Need help ASAP

silver_pilate · 08-05-2001, 06:27 PM

Hey guys and gals,

A buddy of mine just got finished hooking up his new motor in his 1984 GT: 347 with AFR 185 heads, Victor Jr intake (I think), and big 750 carb. with a little 150hp shot of the funny.

Anyway, after he finally got it all buttoned up, he started it up. It started right up and ran just fine after he adjusted the fuel pressure. He ran it for a bit at around 2000 rpm for good measure and then shut it off. After that, he had it on and off about 10 or 12 times working with different bits of tuning of his sytem. No problems.

Then, he started it, and the engine backfired out of the carb and shut off. After some checking, he linked it back to his MSD 6AL box.

Here's what's going on as far as we can tell:

The MSD is powered off the factory Duraspark harness. When he checked the wires, for some reason, his switchable 12V lead is now full time.

The other thing is, the car isn't getting any spark when he tries to turn it over. He says when he takes the coil wire off the distributor and lays it on the A/C and manually sparks it with the magnetic trigger, it arcs just fine.

However, when he does the same thing and plugs the trigger back in and tries turning the motor over....nothing....no spark.

Anybody have any ideas??? Why would the car run fine for about 2 days and then just quit? At least we know the engine itself is sound, but what could have shorted out in the electrical systems that could cause this?

Let me know if you have any ideas. He's calling MSD tomorrow to see if they have any clues.

Thanks.

--nathan

------------------
--silver_pilate

'91 GT, Built 306, Wolverine 1087 cam, ported Windsor Jr. Irons, and all the goodies...click the link to the left to see a full list of my mods...

Tried and True 302 Being Built to Outrun You! heh heh heh...
--Texas Panhandle--
Check out my site

[This message has been edited by silver_pilate (edited 08-05-2001).]

silver_pilate · 08-06-2001, 12:22 PM

Anyone?????

--nathan

08-06-2001, 11:58 PM

We got drunk one night and wired up a MSD 5 years ago(wrong). I drove the car for about a week and then it died, the coil went bad. It appeared to be getting spark, apparently not enough though.

08-07-2001, 12:01 AM

Ummm... we assumed we wired it wrong. We took it off after that. I then got a msd 6al and the wiring haress and haven't had any problems since.

PKRWUD · 08-07-2001, 10:53 AM

Good description, tough diagnosis. As far as the switched wire always being hot, the only thing I can think of is a failing switch. Do any other switched circuits have juice when the key is off and the switched MSD wire is hot? If yes, try jiggling the key while someone else watches the MSD wire (with a DMM or a test light) and see if the signal varies. If it does, replace the switch. If it doesn't, check the fuse box where the other affected circuits meet, and you will likely find a melted lead. If no other circuits are hot when the key is off and the MSD wire is hot, then he's got to disconnect only that wire from the harness, and test it again (at the box, not the harness). If it is still hot, there is a short inside the box, and it must be replaced. If it's not, then he must trace that wire into the harness until he finds the source of the voltage.

As far as the no spark condition goes, this may sound stupid, but has he verified that the rotor is still turning with engine rotation? I've seen distributor gears get stripped before from violent intake backfires. If it is working as it should, try attaching a jumper wire securely to the distributor body and to a good, clean ground, other than the engine. Going straight to the battery would be best. Let me know what happens.

Take care
~Chris

------------------
Retired Moderator
MustangNet

My site: JimPorterRacing

RACECAR spelled backwards is RACECAR

HEY !!! Are you ASE Certified ??? If you are, ask me about iATN. The best tool you'll ever have, and it's free !!!

silver_pilate · 08-07-2001, 11:28 AM

Thanks for the ideas.

So far, John has traced the firing problem back to the magnetic trigger itself. MSD is sending him a new one.

He's still stumped on the hot leads, though.

There are several leads that are remaing hot besides the MSD lead, including several dash warning lights that turn on when the ignition is switched on, so I think you may be on the right track, PKRWUD.

He's got a couple of mechanic buddies coming over tonight to trouble shoot. He's going to check the ignition switch and the fuse box first.

Thanks again for the replies. He's eager to get the beast out on the street, and I'm eager to go for a ride in it.

--nathan

PKRWUD · 08-07-2001, 12:50 PM

I'm glad to hear that. Electrical problems are really pretty easy to fix, and almost always can be traced to either a faulty switch or relay, a bad ground, or an overloaded circuit. If all of the ign. switched circuits are hot at all times, my money is on the switch itself, or the lock and tumbler. If jiggling the key has no effect at all on his dash lights (nice when the problem creates it's own test light for ya!), then it's time to check the fuse box. There is likely a wire or terminal at the fusebox that has gotten too hot, and has melted at somepoint, shorting itself to a live wire nearby, or was a live wire that melted itself to the switched circuit. If that turns out to be the case, he needs to determine which of the ign. switched circuits is causing such a high load, and inspect it looking for problems, or run it's high loads from a relay. Did he, by any chance, wire in an electric fan? If wired, without a relay, straight from any circuit, it will cause overheating of the wires in that circuit. They draw such a high load they really must be switched via a relay.

Keep me posted!

Take care
~Chris

------------------
Retired Moderator
MustangNet

My site: JimPorterRacing

RACECAR spelled backwards is RACECAR

HEY !!! Are you ASE Certified ??? If you are, ask me about iATN. The best tool you'll ever have, and it's free !!!

silver_pilate · 08-07-2001, 10:40 PM

Well, thanks for all the help. He got if figured out.

He was under there tonight tearing the interior apart when his arm brushed against his nitrous pressure line going to the guage. He heard a crackle and a click. He was about to ignore it and come back and insulate it better when he decided to check it out.

When he got up top, all the wires were back to normal.

Apparently, there is a switch under the dash somewhere around the headlight switch which had a little bare wire showing. As it turns out, the pressure guage line for John's nitrous rubbed against that bare wire once which activated the switch. When John bumped it into the wire again, it turned it back off.

As soon as he gets his interior back in and the new magnetic trigger from MSD, that beast should be up and running. He says it sounds pretty freakin' mean at idle.

--nathan

------------------
--silver_pilate

'91 GT, Built 306, Wolverine 1087 cam, ported Windsor Jr. Irons, and all the goodies...click the link to the left to see a full list of my mods...

Tried and True 302 Being Built to Outrun You! heh heh heh...
--Texas Panhandle--
Check out my site

PKRWUD · 08-08-2001, 07:08 AM

Well, of course that's what I was going to suggest next. : )

Glad you got it all figured out! Now go break that puppy in and come back here and brag!!!

Take care
~Chris

------------------
Retired Moderator
MustangNet

My site: JimPorterRacing

RACECAR spelled backwards is RACECAR

HEY !!! Are you ASE Certified ??? If you are, ask me about iATN. The best tool you'll ever have, and it's free !!!

PrplMonster · 08-09-2001, 01:52 AM

uhm... dude i am sorry but, PRAISE FUNKIN JESUS YOUR STILL ALIVE!! good to hear it's a-ok tho.. >

08-05-2001, 06:27 PM	#1
silver_pilate DURKA DURKA!! Join Date: Sep 1997 Location: Lubbock, TX...(TX panhandle) Posts: 1,418	Need help ASAP Hey guys and gals, A buddy of mine just got finished hooking up his new motor in his 1984 GT: 347 with AFR 185 heads, Victor Jr intake (I think), and big 750 carb. with a little 150hp shot of the funny. Anyway, after he finally got it all buttoned up, he started it up. It started right up and ran just fine after he adjusted the fuel pressure. He ran it for a bit at around 2000 rpm for good measure and then shut it off. After that, he had it on and off about 10 or 12 times working with different bits of tuning of his sytem. No problems. Then, he started it, and the engine backfired out of the carb and shut off. After some checking, he linked it back to his MSD 6AL box. Here's what's going on as far as we can tell: The MSD is powered off the factory Duraspark harness. When he checked the wires, for some reason, his switchable 12V lead is now full time. The other thing is, the car isn't getting any spark when he tries to turn it over. He says when he takes the coil wire off the distributor and lays it on the A/C and manually sparks it with the magnetic trigger, it arcs just fine. However, when he does the same thing and plugs the trigger back in and tries turning the motor over....nothing....no spark. Anybody have any ideas??? Why would the car run fine for about 2 days and then just quit? At least we know the engine itself is sound, but what could have shorted out in the electrical systems that could cause this? Let me know if you have any ideas. He's calling MSD tomorrow to see if they have any clues. Thanks. --nathan ------------------ --silver_pilate '91 GT, Built 306, Wolverine 1087 cam, ported Windsor Jr. Irons, and all the goodies...click the link to the left to see a full list of my mods... Tried and True 302 Being Built to Outrun You! heh heh heh... --Texas Panhandle-- Check out my site [This message has been edited by silver_pilate (edited 08-05-2001).]

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08-06-2001, 12:22 PM	#2
silver_pilate DURKA DURKA!! Join Date: Sep 1997 Location: Lubbock, TX...(TX panhandle) Posts: 1,418	Anyone????? --nathan

08-06-2001, 11:58 PM	#3
rbatson Guest Posts: n/a	We got drunk one night and wired up a MSD 5 years ago(wrong). I drove the car for about a week and then it died, the coil went bad. It appeared to be getting spark, apparently not enough though.

08-07-2001, 12:01 AM	#4
rbatson Guest Posts: n/a	Ummm... we assumed we wired it wrong. We took it off after that. I then got a msd 6al and the wiring haress and haven't had any problems since.

08-07-2001, 10:53 AM	#5
PKRWUD Junior Member Join Date: Mar 1999 Location: Ventura, California Posts: 8,981	Good description, tough diagnosis. As far as the switched wire always being hot, the only thing I can think of is a failing switch. Do any other switched circuits have juice when the key is off and the switched MSD wire is hot? If yes, try jiggling the key while someone else watches the MSD wire (with a DMM or a test light) and see if the signal varies. If it does, replace the switch. If it doesn't, check the fuse box where the other affected circuits meet, and you will likely find a melted lead. If no other circuits are hot when the key is off and the MSD wire is hot, then he's got to disconnect only that wire from the harness, and test it again (at the box, not the harness). If it is still hot, there is a short inside the box, and it must be replaced. If it's not, then he must trace that wire into the harness until he finds the source of the voltage. As far as the no spark condition goes, this may sound stupid, but has he verified that the rotor is still turning with engine rotation? I've seen distributor gears get stripped before from violent intake backfires. If it is working as it should, try attaching a jumper wire securely to the distributor body and to a good, clean ground, other than the engine. Going straight to the battery would be best. Let me know what happens. Take care ~Chris ------------------ Retired Moderator MustangNet My site: JimPorterRacing RACECAR spelled backwards is RACECAR HEY !!! Are you ASE Certified ??? If you are, ask me about iATN. The best tool you'll ever have, and it's free !!!

08-07-2001, 11:28 AM	#6
silver_pilate DURKA DURKA!! Join Date: Sep 1997 Location: Lubbock, TX...(TX panhandle) Posts: 1,418	Thanks for the ideas. So far, John has traced the firing problem back to the magnetic trigger itself. MSD is sending him a new one. He's still stumped on the hot leads, though. There are several leads that are remaing hot besides the MSD lead, including several dash warning lights that turn on when the ignition is switched on, so I think you may be on the right track, PKRWUD. He's got a couple of mechanic buddies coming over tonight to trouble shoot. He's going to check the ignition switch and the fuse box first. Thanks again for the replies. He's eager to get the beast out on the street, and I'm eager to go for a ride in it. --nathan

08-07-2001, 12:50 PM	#7
PKRWUD Junior Member Join Date: Mar 1999 Location: Ventura, California Posts: 8,981	I'm glad to hear that. Electrical problems are really pretty easy to fix, and almost always can be traced to either a faulty switch or relay, a bad ground, or an overloaded circuit. If all of the ign. switched circuits are hot at all times, my money is on the switch itself, or the lock and tumbler. If jiggling the key has no effect at all on his dash lights (nice when the problem creates it's own test light for ya!), then it's time to check the fuse box. There is likely a wire or terminal at the fusebox that has gotten too hot, and has melted at somepoint, shorting itself to a live wire nearby, or was a live wire that melted itself to the switched circuit. If that turns out to be the case, he needs to determine which of the ign. switched circuits is causing such a high load, and inspect it looking for problems, or run it's high loads from a relay. Did he, by any chance, wire in an electric fan? If wired, without a relay, straight from any circuit, it will cause overheating of the wires in that circuit. They draw such a high load they really must be switched via a relay. Keep me posted! Take care ~Chris ------------------ Retired Moderator MustangNet My site: JimPorterRacing RACECAR spelled backwards is RACECAR HEY !!! Are you ASE Certified ??? If you are, ask me about iATN. The best tool you'll ever have, and it's free !!!

08-07-2001, 10:40 PM	#8
silver_pilate DURKA DURKA!! Join Date: Sep 1997 Location: Lubbock, TX...(TX panhandle) Posts: 1,418	Well, thanks for all the help. He got if figured out. He was under there tonight tearing the interior apart when his arm brushed against his nitrous pressure line going to the guage. He heard a crackle and a click. He was about to ignore it and come back and insulate it better when he decided to check it out. When he got up top, all the wires were back to normal. Apparently, there is a switch under the dash somewhere around the headlight switch which had a little bare wire showing. As it turns out, the pressure guage line for John's nitrous rubbed against that bare wire once which activated the switch. When John bumped it into the wire again, it turned it back off. As soon as he gets his interior back in and the new magnetic trigger from MSD, that beast should be up and running. He says it sounds pretty freakin' mean at idle. --nathan ------------------ --silver_pilate '91 GT, Built 306, Wolverine 1087 cam, ported Windsor Jr. Irons, and all the goodies...click the link to the left to see a full list of my mods... Tried and True 302 Being Built to Outrun You! heh heh heh... --Texas Panhandle-- Check out my site

08-08-2001, 07:08 AM	#9
PKRWUD Junior Member Join Date: Mar 1999 Location: Ventura, California Posts: 8,981	Well, of course that's what I was going to suggest next. : ) Glad you got it all figured out! Now go break that puppy in and come back here and brag!!! Take care ~Chris ------------------ Retired Moderator MustangNet My site: JimPorterRacing RACECAR spelled backwards is RACECAR HEY !!! Are you ASE Certified ??? If you are, ask me about iATN. The best tool you'll ever have, and it's free !!!

08-09-2001, 01:52 AM	#10
PrplMonster Registered Member Join Date: Mar 1999 Posts: 88	uhm... dude i am sorry but, PRAISE FUNKIN JESUS YOUR STILL ALIVE!! good to hear it's a-ok tho.. >