starting system test specs.

dieseldoc · January 6, 2009

Looking for some specs for a 96' F350 with a 7.3. What I am after is the amp draw for a good starter versus a bad starter? Looking to test a starter that is in the pick-up yet. Looked in the workshop manual but could not find the spec. Thanks guys

Bruce Amacker · January 6, 2009

Remember that amp draw is directly related to how good the batteries are, if battery voltage is low, amperage goes UP, so it may not be the answer you're looking for. On a scope capture, I have a known good Gen 2 7.3 showing a 1364 amp initial spike and an average cranking amperage of about 473 amps. I'd suggest you do a voltage drop test on the battery cables, they should read .3v or less. If the batteries pass a carbon pile load test and voltage drop is good, cranking speed on a 7.3 should be about 175 warm and 150+ cold (outside). Use a scan tool to read the RPM cranking.

Good Luck!

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Jim Warman · January 6, 2009

If you have the Ford workshop manual, check section 03-06 / Diagnosis and testing / Component tests for procedures and section 03-06B/specifications for the numbers...

Factory spec for starter draw is 230 to 630 amps. Obviously, the spec is a bit too "loose" to be of much help.... Get down and dirty for a "better way"... disable the engine (keep it from actually starting) and crank it for 15 seconds... It should maintain at least 150ish rpm for the complete cycle and battery volts should not drop below 9.6ish volts - remember that the glow plugs must be operating normally for this test and the motor should be at ambient when the test is run. (Remember the whole idea is to recreate 'normal' operating conditions). The reason we crank for 15 seconds is to build heat inb the starter - a cool starter can spin quite fast while a hot starter can drag like a SOB...

HTH

Bruce Amacker · January 6, 2009

disable the engine (keep it from actually starting) and crank it for 15 seconds... It should maintain at least 150ish rpm for the complete cycle and battery volts should not drop below 9.6ish volts

I think you'll find 9.6v way too low for a cranking voltage. You're getting a battery load test confused (that uses 9.6 minimum voltage at 1/2 CCA carbon pile amp load). Most 7.3s will crank at about 11v. I use 10.5v as a borderline bad figure in a reasonable climate. You live on the fringe of Hell, however.

Good Luck!

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PS Nice avatar! You shaved your mustache? /forums/images/%%GRAEMLIN_URL%%/laugh.gif

Jim Warman · January 6, 2009

Actually, Bruce, you have once again caught me with my pants down... I still like the 15 seconds in order to build the heat into the starter... but by the time a battery gets under 11 volts, the 150 rpm will be out the window anyway...

As it stands, the critical consideration cranking rpm at the end of the test.

I'm at my best when I don't have the time to overthink what I plan on doing.

dieseldoc · January 7, 2009

Batteries are brand new, fully charged and pass a carbon pile load test. Volt drop through the cables is ok. Will check the cranking speed when I get a chance. Engine starts well but it sounds like the starter is really laboring to turn it over. This is my personal pick-up and I want to avoid the no start one morning when I am in a hurry. There is nothing more embarrassing than being the diesel tech, whos diesel wont start and leaves you sitting. Thanks for the info guys, need to read through my workshop manuals and get more familiar with them.

Bruce Amacker · January 7, 2009

Actually, Bruce, you have once again caught me with my pants down.

I'm getting this urgent feeling I'm about to lose my lunch.

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Shlep · January 7, 2009

Originally Posted By: Jim Warman

Actually, Bruce, you have once again caught me with my pants down.

I'm getting this urgent feeling I'm about to lose my lunch.

/forums/images/%%GRAEMLIN_URL%%/sick.gif