'97 F-250 Starting Problems

[tucker0104]

I started my truck the other day and it seemed like it barely had enough juice to get it going. Ran rough for about 20 seconds once it started then it ran fine. Drove it to work (30 miunutes) and about the time I got to work, the battery light came on and then went off then came on again. When I left work, I barely got it started. Lots of cranking and gas pedal. Drove home fine. Started it up today and it started a little slow. No battery light once it was started. Took the leads off each of the batteries and each one was reading 12.6 volts. I figured it was the batteries. They are about two years old. It was about 40 degrees when I tried to start the truck and it wasn't plugged in. Any ideas?

[rolsmojave3]

To get a good idea of whats going on you have to check the entire starting circuit. Batteries at 12.6 indicate fully charged, but they must be tested under load to determine if they are OK. You can also check voltage at the batteries with the truck running at say 2500rpm. Although you may have 13-14v you will still have to load test the alternator to get an accurate reading. Last but most important. Check all of your battery cables and leads to the alternator. Easy way is a voltage drop measurement.

Voltage Drop Testing

[Maverick1701]

check all your grounds too...almost all of my electrical problems have been caused by bad grounds.

[tucker0104]

I replace both my batteries. They were 3 years old so we will try that and go from there. Thanks for the advice.

[tucker0104]

Replaced the batteries and I am still having problems. How can I check the grounds? What are the symptoms of a bad glow plug?

[rolsmojave3]

Did you do a voltage drop on your battery cables?

[tucker0104]

I did not. How do I do that?

[rolsmojave3]

The link I posted

[tucker0104]

Ok, so I replaced the batteries and turns out that isn't the problems. The current symptons of what is wrong is the battery isn't draining after all. Once I get the truck started, it runs great. The truck is rough starting though. I am starting to think that it is the glow plugs. I never seemed to have a problem until the weather got cold. It will turn for a while and I will press the gas and eventually it starts up even though it doesn't want to. How do you test glow plugs? Do you just measure the resistance across them? What is a good and bad resistance? Should I replace all glow plugs if one is bad? Please let me know what you think.