Problems with my 75’ 25 Johnson

[john8504]

As of now, I cannot get the motor to start. I have a rebuilt the carb, checked compression and it was at 130, I have good spark, Replaced a bad top crank seal, replace the fuel line and primer bulb since the bulb was not holding pressure. I’m about to throw my hands in the air.

It started with a surging issue at wide-open throttle and then ended up with me having to continuously prime the bulb to keep the motor running at an idle or at wide-open throttle.

I’m not sure where to go from here, but if anyone can help me out I would appreciate it.

[Matthew Pieklik]

Fuel pump?

[john8504]

I was thinking that but I can’t find any info on how much fuel is supposed to come out when cranking. I took off the line to the carb from the pump just to make sure fuel was getting there and it definitely is. However, the carb bowl is full and still not starting.

[fleetwin]

Well, back to your original issue, which was a “surging issue” at WOT. Do you think the surging was fuel related, or was it misfiring/ignition issue? You had the mag plate off/apart, this engine has the much loved “low tension ignition” system. Are you sure you connected the primary leads to the proper coils and didn’t reverse them? You didn’t disassemble the fuel pump did you? You mention the fuel bowl is definitely getting filled, but is the high speed jet clean/properly installed? Did you remove it when you had the carb apart? On the other hand, is the carb flooding over?
You mention the engine won’t start, does it make any attempt to fire/start? You might try removing the fuel line, draining the carb, then squirting some fuel oil mix in each cylinder…. Then crank it and see if it attempts to fire.
It always pays to go back to basics, are you sure the fuel/oil mix is fresh and there is no water in it? Did you reconnect the vertical throttle rod to the mag plate arm? Is the mag plate moving freely and advancing properly? Is the carb butterfly linkage properly connected, sync set up properly? Are you sure the choke is working properly? Does the choke plate close fully when the knob is pulled out? The choke knob won’t stay out if that plastic grommet in the air silencer is missing/worn out…

[john8504]

I did take fuel pump apart but I ran it on the lake afterwards and still had to pump the primer just like the last time. I did find that my primer bulb was bad on the new fuel line after I blew threw the check valve and air escaped the other side. Carb was cleaned before it was stored 18 years ago and when I got it, it was still in perfect shape. Replaced all the gaskets and Welch plugs anyway and it didn’t change anything. Main jet is clean as a whistle. Lead a from coils are only 4 inches long so not able to connect to wrong cylinders. I did. Or disconnect leads for ignition when removing armature. I disconnect ground and the linkage and just moved it aside. I took hose off the outlet to the fuel pump and tried starting the motor with the primer bulb hard to see how much fuel it was putting out and it wasn’t a lot. I have a fuel pump coming in Friday just to see how well a new one works since I robbed this one off another motor I have. I will throw a little mixture into the cylinders to see what it does next.

[crosbyman]

fuel needs to sucked in the crankcase to reach the cylinders . can you feel good or some suction on the carb throath …

if not the venturi effect on the LS and HS section of the carb can’t vaporize the fuel . did you blow all orifices with carb cleaner and air dry

did you clear the lower HS jet with a small wire or monofilament

crankcase suction vacum can be lost due to leaky crank seals

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• This reply was modified 4 years ago by crosbyman.

[john8504]

I did clean the passages very well. I have a new pump coming just to make sure it’s not the pump. I will have the check the suction at the carb. If I’m not getting suction at the carb then I may have a bad reed is my thought. I did have a very bad top crank seal but I did replace it and got no change.

[john8504]

I only rebuilt the carb after I was already having a no start issue.

[crosbyman]

the reeds act as a one way valve… you should feel suction but if they are bad you will also feel air pushed out the carb face onthe downstrokes … imho anyway

let’s see what a new pump does since pumping the bulb to keep it going…. generally hints at a bad pump

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[fleetwin]

Well, it ran before, so it would appear as though the issue is something relatively simple. I’m not speaking about the spark plug leads, I am speaking about the primary leads that come out of the mag plate and connect to the external coils…These are the connections that might be reversed, even though I did hear you say that they were not disconnected when you removed the mag plate. How about the mag plate ground wire, good connection there? Have you checked spark with spark tester, or by just grounding the plugs when removed?
I am hearing you say that this engine makes not attermpt to start, or even attempt to fire, is that correct?

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