Scarabdude

My tachometer on one of my 500 efi's is bouncing around at 3000 and higher, I tried a new tach, but it didn't help. I checked all the connections and they seem fine. The engine runs perfect even if the tach goes over the rev limiter, any suggestions?

jhnrckr

If your motor is running properly than it is either the power going into your tach or the signal from the tach. I would trace the signal wire from your tach to your dash and make sure it is in tact or just replace it. Next check or replace the + and - wires going into your tach. It could also be the power for the light when you turn on your navigation lights.

Gary Anderson

Ignition secondary, change the plugs, wires, cap.
Gary

Scarabdude

where is the tach getting its feed, the tach bounces around even with the lights off??

Canada Jeff

I had the same problem, spoke with Mike Lavorsi him self at a Sunsation rally two years ago. He told me it has been a common problem. He told me to run a seperate ground wire from my distributor to the block. I did, and problem is solved!!

Do that, let us know!

FOUNTAINATLAST

What if you have the tach bounce and you have direct ignition (no distributor)??? At idle sometimes it doesn't even read but once you running it works but is all over the place but doesn't interupt the rev limiter at all. This set up is on a 2002 496HO system. Any suggestions would be greatly appreciated, Thanks

satisfactionII

Take Canada Jeff's advice! A bad or weak ground is most likely the cause of any erratic electrical symptoms.

bob_t

The tach bounces on my 500EFI, too, above 2500 - 3000 rpm. Changed plugs, plug wires, rotor button, and distributor cap, and also cleaned off the light rust on everything within the distributor, cleaned connections - applied dielectric grease to them after cleaning, and it still goes erratic above 2500 rpm.

Slow Ride

I have 300 pro max outboards that start jumping around at higher rpm. Cleaned grounds, crank sensor etc. Any ideas?

Strip Poker 388

iTrader: (6)

Mine did that also ,It was in the connection to the ecm .moisture or just needed cleaning?Working ok know.