GT-150 Timer base impedance

qcernie

Cadet
Joined
Aug 23, 2013
Messages
22
1990 GT 150 crossfire. No spark, intermittent spark. Took timer base off and checked wires and physical condition, Looks OK. Checked impedance and got the following;
Starboard White to Blue 1.5M
Purple 1.7M
Green 25.0M

Port Blue 1.5M
Purple 0 (open)
Green 1.5M
Timer Base is kaput ?
 

qcernie

Cadet
Joined
Aug 23, 2013
Messages
22
Been there. Done that. Just thought I'd get a 2nd opinion before I drop 4 bills on a timer base.
 

emdsapmgr

Supreme Mariner
Joined
Dec 9, 2005
Messages
11,551
I'm a fan of testing the voltage output of the timer base when the engine is cranking. Done with a special "peak-reading" voltmeter. Per the factory service manual, at cranking rpm's you should see a minimum of 0.2 volts. See page 3-48. Considering the expense of this device, it's worth your testing time.
 

daselbee

Commander
Joined
Jan 20, 2009
Messages
2,765
You cannot measure the resistance of a timer base. Oh, you can measure it, but you cannot get any real information from the results.
The reason is that the timerbase has active circuits inside it, and they respond differently from timerbase to timerbase, and from meter to meter.
Also, you don't indicate which polarity the meter leads were. Do it again, and see that the readings change when you swap leads.
Except for the first measurement, you only show one side of the connection....are we to assume(???) that one side stayed constant...the stbd white, and then you went thru the rest of the wires....if so....long assumption is required, and I hate assuming anything.

The real questionable reading was on the port purple wire 0....well 0 (zero) ohms is a dead short, not an open. Are we to assume(???) dead short, or as you say open which would be an infinite ohms reading.? If it is a dead short, then #4 would be dead all the time. If it is infinite high resistance, could be because of the meter, and the internal circuitry for that particular purple wire.

No, you cannot accurately measure a timerbase.

Do as EMD says, measure voltages using a DVA adapter.

If you ignore my advice, please take the time to measure the new timerbase you get, and see the difference.
 

qcernie

Cadet
Joined
Aug 23, 2013
Messages
22
Sorry for the confusing post. I connected red lead to white starboard and then checked the other wires with the black lead..Reversing the leads did not give correct readings on any wire. I'm getting no voltage on any wire from the timer while cranking with DVA and Fluke meter. I didn't get this old by ignoring advice. Though I may take some of it with a grain of salt.
This started when I noticed on the spark tester that I had no spark on #4 and intermittent spark on #6. On some occasions I could get no spark on any cylinder. New kill switch, key switch, starter, battery, pack and stator.
 
Last edited:

emdsapmgr

Supreme Mariner
Joined
Dec 9, 2005
Messages
11,551
Are you testing the timer base per the factory service manual? If you've tested the timer base correctly and have no voltage output at cranking rpms, it is condemned. Replace it.
 
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