Logo
FULL SITE MENU

1975 Johnson 4 HP Wonbt Start

B

boatcrazy

New member
"Hi,
I have a 1975 Johnson 4

"Hi,
I have a 1975 Johnson 4 HP that won't start. The problem appears to be the fuel system. It has all new ignition parts including points (gapped at 0.20), plugs (gapped at 0.30), new coils and condensers. The fuel pump screen is clean and I removed the fuel lines between the fuel pump and carburetor and all are clear. I installed a inline fuel filter between the fuel pump and carburetor so I can watch the fuel flow. I made sure that the flow arrow on filter is pointing toward the carburetor. When I squeeze the primer bulb on the tank fuel line I notice that there is no fuel flowing through the inline filter to the carburetor. I don't know if fuel will only flow through the filter when the engine creates compression through starting or if fuel should already be at the carburetor by just squeezing the primer bulb on tank line. The engine did run as recently as a month ago, but when I had it on the lake it ran pretty well for about 30 minutes and then stalled on me a couple of times and the second time it would not restart. When I started troubleshooting at home I pulled the flywheel and noticed there was some questionable looking ignition parts (cracked coils and burn marks on points) so that was my reason for replacing all ignition parts. In addition to what I told you about the fuel system, I did spray some fuel in the carb. and I can get it to pop like it wants to start but that's as much as she does. The motor has been only freshwater used and is overall in immaculate shape for her age. Any and all help is greatly appreciated."
 
"<font color=""119911"">When y

"<font color=""119911"">When you pump the bulb fuel should flow until the carb bowl is full then it will stop (The float rises and shuts the little needle valve on the inlet) The bulb will then feel firm. There's bound to be a bit of air inside it and the more air there is the less firm it will feel but it should feel quite different to what it does when the bowl is empty.

If the ignition system is all Ok you really should be able to get it to fire and run briely if you spray fuel mix into the air inlet.

If you have not done so you should check the sparks at both plugs before doing any more to the fuel system. You may end up cleaning and overhauling the carb but be sure you really do have good sparks first. </font>"
 
"Thanks Guys,
Hey Vic, if the

"Thanks Guys,
Hey Vic, if the primer bulb is hard and won't squeeze anymore why isn't fuel reaching the carburetor?"
 
How to check ignition componen

How to check ignition components on 1975 Johnson 4 HP? Do I need one of those late model ignition testers or can I check everything with a modern day voltmeter?
 
"Steve.... Long posts tend to

"Steve.... Long posts tend to have everything run together. Best to keep the paragraphs short for easy reading.

What are the compression readings? If identical at all compression tests, that indicates a faulty head gasket or improperly torqued gasket which would allow the pressure to cross over between the cylinders.

Spark should jump a 1/4" gap with a strong blue lightning like flame... a real SNAP! Does it?

(Carburetor Adjustment - Single S/S Adjustable Needle Valve)
(J. Reeves)

Initial setting is: Slow speed = seat gently, then open 1-1/2 turns.

Start engine and set the rpms to where it just stays running. In segments of 1/8 turns, start to turn the S/S needle valve in. Wait a few seconds for the engine to respond. As you turn the valve in, the rpms will increase. Lower the rpms again to where the engine will just stay running.

Eventually you'll hit the point where the engine wants to die out or it will spit back (sounds like a mild backfire). At that point, back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed setting.

Note 1: As a final double check setting of the slow speed valve(s), if the engine has more than one carburetor, do not attempt to gradually adjust all of the valves/carburetors at the same time. Do one at a time until you hit the above response (die out or spit back), then go on to the next valve/carburetor. It may be necessary to back out "all" of the slow speed adjustable needle valves 1/8 turn before doing this final adjustment due to the fact that one of the valves might be initially set ever so slightly lean.

Note 2: If the engine should be a three (3) cylinder engine with three (3) carburetors, start the adjustment sequence with the center carburetor.

When you have finished the above adjustment, you will have no reason to move them again unless the carburetor fouls/gums up from sitting, in which case you would be required to remove, clean, and rebuild the carburetor anyway.

Thousands of parts in my remaining stock. Not able to list them all. Let me know what you need and I'll look it up for you. Visit my eBay store at:

http://stores.ebay.com/Evinrude-Johnson-Outboard-Parts-etc?refid=store

(Magneto Coil Alignment)
(J. Reeves)

To align the coils properly, have the metal vertical portion of the coil yokes aligned with the inside edge of the bevel that exists on the top portion of the aluminum seat upon which the coils sit. This creates the proper distance between the coils and the flywheel magnets. Faulty alignment creates friction and the yokes of the coils heat up, turn blue and expand.

Thousands of parts in my remaining stock. Not able to list them all. Let me know what you need and I'll look it up for you. Visit my eBay store at:

http://stores.ebay.com/Evinrude-Johnson-Outboard-Parts-etc?refid=store

(Fuel Pump Diaphragm Test)
(Two Hose Type Only)
(J. Reeves)

Note: This pertains only to the regular Two Hose type fuel pumps.

Leave the hoses attached to the fuel pump. Remove only the two screws that attach the fuel pump to the powerhead. Re-insert those two screws and install a nut to each of them so that the fuel pump is securely clamped together. With the fuel line attached to the engine, pump the primer bulb while observing the pressure/vacuum operating hole on the back side of the fuel pump. Should any fuel leak out that hole, the diaphragm is faulty.

If the diaphragm is faulty, the fuel pump will require rebuilding or replacing. Note that repair kits are not available for all fuel pumps, in which case replacing the pump would be necessary.

Thousands of parts in my remaining stock. Not able to list them all. Let me know what you need and I'll look it up for you. Visit my eBay store at:

http://stores.ebay.com/Evinrude-Johnson-Outboard-Parts-etc?refid=store

Use Champion J6C plugs gapped at .030"
 
Back
Top