Grinding noise
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Junior User
Joined: Dec 2008
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Grinding noise
Hello everyone. I just installed a new battery, new starter, ignition switch, wires and solenoid. The truck starts right up but there's a nasty grinding that sounds like it's coming from the starter. The only way to shut down the truck is to remove the positive cable from the battery. It's a 1978 f150 351m and I don't know what the problem is. Any help would be appreciated. Thanks!
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
If you pull the wire from the 'S' post of the solenoid, does the grinding stop? If so, it sounds like a stuck ignition switch, keeping the solenoid closed, therefore keeping the starter engaged even after you release the key from START back to RUN. It also sounds like the ignition switch may be keeping power to the hot-in-RUN circuit even after you shut off the key.
Senior User
Joined: Sep 2008
Posts: 311
Likes: 1
From: Waterdown, Ont.
78 150,
Try what FMC400 says first.
If that checks out, then it sounds like your starter solenoid isn't releasing, or your starter drive is stuck. Wouldn't be the first time a solenoid was bad right out of the box...
Hope that helps,
John
Try what FMC400 says first.
If that checks out, then it sounds like your starter solenoid isn't releasing, or your starter drive is stuck. Wouldn't be the first time a solenoid was bad right out of the box...
Hope that helps,
John
Elder User
Joined: Aug 2008
Posts: 701
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i am assuming he means the "s" = starter post on the solenoid the "i" post is for the ignition. the "i" post will bring power to the solenoid and the "s" post will transfer the power to the starter.
if this is wrong feel free to throw rocks at me
if this is wrong feel free to throw rocks at me
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
The 'S' post is hot-in-START power to the solenoid; it makes the solenoid close. When this happens, the two large terminals on either side of the solenoid are connected, jumping the battery to the starter.
The 'I' post is the start bypass signal for the coil. It jumps the battery to the coil while the key is in START to bypass the resistor wire in the wiring harness. If the coil were powered through the ballast while the motor is cranking, the voltage would be too low to fire the coil for the first time, since the battery voltage itself drops while the starter is cranking.
To answer the OP's question, the 'S' post should literally be labelled with an 'S.'
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Junior User
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Just to double check. The brown wire is on the I. The red wire is on the S. Is that correct? I wanna make sure I didn't mix them up.
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Junior User
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ok, so i did crank it again, and the truck did start no grinding or anything. now i turned it on and off a couple more times and on the third try it started the grinding again. I did disconnect the s cable and nothing happened. So does that mean that my starter solenoid is bad? Thanks for all the help fellas.
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
If the starter stays engaged after the key is returned to RUN from START, and pulling the wire from the 'S' post of the solenoid does not alleviate the issue, then the starter solenoid is stuck. In most cases it's because the solenoid is bad (slug gets stuck), which has happened to me before. However, I have heard of cases where the solenoid itself is fine, but the starter overdraws current and welds the solenoid shut. The first case, however, is more likely. It seems like starter solenoids and fuel pumps are the most common items to fail brand new out of the box.
Postmaster
Joined: Apr 2000
Posts: 2,881
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From: North of Tulsa, Oklahoma
Don't know if you solved the issue or not, but thought i'd throw this out there too. I replaced my starter late last year. The dead starter was an American made rebuilt from Oreillys Autoparts with lifetime warranty. The new one they gave me was reman'd overseas.......sigh....... The case and exterior dimensions were all the same. I took it home, installed it, and when starting the truck, i had a horrible grinding sound while the engine ran. After troubleshooting i found that the metal geared piece on the starter shaft was the culprit. The foreign made gear teeth had the right angles cut into them, as the old starter did. Unfortunately, they teeth were almost 1/8in too long. So the gear would throw forward, turn the flywheel to start the engine, then drop back. When it dropped back it was just long enough to scrap the gear sides of the flywheel. I carefully took my grinder to each starter tooth and individually shortened and evened them out. That fixed my issue. Don't know if that is what you are experiencing or not? keep us posted.
