Weird Tach Problems

TypeSL_T · 12-27-2009, 12:31 PM

I am driving my dad's '83 while I am fixing my Saturn, and I told him that I was going to look at a few problems he is having. Problem is, some are kinda weird. For instance, when I am giving the car some throttle like when I am getting on the interstate, the tach will kinda bounce around. And normally I wouldn't care, but the car has been running pretty rough as of late, and seems to have lost some power. Could anyone help me figure out which direction I should be going with this? I have been told that I should look for a vacuum leak for the running rough, but they are clueless about the tach issue. I was thinking that there may be a problem with the distributor. I don't know very much about working on carbd stuff though, so maybe the vacuum leak would fix all my problems. Sorry for such a long winded post, but thanks for any assistance.

James

Rogue_Wulff · 12-27-2009, 01:01 PM

The tach gets it's signal from the trailing coil, which is normally the front one. If the tach is jumping around, it could be the ignition system needs attention, which could explain the loss of power.
Start by checking the connections of all wires on both coils, and all of the leads from the coils to the dizzy, then on to the plugs.
While you're at it, look at the underside of the cap to what condition it is in. Might be time for a cap/rotor replacement.

TypeSL_T · 12-27-2009, 02:48 PM

I will look into that. Thank you.

James

codytheoutlaw · 12-30-2009, 06:20 AM

Your car is screwed. Just give it to me. lol

TypeSL_T · 12-31-2009, 12:17 PM

Only in your wet dreams sucker. lol. I started working on my Satty again Monday. I dropped the oil pan so I could clean up all of the debris. Now I just got to get a few rod bolts and start putting it all back together. Let me know what your schedule is like so we can figure out some time for you to come by.

James

codytheoutlaw · 01-01-2010, 12:56 AM

My schedule is probably the exact opposite of yours. Most likely any Friday, or Saturday night I'll be able to swing by. I'm awake from about 7 PM till 10 AM. Third shift sucks.

TypeSL_T · 01-01-2010, 05:34 PM

Dang. That blows. I am off most Saturdays, so we will have to try to meet up soon. I am going to be working on the car a lot the next few weeks to try to get it running again.

James

rx4ur7 · 01-01-2010, 07:27 PM

Bouncing of tach usually indicates igniter or wiring issue. Check igniter, coil, coil wire, wiring to coil and igniter. Check all grounds. Last would be to check tach unit, they do go bad but usually will not effect running.

TypeSL_T · 01-01-2010, 10:59 PM

I took a video of it, but the video is too big to send from the phone. I am going to try to get the video up some time this weekend. One other thing I forgot about was the tach will sometimes not work at all. It only does this when it is really cold out though, so I didn't think too much about it.

James

rx4ur7 · 01-02-2010, 11:10 AM

My experience has been that a cold out inconsistent tach was the tach itself. Hook up a timing light to the trailing ignition when it is not working, or pull the trail coil wire, making sure you are not grounded to the car. If you have spark, you have a bad tach, if it does not, check wiring.

Igniters usually are not inconsistent failures they either work or they don't. Out of the hundreds I have diagnosed I think there was one or two that were.

Bad grounds, broken wires or connectors are the most common failure issues in that order. Just because a wire looks good does not always mean it is. I have found many a broken wire under good looking insulation. Continuity test was the easiest way to find them.

Without being able to put my hands on it and from the symptoms you give my money right now is on the gauge itself.

Other issues that can show at this age of the platform would be with the circuit board. Rust, corrosion or damage circuit.

TypeSL_T · 01-24-2010, 04:43 PM

Last week the car would not start on Monday or Tuesday morning. Pulled the plug wires and found there was no spark at the plug, but there was spark at the distributor. Replaced the plug wires and tried again. Still wouldn't go. Realized I didn't clear out the flood that probably occurred. Pulled all the plugs out and dumped all the gas out of them. Turned the motor over a few times and cleared the rest. Reinstalled plugs and wires and it started and was a little rough, but not too bad.

So basically, after replacing the plug wires and clearing out the flood, the car has never ran better. The tach doesn't act up anymore, and the car doesn't buck. I never realized plug wires could cause so much crazy stuff.

James

angelofragnarok · 01-26-2010, 05:55 AM

I just wanted to thank the OP for this thread. Now I know something else about my 84!

TypeSL_T · 01-30-2010, 09:08 PM

I am glad I could help.

James

12-27-2009, 12:31 PM	#1
TypeSL_T Rotary Fan in Training Join Date: Apr 2008 Location: Murfreesboro iTrader: (0) Posts: 96 Rep Power: 17	Weird Tach Problems I am driving my dad's '83 while I am fixing my Saturn, and I told him that I was going to look at a few problems he is having. Problem is, some are kinda weird. For instance, when I am giving the car some throttle like when I am getting on the interstate, the tach will kinda bounce around. And normally I wouldn't care, but the car has been running pretty rough as of late, and seems to have lost some power. Could anyone help me figure out which direction I should be going with this? I have been told that I should look for a vacuum leak for the running rough, but they are clueless about the tach issue. I was thinking that there may be a problem with the distributor. I don't know very much about working on carbd stuff though, so maybe the vacuum leak would fix all my problems. Sorry for such a long winded post, but thanks for any assistance. James __________________ smf #11

12-27-2009, 02:48 PM	#3
TypeSL_T Rotary Fan in Training Join Date: Apr 2008 Location: Murfreesboro iTrader: (0) Posts: 96 Rep Power: 17	I will look into that. Thank you. James __________________ smf #11

12-31-2009, 12:17 PM	#5
TypeSL_T Rotary Fan in Training Join Date: Apr 2008 Location: Murfreesboro iTrader: (0) Posts: 96 Rep Power: 17	Only in your wet dreams sucker. lol. I started working on my Satty again Monday. I dropped the oil pan so I could clean up all of the debris. Now I just got to get a few rod bolts and start putting it all back together. Let me know what your schedule is like so we can figure out some time for you to come by. James __________________ smf #11

01-01-2010, 05:34 PM	#7
TypeSL_T Rotary Fan in Training Join Date: Apr 2008 Location: Murfreesboro iTrader: (0) Posts: 96 Rep Power: 17	Dang. That blows. I am off most Saturdays, so we will have to try to meet up soon. I am going to be working on the car a lot the next few weeks to try to get it running again. James __________________ smf #11

01-01-2010, 10:59 PM	#9
TypeSL_T Rotary Fan in Training Join Date: Apr 2008 Location: Murfreesboro iTrader: (0) Posts: 96 Rep Power: 17	I took a video of it, but the video is too big to send from the phone. I am going to try to get the video up some time this weekend. One other thing I forgot about was the tach will sometimes not work at all. It only does this when it is really cold out though, so I didn't think too much about it. James __________________ smf #11

12-27-2009, 01:01 PM	#2
Rogue_Wulff Non Member Join Date: Jun 2008 iTrader: (0) Posts: 310 Rep Power: 17	The tach gets it's signal from the trailing coil, which is normally the front one. If the tach is jumping around, it could be the ignition system needs attention, which could explain the loss of power. Start by checking the connections of all wires on both coils, and all of the leads from the coils to the dizzy, then on to the plugs. While you're at it, look at the underside of the cap to what condition it is in. Might be time for a cap/rotor replacement.

12-30-2009, 06:20 AM	#4
codytheoutlaw The Newbie Join Date: Dec 2009 iTrader: (0) Posts: 10 Rep Power: 0	Your car is screwed. Just give it to me. lol

01-01-2010, 12:56 AM	#6
codytheoutlaw The Newbie Join Date: Dec 2009 iTrader: (0) Posts: 10 Rep Power: 0	My schedule is probably the exact opposite of yours. Most likely any Friday, or Saturday night I'll be able to swing by. I'm awake from about 7 PM till 10 AM. Third shift sucks.

01-01-2010, 07:27 PM	#8
rx4ur7 Rotary since 1972 Join Date: Nov 2008 Location: Tucson iTrader: (0) Posts: 231 Rep Power: 17	Bouncing of tach usually indicates igniter or wiring issue. Check igniter, coil, coil wire, wiring to coil and igniter. Check all grounds. Last would be to check tach unit, they do go bad but usually will not effect running.

01-02-2010, 11:10 AM	#10
rx4ur7 Rotary since 1972 Join Date: Nov 2008 Location: Tucson iTrader: (0) Posts: 231 Rep Power: 17	My experience has been that a cold out inconsistent tach was the tach itself. Hook up a timing light to the trailing ignition when it is not working, or pull the trail coil wire, making sure you are not grounded to the car. If you have spark, you have a bad tach, if it does not, check wiring. Igniters usually are not inconsistent failures they either work or they don't. Out of the hundreds I have diagnosed I think there was one or two that were. Bad grounds, broken wires or connectors are the most common failure issues in that order. Just because a wire looks good does not always mean it is. I have found many a broken wire under good looking insulation. Continuity test was the easiest way to find them. Without being able to put my hands on it and from the symptoms you give my money right now is on the gauge itself. Other issues that can show at this age of the platform would be with the circuit board. Rust, corrosion or damage circuit.

01-24-2010, 04:43 PM	#11
TypeSL_T Rotary Fan in Training Join Date: Apr 2008 Location: Murfreesboro iTrader: (0) Posts: 96 Rep Power: 17	Last week the car would not start on Monday or Tuesday morning. Pulled the plug wires and found there was no spark at the plug, but there was spark at the distributor. Replaced the plug wires and tried again. Still wouldn't go. Realized I didn't clear out the flood that probably occurred. Pulled all the plugs out and dumped all the gas out of them. Turned the motor over a few times and cleared the rest. Reinstalled plugs and wires and it started and was a little rough, but not too bad. So basically, after replacing the plug wires and clearing out the flood, the car has never ran better. The tach doesn't act up anymore, and the car doesn't buck. I never realized plug wires could cause so much crazy stuff. James __________________ smf #11

01-26-2010, 05:55 AM	#12
angelofragnarok Wankel Fan Join Date: Dec 2009 Location: Freeport, FL iTrader: (0) Posts: 46 Rep Power: 0	I just wanted to thank the OP for this thread. Now I know something else about my 84! __________________ 04 RX8 - Racing Beat - intake, midpipe, exhaust Centerforce Stage 3 Dual Friction clutch 84 FB - Custom catless exhaust

01-30-2010, 09:08 PM	#13
TypeSL_T Rotary Fan in Training Join Date: Apr 2008 Location: Murfreesboro iTrader: (0) Posts: 96 Rep Power: 17	I am glad I could help. James __________________ smf #11

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