1979 140HP Johnson bringing back on line after sitting for some time.

[James R]

Motor has good compressions at 145 each. Replaced one power pack and plugs. Good sparks. Carbs thoroughly cleaned and rebuilt with new kits. Fuel hoses replaced. Lower unit serviced.
Fired up immediately and ran but started to miss at idle and just shut down. Can restart immediately no problem and throttle back to Idle. Runs for a short time then starts to stumble and shuts down again. I have monitored the sparks using the timing light and they seem to be solid. I tried fuel spray into the carb throats and noted a slight improvement with a little fuel into #2. Removed and recleaned the top carb but no change. Any thoughts on this would be appreciated.

 

[Bosunsmate]

Re: 1979 140HP Johnson bringing back on line after sitting for some time.

How do your plugs look?
Try cleaning all the sparkplugs and then removing the boots and turning it over a few turns and checking for unburnt fuel on all sparkplugs

 

[James R]

Re: 1979 140HP Johnson bringing back on line after sitting for some time.

I understand your point BM and will take a look.
Thanks.

 

[emdsapmgr]

Re: 1979 140HP Johnson bringing back on line after sitting for some time.

None of the original fuel system on that engine was rated for today's ethanol fuels. You've replaced the fuel lines-that's good. You can do a test: when started, constantly prime the fuel hose bulb. This will forces extra fuel into the carbs. If it runs fine as long as you constantly prime the bulb, likely the pump is bad. You need to replace it also. That rubber bladder inside is probably shot from the ethanol. Compression seems a little high, maybe it's just the gauge you used to test. Anyway, it's really strong. I'd expect 135+ on that engine. That's the one V4 engine which uses the V6 type center fire plugs: UL77V Champions. Hopefully that's what you have in it.

 

[boobie]

Re: 1979 140HP Johnson bringing back on line after sitting for some time.

Or else QL16V. Better plug.

 

[V153]

Re: 1979 140HP Johnson bringing back on line after sitting for some time.

I'd stick with UL77Vs. Ya 145 a hole seems a lil high? Definitely go through the fuel pump.

 

[James R]

Re: 1979 140HP Johnson bringing back on line after sitting for some time.

No significant fuel on the plugs. Plugs are the UL77V type. I have used this gauge for years and it compares to a new one I keep as back up.
One hole does in fact get up to 150. noted that even without the motor running the bulb does get soft. I think the fuel pump is leaking and draining the carbs at idle. I have ordered a new pump. The carbs could not be cleaner if I had built them from new. I am very fussy about carbs. Thanks for all the input. Please stay with me on this.

 

[V153]

Re: 1979 140HP Johnson bringing back on line after sitting for some time.

One hole does in fact get up to 150

145 - 150 psi a hole is purty stout. That motor new was 130 - 135. I'd definitely run premium fuel in it.

 

[TD_Maker]

Re: 1979 140HP Johnson bringing back on line after sitting for some time.

Curious: When the motor starts to stumble, does the primer bulb stay hard? Is it collapsed? What about your tank, is it vented?

 

[James R]

Re: 1979 140HP Johnson bringing back on line after sitting for some time.

Thanks for the thought TD. The bulb goes 1/2 soft but this sometimes is no indicator. The small fuel tank I use for testing is venting. With the motor mounted on my stand and the tank on the ground a good fuel pump proves itself. In this case I think the pump is defective. A new one is on the way.
Merry Christmas to all and thanks for your help.

 

[James R]

Re: 1979 140HP Johnson bringing back on line after sitting for some time.

New fuel pump fitted but no improvement. You recall that I thought a shot of fuel mix into the #2 carb throat improved the idle.
Knowing this I stripped the carbs again and recleaned including the removal of the aluminum caps. No improvement. You may recall that I noted a little slop in the butterfly spindles possibly leaking air into the carbs. I had nothing better to do so I pulled a pair of #38 jets from a spare later model carb I have and replaced the #30s in the top carb.
Now it idles. As far as I can see these jets in the 1979 motor regulate fuel flow. Later model carbs with the jets in the throat regulate air flow. Anyway it works. I look forward to your comments on this. Happy new year.

 

[V153]

Re: 1979 140HP Johnson bringing back on line after sitting for some time.

I assume you changed the jets in the bottom carb as well? Hope that's not a stupid question ...

 

[James R]

Re: 1979 140HP Johnson bringing back on line after sitting for some time.

One would ask the question 'why' if the bottom carb is performing well and chokes when fuel mix is sprayed into the throats.