98 12v Electrical problems

jhastings

jhastings

New member
Just got the truck back together and I'm having some electrical issues. I have two brand new batteries and all connections are clean and tight.

When starting, truck is slow to crank sometimes. Also, the speedometer bounces all over the place. Lastly, the windows and accessories are really slow as if there is low voltage. Tonight on the way home, all gauges died and the dash lights were really dim. Then gauges would come back. Voltage is showing 14 or so on the gauge.

Any ideas? ECM....? How do I test it?


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I'd agree that it's most likely ****ty or disconnected grounds.

That being said, I think your starter has a different issue. The only time I've had poor starting speed is:
1) bad batteries
2) bad starter
3) not good enough current running to the motor. Make sure you run some decent 0 awg line from your starter to your battery, jump the ground from the relay to the starter ground (neg), and make sure your positive line from the relay is getting a full 12V when you hit the ignition (easy to test with a multimeter).
 
I agree, you have a ground/connection issue, bad starter, or bad batteries. Most likely a bad ground/connection issue.

Just FYI, 12V's don't have an ECM. There is a PCM (Power Control Module) on the passenger side firewall.
 
Do yourself a favor and don’t buy a reman from a parts house if you replace the starter. They tend to be junk and will have the same issue. There are threads on upgrading the contacts to one with a larger contact patch. Best thing I ever did was drop it off at a place to be rebuilt and cleaned up inside. It was so bad inside the guy said he had to let the dust settle for a couple hours before going back in the workshop. If I. Remember correctly the life expectancy was about 100k with stock parts. Went from cranking very slow and needing throttle to start to cranking over easily.

Larryb - Dodge Cummins starter rebuild kits


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Last edited:
Kryp2nitE said:
Do yourself a favor and don’t buy a reman from a parts house if you replace the starter. They tend to be junk and will have the same issue. There are threads on upgrading the contacts to one with a larger contact patch. Best thing I ever did was drop it off at a place to be rebuilt and cleaned up inside. It was so bad inside the guy said he had to let the dust settle for a couple hours before going back in the workshop. If I. Remember correctly the life expectancy was about 100k with stock parts. Went from cranking very slow and needing throttle to start to cranking over easily.

Larryb - Dodge Cummins starter rebuild kits


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Click to expand...

I've been hearing this for years and when my starter finally went at about 230k, it was too corroded to rebuild. I bought a cheap autoparts store one (Napa I think) and it's been very reliable for 70k. I don't think they're as bad as people have been saying.
 
Napa is still better than AutoZone or the like. I have swapped my father inlaw's cheap starter 3 times in 3 years. He is retired and doesn't mind because I do the work, but I wouldn't want to count on one.

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Yep I think you are correct about the ground. Seems like that is 90% of all electrical problems. I have already rebuilt the starter with contacts/plunger.

What grounds should I check? I have two going to block and one going to body/frame off driver side battery ground cable.


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jhastings said:
What grounds should I check?
Click to expand...

ALL of them. Both ends.

I found the negative terminal on my passenger side battery was not getting good connection. I found it when jumping the truck off. Couldn't get power through the jumpers when clamped to the terminals. The terminal was tight.
 
Ok guys cleaned all terminals, grounds, etc with wire brush. Passenger battery is getting 13+ volts and driver side sits at 11.9v. Alternator is throwing 14.01v at the back of the alternator. The only thing I can find with my tester is the 50A fuse labeled BATTERY is grounded on one side unlike any of the other circuits. Mind you both batteries are brand new and take no charge on my charger.


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Shouldn't both batteries be the same when running since they are directly connected?


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Also, truck can be slow to shut off sometimes like the fuel shutoff solenoid is slow to move. It's new too


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Yes batts should read the same, disconnect the pos cable between the two and load check the batterys, if you don't have a load checker make sure they are both at like 12.8 disconnected from each other. Then if both are the same, hook a set of temporary jumper cables between the two batterys and see how it cranks.
 
Grid heater solenoid were stuck on and they were draining the batteries.


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