No pulse from intake manifold for fuel pump?

[jbjennings]

Need some ideas pretty please....
The motor is a '72 50hp johnson that I just rebuilt. It has 148psi in one cylinder, and 151psi in the other. The timing stop screws weren't tampered with in any way and I'm getting a great 7/16" spark or better. Brand new OEM flywheel key.
I used an OEM intake manifold gasket and cleaned out both reed cages and intake manifold of all crud and made sure the reeds were sealing up nice and tight as far as I know.
It won't crank. It spits and sputters but no actual continuous firing hardly at all. My fuel pump is not pulsing fuel, and the nipple that the pulse hose fits on will not put out vaccum or pressure. What would be the cause of nothing happening as far as vaccum or pulse pressure?
Any ideas would be greatly appreciated.
JBJ

 

[Will Bark]

Re: No pulse from intake manifold for fuel pump?

Have you checked to see if there is any carbon build-up in the port on the block where the fuel pump connects?

 

[jbjennings]

Re: No pulse from intake manifold for fuel pump?

The fuel pump doesn't mount on the block. It has a hose running to a nipple on the intake. THanks, though. I guess I'm going to have to take the carbs and intake off and see what's going on.
JBJ

 

[boobie]

Re: No pulse from intake manifold for fuel pump?

Back in those days they had some intake manifold gaskets that didn't have the pulse hole for the fuel pump cut into them. You may want to take off the intake manifold again and check the passages going to the fuel pump pulse from the cyl that powers it. OMC had a service bulletin on this which states you have to punch a 5/16" hole in to get the c/c pulse to the fuel pump. It was OMC ser bull # 2220,feb 1993. I'd post it but I'm a computer idiot.

 

[F_R]

Re: No pulse from intake manifold for fuel pump?

The pulse doesn't actually come from the intake manifold, but the crankcase. But you know that.

Sounds to me like there is something connecting the upper and lower crankcases, blowing back and forth between them. But I don't have the foggiest notion what that would be.

Reminds me of an old Chris-Craft outboard that gave some of these grey hairs years ago. Turned out that if you didn't tighten the crap out of the carburetor nuts on those, the reed block wouldn't seat and it would blow back and forth between upper and lower crancases.

 

[boobie]

Re: No pulse from intake manifold for fuel pump?

I still say seeing he just rebuilt it to check the gasket. Yes I know the pulses come from the c/c but have to get through the intake manifold to get to the fuel pump.

 

[jbjennings]

Re: No pulse from intake manifold for fuel pump?

Thanks guys,
I just came from taking the intake and carbs off, and you were right----the gasket came from the factory with no pulse hole. AAAARRRRGHHH!!!
WHy???? ....and why did I not notice that???

But not to be outdone by someone else's carelessness, I also rebuilt the carbs and didn't notice a totally rotten gasket on the main nozzle. I hope that's the reason I can't get the darned thing to run!!
Something also made the lower carb's float needle stick open and I filled the bottom cylinder with gas. Luckily I did catch that. I can assure you all that the bottom cylinder and rings and such are lubed nicely, now.

I am hoping I did a better job rebuilding it with the new crank and pistons than I am with the carbs and intake gaskets.
Thanks very much for the help.
JBJ

 

[boobie]

Re: No pulse from intake manifold for fuel pump?

This only happened on the '72 & '73 mtrs. Have to blame this one on the manufacture. That's why they put out service bulletins. Let us know how it all turns out when you're all done.