Tach at 0 when cranking 5.0 MPI

[Stinnett21]

I have a 2002 5.0 MPI A1 G2 serial 0M345638. I noticed my tach acting erratic only for a few seconds the other day. First time I've noticed this in 19 seasons and 1490 hours with the boat. After this I noticed the tach went to 0 when cranking. According to other posts on the forum I think it should be around 300 rpms when cranking. However no indication of anything wrong. Engine ran great. Is this an indication of trouble brewing? Appreciate any input.

 

[achris]

A low battery can also cause the tacho to drop during cranking. How old is the battery/s?

 

[QBhoy]

100% agree with the battery thing. I go on about this loads. Anything less than a perfect battery and it won’t even try to fire when cranking. Not enough left to fire the many many other things that need power to start it.

 

[Stinnett21]

It's a two year old Advance Auto 1000 MCA group 24. I realize it still could be bad. I have an older Everstart. I'll swap it out and see what happens when I get the chance. Thanks for the input.

 

[achris]

Put your multimeter on the battery and measure the voltage while cranking. Should be a minimum of 9.5v.

 

[QBhoy]

It's a two year old Advance Auto 1000 MCA group 24. I realize it still could be bad. I have an older Everstart. I'll swap it out and see what happens when I get the chance. Thanks for the input.

Often a tell tale sign is if she kicks for a second when you release the key. What I’ve found anyway.

 

[Stinnett21]

Put your multimeter on the battery and measure the voltage while cranking. Should be a minimum of 9.5v.

I rarely have a helper but I'll see what I can do. Thanks.

 

[Stinnett21]

Often a tell tale sign is if she kicks for a second when you release the key. What I’ve found anyway.

This occurred near the end of the day so I don't have much history to go on. I'll observe more on next outing. Good point, thanks.

 

[alldodge]

Engine ran great.

Might just need a new tach or maybe corrosion on the wire or connection

The 300 rpm is if its cranking and does not start. The ECM sees what the distributor is doing in milliseconds. So if it sees it firing and pulses the injectors before Tach will react so you can see

 

[Stinnett21]

Might just need a new tach or maybe corrosion on the wire or connection

The 300 rpm is if its cranking and does not start. The ECM sees what the distributor is doing in milliseconds. So if it sees it firing and pulses the injectors before Tach will react so you can see

Good info. Thanks Alldodge. I'll check the connections.

 

[Stinnett21]

Had a chance to further investigate. That's my dad's old Fluke from the 80's. It may not be fast enough but if accurate the reading looks ok. Also I swapped batteries and same result so I'm gonna rule out battery as the problem. Something new this time. Tach read 850 rpms a few times while cranking, most of the time zero. All seems normal except tach reading. Engine cranking speed sounds normal, engine running is all normal, no symptoms. Maybe the tach is getting tired. I have Vessel View Mobile on order. I'll check against it.View attachment IMG_0543.MOV

 

[QBhoy]

Sounds good to me.