72e40e johnson, starts with fuel line off, as soon as i reconnect it, it dies

[Kjruff]

This motor is driving me nuts! please help! So as stated, I have a 1972 Johnson 40hp with electric start/manual start.

OK, lets start with what I know isn't wrong. neutral start switch has been isolated and discounted, new plugs with good blue spark, I have brand new fuel injection hose with fuel injection clamps, brand new primer bulb, brand new inline fuel filter, primer bulb and filter are installed in the correct direction, already removed the pickup screen off of the tank pickup tube, tank is venting properly, fuel pump seems to be pumping properly, almost positive I have the new float adjusted properly. (pump bulb till it firms up little or no fuel dumps from carb intake.) new needle and seat as well. I also replaced the two (looks like lower motor lube lines?) on the left side of the motor. carb is most certainly clean. compression seems fine.

Now for the issue. I can prime up the bulb up and turn the key it will crank right up sometimes but usually it has to be at wide open throttle to start, it will then promptly die. then I can turn the key or pull the starter cord till I'm blue in the face and it will not even fart unless I disconnect the fuel line. With the fuel line disconnected and at WOP( wide open throttle) it will fire up and I have to quickly reconnect the fuel line to keep it going. It will then run pretty good (no misfiring or popping) but it sounds as if its only at 2/3ds power. After about 1-3 minutes it will suck the primer bulb flat and die out causing me to start the entire joyful process over again.
Again sometimes it will idle but sometimes if I mess with the throttle it will burp, fart, and promptly die out. I don't know what else to do at this point and im not about to throw parts at it. IF anyone has any recommendations or a new process to try please let me kno. otherwise im at my end with this thing and am going to part it out. thanks a million hope this works!

 

[racerone]

Re: 72e40e johnson, starts with fuel line off, as soon as i reconnect it, it dies

Inspect the fuel pump diaphragm.

 

[Bosunsmate]

Re: 72e40e johnson, starts with fuel line off, as soon as i reconnect it, it dies

Sucking primer bulb flat shouldnt happen.
Even if you have run out of fuel.
Fuel pump seems to be working to be able to do that.
You say its venting properly, id loosen the fuel cap to double check that.
Are you sure you installed the fuel bulb in the right orientation?

 

[Kjruff]

Re: 72e40e johnson, starts with fuel line off, as soon as i reconnect it, it dies

I've already tried just hanging the fuel line into the tank with the lid off so I know it isn't a venting problem. also the primer bulb is kinda difficult to install backwards with the giant arrow printed on it, plus just in case the manufacturer printed that wrong it only pumps fuel in one direction. Believe me its stumping me as well. I'm almost at the point where I just use it as an anchor and maybe forget to tie the other end to the boat.

 

[F_R]

Re: 72e40e johnson, starts with fuel line off, as soon as i reconnect it, it dies

#1: Something is restricting the flow to the primer bulb or it wouldn't be sucking flat. I have no idea what that something is, you will have to find it yourself.

#2. Conking out as soon as you connect the hose indicates it is flooding when fuel is available. I'd suggest the carburetor float valve. Normally I'd say fuel pump diaphragm is holed, but the fact that it works well enough to suck the bulb flat contradicts that idea.

 

[fm50ford]

Re: 72e40e johnson, starts with fuel line off, as soon as i reconnect it, it dies

I've already tried just hanging the fuel line into the tank with the lid off so I know it isn't a venting problem. also the primer bulb is kinda difficult to install backwards with the giant arrow printed on it, plus just in case the manufacturer printed that wrong it only pumps fuel in one direction. Believe me its stumping me as well. I'm almost at the point where I just use it as an anchor and maybe forget to tie the other end to the boat.

Sounds like the fuel pump is sucking hard to collapse the primer bulb. Since you eliminated the venting problem I would check from the bulb to the tank. Sounds like something is plugged or collapsing . otherwise the bulb should allow air or gas to pass through it. Maybe the end of the bulb and hose connection might be clogged or the gas line may be seperating inside. Did you use hose that was meant for gasoline?
Just my 2 cents good luck

 

[oldboat1]

Re: 72e40e johnson, starts with fuel line off, as soon as i reconnect it, it dies

You have more patience than I do, Kj. I would spend $40 or $50 and go out and buy a plastic tank and the bulb and line assembly with OMC connectors. Or for a middle ground, borrow a working tank and line to fit, and see if that is the difference.

 

[Kjruff]

Re: 72e40e johnson, starts with fuel line off, as soon as i reconnect it, it dies

I am positive that there is no obstruction bc it will do the same thing when the primer bulb is removed from the equation. The fuel line I used is very high pressure fuel injection line for an automobile with high strength mesh in the core. It will not break down for years. I also checked it for collapse with a vacuum pump and it takes almost -60psi to suck it flat. I also put my tank up on my poling platform and gravity fed. It just wants to flood out. Guess ill remove and readjust the carb float maybe try another needle and seat, diaphragm and gasket and see what happens. I wish there was an easier way to adjust the float other than removing the starter and brackets and solenoid. and bending the float tab around. Its a thirty minute process just to make one minor adjustment. and I feel like I'm going to wear out the bolts soon as many times as its already been off.

 

[oldboat1]

Re: 72e40e johnson, starts with fuel line off, as soon as i reconnect it, it dies

would be inclined to simply try a substitute tank and hose/bulb before going back into the carb. -- just a suggestion. I have a couple of complete tanks and lines that I use for testing, so I can rule out that part of the equation when trouble shooting motors. That is, whenever starting to work on one of my new finds, I know the fuel and fuel supply (tank to motor) is good.

 

[boobie]

Re: 72e40e johnson, starts with fuel line off, as soon as i reconnect it, it dies

From what I've read on here it's sounds like a carb problem to me.

 

[Kjruff]

Re: 72e40e johnson, starts with fuel line off, as soon as i reconnect it, it dies

I'm going to pull the carb and check the low speed jet and readjust the float. Hopefully that's the problem. Figure maybe it's sucking the bulb shut trying to pull enough fuel with the clogged jet?

 

[racerone]

Re: 72e40e johnson, starts with fuel line off, as soon as i reconnect it, it dies

When the bulb collapses it is not a problem in the carburetor !

 

[boobie]

Re: 72e40e johnson, starts with fuel line off, as soon as i reconnect it, it dies

It's a fuel restriction on the tank side of the bulb or some check valves in the bulb itself.

 

[Kjruff]

Re: 72e40e johnson, starts with fuel line off, as soon as i reconnect it, it dies

it does the same thing with a different tank, a bucket of gas, different lines, filter, no filter, bulb or no bulb.... same exact reaction every time. what exactly does the cut out switch do and how does it work?

 

[racerone]

Re: 72e40e johnson, starts with fuel line off, as soon as i reconnect it, it dies

Cutout switch shuts ignition off when there is high vacuum in the intake manifold.-----Sounds to me that the problem is excessive fuel going into the engine / flooding when hose is connected again.---Cause would be the float valve or a hole in the fuel pump diaphragm !!

 

[Fed]

Re: 72e40e johnson, starts with fuel line off, as soon as i reconnect it, it dies

Is it a stock standard fuel pump, maybe someone fitted an electric one to it?
That would fit the symptoms.
Edit: Combined with crud in the tank.

 

[Kjruff]

Re: 72e40e johnson, starts with fuel line off, as soon as i reconnect it, it dies

The tank is clean. Its brand new and I removed any excess plastic left inside from the manufacturer before I used it. I also removed the restrictive pickup screen from the tube. I've blown in both ends of every section of fuel line and fitting to check for anyrrestrictions. Same with the primer bulb and fuel filter. As I stated before my fuel pump is pumping fuel and it is the stock vacuum driven pump. I noticed that when I removed the slow speed needle the black packing washers have pretty much disintegrated. Im pretty sure my float is set correctly at this point but ive got another carb kit on the way.

 

[F_R]

Re: 72e40e johnson, starts with fuel line off, as soon as i reconnect it, it dies

I'm going to pull the carb and check the low speed jet and readjust the float. Hopefully that's the problem. Figure maybe it's sucking the bulb shut trying to pull enough fuel with the clogged jet?

That would be impossible.

 

[Bosunsmate]

Re: 72e40e johnson, starts with fuel line off, as soon as i reconnect it, it dies

Does the fuel bulb hold firm with engine off?

 

[Kjruff]

Re: 72e40e johnson, starts with fuel line off, as soon as i reconnect it, it dies

Yes the bulb will hold firm when the engine is off. I meant I was pulling the low speed needle. the packing washers are deteriorated and pieces were down by the jet and all around the needle