2000 nissan ns40d2 40hp running on top cyl #1 only loosing vacuun on cyl 2,3

[bill j]

I have a strange problem I would like to run by everyone. engine is only running on cyl#1. compression is 115psi on all three cylinders. carbs are clean, I realized the engine is loosing vacuum at front of the carbs on cylinders 2,3 when the engine is running. I pulled the carbs and checked reed valves. Reeds check out ok. When turning the engine over with carbs off. vacuum was weak on the two cylinders. while checking reeds I found a loose backed out engine case bolt in the center of the motor near cyl#2 behind the oil tank. I tightened the loose bolt and the vacuum improved and seemed to now be equal on all three manifold openings. When running the lack of vacuum is still present on the bottom two cylinders. 3.
I am assuming there is a leak in the engine cases or lower crank seal? I have the power head off to reseal it. What do yall think?
I wish I had a automotive smoke machine I could leak test it with I think that might reveal the problem?

Before I found the vacuum problem I replaced the head gasket and exhaust cover gaskets.

 

[TOHATSU GURU]

Re: 2000 nissan ns40d2 40hp running on top cyl #1 only loosing vacuun on cyl 2,3

Pull it apart and check the block surfaces and the crankshaft mounting.

 

[bill j]

Re: 2000 nissan ns40d2 40hp running on top cyl #1 only loosing vacuun on cyl 2,3

Pull it apart and check the block surfaces and the crankshaft mounting.

I pulled apart the cases and checked all the surfaces. The anaerobic sealer was oily and wet where the loose case bolt was. So I think resealing the case should fix the problem. I will post my results when done.

 

[bill j]

Re: 2000 nissan ns40d2 40hp running on top cyl #1 only loosing vacuun on cyl 2,3

I resealed the engine and still have the same symptom. I had a guy suggest that maybe the crankshaft might be out of phase? I put each cylinder at tdc and marked the flywheel for each cylinder. The teeth have a different count between each cylinder. 26-28-29 between the three marks. What do you think?

 

[TOHATSU GURU]

Re: 2000 nissan ns40d2 40hp running on top cyl #1 only loosing vacuun on cyl 2,3

I think you have a twisted crank. So, to check that, while the engine is running at idle, pull one of the spark plug boots off. If the engine goes up in RPM you have confirmed it. ***Caution*** Use an insulated tool to remove the boot or you will know what it was like to sit in "Old Sparky".

 

[bill j]

Re: 2000 nissan ns40d2 40hp running on top cyl #1 only loosing vacuun on cyl 2,3

I have a pair of spark plug wire pliers. I did pull a wire off and I didn't really see any difference. But I am pretty sure I finally found the problem and it sucks. I will call a local crank shop here in Jacksonville and see if they will put in phase and weld it if possible. Thank you for your advice!

 

[pvanv]

Re: 2000 nissan ns40d2 40hp running on top cyl #1 only loosing vacuun on cyl 2,3

Only outfit I'm aware of that does that work is:

Ackermann Marine Services Inc
3416 Enterprise Drive
Wilmington, NC 28405
(910) 762-0432

 

[bill j]

Re: 2000 nissan ns40d2 40hp running on top cyl #1 only loosing vacuun on cyl 2,3

Ok here is what was really wrong and causing my troubles. I feel sooo stupid. The carb linkage was way off. the top carb was way open and the bottom two were all the way shut. Yea the carbs won't show any vacuum at the front if they are shut all the way. Lol
I went back to the basics found it. I should have done the link&sync first.
I was putting too much thought into it and making it harder than it needed to be.
And I'm a ase master tech. Lol