Bouncy revo-meter

Sævar · Post by **Sævar** » Mon Nov 29, 2010 2:45 am

Hi

Just a few mornings ago I went to start my 1986 GL Series, it has the EA82 N/A engine, 4x4 hi/lo and generally is in great running order, and this really is the first issue with the car in almost a year ive driven it.

The engine revolutions meter bounces up and down when I rev it, specially when I am using big electrical currents like headlamps, heater fan, fog light, turning all of these on makes the meter bounce, and it will be bouncy for a while after turning any power consuming devices in the car on.

Now Im thinking this might be the alternator flicking me off, or the battery, or both, it´s not in the best of shape, maximum starting time on a cold start is 10 seconds and then its completely dead, so it will eventually need replacing, but I haven´t bothered since the L series generally is quite easily started.

but what bothers me is that in contract with the bouncy meter, there is misfire, just very very very slight power loss, found almost only at WOT.
feels like it´s losing spark for only a few miliseconds, following the bouncy meter EXACTLY.

So I dont know guys, any suggestions?

Next weekend I will have a 1987 GL with the same engine to tear parts out of and try to swap a few things cheaply so please, give all your brightest and lightest of ideas.

steptoe · Post by **steptoe** » Mon Nov 29, 2010 7:54 am

My 86 turbo 4GLTA tacho does not bounce just a bit retarded sometimes, or refuses to move at otheres, then occasionally rests at 1600 when engine is stopped ! No idea other than old age, sitting arund not used for years (in a wrecking yard)

Sævar · Post by **Sævar** » Mon Nov 29, 2010 8:19 am

We dont seem to have the same problem, sorry.

My tach works pretty good and at idle it shows a very reliable value, and if you keep it steady at a certain RPM it will not bounce, but if you stay with it at the same RPM and suddenly put the heater fan on full, or hazard lights on, or headlights on, it will bounce a little bit but eventually come at rest. And under load, going up hill at lower RPMs it will misfire at the same exact moment as it bounces(e.g. I put heater on, or apply brake lights...)

this really sounds like an alternator/battery problem to me. But I´m no genious in Subarus, I hear alternators are a common excuse for many electrical problems in Subarus, but I have no personal experience with it.

The tach gets its readings from what? alt or distributer?

Bad grounds somewhere could be causing this???

Busdriver · Post by **Busdriver** » Mon Nov 29, 2010 11:44 am

Check the coil connections, most tachos use the coil as a source of the engines firing and a bad wire or connection here could cause a misfire when WOT is used.

Post by **Alex** » Mon Nov 29, 2010 2:36 pm

id call for a dodgy earth.

steptoe · Post by **steptoe** » Tue Nov 30, 2010 6:14 am

A mate had same bouncy tacho in a Holden V8 ended up taking it to specialist tune shop who found the cause was a dud spark HT lead - you now mention a miss - concidental.

All tachos in these read from coil

Sævar · Post by **Sævar** » Tue Nov 30, 2010 10:06 am

Thanks, i replace battery and problem persists, so next I´ll try alternator, I think its acting a little strange lately and not producing a lot of charge either... So thats my likeliest call.

Ill fill you in on it once I find out whats going on, I dont know why it would cause a misfire though unless somehow the alt is shorting to earth when its spinning under load and voltage dropping severely

Sævar · Post by **Sævar** » Wed Dec 01, 2010 10:00 pm

Ive isolated the problem, I disconnected the B+ feed from ALT and rev-o stops bouncing, car running on battery alone.

so this confirms it is an alternator problem, Ill just have to get it rebuilt or find another one.

ps... everything ignition wise is brand new... except coil

thanks guys!

steptoe · Post by **steptoe** » Thu Dec 02, 2010 9:32 pm

Interesting discovery. Thanks for sharing the result with us.

Sævar · Post by **Sævar** » Fri Dec 03, 2010 3:44 am

no problem, ive got my hands on a spare car to rip parts out of, and I will be replacing the alternator to clarify that is the problem.

The car I am getting is a GL high roof just like mine, it has better seats, cleaner headlight mirrors and better bumper plastics and a hood with only minor dents compared to mine, so I will be keeping these parts.

it also has the standard Hi-lo range gearbox which I will be keeping and a working condition EA82 engine with low miles, body has 249.000 kms on it but owner says this is the 2nd engine in the car and was replaced around 1998 last time, so maybe 150k on this motor max. So that will be a keeper aswell.

Along with it comes a boxfull of carburettors brake shoes and other misc. items.

and some rims and tires as well.