No fuel being drawn into lower cylinder Johnson 7.5hp

[Msc19671]

Hi I have an old Johnson 7.5hp, which I beleive is a 1983 (J8BACTA),
The engine was becoming more and more difficult to start, on inspecting the heads with a camera, we noticed water had been seaping into the top cylinder, so head was removed and the head gasket was subequently replaced, head flatened and cleaned and cleaned the areas where water had got into. Doing a pressure test afterwards it is 75psi on each cylinder.

We also serviced the carb, with new gaskets and clean, but the new jet from the carb service kit didnt screw down properly, so the origional was re-fitted. The water pump impeller was also replaced, and new spark plugs fitted. The sparks appear to be firing 10mm with a tester.

The engine seems better starting now, but only appears to be firing on the top cylinder, and he doesnt think there is any fuel getting into the lower cylinder for it to fire as the spark plug is still clean and on testing the spark with a tester its sparking at 10mm, so it doesnt look like that is the issue, plus the plugs have be swapped over incase it was faulty.

Does this engine have any reed valves on the other side of the carb that could be causing the problem?, or what else could be causing no fuel to reach the lower cylinder? Any help would be most appreciated

 

[racerone]

There are 2 separate crankcases.----Each crankcase has a set of reed valves.-----Did you buy a factory carburetor kit or something else?----Offshore carburetor kits are known to have issues with the float valve threads.----Have you checked fuel pump diaphragm ?----

 

[Msc19671]

We purchased a Johnson Evinrude 9.9 HP 15 HP 1974-1988 398453 Carburetor Carb Kit w/ Float on ebay (not a Johnson factory kit) the carburetor is the origional, but it is firing on the top cylinder.
These reed valves how accessable are they, and are they behind the carb plate?

Regarding float valve thread, would you suggest trying to cut the thread ourselves, or just keep to the origanal?

 

[racerone]

There is a float valve shown in that kit.-----No jets shown in that kit.----I suggest you check the fuel pump diaphragm.----The 7.5 shows a different part # for the carburetor kit.-----Reed valves are easy to find and check.-----Behind the carburetor.----Just a few screws and gaskets.----Was the old head gasket blown?----Could be the bottom crankshaft seal has an issue.----Or you have crankcase. compression issues

 

[Msc19671]

There is a float valve shown in that kit.-----No jets shown in that kit.----I suggest you check the fuel pump diaphragm.----The 7.5 shows a different part # for the carburetor kit.-----Reed valves are easy to find and check.-----Behind the carburetor.----Just a few screws and gaskets.----Was the old head gasket blown?----Could be the bottom crankshaft seal has an issue.----Or you have crankcase. compression issues

Its the gold valve (ebay https://www.ebay.co.uk/itm/166838223579), the carb kit says it was for a 1982-83. The other noticeable thing my friend noticed today was fuel being spat out into the air box. The fuel pump diaphram has been changed, and there looks like a good pressure flowing on removing the fuel pipe to the carb
The old head gasket had blown by the thermostat area, and looked like it had gone a bit between the two cylinders, which affected the top cylinder which is the one firing okay.
We also removed the water jacket and cleaned it all out and used gasket sealer when putting it back , not on the head gasket.
I have added some photos showing the state it was in

We will remove the carb and have a look at the finding the reed valves, just there didnt appear to be any info I could find of reed valves on a 7.5hp

 

[racerone]

First picture shows the float valve seat.----That is NOT a jet.

 

[Msc19671]

First picture shows the float valve seat.----That is NOT a jet.

my apologies, my friend was calling it a jet, all this time but the new one just wouldnt screw down all the way so we just kept to the orig

 

[Msc19671]

What do you think then, examin the reed valves see if it is stuck closed, you also mentioned -"Could be the bottom crankshaft seal has an issue.----Or you have crankcase. compression issues" , what tests can be done on these?

 

[saltchuckmatt]

Am I understanding you correctly? You used a 9.9/15 carb kit for a 7.5?

If so, yes it won't run correctly.

 

[Msc19671]

Am I understanding you correctly? You used a 9.9/15 carb kit for a 7.5?

If so, yes it won't run correctly.

We only used the new gaskets, float and pin , but not float valve as wouldnt fit so kept orig and fitted new welch plug , but it states its also for :-
#398452
#391305
#439072
#391937
Compatible models:

For Johnson evinrude 4hp, 1983-1993
For Johnson evinrude 6hp, 1984-1985

For Johnson evinrude 7.5hp, 1982-1983

For Johnson evinrude 8hp, 1984-1985
For Johnson evinrude 9.9hp, 1974-1988
For Johnson evin 14hp, 1968
For Johnson evinrude 15hp, 1974-1988

I cant see why only changing these parts could cause no fuel to reach the lower cylinder but reach the upper cylinder, thats why I am thinking it could be the lower cylinder reed valve stuck closed, and block the flow of fuel from the carburetor, but I wasnt sure if this engine had them and where it was located, as I am only a novice and not experienced, and couldnt see any videos on this size engine

 

[saltchuckmatt]

I think sometimes they leak, not stuck closed, but reeds don't fail often on those little motors.

Hand over carb....does it spit gas in your hand? When doing this don't suffocate the motor.

Here's a parts drop.....

 

[Crosbyman]

behind the carb is a plate behind that plate are reeds ... intake manifold

no fuel sucked in could be CC vacum losssomewhere ( but check the delicate reeds on the failing half of the engine cc.

 

[Msc19671]

Thanks for you assisitance so far everyone, we will take a look at the reeds, probably tomorrow, and take some pics and get back to you further, if that doesnt seem to be the issue.

 

[racerone]

Very common for these JUNK carburetor kits to have a float valve seat with the wrong thread !

 

[ct1762@gmail.com]

just gently poke the reeds with a pencil. they should move easily. if not carb cleaner and a slightly manlier poke should get em moving. slow speed needle... if its in too far (lean) will cause issues. start with 1.5 turns gently seated. fyi your gauge is probably reading low. i believe these were around 120psi new but could be 100 forgot

 

[Crosbyman]

whatever you do don'T force/bend the reeds !!

 

[Msc19671]

We pulled the reed plate out and all looked good with nothing, noticeable wrong so we gave it it all a clean and re sealed it. we also took off the water exhaust jacket. You can see carbon on top cylinder and nothing on bottom and the new spark plug is as clean as we put in so we are at a loss as to what else we can do and any other tests if its is crank case compression loss somewhere to one cylinder where it will involve removing the power head and major strip down. What I can say was well when we first started the engine after doing the head gasket, and cleaning exhaust/water jacket and it was running on both cylinders and then after that appearing to be firing on only one, and if we have to do that we might as well home the cylinders and get and put new rings in. Could a leaking crankshaft seal cause this problem only to one cylinder ?

There had been previously water getting into top cylinde caused by head gasket but which is firing ok but bottom looked still guite good . Psi on my gauge was measuring 75psi on both cylinders.

Adjusting lean control which was already starting at 1.5 made no difference

We also swapped over cdi coils changing wires over and to plugs to rule that out.

I also attched a picture of the difference in float valve from the carb kit to the orig

 

[Crosbyman]

each half of the CC is independent. if a vacum loss is suspected and you still have the reed plate out can you feel equal pull of vacum of the left and right intake port if you place your hand in front of each section feel the vacum pulll on the upstrokes.

one utube shows a possible means of testing for CC vacum loss using propane gas.

another could be a home made plate& nipple to cover the CC intakes since you have it apart. a vacum meter could measure the difference.

 

[Msc19671]

The strange thing today it fired on both cylinders although rough and wouldn't stay idling, maybe carb adjustment required on the slow running.

On removing the exhaust water jacket as was leaking you can see what appears to be a hole, should any hole be there or has corrosion caused this ? Could this hole cause the issue we been experiencing? And if it is a hole could it be repaired with chemical metal or would it need to be alloy welded?

 

[Crosbyman]

welding ($$$) would be best but you can try this stuff . properly shaped it may do the job .. it gets pretty hot in that section

1983 is not " old" old is 1950's ...an old 50-60s J or E 7.5hp model can be found in much better shape sometimes $100-150$ if you search and are patient .

Your's must be a salty for having been corroded so much.

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