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 Post subject:
PostPosted: Sat Dec 27, 2008 9:33 pm 
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TBI Slant 6
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Location: Mandeville, LA, USA
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I found this on a previous post.
Quote:
I'm having trouble getting my truck to start. It's a 1976 D-100 with 225 manual trans. When I turn the ignition to start position and everything works just like it should. The engine turns over but will not "take off" instead, I release the igniting from the start to the run position sometimes the engine will continue to run, other times it won't. I have replaced the ballast resistor, voltage regulator and coil. I don't know where to go from here and was hoping someone here has maybe experienced this before??

SS Dan responded: Probably a faulty ignition switch or wiring between the ignition switch and the ignition system — I bet you're not getting voltage to the ignition system when the key is in the "start" position. To test this, first make sure the parking brake is on and the transmission is in Neutral. Turn the key to "On" (not "Start"). Then go under the hood and operate the starter by using a screwdriver to connect the two large terminals on the starter relay or the two terminals on the starter itself. If the engine starts and runs, replace your ignition switch and/or repair the wiring.
So I tried this test by placing transmission in neutral, putting key in run and using large screwdriver to touch both terminals of starter. The starter engaged, however the engine did not start. The starter has been tested and is good. The voltage regulator is new. The Electronic Ignition Control Unit is new. The coil and ballast resistor are not new. The distributor cap is new. The distributor and rotor are not new.

Wiring problem?

Starter solenoid?

Starter relay?

Fusible link?


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 Post subject:
PostPosted: Sat Dec 27, 2008 10:31 pm 
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Supercharged
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Joined: Sun Nov 03, 2002 9:20 pm
Posts: 13095
Location: Fircrest, WA
Car Model: 76 D100
It sounds like you have a bad connection somewhere in the coil power circuit. You should be getting at least 12 volts at the coil + terminal. If the motor turns over, you have no problems with any of the starting circuit. It sounds like your problem is somewhere in the coil power circuit.

Using your multimeter and a wiring diagram, start at the battery and trace the voltage level through the entire power circuit for the coil. Check voltage at the battery, the bulkhead connector on the firewall, the fuse box, the ignition switch (before and after the switch), the firewall connection (again), both sides of the ballast resistor, etc...

Note where the voltage drops from 12+ and start searching there for the short or bad connection.

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 Post subject:
PostPosted: Sun Dec 28, 2008 12:46 pm 
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Supercharged
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Joined: Mon Jan 15, 2007 5:05 pm
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Location: Black Diamond, WA
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I had the same problem and ended up buying new wire ends/terminals, they had them in bulk at out local auto parts and rewired the engine harness. One of the alternator wires burned through and melted a portion of my harness causing the oil light to flicker and low voltage at the coil. It didn't take long after I had purchased all the correct colors of wire. I just did them one at a time.

So with new ends and wire I got the full 12 volts at the coil.

If your fire wall resistor connectors look burned from getting hot over the years, I would replace them for a good connection. I also switched to the resistor that is fully potted/sealed.

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 Post subject:
PostPosted: Sun Dec 28, 2008 1:36 pm 
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Quote:
Wiring problem?
Quite possibly.
Quote:
Starter solenoid? Starter relay? Fusible link?
No, no, and no. Don't just guess at random. It won't get you anywhere, it'll just suck up your time and money. Done your reading assignment yet…?

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PostPosted: Sun Dec 28, 2008 2:03 pm 
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Turbo Slant 6

Joined: Tue Jun 14, 2005 8:29 pm
Posts: 797
Location: Raleigh, NC
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Hello,

Because I am a truck man I have followed this with interest. I wish I was there to show you because no doubt about it, you are trying very hard to master many interrelated fundamentals from what seems to be a your first entry into doing mechanics more advanced than a tire change. Stick with it because just as with calculus there comes a time when you don't remember not knowing what to do. It just happens if you work systematically as your correspondents regarding the ignition parts of the thread are suggesting.

There is still something that you can do that I have done and still do that moved me from totally ignorant to being a diagram reader to being an understander of auto electronics. Since you have a published wiring diagram (be aware they change from year to year) I think you should make what I call a functional wiring diagram....your own map of your wires.

Open the hood. Take a blank piece of 11 x14 paper. Put it on a flat board and put the board on your fender. Lean in and sketch every wire you see. Make whatever symbols you want for the coil, alternator, distributor, temp sender, headlights, everything. Make pencil lines representing each wire you see and "connect" each one to where it goes to and comes from. Make notes about its color and size. It is useful to do the heavy ignition side (battery, starter,) but since you know your starter is fine, not so important now. Just sketch everything else.

Undo your starter from the dash by unscrewing its bezel. Look how the wires mate up to the back of the switch. See if all the wires you are looking at and sketching match to the ones on your diagram. Once you know your published diagram matches what you are finding (or not) you should begin to feel that you could run wires to substitute for what is on your published diagram if need be. At that point you should be able to say to your self I see an electrical path runs straight from IGN to the coil by going from A to B to C. Now you need to know what that switch is switching on or off.

Now sit in the cab with your switch. You should be able to pull the metal part that the key goes in loose from the back...the "switch" merely plugs into a multi wire socket. Hold the switch in one hand and with the other set your voltohmmeter to "ohms". Put your probes into the tabs on the back of the switch (the tabs that plug into the socket) On your pad of paper make a sketch of what happens to continuity when your key moves from Run to ST. When they key is turned to ST you bypass part of your circuit and that will be shown in continuity from some tabs and not from others. Look at your sketch and see which wires have continuity when the key is on ST, and which have continuity on RUN. You need to know these things to troubleshoot instead of just guessing what might be wrong.

Now check your understanding of where continuity and thus voltage should be at different key positions by making a prediction on you sketch and check it with jumpers. Get one or two 10 to 15 fool long pieces of wire to jump from say, a coil (+) or (-) or two sides of the resistor , all the way around your cab through the window. Mash your switch back into the socket but leave the switch undone from the dash. With the voltmeter and jumper wires that you KNOW where they are coming from you can rotate your ignition switch from IGN to ST to ACC . Measure your voltages on your jumpers and see if you have voltage where you predict.

This is not hard to do, but will take a mellow saturday if you go slow. Once you know what is supposed to be happening it is easy to see if it not happening. On the other hand, measuring voltages without knowing what is supposed to happen will only get you a table of voltages and not much advance in understanding. Once you understand you can do all kinds of rewiring safely. I could never have put in a GM alternator plus a pertronix dizzy and an MSD system and removed the ballast and firewall voltage regulator without know what was supposed to happen when that key moves from Off to ST to Run. Knowig that you can add the relays and fusible links and other things the accountants had Mopar leave out. you can put your components where you want them, too.

rock
'64d100


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 Post subject:
PostPosted: Sun Dec 28, 2008 5:32 pm 
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Turbo EFI

Joined: Tue Jan 06, 2004 11:21 pm
Posts: 1391
Location: long beach ca
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Been shakeing my head all tru this post,I am sorry,,,,if you dont know what a test light is,and dont own one,you need to bring the car to someone that does,not trying to put you down,but this is takeing way too long,I think a good mechanic could get it running in less than a hour,I know I could,PLEASE get anouther set of mechanic eyes on it,and have him explain to you what you missed.MY OPINION.mark


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 Post subject:
PostPosted: Sun Dec 28, 2008 6:30 pm 
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TBI Slant 6
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Joined: Sat Jan 21, 2006 11:47 pm
Posts: 236
Location: Mandeville, LA, USA
Car Model:
Quote:
If you don't know what a test light is and don't own one, you need to bring the car to someone that does.
Test Light - A tool for automotive technicians to use to diagnose electrical problems on automobiles. This tool consists of a case to hold probe, circuit, LED's and a means to connect said tool to an automobile. Two lights, first light to tell the operator the tool is ready for use and that the electrical connections to the storage battery are complete to the second light. Second light illuminates when said probe is in contact with automobile system and continuity of said circuit exists. SOUNDS EASY. I'LL HAVE ONE TOMORROW.

That defeats the purpose of this restoration. This project is for my son and I. It would be too easy to give it to a mechanic to fix. What would my son and I learn?
Quote:
Not trying to put you down, but this is taking way too long. I think a good mechanic could get it running in less than a hour. I know I could. PLEASE get another set of mechanic eyes on it, and have him explain to you what you missed.
I apologize if this inconvenient to anybody. If it bothers you, then don't respond. If it is such an inconvenience, complain to the moderators and request they kick me off this site.

madmax/6 in California, I also wish you were closer to me here in Louisiana, however I couldn't take advantage of you and allow you to do my job. Your responses on this forum are very much appreciated. Thank you for your offer.

All in all, I am having fun. It is satisfying to diagnosis and solve one problem, even though another pops up. I'll get there.


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 Post subject:
PostPosted: Sun Dec 28, 2008 6:35 pm 
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TBI Slant 6
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Joined: Sat Jan 21, 2006 11:47 pm
Posts: 236
Location: Mandeville, LA, USA
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Quote:
Done your reading assignment yet…?
Thanks Dan, I have several manuals including the 73 FSM. I'll pick up the two other books. I also have a 73 Dart Sport waiting in the wings to restore. More good reading and I even don't have to pay for mechanic school.


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 Post subject:
PostPosted: Sun Dec 28, 2008 8:49 pm 
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4 BBL ''Hyper-Pak''
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Joined: Tue Dec 23, 2008 6:00 pm
Posts: 37
Location: Fayettenam NC
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been watchin this and i say keep on goin.i have an 84 w150 p/u that i rebuilt. I tookout the lean burn and replaced it with an elec. ign. i also studied the wiring diagram for 2 months in order to rewire the underhood and dash harnesses.been at it for a year now but rosie :twisted: purrs like a kitten gettin a good stroke. nothin like gettin that rumble good luck 8)


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 Post subject:
PostPosted: Sun Dec 28, 2008 8:54 pm 
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Turbo EFI
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Joined: Sat Nov 29, 2003 5:45 pm
Posts: 1903
Location: Hamilton the STEEL CITY, ON
Car Model:
Quote:
2. I removed the coil, took it to Advance Auto, and watched as they put a multimeter on 20k, the number 1 came on, the store manager put the black lead on the negative coil terminal and the red lead on the positive coil terminal. The multimeter went to zero. The store manager said the coil was good.
If the multimeter went to zero resistance when testing any combination of terminals on the coil that means it is SHORTED, smack the manager on the head. Then buy a new coil from another store not staffed by idiots. Try that out and we will move on to the next problem.
Quote:
Test Light - A tool for automotive technicians to use to diagnose electrical problems on automobiles. This tool consists of a case to hold probe, circuit, LED's and a means to connect said tool to an automobile. Two lights, first light to tell the operator the tool is ready for use and that the electrical connections to the storage battery are complete to the second light. Second light illuminates when said probe is in contact with automobile system and continuity of said circuit exists. SOUNDS EASY. I'LL HAVE ONE TOMORROW.


No, don't do that. Buy a multimeter and learn how to use it. I am currently working on an article that will walk you through it, watch for that in the articles section.

Test lights will NOT tell you how much voltage you have at your test points. that is essential information when trying to isolate a bad connection. mark this is the worst time to introduce someone to test lights, it will start a lifetime of bad habits. Take the time to teach someone the right way and they will become a better mechanic, faster.

my opinion...

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 Post subject:
PostPosted: Sun Dec 28, 2008 9:41 pm 
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4 BBL ''Hyper-Pak''

Joined: Wed Nov 19, 2008 5:29 pm
Posts: 47
Location: boise idaho
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Your engine should start with a bad ballast resistor, since the resistor is bypassed with the key in "start" position. As soon as you release it to run, it should die. You could temporarily connect the two terminals from the ballast with a jumper wire to see if that is the problem.
I had this same aggravating no start situation when I was a bit younger. Called an old timer mechanic. He said to squirt some oil into the cylinders, replace the spark plugs and give it a try. He explained that we had probably flooded the cylinders with gas, and there may not be enough compression to fire. We tried it and it caught in about two cranks!
The other thing I would say is to pull number 1 plug, stick a finger in the hole and when compression blows out your finger, line up the timing mark. Then make sure your wires are lined up correctly. This timing should be plenty close to start the engine, then do your fine tuning. Good luck

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I'm sure I can do this without disconnecting the battery. What could possibly go wrong?


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 Post subject:
PostPosted: Mon Dec 29, 2008 10:10 pm 
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TBI Slant 6
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Joined: Sat Jan 21, 2006 11:47 pm
Posts: 236
Location: Mandeville, LA, USA
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Bought a new coil today. Did all the tests on it with multimeter. The new coil had the same readings as the old coil.

So I pulled the wire from the distributor center tower and the other end that plugs into the coil tower. Using the multimeter I put the red lead in one end of the wire and the black end in the other end of the coil/distributor wire expecting the multimeter to go from 1 to zero. It bounced around 16 and never went to zero. Could this be the problem?


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 Post subject:
PostPosted: Mon Dec 29, 2008 10:13 pm 
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Supercharged
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Joined: Sun Nov 03, 2002 9:20 pm
Posts: 13095
Location: Fircrest, WA
Car Model: 76 D100
What setting was your multimeter on? Ohms? Volts?

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 Post subject:
PostPosted: Tue Dec 30, 2008 7:46 am 
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TBI Slant 6
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Joined: Sat Jan 21, 2006 11:47 pm
Posts: 236
Location: Mandeville, LA, USA
Car Model:
Quote:
What setting was your multimeter on? Ohms? Volts?
It was set to ohms. I set it to 20k, 200k, and one other setting in the ohm section of the multimeter. Same results on all settings. I did not use the volts setting to test resistance on the wire.

I was told this morning that the coil/distributor wire will not go to zero - they are designed to have some resistance in them. Is this correct?


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 Post subject:
PostPosted: Tue Dec 30, 2008 9:40 am 
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Supercharged
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Joined: Sun Nov 03, 2002 9:20 pm
Posts: 13095
Location: Fircrest, WA
Car Model: 76 D100
Usually, yes.

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