1GM10 running issue under load. Help please!

[tillergirl]

It got progressively worse to start, no change in exhaust smoke. What had happened was the engine overheated despite ample water apparently being circulated. It seems the compression was the clue but wasn't as obvious: i.e. it was starting, had some compression, no wheezing. When I lifted the head (not difficult I could see that the water passages in the head (which are small) were clogged and part of the gasket had blown. While at it I ground the valves and seats and replaced the exhaust valve as the valve was starting some deeper pitting. When alll back together the starting was instant and back to full revs. While I don't know the age of the engine I think it was suffering from lack of use - it is described as the 'emergency' engine! The installation was nicely done but a mistake as it is too small (i.e. 10hp v 120hp on the main engine)

 

[coveman]

Is the air filter clean?

 

[winch2]

Interesting read. Hows this for left field. Is there a chance the throttle cable/linkage is slipping when your gunning it? Chk for full tavel?

 

[tillergirl]

Funnily, one of the first thing I did was check for a slipping cable. I would have loved that if it was responsible but for me, sadly it wasn't. But actually doing the head wasn't difficult. Certainly a worthwhile check.

 

[Metalicmike]

Sounds to me like your Throttle cable or another part of that system is sticking.

 

[vas]

good luck sorting it, I have a 2GM that has caused me lots of headache over the last many years, but luckily it's on my 8kva generator, so not that critical...
if you search in pbo you'll find various threads of mine on that.
To keep it short, it was a combo of leaking lift pump (dumped it and replaced it with an electric one) and cross/strip threaded bleeding screws on the godawful yanmar main filter.
Once these were fixed, it's running fine, which is always at 3K rpm and decent load.

cheers

V.

 

[38mess]

Interesting read. Hows this for left field. Is there a chance the throttle cable/linkage is slipping when your gunning it? Chk for full tavel?

See my post #27

 

[bamboozle]

Is the air filter clean?

Yes, air filter is clean. Ive also ran the engine without the filter to confirm that its not an airflow problem.

 

[bamboozle]

Interesting read. Hows this for left field. Is there a chance the throttle cable/linkage is slipping when your gunning it? Chk for full tavel?

Quite sure its not this as Ive been revving the engine using the governor lever on the engine itself to check. Ive checked the throttle cables etc too and all seem to be working properly. The engine revs up no problem in neutral too.

 

[bamboozle]

good luck sorting it, I have a 2GM that has caused me lots of headache over the last many years, but luckily it's on my 8kva generator, so not that critical...
if you search in pbo you'll find various threads of mine on that.
To keep it short, it was a combo of leaking lift pump (dumped it and replaced it with an electric one) and cross/strip threaded bleeding screws on the godawful yanmar main filter.
Once these were fixed, it's running fine, which is always at 3K rpm and decent load.

cheers

V.

Thanks for sharing. I'm at a bit of a loss now as I feel ive checked and re checked everything. I'm going to have another go at the filter housing / bleed screws to check for leaks.

One thing I was wondering though, does anyone know if running the engine the way it is will cause any damage? It feels like fuel starvation limiting revs and not something else, so I would assume that is not causing much in the way of damage or wear?

 

[vas]

Do you have two filters on it? I mean a "pre-filter" leading to the lift pump and then to the awful yanmar contraption?
If so, maybe bypass the yanmar one for confirmation.
Also if you're using temporarily an external fuel can if you can have it higher than the top of the engine, you can get away with the lift pump as well (for testing purposes)
Maybe do one at a time and see if you can identify the culprit.

good luck!

V.

 

[Rappey]

Have you had someone move the throttle lever in the cockpit back and forth so you can look at the injector pump connection to make sure its opening all the way?
I would say its unlikely to be a compression issue on a fairly new, easy to start when cold engine .
You need a lot more fuel to rev an engine under load compared to in neutral so fuel starvation could still be the problem.
I would have thought that if air ingress was the problem that would make it hard to cold start ?

 

[Rappey]

My engine is horrendous to bleed so changing filters is somewhat avoided. Last set did 7 years
Now ive fitted a vacuum guage between my primary filter and lift pump. With the engine running with new filters the guage reads -3.
When i next go out to the boat the guage is still held at -3 which tells me i have no air leaks in my fuel system.
As the filter blocks the readings go up so around -7 you should be changing filter and if you hit -10 you wont be running much longer !
Makes more sense knowing the condition of the filter rather than changing every year?

Stainless £12.99 on ebay

 

[bamboozle]

Do you have two filters on it? I mean a "pre-filter" leading to the lift pump and then to the awful yanmar contraption?
If so, maybe bypass the yanmar one for confirmation.
Also if you're using temporarily an external fuel can if you can have it higher than the top of the engine, you can get away with the lift pump as well (for testing purposes)
Maybe do one at a time and see if you can identify the culprit.

good luck!

V.

When i tested with fuel can it was higher than the engine. I'd like to connect straight into the injector pump, but the connection between secondary filter and pump is a metal line, so not sure how id connect it up properly.

 

[bamboozle]

Have you had someone move the throttle lever in the cockpit back and forth so you can look at the injector pump connection to make sure its opening all the way?
I would say its unlikely to be a compression issue on a fairly new, easy to start when cold engine .
You need a lot more fuel to rev an engine under load compared to in neutral so fuel starvation could still be the problem.
I would have thought that if air ingress was the problem that would make it hard to cold start ?

already checked all this. The throttle on engine is maxed out.

 

[Royedge]

Hi All, I've tried to research this the best I can, but thought I'd start a new a thread incase someone might be able to help with my particular case.

I have a 1GM10 that starts and runs well (up to max rpms) in neutral / when not in gear, but as soon as its in gear under load it's unable to reach max revs and throttle response (especially mid range) is non existent. In gear the throttle responds quite well up to say 1200 rpm, then the throttle has no effect on revs until its almost pinned at full throttle - then the revs rise and settle around 2-2500. I understand that I should be able to get this engine up to 3600 rpm, cruising at 3400 or so. When applying more throttle, there is no change to exhaust fumes which makes me feel like its a fuel starvation issue not an overloading issue (overloading, dumping more fuel would make black smoke?). Generally there is no smoke from exhaust at all.

Things i've done so far -

- checked hull and prop, both are clean and free of debris. Prop turns easily by hand and is the original prop for the boat, so I dont think its overpropped. The boat has also performed fine before, reaching circa 6 knots.
- cleaned out both primary and secondary filters. There was some crud and water in secondary fuel filter that ive cleaned out now. Not sure if this might have caused damage further down the line in injector pump etc?
- Bled whole system multiple times using outboard motor hand pump. Only part im not sure ive bled properly is at the injector itself, do I need to bleed this with the engine is running? Engine has always started on the button straight away, so I feel system has been bled well previously.
- rigged up a fresh can of fuel straight into the lift pump to bypass the normal fuel tank, fuel lines, racor filter etc. Boat ran the same as it did when normal tank etc was connected, which makes me think that system is working fine. Next idea was to bypass the lift pump too and see if I have the same issue.
- Ive not checked the exhaust elbow just yet, but its on my list. Its only 2 years old, so I suspect it should be fine?

Wondering if anyone has had a similar issue and did you find the fault in the end? Thanks

You should indeed bleed the injectors while the engine is running. This involves loosening the high-pressure line at the injector slightly until you see fuel without air bubbles, then retightening it. This ensures no air is trapped, which could prevent the engine from reaching full rpm under load.

 

[vas]

is there any chance whilst doing bleeding at the high pressure pump (if you did that is!) that the lower nut turned at all?
had that, meant pump lost it's settings, had to remove it take it to a local diesel expect to re-tune it.
Had that happen on one of my two pots, would start, run and not be able to keep the 3K rpm I needed for the generator at any serious load. Would rev fine with minimal load...

I'd try all other solutions first though as it's not a v.straightforward job to remove the thing (could be on a single pot gm though, not sure.
Agree with Rappey, if it's starting easily, it's highly unlikely it's got air in the system.
Mine was a b1tch to start when so. Also fitted a vacuum gauge and I know I'm at minus half a bar or so indefinitely with all leaks fixed.
However, lift pump maybe not working right...

V

 

[bamboozle]

PROBLEM SOLVED!

Well not quite solved, but I now know the issue which I came across randomly and thought it would be helpful to share.

I was about to head out on the boat, so turned the engine on to warm up and to check everything was working. 5 mins later I turned the engine off and noticed that the alarm from key panel was not sounding as it usually does (it has never done this before). I then went down below to check the battery as I thought the no buzzer issue could have been a power related problem. Voltmeter across the battery showing 14.5 volts when engine was NOT running, which I thought was odd. Started the engine again and the voltage across the battery showing 18 volts (overcharging issue I guess). I still wanted to head out on the boat for the day, so I decided to just remove the alternator belt completely to avoid any overcharging (the belt only powers the alternator and nothing else. With belt removed the engine is running perfectly, revving up to what I think is full RPM very easily both in and out of gear. Managed to get up to hull speed 5.6 knots no problem at all.

Has anyone come across this sort of issue before? My alternator only powers the engine battery and nothing is attached to this apart from the engine itself. I will aim to fix the alternator at some point (I guess a regulator issue?), but in the meantime I was thinking of just attaching a 20w solar panel to the engine battery to keep it topped up. Has anyone done this before? Just deleting the alternator all together and going solar?

Thanks again for all the info and advice above.

 

[Boater Sam]

I have had alternators go se

PROBLEM SOLVED!

Well not quite solved, but I now know the issue which I came across randomly and thought it would be helpful to share.

I was about to head out on the boat, so turned the engine on to warm up and to check everything was working. 5 mins later I turned the engine off and noticed that the alarm from key panel was not sounding as it usually does (it has never done this before). I then went down below to check the battery as I thought the no buzzer issue could have been a power related problem. Voltmeter across the battery showing 14.5 volts when engine was NOT running, which I thought was odd. Started the engine again and the voltage across the battery showing 18 volts (overcharging issue I guess). I still wanted to head out on the boat for the day, so I decided to just remove the alternator belt completely to avoid any overcharging (the belt only powers the alternator and nothing else. With belt removed the engine is running perfectly, revving up to what I think is full RPM very easily both in and out of gear. Managed to get up to hull speed 5.6 knots no problem at all.

Has anyone come across this sort of issue before? My alternator only powers the engine battery and nothing is attached to this apart from the engine itself. I will aim to fix the alternator at some point (I guess a regulator issue?), but in the meantime I was thinking of just attaching a 20w solar panel to the engine battery to keep it topped up. Has anyone done this before? Just deleting the alternator all together and going solar?

Thanks again for all the info and advice above.

I have had alternators go seriously overvoltage. On a bigger engine the load on the engine is hardly noticeable but yours is only half a step up from clockwork so it will make a huge difference as you have found out.
I am surprised that the battery did not give you any warning, gassing and smelling, before you made the discovery.

 

[bamboozle]

I have had alternators go se

I have had alternators go seriously overvoltage. On a bigger engine the load on the engine is hardly noticeable but yours is only half a step up from clockwork so it will make a huge difference as you have found out.
I am surprised that the battery did not give you any warning, gassing and smelling, before you made the discovery.

The battery is usually hidden away, so hard to hear / see any issues. When I checked the voltage I did hear a slight hissing noise, I guess off gassing. I stop started the engine maybe 6 times during our trip yesterday and the battery voltage is down to around 13.3 (no alternator attached), which I guess is still a bit high? The can still hear off gassing once in a while, but not really now. I was going to just use the battery until it was below 13v and then add a solar panel to it - not sure if this is safe / sensible? I'm not sure what damage, if any, I have done to the battery - is there anyway to tell? Battery still seems to be functioning properly and starting the motor no problem, but honestly I dont know how long I have had this overcharging issue. The alternator was destroying cheap alternator belts a few months ago, so I imagine ive had the issue a while. I changed to a better belt and it stopped shredding.