1GM10 running issue under load. Help please!

[bamboozle]

I wasn't thinking about the engine being worn out. I lost power because the head gasket went - not badly enough to stop it actually running but stopped it to achieve full revs. Turn the engine over with and without the decompressor. If there is no or little difference I would consider the head gasket as a suspect.

Did that and seems the same both ways. Thanks for sharing

The culprit could be the on engine filter. It's a mother effer to deal with and very easy to cross thread the knurled nut attaching the bowl to the filter and also very easy to nip the gasket that between those 2 parts. Also the bleed screws could be a bit mullered and not seating properly., both on the filter and the injector pump.
I eventually solved the air in and then went and bought a Beta 14 (slightly extreme solution) !
Good luck, you seem to be on the right lines.

Thanks for your reply. How did you solve the air leak in the end? The bowl nut seems to go on easily, not cross threaded and I put a new o ring on, but maybe it still leaks. I also thought replacing the nylon washer and copper washer on bleed screws could solve any leaks. I dont know what else to try really - I wonder if anyone has had any luck fitting a pressure gauge between certain points in the engine to try and find the leak. To confirm, would a simple air leak cause the issues im having? (max rev in neutral, poor performance in gear?)

 

[pioneer]

Did that and seems the same both ways. Thanks for sharing

Thanks for your reply. How did you solve the air leak in the end? The bowl nut seems to go on easily, not cross threaded and I put a new o ring on, but maybe it still leaks. I also thought replacing the nylon washer and copper washer on bleed screws could solve any leaks. I dont know what else to try really - I wonder if anyone has had any luck fitting a pressure gauge between certain points in the engine to try and find the leak. To confirm, would a simple air leak cause the issues im having? (max rev in neutral, poor performance in gear?)

i had 2 different situations, firstly the engine was "surging" kept wanting to develop power and then wouldn't. Fine out of gear. Solution was dirt in the lift pump diaphragm. The second was trapped air in the system caused by the spill pipe returning to the off engine filter so nowhere for any air to escape. It had to be back bled, not sure how that was done, as, in despair and time poor i got my favourite engineer to solve it and went sailing. When it re-occurred the spill pipe was re-routed to the main tank and the problem went away. Then i changed engines. I expect you've already do it but start at one end of the system and work towards the other, tedious but hopfully that'll find the ingress of air. Just a random thought but is the fuel tank level above the spill pipe return entry and is the spill pipe clear. might be worth a check.

 

[chriscallender]

Did that and seems the same both ways. Thanks for sharing

Thanks for your reply. How did you solve the air leak in the end? The bowl nut seems to go on easily, not cross threaded and I put a new o ring on, but maybe it still leaks. I also thought replacing the nylon washer and copper washer on bleed screws could solve any leaks. I dont know what else to try really - I wonder if anyone has had any luck fitting a pressure gauge between certain points in the engine to try and find the leak. To confirm, would a simple air leak cause the issues im having? (max rev in neutral, poor performance in gear?)

One trick I've used in the past is to temporarily put a section of clear tube in and look for bubbles. You could start with the return plumbing, if there is no bubbles there its probably all sound on the outbound side too (where the pump pulls a vacuum). I'm not convinced a pressure (or suction) guage would show much difference with/without a leak, well anyway I never tried it.

 

[tillergirl]

"Did that and seems the same both ways. Thanks for sharing"

There are two ways of interpreting that: Do you mean that it is no harder to turn with the decompressor released. If so you need to look at the head.

 

[Porthandbuoy]

If it starts okay then I'd be tempted to think the compression was okay. Worth checking the tappet clearances and make sure the decompression lever is fully disengaging before you start dismantling though.

Miniscule air leaks on the suction side of the lift pump can be a bugger to locate and cure. My solution was to paint all the joints with 'liquid whipping', some sort of rubbery paint used to stop rope ends fraying. Do it while the engine is running to suck the stuff into the leak. A bodge I know, but it cured the problem.

You mentioned "a touch of diesel bug". That's like saying "only a little bit pregnant". That slimy horrible stuff will clog a filter in no time. Cleaning the filters is no good, they need to be changed and biocide added to the tank.

The metal pipe running from the secondary filter to the injector pump. Check it for any dents. It's pretty small bore and any restriction there could limit rpm under load.

 

[barryhall]

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

It may be that you have already eliminated this but have you checked that the throttle linkage on the engine is actually going to full travel and it’s not a linkage problem?

 

[38mess]

It may be that you have already eliminated this but have you checked that the throttle linkage on the engine is actually going to full travel and it’s not a linkage problem?

Good point.
In the summer my Perkins wouldn't rev over 1500 in gear, checked everything as you do. Turned out to be the cable clamp came loose in the morse control, it was just gripping the cable at low revs but slipping through the grip the further the lever was pushed forward.

 

[bamboozle]

I wasn't thinking about the engine being worn out. I lost power because the head gasket went - not badly enough to stop it actually running but stopped it to achieve full revs. Turn the engine over with and without the decompressor. If there is no or little difference I would consider the head gasket as a suspect.

Did this stop the engine getting to full revs out of gear as well as under load?

 

[bamboozle]

i had 2 different situations, firstly the engine was "surging" kept wanting to develop power and then wouldn't. Fine out of gear. Solution was dirt in the lift pump diaphragm. The second was trapped air in the system caused by the spill pipe returning to the off engine filter so nowhere for any air to escape. It had to be back bled, not sure how that was done, as, in despair and time poor i got my favourite engineer to solve it and went sailing. When it re-occurred the spill pipe was re-routed to the main tank and the problem went away. Then i changed engines. I expect you've already do it but start at one end of the system and work towards the other, tedious but hopfully that'll find the ingress of air. Just a random thought but is the fuel tank level above the spill pipe return entry and is the spill pipe clear. might be worth a check.

Ive already had the lift pump apart, cleaned it and all looks well. My return hose goes back to tank - Im going to check that its not blocked etc, but shouldnt have trapped air issue. Ive worked through the system alot already, but i guess the secondary filter set up could still be leaking, its just hard to confirm.

 

[bamboozle]

Good point.
In the summer my Perkins wouldn't rev over 1500 in gear, checked everything as you do. Turned out to be the cable clamp came loose in the morse control, it was just gripping the cable at low revs but slipping through the grip the further the lever was pushed forward.

Ive checked all the hoses and clamps, but will check again, ive tightened everything I can see

 

[bamboozle]

If it starts okay then I'd be tempted to think the compression was okay. Worth checking the tappet clearances and make sure the decompression lever is fully disengaging before you start dismantling though.

Miniscule air leaks on the suction side of the lift pump can be a bugger to locate and cure. My solution was to paint all the joints with 'liquid whipping', some sort of rubbery paint used to stop rope ends fraying. Do it while the engine is running to suck the stuff into the leak. A bodge I know, but it cured the problem.

You mentioned "a touch of diesel bug". That's like saying "only a little bit pregnant". That slimy horrible stuff will clog a filter in no time. Cleaning the filters is no good, they need to be changed and biocide added to the tank.

The metal pipe running from the secondary filter to the injector pump. Check it for any dents. It's pretty small bore and any restriction there could limit rpm under load.

liquid whipping idea sounds good, will try that.

By a touch of diesel bug, I mean that I think it was starting to form / spread and I treated it quickly - sucked and ditched the fuel in tank and have changed filters since. Still a bit of grime in tank, that I need to get out. I think the lines from the tank to lift pump are okay though, as I rigged up a fresh fuel can straight to the lift pump and all symptoms remain the same - suggesting to me that all lines, main fuel tank, racor etc are all ok. The issue must then be from the lift pump and onwards. Ive already have lift pump apart and cleaned it, so next step was the secondary filter. I put new filter in and changed o rings, washers etc. I really want to check the line between the secondary filter and injector pump, but its a metal line, so wouldnt know how to check. As mentioned before, when bleeding injector pump screw when engine running I get alot of air bubbles that never clear, is this normal or should fuel spray out of here when engine on, screw cracked? Thanks

 

[bamboozle]

It may be that you have already eliminated this but have you checked that the throttle linkage on the engine is actually going to full travel and it’s not a linkage problem?

already checked all this

 

[bamboozle]

One trick I've used in the past is to temporarily put a section of clear tube in and look for bubbles. You could start with the return plumbing, if there is no bubbles there its probably all sound on the outbound side too (where the pump pulls a vacuum). I'm not convinced a pressure (or suction) guage would show much difference with/without a leak, well anyway I never tried it.

I read that the injector pump can often create bubbles in the final line up to the injector (as in its normal for this) and so the return line can often have bubbles in it anyway? This may be incorrect, but just read on other forums multiple times. I'll try the clear pipe idea anyway and see

 

[38mess]

Ive checked all the hoses and clamps, but will check again, ive tightened everything I can see

Not the hoses, but the morse control cables inside the throttle/gear controller. You can't see from the outside. On mine I had to dismantle the controller to get at the loose clamp.

 

[tillergirl]

Did this stop the engine getting to full revs out of gear as well as under load?

Fine out of gear, reduced revs under load. At about half revs in gear it could not increase. There was enough compression to start the engine but I could see little different in the compression with and without the decompressor activated. I lifted the head and could see the gasket had been blowing. Clearly the 'blow' was small enough to accept moderate compression. I guess it would have got worse and eventually impossible to start. New gasket solved it. Starting was improved and back to full revs.

 

[chriscallender]

I read that the injector pump can often create bubbles in the final line up to the injector (as in its normal for this) and so the return line can often have bubbles in it anyway? This may be incorrect, but just read on other forums multiple times. I'll try the clear pipe idea anyway and see

That could be true. When I did this, air was getting in at the filter and it was pretty obvious, the bubbles in the return weren't minor. It was certainly much better when I fixed the leak but I don't really remember if there were tiny bubbles still remaining from the injector pump - it was a long time ago now. As far as I remember, mine needed PTFE tape on the BSP hose connectors that screwed in to the filter ports to fix it.