470 poor starting after rebuild

Rake722

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Apr 23, 2012
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Well I finally got her started today and she runds nicely.

She did take a long time to get started but once running the engine is like a sewing machine so I am pleased.

Residual issue is that she is hard to start even once warm. I set the ignition timing using a strobe to 5 degrees btdc. I did this using the strobe pointed at the middle TDC notch and turned the distributor so that it read 05.xx with the timing mark aligned to the centre mark on the engine casing.

She is fitted with pertronix ignotion so no condenser or points.
Battery is good and showing 13 volts.
Fuel is fresh.

I have primed with 3 full strokes of the accelerator then crank. sometimes she will fire up but nore often she wont.

Am I flooding the chambers or is there not enough fuel coming through ? If I pump the accelerator I see a solid squirt of fuel from the carb looking down in to the flame arrestor.

Choke is working fine but fully open by the time I shut off and wat to restart.

I have removed the resistance wire and run in a new regualr wire between the coil and choke. 12 V present at the coil.

Any Ideas ? My gut feeling is either too much fuel or too little.

I'd like this engine starting reliably and every time before taking her on a test ride.

Vid - https://youtu.be/E6xzFMlSRlY

Any help gratefuly received.
 

kenny nunez

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When you look down the throat of the carburetor and work the throttle does fuel discharge from the accelerator nozzles?
If not that could be the problem.
 

Rake722

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Apr 23, 2012
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Hi Kenny - yes there are 2 jets of fuel when actuating the throttle linkage by hand
 

Rake722

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Is there a way of finding out if it’s flooding or getting too little fuel to eliminate those possibilities?

i guess fuelling can’t be too far out as when she does run she finds well.
 

garbageguy

Lieutenant Commander
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May 8, 2012
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what happens when it's warm from previous good run, and you try to start with no throttle?
 

Rake722

Chief Petty Officer
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Same thing - no start.

timing wise I have a gunson strobe with timing readout on a small screen.

when setting the timing I am using the centre notch on the engine casing which denotes TDC to time to.

I fire the gun at the balancer and adjust the distributor
little by little until the balancer white line aligns with the TDC notch on the casing when the dial on the gun is rotated until the gun says 4 degrees when the tdc mark and balancer line match up.

im now questioning if I’m doing this correctly ?

this is the link to the light
http://www.gunson.co.uk/product/G4123
 

Rake722

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From the manual -

the advance control knob (D) fully anticlockwise. Press the trigger; the light will flash and the display will show 00.00. Direct the timing light at the timing marks on the engine. Rotate the advance control knob slowly clockwise until a rotating timing mark lines up with the fixed mark or tag. If the marks that are lining up represent TDC, then the ignition timing of the engine is the number of degrees shown on the display. For example, if (when the marks line up), the display reads 08.00, then the timing is 8o BTDC. If the timing marks do not represent TDC, but some other timing angle, then add this to the display angle. For example, if the timing marks represent 8o BTDC and the display is showing 00.00, then the ignition advance is 8o BTDC

looks like I’m am timing correctly so maybe back to fuel
 

kenny nunez

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Connect a volt meter to the + or BAT side of the coil and read the voltage when the starter is engaged. There should be at least 11-12 volts then should drop to 7-8 volts when the engine is running. The “bypass” circuit from the start relay could be the problem.
 

Rake722

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Thanks Kenny I’ll check next time at the yard.

what is the bypass circuit and how would it cause a poor start issue ?
 

Bondo

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I have primed with 3 full strokes of the accelerator then crank. sometimes she will fire up but nore often she wont.

Ayuh,..... After ya do the 3 stroke prime,..... Where do ya set the throttle before ya turn the key,..??
 

kenny nunez

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The “bypass circuit” provides current when the key is turned to “start” because only the start side of the ignition switch has current. Think about your car how every thing, radio, wipers,etc. goes off when the key is turned to start.
 

Scott06

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Apr 20, 2014
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Flooding chambers ...probably not. When it finally does start do you get black smoke? If so may be flooded.

I think more likely you have weak or mistimed ignition. If you get a good stream of fuel when pumping the throttle and you have a good spark it will fire right up.

would try a spark tester see if you get a good hot blue spark that jumps a decent gap. If orange or weak fix the ignition. If you do have a good hit spark , try rotating the distributor while someone turns the key. Thought being if you are ATDC vs BTDC.

Every hard to start engine ive had has been related to weak spark. Fixed the ignition just look at the key and it starts ...
 

Rake722

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Thanks for the advice Scott, you might be on to something, when I last checked the spark I wasn’t too impressed, it was small and possibly orange. I’ll have to go back and re check but it’s hard being at the helm and seeing the spark at the aft. I’ll hwve to find and assistant and re check
 

achris

More fish than mountain goat
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The “bypass circuit” provides current when the key is turned to “start” because only the start side of the ignition switch has current. Think about your car how every thing, radio, wipers,etc. goes off when the key is turned to start.

Merc ignition switches leave power on the 'RUN' post when turned to 'START'. So he's not losing spark because of the switch being turned to start.

Rake722 What sort of compressions do you have? Have you verified that the TDC position you're using is actually TDC?

Chris.......
 

Rake722

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Hi Chris, thanks for the reply - its been a long road this project and hopefully close to the end.

OK I verified TDC using the engines compression to identify firing stroke and then I lined the balancer mark to the center notch on the engine casing and used a driver in the plug hole of pot 1 for TDC.

Compression has not been tested as I lost my tester but I am pretty certain that it is good as turning the engine over by hand is significantly more difficult with plugs in rather than out. Pistons and rings are new and correctly fitted. ( I Know this is not a real measure but I dont suspect compression as the issue).

When I tested the spark it was admittedly orange and not very big.
 

Lou C

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Nov 10, 2002
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Are you sure there are no vacuum leaks between the intake and head and the carb and intake? It looks like rough running that could be a vacuum leak/carburation issue. Also, do these engines have hydraulic tappets and if so did you adjust them to specs? Was the carb rebuilt as well?
 

Rake722

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Apr 23, 2012
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Hi Lou, the intake had a new gasket and torqued to specification.
The carb was not rebuilt as the engine has only seen 60 hours of use.

The tappets are new and adjusted to spec yes.

If there was a vacuum leak I would expect to hear it ?
 

kenny nunez

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If your ignition switch is of the “GENERIC” style which plenty of the boat manufacturers along with the wire harness use to hold down cost and not the genuine Mercruiser there will be no voltage from the switch in start mode.
If there is no blue spark when cranking then the bypass circuit needs some attention.
Genuine Volvo ignition ignition switches have the bypass circuit built into them. Those are the ones that require the key to be turned over 180* to engage the starter.
A good example is when Bayliner installed Volvo 4 cylinder packages. They used the cheapest generic instrument panel and harnesses. A jumper wire had to be added from the starter solenoid to the + side of the coil to get the blue spark needed.
 

Rake722

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Apr 23, 2012
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474
A thought - installed is the ignitor 1146a and flame thrower coil.

i cut the resistance wire at the choke and ran another regular wire from the purple yellow on the coil to the choke - did I get this right ?
 
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