starting yanmar 1GM10

[wiggy]

Batteries are fine but engine slo to start. Starter turns fine first go but then seems to struggle. Any suggestions.

 

[Topcat47]

Starter motor brushes sounds likely. If the motor turns over well, it's possible that you've poor compression (broken piston rings/re-bore needed) or possibly injector problems, it depends how old it is and how many hours it has run. I'd have the pump and injector serviced by a truck specialist, if it were my final diagnosis, they're so much cheaper than marine engineers. Halfords sell a compression tester for around £16.00, but you need to remove the injector to carry out the test.

 

[Topcat47]

BTW if the starter runs fine first time then slows down, it sounds like sulphation of the battery.....your local TAB agent will be able to do a drop test on the battery for you. Now I think abut it, it would be my first move. They'll not usually charge for the test, hoping you'll buy a replacement from them if needed.

 

[neilmft135]

if you are having starting problems, I would check the battery, isolator switch to make sure your electric connections are good at all points going to the starter & solenoid.
Being a marine engineer I would not advise pulling off your fuel pump and injectors as the chances are it is not the problem you can get new injector nozzles for around 10 pound each but you will need to get an engineer to crack test the injector once rebuilt. and to calabrate the fuel pump can be expensive. As said before check the electrics & starter then start to look further.

 

[Birdseye]

[ QUOTE ]
Batteries are fine but engine slo to start. Starter turns fine first go but then seems to struggle. Any suggestions.

[/ QUOTE ]

Not quite clear what you mean about the starter. Does it turn over fast at first and then progressively slower? If so, then you probably need look no further than the battery which sounds to have reduced capacity. In other words the voltage is dropping off rapidly, but dont be deceived by putting a voltmeter across the terminals when the battery has had a rest for a few seconds. A battery can give 12.7v at the terminals and still hold very little leccy.

Its worth checking the connections simply to make life easier for the battery, but connections arent likely to be the problem - it would turn over slowly all the time if they were.

At this time of year, an engine without pre-heat will take more churning before it starts and this will be made worse if there is wear and compression is a bit low. It will also take longer to start if there is drain back of the fuel. But the first place to look is the battery.

 

[Anonymous]

Welcome to the forum - it's good to have a professional contributing to these threads. Your input will be MUCH in demand /forums/images/graemlins/smile.gif

 

[wiggy]

I have tried on starter battery and domestic nd get same results on both banks. Batteries seem fine with clean contacts and fully charged. What are the chances that it is the starter motor?

 

[Anonymous]

Sorry if I'm teaching my grandmother, but how do you know that the batteries are fully charged?

 

[LadyInBed]

How well does it start if you turn it over with the decompression lever up for a few revs first?
It sounds like weary batteries to me.

 

[pampas]

before doing any of the advised procedures clean and grease the main Negative connection on the engine.

 

[mortehoe]

You\'ve got a bent conrod ... (Bad Yanmar design)

Have a compression test done: 590psi = max manufacturers design; 493psi = extreme sub-limit for starting .....

 

[ems]

Whilst agreeing with the initial suggestions about poor battery performance. Before going too deeply into injection equipment, I would check the exhaust system. A partially blocked exhaust could eventually cause a back pressure which could slow down the cranking revs. Check the exhaust pipe for damage, if a gate or ball valve is fitted check it is fully open. The exhaust elbow has a s/steel water deflector inside it, if this has come loose and and dropped down the exhaust this could cause a partial blockage. At the last refit I had this deflector welded back into position. I am sure somebody will tell me if this is twaddle, but it may help.
Good Luck.

 

[sailorman]

wot grade of oil r u using

 

[wiggy]

Thanks for all the tips, i'm off down to the boat today so will definately check the obvious.

 

[Topcat47]

I had no problems with my engine starting or instruments but on checking out my battery cables I found one that had almost abraded through, rubbing on something.....corrosion waevident for nearly six inches either sode of the exposed cable.....and another one was literally hanging by a single strand to the battery terminal.

The blocked exhaust idea is a new one on me. I'm not sure that it would have the symptoms described but it would certainly hamper starting and result in very poor running. I'd be interested to see what "MFT 135" thinks about it.