Help with engine grounding please.
Thread Starter
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Fleet Mechanic
Joined: Apr 2004
Posts: 1,443
Likes: 5
From: Willamette Valley, Oregon
Help with engine grounding please.
I have been having an unbelieveable amount of trouble figuring out why my 302 runs poorly at an idle. I have changed most evrything. Someone mentioned checking the ground from the engine.
Well, here is what I found: There is the negative cable from the battery(12V) going from the bat to one of the starter bolts. there is no cable going to the frame from the bat. there is no cable going from the engine to the frame.
Please, two questions.
1. What should the cable situation be?
2. Could this be responsible for a idle problem/miss?
ANY comments very welcome!!! I am pulling my hair out at this point (and I aint got much left!)
Thanks!
56 F-100 with a 73 302.
Well, here is what I found: There is the negative cable from the battery(12V) going from the bat to one of the starter bolts. there is no cable going to the frame from the bat. there is no cable going from the engine to the frame.
Please, two questions.
1. What should the cable situation be?
2. Could this be responsible for a idle problem/miss?
ANY comments very welcome!!! I am pulling my hair out at this point (and I aint got much left!)
Thanks!
56 F-100 with a 73 302.
Postmaster
Joined: Dec 1999
Posts: 2,813
Likes: 6
From: Connecticut
Most of the 302's were grounded to a spot in the area under the alternator on the block. I would find a spot and ground it off the bock. Make sure it's clean and the cable end is good and tight and clean. It probably wouldn't hurt to ground it from the frame to the block also. The starter is a bad place to do a ground.
Your problem at idle could be many things. If you've checked all the usual things such as carb, plugs , wires, all specs, I would look and see if it has the carb spacer with the PCV hose on it still. Check for vac leaks around the gaskets and the hose itself.These plates get clogged after years of use and I've even seen some rot out. They will suck air thru this area and it will run really bad at idle.
Barry
50 F-1
Your problem at idle could be many things. If you've checked all the usual things such as carb, plugs , wires, all specs, I would look and see if it has the carb spacer with the PCV hose on it still. Check for vac leaks around the gaskets and the hose itself.These plates get clogged after years of use and I've even seen some rot out. They will suck air thru this area and it will run really bad at idle.
Barry
50 F-1
old and in the way
Joined: Jul 1997
Posts: 5,923
Likes: 1,052
From: Lovely Hueytown Alabama
Pack,
I don't know about the miss at idle but I can approach your problem from the electrical side.
You need a good ground path for all electrical systems in the truck. Lights, heater, radio, etc.. I've chased enough intermittent problems with stereos and ham radios to know. Your engine should be grounded to the frame. The body of the truck, bed of the truck and front sheetmetal should also. You can't depend on body bolts or sheet metal bolts to do this. A good bare metal connection on each end and perferrably a soldered lug(but crimp will do) connected by a heavy guage wire ( I used to use regular battery cable)
You can eliminate static and ignition noise in your stereo, dim lights in the instrument panel and flickering tail light and trailer lights with a good ground system.
I can see where insufficient ground could cause a low speed miss simply due to low voltage. The frame is the return path for the 12 volt dc system. Besides, what can it hurt ?? you can hide all of these ground straps easily enough and then you know you've done away with a potential problem...
later
John
I don't know about the miss at idle but I can approach your problem from the electrical side.
You need a good ground path for all electrical systems in the truck. Lights, heater, radio, etc.. I've chased enough intermittent problems with stereos and ham radios to know. Your engine should be grounded to the frame. The body of the truck, bed of the truck and front sheetmetal should also. You can't depend on body bolts or sheet metal bolts to do this. A good bare metal connection on each end and perferrably a soldered lug(but crimp will do) connected by a heavy guage wire ( I used to use regular battery cable)
You can eliminate static and ignition noise in your stereo, dim lights in the instrument panel and flickering tail light and trailer lights with a good ground system.
I can see where insufficient ground could cause a low speed miss simply due to low voltage. The frame is the return path for the 12 volt dc system. Besides, what can it hurt ?? you can hide all of these ground straps easily enough and then you know you've done away with a potential problem...
later
John
Thread Starter
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Fleet Mechanic
Joined: Apr 2004
Posts: 1,443
Likes: 5
From: Willamette Valley, Oregon
So, the negative cable SHOULD be going from the battery to the block? What bolt? and it would be good to have a seperate (flexable) strap from the frame to the block?
Thanks..
Thanks..
Posting Guru
Joined: Jul 2001
Posts: 2,119
Likes: 2
From: Southern New Hampshire
If the battery is mounted under the passenger side floor then going directly from the - terminal to a starter bolt is a GOOD idea as it is the shortest path to the engine. Ford originally ran a battery ground to the frame and then ran another cable from further foreward on the frame to the front of the engine. Over the years the frame connections become poor plus the total path length is overly long.
I use 1 to 1.5" wide flat braided cable for most of my grounds as I can usually find a large variety of lengths premade with lugs at ham radio fleamarkets as well as at computer and other electrical scrap shops; prices are a lot cheaper than store bought cables. It comes either bare or with various colors of insulation from clear to black. Since it is flat it is easy to maneuver and dress so as to be unobtrusive. Im another believer that you can never have too many grounds; cab, bed, front sheet metal, hood, etc. With almost 50 years of operating ham radio in vehicles Ive learned most of the tricks to a quiet and trouble free electrical system.
I use 1 to 1.5" wide flat braided cable for most of my grounds as I can usually find a large variety of lengths premade with lugs at ham radio fleamarkets as well as at computer and other electrical scrap shops; prices are a lot cheaper than store bought cables. It comes either bare or with various colors of insulation from clear to black. Since it is flat it is easy to maneuver and dress so as to be unobtrusive. Im another believer that you can never have too many grounds; cab, bed, front sheet metal, hood, etc. With almost 50 years of operating ham radio in vehicles Ive learned most of the tricks to a quiet and trouble free electrical system.
