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could a ground connection (the actual EARTH) affect electronic ignition?

DS
dave silva
Sun, Jun 6, 2021 4:36 PM

First, i was an aircraft electrician in another life, i understand about gremlins and weird things that suddenly start working for no apparent reason.

SO this happened, the other day i went to start the coach to move it so it could  be a guest cottage for visiting family.  It would not start, i
ordered new distributor, got educated on HEI components and everything was fine.

I moved the coach and plugged it in.

A while back i had a problem with hot skin. I never figured it out and it was no longer happening but just to  be safe i drove a  rod in the ground
and and put a jumper cable to the bumper.

The family came, we had a nice visit and they left.

Today the coach won't start- no spark.

I revisit all my previous troubleshooting, i have voltage to the coil but no spark.

So, i get another cup of coffee then return to the coach, look everything over once more, and prepare to pull it with my truck.

I unplug it and remove the ground rod.

For no good reason i turn the key and it starts right up.

Electrically, the only thing different was the removal of the ground rod.

Does this make any sense ot anyone? Or do we chalk it up to gremlins ?

Thanks

Dave & Ellen Silva
Hertford, NC

76  Birchaven, 1-ton and other stuff

Currently planning the Great american Road Trip Summer 2021

It's gonna take a lot of Adderall to get this thing right.

First, i was an aircraft electrician in another life, i understand about gremlins and weird things that suddenly start working for no apparent reason. SO this happened, the other day i went to start the coach to move it so it could be a guest cottage for visiting family. It would not start, i ordered new distributor, got educated on HEI components and everything was fine. I moved the coach and plugged it in. A while back i had a problem with hot skin. I never figured it out and it was no longer happening but just to be safe i drove a rod in the ground and and put a jumper cable to the bumper. The family came, we had a nice visit and they left. Today the coach won't start- no spark. I revisit all my previous troubleshooting, i have voltage to the coil but no spark. So, i get another cup of coffee then return to the coach, look everything over once more, and prepare to pull it with my truck. I unplug it and remove the ground rod. For no good reason i turn the key and it starts right up. Electrically, the only thing different was the removal of the ground rod. Does this make any sense ot anyone? Or do we chalk it up to gremlins ? Thanks -- Dave & Ellen Silva Hertford, NC 76 Birchaven, 1-ton and other stuff Currently planning the Great american Road Trip Summer 2021 It's gonna take a lot of Adderall to get this thing right.
BH
Bruce Hislop
Sun, Jun 6, 2021 5:58 PM

One thing on the Hot Skin issue.  Do you have an electric hot water heater?  If the heating element goes bad (usually from low water in the water
heater tank), you can get issues like hot skin and/or tripping GFI outlets.

One cause of intermittent HEI problems is the pickup coil in the distributor.  The vacuum advance is continuously moving the plate on which the pickup
coil is mounted, back and forth causing the wires from the pickup to the module to flex continuously. Eventually they break.  This will cause
intermittent issues as the tips of the wire strands where the break is will connect/disconnect.

Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that

One thing on the Hot Skin issue. Do you have an electric hot water heater? If the heating element goes bad (usually from low water in the water heater tank), you can get issues like hot skin and/or tripping GFI outlets. One cause of intermittent HEI problems is the pickup coil in the distributor. The vacuum advance is continuously moving the plate on which the pickup coil is mounted, back and forth causing the wires from the pickup to the module to flex continuously. Eventually they break. This will cause intermittent issues as the tips of the wire strands where the break is will connect/disconnect. -- Bruce Hislop ON Canada 77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.1 ton front end http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001 My Staff says I never listen to them, or something like that
JR
John R. Lebetski
Sun, Jun 6, 2021 7:55 PM

Even if there is hot to chassis, the ground in the mains cable should earth it and take care of hot skin.  Which indicates multiple issues.
Depending where your faults are there are different scenarios. Assuming your hot skin is 125 to the body (aluminum) and you put the added ground to
bumper (frame), that would put 125VAC across the ground that ties body to frame which I think is a woven strap at rear of engine. There may be other
loop paths as well.
If you know your building receptacle is known good, I would remove and inspect your shore 14-50 cord set and inspect it’s termination in fuse panel.
Any lumps or bulges in cord indicate compromised conductors or Insulation. You can buy a replacement cord set on Amazon or cut the female end off a
14-50 extension cord to make a nee one.  I always “ over/under” coil my cord into the storage area to prevent stressing the 4 conductors.
As far as the water heater goes, disconnect neutral and hot at element and put wirenuts on ends. Use Ohms low scale on BEEP and you should have
nothing from either heater terminal to case ground.

--
John Lebetski
Woodstock, IL
77 Eleganza II

Even if there is hot to chassis, the ground in the mains cable should earth it and take care of hot skin. Which indicates multiple issues. Depending where your faults are there are different scenarios. Assuming your hot skin is 125 to the body (aluminum) and you put the added ground to bumper (frame), that would put 125VAC across the ground that ties body to frame which I think is a woven strap at rear of engine. There may be other loop paths as well. If you know your building receptacle is known good, I would remove and inspect your shore 14-50 cord set and inspect it’s termination in fuse panel. Any lumps or bulges in cord indicate compromised conductors or Insulation. You can buy a replacement cord set on Amazon or cut the female end off a 14-50 extension cord to make a nee one. I always “ over/under” coil my cord into the storage area to prevent stressing the 4 conductors. As far as the water heater goes, disconnect neutral and hot at element and put wirenuts on ends. Use Ohms low scale on BEEP and you should have nothing from either heater terminal to case ground. -- John Lebetski Woodstock, IL 77 Eleganza II
KB
Ken Burton
Mon, Jun 7, 2021 7:15 AM

There are 3 different electrical systems on a GMC:

  1. the 12 volt DC system powered by the engine alternator
  2. the 12 dc sstemm powered by the converter and storage batteries for things in the house.
  3. the 12-/240 volt AC system powered by the shore power cable which plugs into a commercial power pedestal or the Onan.

The only system that has a reference to earth ground is commercial power. (#3)  There is no connection between #1 one above which run the engine
ignition and #3 about which is commercial power.

Your "hot body/skin." has has two issues.  What made it hot in the first place and why did not the green wire ground in the shore power cable not
conduct the voltage back too earth ground.

You have 2 or 3 different issues here.

Shoot them one at a time.

Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

There are 3 different electrical systems on a GMC: 1. the 12 volt DC system powered by the engine alternator 2. the 12 dc sstemm powered by the converter and storage batteries for things in the house. 3. the 12-/240 volt AC system powered by the shore power cable which plugs into a commercial power pedestal or the Onan. The only system that has a reference to earth ground is commercial power. (#3) There is no connection between #1 one above which run the engine ignition and #3 about which is commercial power. Your "hot body/skin." has has two issues. What made it hot in the first place and why did not the green wire ground in the shore power cable not conduct the voltage back too earth ground. You have 2 or 3 different issues here. Shoot them one at a time. -- Ken Burton - N9KB 76 Palm Beach Hebron, Indiana
JB
Johnny Bridges
Mon, Jun 7, 2021 12:27 PM

What Ken said.  First, find and correct the hot skin... that one has the potential to hurt you.  Once you've got the AC system happy, go looking at
the spark/lack of spark problem.  If you go to a new distributor, be wary if it's from a Web provider.  Many of these use 'hashimoto mouse' modules
which may or may not be particularly robust.  I like Delco modules - they may be overseas sourced, but to a higher quality standard.  I'd look real
hard at the contact pin in the middle of the distributor cap, and pop off the rotor and look for carbon tracks.  There are a lot of places where the
high voltage gets reasonably close to the housing... any which show lower resistance to ground than a wire/plug gap will kill the spark.  Keep after
it, better to heal it in the backyard than beside the highway.
50+ years of broadcast engineering taught me, gremlins (intermittents) NEVER go away by themselves, they eventually recur, usually at 7AM on Thursday
morning.  It's advantageous to chase them down when the aux plant is running and they're not going to cost money when they appear, pretty much
regardless the time involved.

--johnny

--
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs.  They must answer to me in hell

What Ken said. First, find and correct the hot skin... that one has the potential to hurt you. Once you've got the AC system happy, go looking at the spark/lack of spark problem. If you go to a new distributor, be wary if it's from a Web provider. Many of these use 'hashimoto mouse' modules which may or may not be particularly robust. I like Delco modules - they may be overseas sourced, but to a higher quality standard. I'd look real hard at the contact pin in the middle of the distributor cap, and pop off the rotor and look for carbon tracks. There are a lot of places where the high voltage gets reasonably close to the housing... any which show lower resistance to ground than a wire/plug gap will kill the spark. Keep after it, better to heal it in the backyard than beside the highway. 50+ years of broadcast engineering taught me, gremlins (intermittents) NEVER go away by themselves, they eventually recur, usually at 7AM on Thursday morning. It's advantageous to chase them down when the aux plant is running and they're not going to cost money when they appear, pretty much regardless the time involved. --johnny -- Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons. Braselton, Ga. I forgive them all, save those who hurt the dogs. They must answer to me in hell