Engine slow to crank - battery, alternator, starter?

[Zygrene]

I posted this on the Prime Facebook group a couple weeks ago but wanted to get some more feedback. My car occasionally takes several seconds to start. It seems to happen randomly, and only about 1 in 10 starts. When it happens, it sounds like the starter is struggling to crank the engine.

The first time this happened a month ago was after I drove the car and left it in the outdoor heat for an hour. First start took about 3-4 seconds, then subsequent starts were back to normal.

I got the battery tested at O'Reilly and it apparently wasn't fully charged. So they charged it and performed a load test, which passed with no issues. I also used a multimeter to test the battery voltage with the engine on vs off. IIRC, engine off voltage was around 12.6V while engine on voltage bumped up to 14 something and held steady.

Last weekend I drove the car hard on the track for 5 x 20min sessions, turned it off for a while, and it struggled to start again. But this time the subsequent 2 or 3 starts were also slow. Only when I cranked the car several times in a row did it go back to normal.

At this point, I'm not sure how to diagnose the issue. Any ideas?

 

[mrbythatmuch]

12.6 is great for a battery. 14 is when the alternator is running. I would start with inspecting the battery connections and cable ground to the chassis under the heater. I suspect when you try and start you have a high current draw. Make sure you have solid connections ie no corrosion. Then I would have the starter rebuilt depending upon your miles.
Next you have the ignition switch, main relay but they would more likely be starts then won't start vice sluggish, which makes me think you have a high current draw on start.

 

[Zygrene]

12.6 is great for a battery. 14 is when the alternator is running. I would start with inspecting the battery connections and cable ground to the chassis under the heater. I suspect when you try and start you have a high current draw. Make sure you have solid connections ie no corrosion. Then I would have the starter rebuilt depending upon your miles.
Next you have the ignition switch, main relay but they would more likely be starts then won't start vice sluggish, which makes me think you have a high current draw on start.

When I took the battery out to get it tested a few weeks ago I checked the connections for corrosion. They seemed fine. Would it help to disconnect the terminals and clean them with a wire brush?

I'll have to check the cable ground too. Is there a simple diagram for this somewhere?

 

[Gary W]

 

[Larry Bastanza]

Make sure the terminals are tight on the battery posts. This is a common issue I see all the time. Once they are tight, you must not be able to twist then. They stretch when they get over-tightened, happens a lot.

HTH,
LarryB

 

[Zygrene]

Make sure the terminals are tight on the battery posts. This is a common issue I see all the time. Once they are tight, you must not be able to twist then. They stretch when they get over-tightened, happens a lot.

HTH,
LarryB

Just checked the negative terminal and I'm able to twist it. I'll try to tighten it more tonight, otherwise I assume I'll need new terminals.

 

[BTL3.0]

Redbird82(Ben) is your guy if u need a new ground cable. His cable are4 solid.

 

[Larry Bastanza]

When you install it make sure the connector is all the way down on the post of the battery. The post is slightly tapered, so if you do not have the connector bottomed out, it will be loose.

HTH,
LarryB

 

[Old Guy]

You say slow to crank. Do you mean that the engine is turning over slowly or that it is slow to start sometimes. If the engine is turning over slowly, then all of the preceding comments are spot on. However, if you mean that the engine is slow to start, that is a separate issue.

The occasional slow to start problem is usually caused by loss of fuel pressure while the car is parked. The fuel pump has a check valve on its discharge which keeps the fuel system primed when the car is stopped. If the check valve leaks, or one or more of your injectors is leaking, you are loosing pressure and the start takes longer because the pump has to prime the fuel system. When you did those subsequent restarts you talked about, the restarts were quick because the fuel system has not had a chance to lose pressure.

 

[mrbythatmuch]

Don't forget to check both ends of your negative cable. I can surprised how much corrosion was once chassis end. After cleaning that and putting dielectric grease to keep it dry/clean my car starts great.

 

[JD Cross]

Don't forget to check both ends of your negative cable. I can surprised how much corrosion was once chassis end. After cleaning that and putting dielectric grease to keep it dry/clean my car starts great.

It should be noted that dielectric grease is a non-conductor so should only be used to seal a good connection.
If it is used within a connection it can cause problems.