Ground issues maybe?
Thread Starter
|
New User
Joined: Mar 2018
Posts: 7
Likes: 0
Ground issues maybe?
Been working on my 72/78 f100 4x4 with the 300 6cyl. Pulled engine trans and t case, re installed everything after doing some work and now barely spins over with a good battery and within 10 seconds 1 of the brake lines coming from the master heats up and starts smoking. ( hot to touch ) anyone had this issue or something similar to it. It's grounded to the block and body.
Logistics Pro
Joined: Jul 2005
Posts: 4,217
Likes: 154
Hook up a ground from your engine to your cab. I've never heard of the brake line heating up before! But I have heard of automatic shifter cables frying and seizing in their insulations, due to becoming the body ground by default.
Your battery negative cable runs to the engine block? If it runs to the inner fender, then you need a heavy cable from the inner fender to the engine.
Running the negative battery cable to the engine allows you to run a smaller cable to the body, because the starter is about the only current-draw which requires a fat battery cable-sized ground.
Usually the body ground on Fords is an uninsulated braided flat cable running from a bellhousing bolt to the firewall, where it's attached with a small pointed bolt.
My truck is a '77, but when I got it, the cab ground was missing, and the only symptom I noticed was a bad starter run-on condition. Once I noticed the missing ground and installed one, the problem went away. (Though I changed the solenoid at the same time anyway.)
Your battery negative cable runs to the engine block? If it runs to the inner fender, then you need a heavy cable from the inner fender to the engine.
Running the negative battery cable to the engine allows you to run a smaller cable to the body, because the starter is about the only current-draw which requires a fat battery cable-sized ground.
Usually the body ground on Fords is an uninsulated braided flat cable running from a bellhousing bolt to the firewall, where it's attached with a small pointed bolt.
My truck is a '77, but when I got it, the cab ground was missing, and the only symptom I noticed was a bad starter run-on condition. Once I noticed the missing ground and installed one, the problem went away. (Though I changed the solenoid at the same time anyway.)
Post Fiend
Joined: Apr 2002
Posts: 19,311
Likes: 97
From: Waterloo, Iowa
The symptoms described tell the tale.
The starter is the highest current draw by far, somewhere around 200 amps DC @12 volts, it is obviously "hunting" for a ground. It doesn't care where it gets it, but it might get the current it needs through something not designed to carry electricity. This is one reason why good fresh cables of adequate gauge, tightened securely, are so important. Shift cables and throttle cables are other usual culprits.
Make sure there isn't any paint interfering with any of the ground points or cable connections too. Three main cables - from (NEG) battery terminal direct to engine block, or maybe a starter bolt. From block to frame. From block to firewall.
The starter is the highest current draw by far, somewhere around 200 amps DC @12 volts, it is obviously "hunting" for a ground. It doesn't care where it gets it, but it might get the current it needs through something not designed to carry electricity. This is one reason why good fresh cables of adequate gauge, tightened securely, are so important. Shift cables and throttle cables are other usual culprits.
Make sure there isn't any paint interfering with any of the ground points or cable connections too. Three main cables - from (NEG) battery terminal direct to engine block, or maybe a starter bolt. From block to frame. From block to firewall.
Laughing Gas
Joined: Mar 2010
Posts: 1,028
Likes: 5
From: San Francisco East Bay
Been working on my 72/78 f100 4x4 with the 300 6cyl. Pulled engine trans and t case, re installed everything after doing some work and now barely spins over with a good battery and within 10 seconds 1 of the brake lines coming from the master heats up and starts smoking. ( hot to touch ) anyone had this issue or something similar to it. It's grounded to the block and body.
My suspicion is that something hot is grounding through the Dual Brake Switch.
Follow through the ignition sequence:
Yeah, I wrote this up for a 1970, but your's should be close enough.. maybe some of the wire colors are different.
It almost sounds like it's shorting at the ignition switch.
Assuming that it wasn't doing the same before your work, what work did you do that might have impacted any of the wiring?
Trending Topics
Posting Guru
Joined: May 2001
Posts: 1,395
Likes: 4
From: Cupertino
Ground battery to block.
If the ground is put to the frame or elsewhere on the chassis, starter current has to find paths as descried above. Like through brake lines.
If the ground is put to the frame or elsewhere on the chassis, starter current has to find paths as descried above. Like through brake lines.
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
10 Best Ford Truck Engines We Miss the Most!
Joe Kucinski
2026 Shelby F-150 Off-Road: Better Than a Raptor R?
Brett Foote
2027 Super Duty Carhartt Package First Look: 12 Things You NEED to Know!
Michael S. Palmer
10 Most Surprising 2026 Ford Truck Features!
Joe Kucinski
Top 10 Ford Trucks Coming to Mecum Indy 2026
Brett Foote
5 Best / 5 Worst Ford Truck Wheels of All Time
Joe Kucinski
Ford Super Duty: 5 Things Owners LOVE, 5 Things They LOATHE!
Joe Kucinski
Every 2026 Ford Truck Engine RANKED from WORST to FIRST!
Michael S. Palmer
The Best F-150 Deal of Every Trim Level (XL through Raptor)
Joe Kucinski
Hotshot
Joined: Mar 2013
Posts: 14,255
Likes: 199
From: Phoenix, Az.
2X. Funny how 12V DC electrical gremlins are usually ground related.
Thread
Thread Starter
Forum
Replies
Last Post
WindsorF100
Brakes, Steering, Suspension, Tires, & Wheels
4
Jun 27, 2007 11:56 PM
zsir
1967 - 1972 F-100 & Larger F-Series Trucks
7
Apr 24, 2003 10:38 PM