M998: Loud Pop when trying to start

[FlameRed]

Folks,

Once again I need the assistance of the experts here. Was returning from a car show and stopped for diesel and I made the mistake of shutting off the engine.

When I attempted to restart we heard a huge pop! Sounded like maybe it came from the battery area under the passenger seat?

The starter did not crank at all. The brake light dimmed out completely perhap like one of the batteries was weak. Or the starter draines too much current because it went bad?

I let it cool while waiting for a tow. After hours it made the same pop when I tried to start it again! No cranking noise from t h e starter at all.

Is this some breaker there that makes this pop in that battery compartment?

Cannot really diagnose anything till I get it home if the tow truck ever shows up .

All help would be greatly appreciated!

 

[Mogman]

Could be a loose/poor battery connection or other connection in the large power cables, a loose/poor connection can get pretty loud on a 24V system.
BE CAREFUL things can get rip your flesh right off hot!!!

 

[TOBASH]

Hard to say for sure. Look at the starter underneath. Pull and clean and inspect all the wires. Wear electrical gloves. Look for burn marks and frayed wires and damaged insulation. Make sure the batteries and wires didn’t break free and didn’t shift to contact the body.


Are you sure the pop isn’t on the left under the dash (PCB/EESS area)? Does the “wait light” come on?

 

[FlameRed]

Yes, the wait light and break light come on but dim out when i try start. The pop definitely coming below the passenger seat. My wife jumped!

The stater is caked in dirt. Probably the original one.

Plan is, if the tow truck ever shows, is to try and clean the starter as well as I can on the car. And maybe try tapping it with a hammer. But I'll make sure the engine can spin first.

The bateries and connectors looked fine earlier this week.

 

[Retiredwarhorses]

have You pulled the seat for the battery box and inspected battery condition?

 

[Mogman]

have You pulled the seat for the battery box and inspected battery condition?

I cannot imagine that not being the first thing anyone would do, long before calling the tow truck.

 

[Mogman]

If you have not looked at the batteries do not try and start it again, you can easily burn a terminal completely off of a battery with 24V, much different than 12V

 

[FlameRed]

Sorry for the late reply - long day.

I looked at the battery compartment - looks good to me. Terminals were tight. No signs anything melted or burnt. Insulation does not look melted. Batteries did not look like they were bulging but I did not remove them. Nothing exploded.

Plan is to try to turn the engine with a socket wrench and make sure it turns by hand. Then I will look at the started, cleaning off all the dirt, etc.

EDIT: Engine turns freely

What is safe to use to clean the starter? Brake cleaner?

 

[Mullaney]

Sorry for the late reply - long day.

I looked at the battery compartment - looks good to me. Terminals were tight. No signs anything melted or burnt. Insulation does not look melted. Batteries did not look like they were bulging but I did not remove them. Nothing exploded.

Plan is to try to turn the engine with a socket wrench and make sure it turns by hand. Then I will look at the started, cleaning off all the dirt, etc.

What is safe to use to clean the starter? Brake cleaner?

.
Brake parts cleaner will work.
Electrical parts cleaner might be better.

DISCONNECT THE BATTERIES before you try to clean anything!

 

[bprzyw]

.
Brake parts cleaner will work.
Electrical parts cleaner might be better.

DISCONNECT THE BATTERIES before you try to clean anything!

YES! Disconnect batteries!!! Or remove starter an disassemble for a good cleaning

 

[Mogman]

I would not condemn the starter yet, you need to check all the large cable connections pos and neg first

 

[FlameRed]

I ordered a can of electronics cleaner which says it can be used on motors and alternators, and the like.

I will remove the starter and give it a good cleaning and look for anything which might be obscured while it is on the car and covered in dirt.

There are a few places in town that say they can rebuild starters but I'll call them and make sure they can deal with this 24 stuff. Hopefully one will be able to test it for me. I know the auto parts stores have starter testers but I doubt theirs can deal with the 24 volt ones.

I disconnected the battery cables and now I just noticed that one of the twist off vent caps was off. I found it at the bottom and put it back. I also noticed a wasp nest in the compartment, but they were gone. We have Mud Daubers here and they are nasty critters. I saw a few flying around the last couple of weeks but I could not find their nest. Now I know why!

Perhaps that super loud pop noise I heard and the wife felt was hydrogen gas exploding in the compartment from a spark of some kind?

 

[Mogman]

Why are you removing the starter????
How have you determined the starter is the problem????

 

[FlameRed]

Why are you removing the starter????
How have you determined the starter is the problem????

How would one test it with it on the engine?

 

[Mogman]

You need to eliminate the most likely causes first, you have 4 battery terminals, and several stud terminals in and outside of the battery and the large cable connections to the starter to check.
1ST check the battery terminals, then starting at the batteries check and see where you are losing the 24V both on the pos and neg side, from what you have described the starter would be the last thing I would suspect, you have a poor connection somewhere.
wear safety goggles when working around a bad connection at all times, a poor connection can spit molten lead and or copper when troubleshooting!!

When you have a HMMWV you can ether just swap parts until you eventually find the problem or learn to troubleshoot the issue correctly.

 

[Mogman]

It is also possible that battery that spit the cap opened up inside so start with the voltage at each battery while trying to start it, again with eye protection and a water hose on standby in case the battery explodes, wash yourself down first then worry about the HMMWV.
Apron and face shield would be best

 

[Mogman]

I take that back, check the battery voltage with just the lights on first to see if one is open, a little safer that way.

 

[TOBASH]

If you are going to spray the starter, you must disconnect the batteries first unless you want that cleaner to become accelerant and provide third-degree burns.

I agree with Mogman. Check your battery fluid first before doing anything else. Then check the voltage. The fact that you blew off one of those caps is a dangerous sign. It is not easy for those caps to fall off. You need eye protection and explosion protection. If it were me I would just get rid of those batteries.

 

[Mogman]

I am not a fan of non sealed lead acid batteries in an enclosed area with no ventilation and would never have MY wife sit on a hydrogen bomb!

 

[Mogman]

Actually TOBIAS has a good point, given you waited so long to disclose a cap had been blown off a battery and your limited troubleshooting skills it would be best at this point to pull the batteries and have someone test them before proceeding.