Weird no start issue - Not starter, relay, battery, ground, or voltage drop

[98GTAZ]

I have a very strange starting issue. Over the past few months, my 1998 GT (4.6 2V) became harder and harder to start and now will not start at all.

The engine will crank slightly. Standing in front of the car, I had my wife crank it. I can hear everything engage and see the motor turn about a quarter turn, but that's it. It will not turn the engine over multiple revolutions and after a few tries it cannot turn the engine anymore.

This all started in June. First, when the motor was hot it did not want to start after being driven for awhile. When it cooled down it would start again. I was thinking heat soak, but then it started happening when the engine was cold. It got progressively worse and graduated to no start.

Here's what I have done/tested so far:

1. Battery fully charged - Tested and recharged multiple times
2. Battery voltage tested - Consistently about 13.5 volts or so when charged
3. Battery load tested - Used my load tester and battery passed
4. Took battery to auto parts store and had them test it - passed all tests
5. Replaced starter
6. Voltage tested to starter - Consistently good voltage with no voltage drops
7. Tested relay - operates as it should
8. Swapped in other known good relay - no change
9. Tested voltage to relay - good with no voltage drop from battery
10. Tested ground at multiple places across engine - all good
11. Tested block to frame ground - Good with no voltage drop
12. Turned engine with breaker bar and socket on crank pulley - Turns freely

The components all seem to be working. Even in its current condition, I can hear the relay click, the starter engage and see the engine turn - It just doesn't turn enough to start.

I am out of ideas and things to test. Any suggestions are greatly appreciated.

 

[ttocs]

how are you testing the grounds?
is the battery in the trunk?

 

[98GTAZ]

Battery is in the stock location using the factory stock wires.

I tested the grounds using a multimeter. I get consistent voltage across each ground with positive lead attached to the positive battery post and the black lead on the grounds.

 

[lwarrior1016]

It wouldn’t hurt to pull the grounds off and clean them, then reinstall. You could also try running a different power cable from the battery to the starter to make sure it’s not building too much resistance in the stock power cable. You may not see voltage drop at the starter, but it could be dropping amps not sending enough to spin the engine.

 

[Adfalenski]

Make certain that BOTH battery connections are clean and tight as well as the engine block ground connection and the starter connection.

 

[weendoggy]

When testing the starter during cranking attempt, are you using a load test on the battery to starter cable? What is the amperage draw during that time? You should be under 200A.

 

[ttocs]

It wouldn’t hurt to pull the grounds off and clean them, then reinstall. You could also try running a different power cable from the battery to the starter to make sure it’s not building too much resistance in the stock power cable. You may not see voltage drop at the starter, but it could be dropping amps not sending enough to spin the engine.

even though you have measured them and then seem good I would start with the grounds like he said. I have also added another ground from the chassis to one of the bolts holding the starter in place just because it draws so much current.

 

[98GTAZ]

SOLVED!

Amperage draw as in range and I did go ahead and clean the ground connection.

It turns out, however, that it was a bad ignition switch. it had poor continuity in the start position between the power lead and the starter lead.

I made a video about how to test the ignition switch for bad continuity and posted it to my Youtube channel:

 

[lwarrior1016]

I’m glad you got it solved. I thought you had already checked for voltage on the small wire for the starter, based on the first post. Either way, good job.

 

[98GTAZ]

My no start moved from weak crank to no crank. I had checked the small wire initially but should have checked it again before I pulled the starter. My starting issue was intermittent for a month which is why I was thinking it was heat soak at first. That’s what got me so focused on the starter itself. I think the switch was in the process of failing but hadn’t totally failed when I first checked everything.