Engine noise from cold start

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russ

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My boat went back in the water today and when starting my Mercruiser 5.7 engine this evening the noise that we thought was the exhaust flappers was still present after both being replaced.
Its a kind of rattling, clackling sound which goes once the engine has warmed up. My only other thoughts would be something to do with the thermostat which was changed last year.

I do also have a starting problem which I dont think is connected but you may know better?
The engine needs to be kept throttled up until warm or else it will stall. Put some carb cleaner in today but wont know if its made any difference until i start it up from cold again. Its a 2005 TKE system. Already changed the choke module.
Any ideas?:confused:
 
oGaryo said:
sticking valve lifter maybe
Click to expand...


2nd that diagnosis....

Carb....check the clear pipe that runs from the pump diaphragm to the carb....if you see air bubbles its a sure sign the diaphragm (spelling) has failed...

Spent hundreds and hundreds on a the same prob a decade ago, even replaced the carb before finding out this gem of info!

May not be mind but worth a look see.
 
Another thought ref the clacking! your new risers,have they the hard rubbery flaps or the steel ones? Cos if the hard rubber ones they do "clack" until softening with the exhaust temp warming up!
 
New rubber ones fitted.
One of the old flappers was on the verge of falling apart so just caught it in time. Only replaced flappers though not the risers.
Should the risers be hot to the touch as mine were only slightly warm.
 
Risers should be slightly warm to the touch assuming they're relatively new, but be careful as they heat up once the engine is shut down as the same water is trapped in there so absorbs all the heat.
 
Dont know about the noise but have had the same cold start issue. When you said TKE did you mean TKS?
If the TKS isn't 'choking' the carb you need a higher tick over to keep it running. On mine the problem was the connection of the wire to the oil pressure sender. The sender itself was OK but the connection of the plug into it wasn't good. Went through two senders before geting to the problem.
In the end I soldered leads to the sender terminal and put a better type of plug remotely and no problems since.
You can test if its this or the sender by shorting the correct lead to simulate the sender detecting pressure. Have to do it just after you fire up the engine, you can then usually hear the TKS valve hissing till the engine warms up.
 
dpb said:
Dont know about the noise but have had the same cold start issue. When you said TKE did you mean TKS?
If the TKS isn't 'choking' the carb you need a higher tick over to keep it running. On mine the problem was the connection of the wire to the oil pressure sender. The sender itself was OK but the connection of the plug into it wasn't good. Went through two senders before geting to the problem.
In the end I soldered leads to the sender terminal and put a better type of plug remotely and no problems since.
You can test if its this or the sender by shorting the correct lead to simulate the sender detecting pressure. Have to do it just after you fire up the engine, you can then usually hear the TKS valve hissing till the engine warms up.
Click to expand...
Yes sorry TKS system.
So from the pressure switch where does the wire go to. Oil pressure gauge is working fine though.
I think the choke is coming on as the engine seems to be running too rich.
 
oGaryo said:
sticking valve lifter maybe
Click to expand...

+
1 for a sticking lifter....or the rocker arms need resetting. I have heard somewhere that the shop manual procedure for setting the lifter stroke can cause rattles and experienced guys do it a different way to alleviate this.

As for the choke...I deep sixed my choke years ago and rely on manifold priming instead via the accelerator pump, this never lets me down.


Unfortunately an eyeball popping hangover prevents me from accessing the relevant filing cabinets for those particulars in me head. Don't want to go in there if I can help it, all angry reds, blacks and loud noises. :eek:
 
I think the enrichment system is working.. I've checked for 12v at the enrichment valve on start up and it's good, also there is a hissing sound.

Note, the enrichment valve is by default on (valve open) the application of power heats a wax pellet which slowly closes the valve, de choking the engine over a period of 10 or so minutes. Oil px switch failure would leave the enrichment valve open, choking the engine. Russ' problem is the opposite of this on initial start (ie won't idle cold.)

Note, it's not actually a choke. The enrichment valve opens a passageway in the carb that lets an extra fuel AND air mixture boost engine revs when cold. It's not a great system as there's no temperature feedback to the system - oil pressure on = power to valve and slow closing of the valve.
 
Just another one of my novice guess's Ross, could the carb butterfly flaps be closed too much on choke and just need adjusting to be letting in more air when cold. Maybe thats why its running very rich & stalling until warm.

I remember on one of my old American cars I owned that you had to bend the butterfly arm until you could get a 1/8 drill bit in when closed.
 
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