starter amp draw
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
The starter does not draw current after the key is released, except for a brief moment as the inductance of the starter motor windings continues to pull current after the solenoid disengages. This only occurs very briefly.
When the starter draws current, the battery voltage lowers. This is because the current draw causes a voltage drop across the internal resistance of the battery. Most Ford ignition systems (even back to the days of breaker point ignition) are set up so that the coil is given the maximum available voltage during cranking, rather than a dropped voltage (many older Ford ignition systems contain a resistive divider to lower the coil voltage when the key is in run). However, if the battery is low enough, the starter current will pull the battery voltage low enough that the plugs can't fire while cranking, which produces a no-start situation.
When the starter draws current, the battery voltage lowers. This is because the current draw causes a voltage drop across the internal resistance of the battery. Most Ford ignition systems (even back to the days of breaker point ignition) are set up so that the coil is given the maximum available voltage during cranking, rather than a dropped voltage (many older Ford ignition systems contain a resistive divider to lower the coil voltage when the key is in run). However, if the battery is low enough, the starter current will pull the battery voltage low enough that the plugs can't fire while cranking, which produces a no-start situation.
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New User
Joined: Feb 2004
Posts: 7
Likes: 0
fmc400
the reason i ask ! the engine is out of a 93 f-150 powering a 84 f-250.
the starter on the f-150 was a gear reduction low amp starter the starter on the f-250 is 1 wire higher amp starter. the spark is intermitent,and seems to be best when ignition is released thanks for any reply.
the reason i ask ! the engine is out of a 93 f-150 powering a 84 f-250.
the starter on the f-150 was a gear reduction low amp starter the starter on the f-250 is 1 wire higher amp starter. the spark is intermitent,and seems to be best when ignition is released thanks for any reply.
Cargo Master
Joined: Mar 2008
Posts: 2,573
Likes: 207
From: Washington
what type of coil are using... round or square?
If it is a round one does it have an internal resistor?
What voltage do you have on the coil positive with it running at idle?
What is battery voltage at idle?
If it is a round one does it have an internal resistor?
What voltage do you have on the coil positive with it running at idle?
What is battery voltage at idle?
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
Refer to this post to make sure you have it wired correctly. It explains how to convert standard bendix starter wiring to PMGR starter wiring.
https://www.ford-trucks.com/forums/7...ml#post6485940
https://www.ford-trucks.com/forums/7...ml#post6485940
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New User
Joined: Feb 2004
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new information!!! truck will start when bump started , but will not start when using key. turns over but no spark. whats up with that!!!
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MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
The starter is drawing too much current, and bringing the battery voltage down low enough that the coil will not fire. Your starter has too work too hard. This is either because the starter itself is failing, or something is making the engine harder to turn over such as improperly adjusted ignition timing.
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