Starter Motor starts slow and then speeds up....

[davenay67]

My wife told me a couple of weeks ago that the TrailBlazer was getting a very weak start in the morning and that she was worried it may not start at all shortly. I charged the battery and it didn't seem to help very much. She ended up taking it to an Interstate store where they tested the battery, it only produced 400 when it has a capacity of 700CCA. They were warrantly left on the old battery and she had it repalced.

Fast forward a week. The car continued to have a very slow starter motor when the ignition is first turned and then it speeds up and starts the care easily. I don't thnk the replacement of the old battery is the problem (unless we have a parasitic draw somewhere in the system). I don't think this is the case as the starter started getting slow last year, but Spring arrived and we never saw the issue again. Now that Winter is back we are seeing the problem re-emerge. I think it is cold-related....I would think that the parasitic draw would be with us at all times of the season.

so, I left thinking it might be either the start motor or possibly a connection; bad battery cables or bad battery cable connection. Again, I would think the battery cables and connections would be bad at any time of year. Am I on the right track in wanting to blame the starter motor...??

I will have Advance Auto Parts run a test on the starter tonight, but not 100% sure if that will tell me the whole story. Not looking forard to the prospect of a new start motor, based on either replacement part cost and the total pain of that upper nut hidden between the start solenoid and the block. Another GM part that is in fairly plain view but not even remotely easy to get a tool to..!!

These GM engineers are killing me. My VW engine is WAY more crammed into the engine bay, but most everything (just ask anyone about the sick joke that it is the failure-prone temperature sensor) is still easier and more logical to access.

Any thoughts or insights of clarity are most welcome....


Dave.

 

[The_Roadie]

If you put a meter on the battery before and while you spin the starter, it will tell you a lot. Do you have a meter? If not, why? Have you checked the cables for a good connection and no corrosion at the battery, starter, and fender ground?

Parasitic draw will show up as a lower battery voltage in the morning compared to the evening before. But it all depends on having a meter.

Did I mention meters are cheap at Harbor Freight, especially when on sale at $2.99? I keep 3-4 on hand to give out to destitute friends who never seem to have a meter when they call me to help them diagnose an electrical problem.

 

[RayVoy]

From your description, I think your "cold related" suggestion is correct.

Sitting overnight, in the cold, can cause a lot of things to change. Consider a battery cable that becomes loose when the metal contracts (under the fastener, as well as inside the wire terminal); might be a cold related problem inside the starter; might be caused by thick oil in the engine (switch to synthetic).

 

[davenay67]

If you put a meter on the battery before and while you spin the starter, it will tell you a lot. Do you have a meter? If not, why? Have you checked the cables for a good connection and no corrosion at the battery, starter, and fender ground?

Parasitic draw will show up as a lower battery voltage in the morning compared to the evening before. But it all depends on having a meter.

Did I mention meters are cheap at Harbor Freight, especially when on sale at $2.99? I keep 3-4 on hand to give out to destitute friends who never seem to have a meter when they call me to help them diagnose an electrical problem.

I do have a multi-meter, and what's better is that I know how to use it....wonderful device to determine if a wire is 'hot' when I am working around the house.

I am also considering the alternator as a suspect in addition to the starter and the battery cables. The multi-meter wil give me a voltage input to the battery from the alternator, but it won't tell me the current output from the alternator....I will need a place with a fancy meter to tell me that.

The wife is taking it into the Interstate battery place today, so I am hoping they have the equipoment to tell me all the necessary electrical stats. I will base my fix / next steps of investigation on what they can tell me....

 

[RayVoy]

Having the battery and the alternator professionally tested is a great idea.

They may tell you one, or the other, needs to be replaced; but, consider this:

- a good alternator is required to keep the battery fully charged,
- when your starting, the alternator plays no role,
- a battery that is not fully charged will not spin the starter at full speed,
- a battery that is not fully charged, will not spin the starter faster after the starter has been pulling current from the battery while it is spinning slowly,

If you are unsure, after the testing, tomorrow morning (the next cold morning) connect a second battery, in parallel, before you try to start the truck. If it acts the same as it does with one battery, the problem is probably not the battery.

 

[davenay67]

hank

Having the battery and the alternator professionally tested is a great idea.

They may tell you one, or the other, needs to be replaced; but, consider this:

- a good alternator is required to keep the battery fully charged,
- when your starting, the alternator plays no role,
- a battery that is not fully charged will not spin the starter at full speed,
- a battery that is not fully charged, will not spin the starter faster after the starter has been pulling current from the battery while it is spinning slowly,

If you are unsure, after the testing, tomorrow morning (the next cold morning) connect a second battery, in parallel, before you try to start the truck. If it acts the same as it does with one battery, the problem is probably not the battery.

Excellent info.

Check the battery tonight - 12.74 volts....so I know it's fully charged and the alternator is doing it's job. I will check the voltage again in the morning. This will tell me is I am losing anything excessive in the volts department....this is leading me back again to thoughts of a failing starter motor.

 

[RayVoy]

The voltage will be a little lower in the morning.

This is normal, you checked it while warm (maybe only at room temp). In the morning, it will be lower because of the colder temps.


Edit: just looked it up, voltage will go go down by 0.022 volts per degree C drop.
This is for an open circuit battery (not connected to vehicle) after having been off charge for at least an hour.
So, just use it as a guide.

 

[gmcman]

hank


Check the battery tonight - 12.74 volts....so I know it's fully charged and the alternator is doing it's job. I will check the voltage again in the morning. This will tell me is I am losing anything excessive in the volts department....this is leading me back again to thoughts of a failing starter motor.

That's good voltage but will not tell you anything about load capacity. I'm leaning towards a starter as well but much easier to double-check the easier possible culprits.

Make sure the cables are tight and CLEAN. Like Roadie stated, check the ground strap and make sure there aren't any frayed strands of the cable.

 

[davenay67]

Re-cjecked the voltage before I turned in for the night....had gone down from 12.74 to 12.71. I checked again this morning (cold but not bone-numbingly icy) and it was 12.51.

I turned the key and the starter was sluggish (roughly half speed) for about a second before it picked up speed and started the engine. I stopped the engine and proceeded to repeat the start / stop process another 3 times. On each of the 3 restarts the starter was lively immediately and the engine started quickly. If the battery / wires/ grounds were the culprrit I don't imagine the results I got would be typical. So, am I thinking more than ever it may be a starter motor entering it's golden years. I guess the question is, how long can it go before it passes away altogether..??

For sure though I will check / clean / grease (dielectric) the cable ends and grounds.

Thanks for all the input and help so far....


Dave.