# 650 AMPS!

Discussion in '1982-Present GM Diesel' started by calcide, Mar 19, 2002.

1. ### calcide1/2 ton status

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Parf and I did some checking (he bought a fancy fluke clamp-on ammeter) to see how much current the starter draws in our 6.2s. Both of our trucks took 650 amps to crank over, and both were warm from being driven recently. My starter is newish, only 4 months old. Glow plugs took 153 amps, but the current dropped as they heated up (we both have a set of 60Gs).

As a side note, the ford powerstroke that hangs around the house took 710 amps to start and 160 amps for the glow plugs. The 600 watt amp in my Bug took 70 amps peak, about 45 amps average.

Maybe we will be able to see how much current it takes to crank over a 6.2 on a cold morning before winter is over. I'm guessing it will be around 900 amps.

2. ### René1/2 ton status

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I understand your calculation not completely.
Each glow plug has a performance of 85W. That results in 57A. If your starter takes 650A, it would have a performance of 7800W. That cannot be...

3. ### calcide1/2 ton status

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These readings are not derived from a calculation, they are direct readings from an accurate instrument. The fluke 36 we used has a DC current accuracy of plus or minus 3%+4 counts.

That said, power equals voltage times current. 153 amps for the glow plug system works out to about 19 amps for each plug. Assuming the system was at 12V, that would be 228 watts per glow plug. 7800 watts for the starter is accurate, at 12V and 650 amps. 7800 watts is 10.45 horsepower.

I did not measure the battery voltage, so these power figures are estimates. Also, this measurement includes power lost due to bad connections, wire restances, etc.

It would be cool to see how much voltage that #4 battery cable drops at 650 amps. I can't believe GM put in a cable that small.

Measurement is my life. I gotta get out more.

4. ### NewK5Guy1/2 ton status

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Stupid question. You said "assuming system at 12 volts" or something to that effect. I thought the glow system on the 6.2 was 24 volt. Would that not change anything? I still am interested in those readings you took.

5. ### Tybee1/2 ton status

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Miltary vehicles operate on a 24 volt system.

6. ### René1/2 ton status

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Only the military versions have 24V. However their glow plugs (13G) need only 8V for the remainder are responsible the resistor behind the air cleaner.

7. ### René1/2 ton status

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In the Diesel Engine Repair Manual of Haynes, chapter 2, side 73, the test of the glow-plug system is described…
G-Van 50A min.
C, K, P 55A min.
CUCV 35A min.

About the starter I did not find anything, but it must have for instance 1500W. That makes then 125A.

8. ### ParfRegistered Member

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Thats great.

My truck's glow plug system drew 153 amps.
While cranking the starter over, it took 650 amps.
<a target="_blank" href=http://www.tequipment.net/FlukeClampMeter36FE.html> This </a> is the meter we used.

9. ### René1/2 ton status

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I believe it to you!
But I can't understand it...

10. ### OFFRDK51/2 ton statusPremium Member

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After I melted my starter cable twice I went to a 0 cable...aut cable.....no problems with starting after that!!!

11. ### calcide1/2 ton status

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Perhaps those values given were for stock plugs, the measurements I gave are for 60g plugs.

Starters draw a lot of power period. A powerful starter for a gas engine produces 1700 watts, but you have to keep in mind that nothing is 100% efficient. I do not know what the efficiency rating is of the average starter, but I DO know that drawing 200 amps for a starter is not uncommon. I measured a chevy 350 gas motor as drawing 250 amps for the starter. There is a reason the diesels have dual batteries, and it's not so your lights will work longer with the engine turned off.

If you want me to explain why your book is wrong, maybe you should contact the publisher instead. I didn't write it.

12. ### SlickCUCVRi ckRegistered Member

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Helllppp I am installing a duel alt 24 volt system out of a military AMB and will install in CUCV blazer with standard stuff.. where can I go to research this topic

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