Engine over revving

[colin.marshall]

Trying to diagnose a problem where my lister petter 3cylinder marine revs to limit when in neutral.
This first occurred after initially the engine revs lowered when motoring. With no fuel gauge I topped up fuel and all seemed fine until I next put in neutral. This could all be coincidence.

I had recently replaced raw water shaft seals. A leaking oil pressure switch. Replaced oil filter and oil too.
Trying to sort this I have since replaced primary and secondary fuel filters and bled system. Engine does start but still it revs high. Whilst I cannot control this with the throttle, I can can control revs by half closing the engine stop. I welcome any suggestions and have some questions to start.
Can air in system cause the engine to rev like this?
I am assuming the fact I can easily stop the engine means it’s not sump oil that’s feeding the engine?
Does the fact the engine stop can control the rpm mean the injector pumps and fuel rack are ok. I am believing the engine stop adjust the fuel rack via the governor?

Accessing the governor and trying to repair would be new to me so I’m trying to understand what might be going on.

 

[jwfrary]

I would hazard a guess that the throttle linkage has come adrift, I would be checking that first.

 

[colin.marshall]

I would hazard a guess that the throttle linkage has come adrift, I would be checking that first.

Linkage outwith governor is fine if that is what you mean.?
I have removed cable to operate throttle on engine. Anything else would be inside governor. Whilst I am resigning myself to the possibility I might need to get in there, I am trying to ensure its not something else first. I could probably dig a big hole in there.

 

[jwfrary]

Exactly which lister Peter do you have?

Can't see anything you have done would be directly causing this behaviour, and if the linkage is intact then it does point in the direction of the governor (or the rack)

The governor is probably a spring/lever type but I'm not a lister person. Obtaining the right workshop manual would be the first trick!

 

[jwfrary]

On the engine stop thing, it depends as there is a few different methods to function.

 

[colin.marshall]

On the engine stop thing, it depends as there is a few different methods to function.

It's an lpw3.
I have manuals but nowhere near enough experience. My understanding is that both the throttle and engine stop act on the rack to control fuel to injector pumps. The governor does same automatically. I'm leaning towards thinking that if stop can control the rack, it can't be stuck injector pumps or stuck rack. Therefore just leaves the governor.
I have had mixed advice that air in system can cause over revving and that could make sense that I have air, but engine starts and I can't think how air would cause revving.

 

[jwfrary]

Air would cause it not to run! However it couldn't hurt to purge the system.

I'm wondering if the throttle lever has spun on the shaft or something like that.

The stop may not be linked in the same way to the rack, and I'm not sure on that engine as I dont come across many listers! Sound like a governor issue, which have a propensity to fall to bits as you remove them theres usually a methodology to it. But in essence they are two springs balanced against each other so relatively simple things.

 

[Boater Sam]

I think you have lost a spring, the ends wear until they disconnect.

 

[colin.marshall]

Thanks guys. I think I need to bite the bullet and get in there. Ots just a crankshaft pulley and a few bolts eh...
One thing I forgot to mention is that when in gear, the throttle revscengine fine I think. I am going to retest that point later.

I'm new to forum. How do you see where everyone is?

 

[colin.marshall]

Ah click on their name

 

[coopec]

Just looking for links that you might find useful

https://www.facebook.com/listerpetteruk/


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