I agree that definately may be the case even though I also agree that 750 is not the appropriate level of power for these trucks. However, now that I understand how to do it, I will be doing the voltage drop test on both my positive and negative battery cables. It may not only be the under powered battery, but that in combination with a bad cable under load causing issues. I suppose I will disconnect the fuel shut off selenoid power connection so it won't start will cranking. Also, I will probably plug it in for a couple hours so the grid heaters won't cycle while I am doing my testing. Is this the best method for a no start and no grids while testing?Any other ideas for things to check or test?

 

I think grid heaters cycle based on ambient air temp. Not coolant temp so you better disconnect them.
I don't think plugging it in will stop grid heater cycling

 

Sensor's in the intake manifold. If the engine is warm, the grid heaters won't run until after the engine is started, and then only if it's pretty cold out.

OP. What yer looking at is probably a combination. A weak battery puts a strain on all things starter, and they get bad over time. It's good to take a close look at everything so you know where your weak points are.

 

Yes, that is what I plan on doing. Good to check everything out instead of concluding battery power as the entire solution or cause. I will be putting the more robust battery from our 92 into the 91 for the testing. I don't think that the 750 CCA battery will make it through all the on and of cranking while measuring drops.

I found this step by step write up and check list for measuring voltage drop through the entire starting and charging circuit. I am posting it below should anyone else find it helpful. I will be following it and will report back results:

1. Battery voltage drop during crank – post to post
Starting Circuit -
2. Connect positive lead to the battery terminal stud on the starter and the negative lead to the starter housing. Crank the engine and record the voltage reading. If the voltage reading at the starter is not within 1 volt of battery voltage then we have excessive voltage drop in the starter circuit.
3. Check total voltage drop in the positive side starter circuit: Connect positive meter lead to positive battery post and the negative lead to the battery terminal stud on the starter and read the voltage while cranking the engine. Anything over .6 volts is an excessive voltage drop and can be isolated using the following steps:
a. Battery post to cable connection: positive meter lead on battery positive post, negative lead on battery's positive cable clamp. Crank the engine and note the reading. A good connection should have zero voltage drop
b. Check the positive cable: positive meter lead on positive battery clamp, negative lead on starter terminal connector. A good cable will show a voltage drop of .2 volts or less while cranking.
c. Check the starter connection: positive meter lead on positive battery terminal on the solenoid, negative meter lead on actual starter stud. A good connection will have a voltage drop of near zero volts.
4. Negative side starter circuit drop test. Total drop on the ground side should be .3 volts or less
a. Place positive meter lead on starter housing and negative meter lead on battery ground post. Take reading while cranking the engine, and be sure your connection at the starter is solid and clean. If total voltage drop on this side of the circuit is excessive, complete testing at all connections in the same fashion as the positive side of the circuit.
b. Check: Between battery post and clamp (zero voltage drop)
c. Check: Cable end at battery to cable end at engine. (.2 volts or less)
d. Check cable end at engine to engine itself (near zero voltage drop)
e. Check between starter housing and engine block (.1 volts or less).
Charging Circuit –
1. Positive side charging circuit check for excessive voltage drop:
Connect meter positive lead to the alternator output stud and negative lead to battery positive post. Run engine at 2,000 RPM with all lights, blower motor, radio etc. on and check voltage reading on meter. An acceptable reading is .5 volts or less. If you have an out of spec. voltage drop, check connections at alternator and battery as well as for an use of undersized cable. Check the negative side for the charging circuit the same as the positive with your meter's negative lead on the alternator case, or ground strap if equipped, and the positive lead on the battery negative post. Voltage drop on this side of the circuit should be .2 volts or less.

 

Thought I would post back the resolution. Did complete voltage drop testing on positive and negative starting circuit. No issues. Ended up being the starter. I took out the starter and brought it to Auto Zone for bench test. Tested bad. The manager saw a sticker on the old starter that was the same as the ones on their rebuilt units. He asked me about the history of the bad starter. I said I had no receipt for the starter as it was replaced some time ago before I bought the truck. Then he went to the back and just gave me another starter as a warranty exchange! Couldn't believe it.
Put the new one in and now it starts up in a fraction of a second with lots of cranking speed, even with the 750 CCA battery and working grid heaters. Definately good to know voltage and connections tested good before removing the starter though. Thanks for the input everyone.

 

Hmmmm, I think that was mention a few weeks ago in this thread














Yep, Post #12

 

...and you were correct on that call. Just wanted to make sure wiring/connections in starting circuit were good before replacing starter.

How's the crash parts R&R coming along?

 

I got most of my crash parts, and got a lead on another clean bumper. We just got about 13" of snow this weekend so it'll be a bit before I tear into it.

 

I wish I had a large HEATED garage to work in during the winter. Are you doing your work outside?

 

I wish. It would be fixed by now if I did.