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Discussion Starter · #1 ·
Hey Guy's have a 69 Firebird that I have replaced the original 350 engine with a warmed 455. I also restored the body at this time. Esentually the car was compleatly apart with all of the harneses disassembled. The car also is a 4spd that I had to remove the interlocking steering wheel satey that basicly makes the driver put the car in reversek in order tremove the key and lock the wheel. Anyway the original Dist.was rplaced with an Hei that was gone through by a well known builder of dist. All parts were new or restored as new in the Hei and then wired with a trigger wire from the harness that piks a new relay to 12v from the battery to module. This starts the car and seems to work better than just powering the dist. Directly from the harness.
Now this is where the isue is the car will shut down when the ignition switch is shut off. The relay is getting back fed wih just enough power to keep the pick relay pulled and keep the engine running. I have isolated the back feed to under the dash and I belive that is may be in the steering colum or the ignition switch itself? I ran out of time the other day but just before I didmy little guyvreached in and turned the signel light on and then all of a sudden tge engine shuts down! WTF! Anyone have any ideas? Ignition switch? Grounding issues??
Sorry about the long winded deal just waznted to get it on throad soon and thought maybe someone might have seen this one before?
I do know this th next restoration will without a doubt will be rewired from scratch! I highly recamend it lol!
Thanks :confused:
 

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My thought is that turning on the light by your kid lowered the backfeed enough to allow the relay to drop out. Try putting a blocking diode in series with the relay coil. Or a capacitor in parelle with the relay coil.

You could try disconnecting fuses or wires until the problem goes away. This woill isolate the problem to a known circuit. Then you can track down the problem from there. :welcome:
 

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There's no performance advantage in using a relay, all the HEI knows is the current it's getting- and if it's a switched full battery current circuit, it would have been fine and would have caused no issues.

Unless the relay is also being used as an anti-theft device, I wouldn't use it. Unnecessary complexity. If you keep the relay and use a diode, be sure to put the diode in the wire to the relay "solenoid" (pin 85 or 86, depending), not to the HEI itself. ;)
 

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Discussion Starter · #5 ·
Hey Guy's thanks for the reply's! Much appreciated!
Ok so I have thought about a Diode But this unfortunetly will help me shut the car down but I will no doubt have some sort of issue which may in time possibly come back to bite me in the arse! What puzzles me the most is why do I have an issue with just using a wire from the harness? Voltage seems ok but the car seems like it has a much tougher time starting like this no matter the wire that I use and I do believe that the correct wire is being used to energize the module which is an Msd Heat Module pt#83647. I certainly believe the issue here is my unfortunet inability to afford to do this restoration the correct an proper way. That would have been replaceing the electrical Harness compleatly front to back! Then again there are a bunch more things thatbI would have done that I didn't for the same reasons. Anyway what is the best way to try and pinpoint this sort of issue? I'm still kicking this aound? I might just go out and buy that harness but I 'm not sure it will help at this point?? The issue is under the dash someplace?
Any help is a plus!
 

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Schoust said:
Hey Guy's thanks for the reply's! Much appreciated!
Ok so I have thought about a Diode But this unfortunetly will help me shut the car down but I will no doubt have some sort of issue which may in time possibly come back to bite me in the arse! What puzzles me the most is why do I have an issue with just using a wire from the harness? Voltage seems ok but the car seems like it has a much tougher time starting like this no matter the wire that I use and I do believe that the correct wire is being used to energize the module which is an Msd Heat Module pt#83647. I certainly believe the issue here is my unfortunet inability to afford to do this restoration the correct an proper way. That would have been replaceing the electrical Harness compleatly front to back! Then again there are a bunch more things thatbI would have done that I didn't for the same reasons. Anyway what is the best way to try and pinpoint this sort of issue? I'm still kicking this aound? I might just go out and buy that harness but I 'm not sure it will help at this point?? The issue is under the dash someplace?
Any help is a plus!
Make sure the wire from the harness is large enough (12-14 gauge I would guess, but consult the owners/installation manual for specifics). Also make sure the ignition is connected to a circuit w/adequate fuse protection for the current draw of the ignition box PLUS whatever else the circuit supplies current to.

I like to use an empty circuit in the fuse box for supplying switched 12 v current for the ignition- there's usually circuits (sometimes marked "Aux" or "Acc") supplied for accessories added by the owner.

If you don't have any extra circuits in your fuse box, just be sure the circuit you use is switched w/the ignition key (power w/key in the "ON" and "START" positions only), and that the fuse rating and wire size is adequate for the combined maximum loads.

There should be no difference in how the engine starts when the ignition is powered through the relay or the relay is removed. If you toss the relay you may not be able to use the same circuit that the relay is switching to, to power the ignition- that circuit may be normally powered even w/the key off, like if it was the horn or headlight circuit, for instance.

I would find out what circuit the relay is switching to to power the ignition. If it is a switched 12 v circuit w/adequate wire and fuse capacity, delete the relay and the engine will run the same. If the circuit isn't switched, or has some other fault, use a different circuit, and I suggest looking at the fuse box as I mentioned above for those accessory circuits.
 

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The issue is..... the wire you are useing is getting residual feed back from what ever else is hooked to that circuit..... ie radio memory or something like that. Best bet is to run a new wire, 12 gauge at least, from the ing switch it's self, I used the same terminal that the old dizzy wire was connected to. I eventually bit the bullet and got a wireing kit with a new fuse box etc........ It was the best thing I ever did for the old girl...... eliminated all the elec gremlins and she runs and works like she should........
 

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Discussion Starter · #8 ·
Guy's I have tried this already and there continues to be an issue. In fact that is how I started this project when I put the hei in. Im thinking there is a wire that must be grounding somplace under the dash. Honestly I should have started from scratch and gone with a new fuse box and harness. Anyone have one? Seriously this is sometHing that I do not intend to give up on! So if there is something you can think of that I may be missing don't hesitate to advise!
Thanks!
 

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Discussion Starter · #10 ·
Well I have been kicking this around in my head and have tried to think just what could this issue be related to? Just what did I do besides changing the engine? The only thing that keeps comming back to me is the alternator and charging system. The car has been converted to a later G.M. Two wire plug style. And as I have said HEI Distributor. That utilizes an MSD high perfomance module with rev limitor.
Is it possible that the wireing of the alternator is not correct? Can this backfeed be due to an improperly wired alternator? Does anyone have an example of how this sort of alternator should be wired to an old school charging system? I hate to try and make a problem go away with a diode but if this is the one and only way it can be done then I will go that way. What seems wierd is why does the car seem to start and run so much better useing the pick relay and hot wire directly from the battery?
Guy's there has to be somthing that I'm missing here
 

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Discussion Starter · #12 ·
Funny there was nothing in the instructions indicating that this was required? If there was I surely would have tried it. Is this with all MSD ignition product's? Or just there CD box's? I will try it and see what happens. Any idea what diode I should use and where to get it?
Thanks
 

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New wire directly from the ing switch to the HEI would solve the problem as long as it's straight to the ing sw and nothing else........ a diode placed in line with the existing 12v switched wire to the #1 terminal (exciter wire) on the alt would also solve the problem. (you physicaly cut the wire in half and place the diode in between) remember the band on the diode goes towards the alt

I ran a new set of dakota Digital VHX gauges that use a volt meter and doesn't even have provisions for the idiot light, the light wasn't that critical to me, so for my app I chose not to run a seperate light etc.....

The #1 terminal on the alt is the exciter wire....... tells the alt to start producing juice

The #2 terminal is the sense wire......... tells the alt to produce more or less juice depending on the electrical demands of the system...... GM connected this wire well downstream of the battery and alt to take advantage to the length of wire.... resistance.... to the battery and kinda smooths out the on-off/high-low charging cycle.
 

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Discussion Starter · #14 ·
Do you know what terminal on the switch that I should use? I would prefer to go that route if it will work? Do you know where to get this diode? And what the part # is? Killed me to take my truck to the biggest Muscle car show of the spring in my area! I just have to get to the bottom of this!
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looks like a 1 amp - 400 volt diode would work, I've used them in the past but don't remember where I got them..... Radio Shack carries them....... Model: NTE574 | Catalog #: 55052249 or any electronics parts store in your area, the actual value can vary but the one amp is critical, don't use the mini as this thing will produce a little heat and the smaller ones tend to burn out etc.....


When I dug under my dash for the ing switch problems it was such a mess...... but if I remember there was a large blak switched 12v and a large pink..... but for the life of me I can't remember which one I used to make the connection.
 

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Schoust said:
Funny there was nothing in the instructions indicating that this was required? If there was I surely would have tried it. Is this with all MSD ignition product's? Or just there CD box's? I will try it and see what happens. Any idea what diode I should use and where to get it?
Thanks
Those instructions are for a box like the MSD 6-series, etc. But in cases where the feedback of current is coming from the alternator wire to the indicator lamp in the dash, installing a diode will work, regardless.

There is no reason not to simply use a switched auxiliary or accessory circuit located in the fuse box if you have a "normal" fuse box. There are almost always extra circuits supplied for added on components. Another acceptable way is to cut the resistor wire off a few inches past where it comes out of the firewall bulkhead connector and splice in a non resistor wire in its place. The couple inches of resistor wire makes no difference in the current supplied.
 
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