40hp dies as soon as it cranks.

[whiskerchasin]

I obtained an 85 40hp Johnson J40elc0. After removing the VRO pump I installed the non-vro fuel pump from sierra. Pumped the bulb tight and cranked it up.With the manual primer valve in the manual start position it fired right up for about 1 second then died. It done this 2 or 3 times, i don't know what's wrong with it. It doesn't slowly die it just shuts right off.

It may be electrical because it does not have the original omc controls on it, that was attempted to be installed by the previous owner. The controls are taken apart with the ignition hanging out of it with ground wires exposed and twisted together. I'm in the process of getting some omc controls (dang they're not cheap) so maybe that'll help.

any help is greatly appreciated, Thanks.

 

[FillupD]

Re: 40hp dies as soon as it cranks.

If it at least runs, sounds like a fuel issue. I would spray a little pre-mix in the carbs when it is running to see if it will keep going.
I'm sure if it does, it will run rough, but if you can keep it chugging along with external fuel source, you found a fuel delivery problem.
Probably not the most desirable test, but it will take a couple of minutes for an answer. There is probably better advice out there than the shade tree
advice I just gave. You're heading in the right direction with wiring and manuals though.( I doubt you will find the previously described test in the troubleshooting guide.)

 

[whiskerchasin]

Re: 40hp dies as soon as it cranks.

Thanks for the reply FillupD.
That makes sense, I will give it a try. That advice seems appropriate because I am working on it under a shade tree.

 

[whiskerchasin]

Re: 40hp dies as soon as it cranks.

Alright after messing with it more I saw that after pumping the primer bulb the fuel-filter starts to slowly fill up with tiny bubbles. So im guessin i have an air leak somewhere.

Should i have used a thread sealer of some kind on the brass fitting to the fuel-tank?

 

[whiskerchasin]

Re: 40hp dies as soon as it cranks.

No luck on finding the air leak. Is there a way to narrow down the general area of the leak?

It has a new 6 gal. gas tank that says it's "automatic venting", but after pumping the bulb the tank seems to get sucked in with pressure. when i unscrew the cap you can hear and see the release pressure anyone use one of these tanks? I'm not a mechanic by any means, and at a stand still. Any help would be great.

 

[whiskerchasin]

Re: 40hp dies as soon as it cranks.

Should I use thread sealent/ teflon tape or something on the brass fitting that screws into the gas tank?

After looking at the ignition wiring diagram in the "top secret files" I found that i may have a problem. The diagram shows a yellow and red wire coming from the red plug to the neutral safety switch and then to the ignition switch. On my boat the yellow and red wire goes from the red plug straight to the ignition. I don't see a neutral safety switch anywhere in the controls. As stated in a post above the controls on my boat are a complete mess.

Will not having the neutral safety switch prevent the engine from running or even turning over? Thank all of you for reading.

 

[FillupD]

Re: 40hp dies as soon as it cranks.

You can always start by replacing all the fuel lines, thats relatively cheap and probably would be a good idea anyway if they are original. Yout tank sounds like it is sealing, If it runs and fires, your getting spark. Your issue sounds more like fuel delivery and dirty carbs. Carbs are pretty easy to clean and rebuild.
I can't help much with the wires.

 

[whiskerchasin]

Re: 40hp dies as soon as it cranks.

Thanks Fillup. I did replace the fuel lines today, and have already cleaned the carbs. I didnt rebuild the carbs but just a quick clean, and adjusted the floats, they were pretty clean. I should go ahead and order some carb rebuild kits and a manual though.

I'm starting to think the engine fired up on some carb cleaner spray that was in there and not premix, i didnt spray in the carbs while trying to crank though. It did backfire after cranking, i forgot to mention that earlier.

This morning my tank was swollen up alot with a little bit of gas leaked out from the plastic black thing that the brass fitting screws into. This tank does not have a vent screw and says it's automatic venting, but I'm having a hard time believing its woking properly. Is anyone running one of these tanks, or have expeirence with one? It is a 6gal. made by attwood.

 

[fireman57]

Re: 40hp dies as soon as it cranks.

You have to have the fuel tank vented. There is either a small screw on the top or loosen the cap and try it. If it is not vented you run out of fuel. Try this then we will get to your wiring problem. If you do not have a neutral safety switch installed you can touch the yellow.red strip wire to the red one to start it. The yellow/red goes to your starter solenoid. You will have to touch the black/yellow wire to the black wire to kill it.

 

[Silvertip]

Re: 40hp dies as soon as it cranks.

You said you placed the "manual primer valve" in the manual position. Wrong! That valve position is used ONLY in the event you need to pull start the engine (as in the battery is dead). In the manual position fuel flows through the solenoid valve directly into the intake so you very likely are flooding the engine. Put the valve the other way, remove the plugs and clean or replace them and try again. Whe you push the key in during the starting process that is what actuates the primer solenoid.

 

[whiskerchasin]

Re: 40hp dies as soon as it cranks.

Thank you silvertip. I now have that valve pointed forward towards the bow. I pulled the plugs and they were in fact wet, one was also fairly black. I cleaned cleaned them off and and tried to crank and nothing. It has spark and compression. The fuel pump shoots steady spurts of fuel as it should. I unscrewed the bowl drain plugs and both bowls are getting fuel into them.

fireman57 I agree with you the tank should be vented some way. There is no vent screw on this tank. It says "automatic vacuum valve ensures proper fuel flow and eliminates the need for manual vent". It also says to use thread sealant on the fitting which i did not do but will do tonight.

Today i noticed on the back of the new fuel pump there is a clear tiny plastic tube sticking out of the back of the fuel pump. I'm PRETTY sure that wasn't there when i put it on, but im not positive.

Thank all of you for taking the time to help me. This is a great site and the amount of information available is invaluable. I'm on my first vacation week ever and really enjoyed working on this johnson, not getting much progress but enjoying it anyways.

 

[whiskerchasin]

Re: 40hp dies as soon as it cranks.

Sprayed some premix into the carbs and it did crank and run, but it will not on its own. It did not crank but only back fired when sprayed into the top carb. Then sprayed into the bottom carb while cranking it fired right up.

The fuel-manifold on my motor has been rigged, one of the stems must've broken off, and someone put a bolt with thread sealer into the broke end. Then from one of the two remaining stems there is a plastic "T" which splits into two lines going to both carbs. I'm gonna look into ordering a new manifold now.

 

[whiskerchasin]

Re: 40hp dies as soon as it cranks.

After reading around on this forum I'm thinking my problem is in the carbs.

If i pull the plugs and spray premix in the cylinders and it cranks,will this tell me if my problem is in the carbs?

 

[fireman57]

Re: 40hp dies as soon as it cranks.

If you think you are not getting fuel to a cylinder pull your plugs out and crank it and watch for a mist of fuel to come out of each plug hole. If you want you can hold a piece of cardboard up to them. Whichever one doesn't have fuel coming out that is your bad carb.

 

[whiskerchasin]

Re: 40hp dies as soon as it cranks.

If you think you are not getting fuel to a cylinder pull your plugs out and crank it and watch for a mist of fuel to come out of each plug hole. If you want you can hold a piece of cardboard up to them. Whichever one doesn't have fuel coming out that is your bad carb.

genius! I will try tomorrow.

 

[whiskerchasin]

Re: 40hp dies as soon as it cranks.

did the the above test with cardboard and no mist from the top cylinder.

I pulled the carbs and attemped a rebuild but could not get the slow speed needle valve out, without having the proper tool i did not want damage it. sprayed compressed air through every passage i could find. Put back on and no difference. It will only run if i spray premix into the carbs, and then press in on the key.

I think i'm going to accept defeat and tow my boat to a mechanic with my tail between my legs.