Con't saga of HEI weak spark - Doc (or anyone) take a look at these pics please! - Page 2 - Hot Rod Forum : Hotrodders Bulletin Board
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  #16 (permalink)  
Old 02-16-2007, 03:10 PM
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I've had cars that the module in the HEI did some strange things. That is why I suggest borrowing one if you can - because I'm not sure

Also, did you put dielectric grease under the module before you installed it?

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Old 02-16-2007, 03:11 PM
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Quote:
Originally Posted by docvette
Doc here,

Because the Module as well as the coil relies on a good ground..If your engine as well as your Dizzy is not getting THE SAME good ground, it won't fire..REMEMBER: The PLUGS share the same ground..

A weak coil may provide enough of a jolt to fire ONE plug with a spark, but not enough to fire 8..with a usable spark.

If the module were going thermal, It may be shutting down after a few seconds..Did you have that tested?

Doc
I don't think it's a ground problem, because the engine is well grounded. I have all new battery and ground cables, hooked up to everything using all new hardware. Everything is very clean and tight.

The coil, or the module, or something else in the distributor, may be weak. I've called every NAPA, Pep Boys, Kragen, etc. in my area, and none of them say they can test it!
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Old 02-16-2007, 03:21 PM
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Quote:
Originally Posted by Porschev
Yes, the ground from the battery to the block is good, it is all new hardware and cabling.

The grounding from the alternator to the block, hmm, I don't see any, that seems to rely on mechanical connections. And the alternator is held to the block by way of a long aluminum bracket. Is that not sufficient? (That is how the car has run for 14 years).

Also, I intend to test run the distributor off a completely separate battery. If I connect the + post on that battery to the BATT post on the distributor, and connect the - post on the battery to the body of the distributor (using jumper cables), the distributor should fire, correct?
Doc here,

Even though it ran fine for 14 years...you just had it out..a lot of things can change!

For grounding:

Run a properly gauged Ground cable from the battery to any handy bolt at or near the starter, From that same bolt get a 4 Ga Battery cable at the parts store, that has two 3/8 ring terminals on each end and attach it there and to the Frame.

Next get some 10 gauge wire and ring terminals and run that from your bolt on the block to the Firewall, and another to the Alternator bracket or mount bolt or Grounding lug on the alternator..


HOLE #4 ON THE ILLUSTRATION IS GROUND.

Next get some Wire Braid, (Radio Shack) and install braid from the radiator support to the frame, Fenderwells to frame , hood to firewall, Doors to door posts, gas flap to body, tailgate / Trunk to body.

At each point the wire is grounded, Burnish ALL the paint and grease off to bare metal. Use a proper star-washer and lock. Use sheetmetal or Tech screws where no screws are available.

For testing the coil,




The module can be tested at the Auto parts store, (while your getting grounding supplies) and have it done several times to be sure it is warm and not going thermal....

Another possibility, is if the TACH wire were shorted some where in the body, OR if the calibration card in the tach were going south, Do all your testing with the tach wire OFF at the cap...a bad tach / wire will reduce or kill spark.

Lastly, If all else fails, check the magnetic pickup, inside the dizzy, bad, or intermittent or bent out of adjustment as well as any magnetic shavings can kill spark too..you HAVE to disassemble the Dizzy to repair or replace this part.

Doc
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  #19 (permalink)  
Old 02-16-2007, 03:28 PM
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Quote:
Originally Posted by Porschev
I agree - although the meter seems to read correct on some measurements (for example, the measurements between the BATT and TACH prongs shown in the pictures above seem to be accurate), something seems wrong with the meter and I am no longer relying on it.

Doc here,

If your refering to the "1" on the readout in the photo...

That is ABOVE maximum value..the spec is LESS than an ohm..more like 0.60 Ohms is what your looking for.

Doc
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Old 02-16-2007, 03:34 PM
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Quote:
Originally Posted by Porschev
I don't think it's a ground problem, because the engine is well grounded. I have all new battery and ground cables, hooked up to everything using all new hardware. Everything is very clean and tight.

The coil, or the module, or something else in the distributor, may be weak. I've called every NAPA, Pep Boys, Kragen, etc. in my area, and none of them say they can test it!
Doc Here,

Even the slightest grounding issue can cause resistance to the devices it supplies, which translates to the AMP inside the module not running at full value..The module is a Buffer, and high speed switching amplifier..If it were seeing a bad ground it may not be fully operative. (weak, No spark). Do you have another GM vehicle RUNNING that shares the same parts? Swap them ONE AT A TIME to verify they are good...

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  #21 (permalink)  
Old 02-16-2007, 05:10 PM
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To further clarify the mechanical connections of brackets and bolts, each time you have a mechanical connection this creates a resistance point. If all connections are perfectly clean the resistance or oms is small. If there is the smallest amount of dirt or corrosion, the ohmic value goes up. Do like Doc said with the wiring. You will be right impressed with just how fast your starter turns over as well as how your radio and lights work too.

Basic ohms law is voltage = amps x ohms. when you run the power, amps, thru all of those mechanical connections, including the dizzy to block, if the resistance is too high, you get what is called a voltage drop. This will reduce the amount of voltage available to the dizzy to properly fire the plugs. Having 4 or 5 mechanical connections to the dizzy makes this all the worse.

Your test of powering the dizzy directly and seeing a spark is valid to the point of being a NON LOADED test with full voltage applied. You might actually connect the voltage scale to the coil + and dizzy body and measure the voltage you are putting to the coil. You need not run the engine initially. Then have some one try and start the engine. Measure the to the coil now.

Additionally, measure your battery with nothing turned on. Then crank the engine and see what the voltage drops to. I will drop 1.5 to 2 volts. More than 2 volts indicates too many mechanical connections and voltage drops.
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Old 02-16-2007, 05:19 PM
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Hi guys, thanks for the help and the patience.

I just got back from a shop that tested the distributor and they said it tested fine.

So lots to digest in your most recent posts, I'll start working through it and let ya know!

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Old 02-16-2007, 05:32 PM
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Check the hold down clamp for the dizzy. This clamp must be in place as it is the only ground path for the dizzy.
The gasket under the flange is an insulator and will NOT provide a ground path.

vicrod
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Old 02-16-2007, 11:46 PM
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Bought a new distributor - exact same as the old - some spark at the plugs, but very faint.

I did all of the grounding, except the wire braid stuff on the gas lid, etc.

I rechecked all the existing grounds, took them apart, sanded down the connections (they were all clean), made sure they were all tight (they were), tightened them down again.

Checked the distributor clamp - fine. Tried grounding the distribtor body to the block with jumper cables, made no difference.

Measured at the red 12V wire to the distributor, shows 12V with ignition on, drops to low 10s when cranking.

Took all the plug wires off and reconnected them, one by one, to make sure they were right (although I don't think this should matter, if you pull one plug and it has a weak spark, I can't see how miswiring the plug wires could cause that).

The spark is very, very weak, and the engine shows no signs of starting.

I'm doing all of this with the tach wire disconnected.

Would having the rotor installed 180 degrees off cause the problem? From what I can see, it doesn't matter which way the rotor is mounted to the distributor, as long as it is pointing in the same direction as it was when the distributor was removed from the car.

Also, it is possible, although highly unlikely, that I reinstalled the distributor 180 off. Here's what I did: I pointed the rotor to cyl 1 and took several pictures of the distributor with the cap off BEFORE I removed it from the car. During my work on the engine, I didn't turn the crank. I then reinstalled the dist with the rotor pointing in the same direction.

Question: There is no "fine" adjustment on installing the distributor into the engine. If it easily goes fully down into the block, it is either in correctly, or off exactly 180 degrees, there's nothing in between, right?

I'm really stumped. In 25 years of car ownership, doing all the work on all my cars, I've never, ever had to turn one in to a shop for a no start. I've always been able to just track down air, fuel and spark, and get it running!
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  #25 (permalink)  
Old 02-17-2007, 02:02 AM
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Doc here,

If you installed the Dizzy 180 out, it would backfire (loudly!) I doubt you did that..

You have eliminated every possibility (assuming you have tested properly) that exists for poor spark EXCEPT plug wires..unusual to have them all fail at once, but maybe something got to them chemical wise while cleaning..

There are no other possibility's electrically..

I'd try filling the throat with start fluid and cranking again..It may be a fuel problem.

Doc
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Old 02-18-2007, 12:52 AM
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Wow, what a day, 12 hours of straight work . . .

BUT IT RUNS!!!!

Short version: I f'd up on setting the timing. It was all wrong. Once corrected, it fired up.

Long version, in case your interested. This is kinda embarassing, but what the heck:

Well, I've worked on cars a long time, but this is my first SBC, first American car engine at all. So I'm not well versed on pushrods, distributor driven oil pumps (ahem - clue!), etc. The architecture is just a lot different than the engines I'm used to (CIS and Motronic injected German).

Sooo, when this engine was out, I changed all of seals, including the rear main seal (second clue!).

This is a project that has now stretched out over 5 weeks (third clue).

When I took the engine out, I carefully marked the position of the distributor, and the position of the rotor. I figured since I wasn't planning on moving the crank position, that would ensure the distributor would go back in correctly. In theory . . . I still think that's right.

So a few weeks ago, I change the RMS. As you know, that means remove the oil pump, and remove the bearing end cap. Did that. Put it all back together. Moved on to other projects, which did NOT include putting the distributor back in. I didn't put it in, because it has to be off the engine to get the engine mounted back in the car! It is put in from underneath the car, not dropped in from above like most cars, and it needs to be off for clearance purposes. (More clues).

So several weeks later, I go to put the engine back in, I get it in the car. Time to put the distributor in. I'm thinking, since I didn't turn the crank at all during the process, the distributor can only go in in two different positions, otherwise it won't fit (of course, wrong!). So I'm thinking I only need to make sure the rotor is pointing towards the #1 position on the distributor cap, not 180 degrees the other way.

So I put it on facing towards 1. It goes in. Unfortunately, by pure dumb luck, it goes in completely, and it is pointing ROUGHLY towards 1. It was just pure dumb luck, because I had removed the oil pump, and the position of the driveshaft when I put it back just happened to be such that it would allow the distributor to mount with the rotor roughly pointing to 1. Close enough to make me think it was fine. Had it been turned 45 degrees in either direction, I wouldn't have been able to mount the dist with the rotor pointing anywhere near 1, and I would have had to investigate and probably would have figured it out.

So, off I go, with the distributor many degrees off, thinking it is mounted correctly.

So, no start because the timing is way off. The odd thing, and what I still can't quite figure out, is if the timing is way off, it apparently discombobulates something in the ignition system so that you get weak or no spark if you pull a plug and ground it. Because I was getting no spark most of the time, and very, very weak other.

So that really throws off my diagnostics. I think it has to be some ignition component, falsely believing that even if somthing like timing were way off, or the wires were strung incorrectly (they weren't), it wouldn't matter - it should still spark.

I finally called a friend of mine last night, after midnight (these things gnaw at me until I figure them out). He's a very experienced and knowledgeable mechanic (hi clayton!). After talking it through with him for about 10 minutes, I tried cranking the car. He could tell, from hearing the engine *trying* to crank in the background, over the phone, that something was wrong! Within a couple of minutes, he figured out what I had done wrong. I tried to get working to fix it, but it was almost 1:30 and my wife forced me to get some sleep!

So, today I started to try to fix it. Finding TDC compression for No. 1 was harder than normal, though. Because on the conversion for using the V8 in the engine, they apparently have to use a 6 cyl harmonic balancer! So when the No. 1 cylinder is nearing TDC, the mark on the balancer is never near the pointer (which in fact has been largely ground off the front timing cover, but the remnants can be seen).

I had a bunch of issues trying to find TDC compression No. 1 (see my post in the Engine section if interested). In fact, I'm STILL not sure how to do it. But I gave it my best try, using the "finger in the plug hole" method, followed by the straw in the hole method. Got the cyl to the top, pointed the rotor to 1, and buttoned up.

Still no start.

After more head scratching, I finally tried cranking the engine while rotating the distributor. It finally got to a position where the engine would give some signs of life. Twisting it way to the counterclockwise, I finally got it to fire, but it ran very rough. When I turned the dist clockwise to the right, where it would normally sit, eng would die.

So I figured I still had the rotor positioned a bit too far to the left. Took out the distributor, turned the oil pump tang with a screwdriver, and positioned the rotor one spot to the right.

Fired it up, and it runs now!

So, all the odd things that went wrong:

1) No cranking at all when first reinstalled. Tap on the starter with a hammer freed it and fixed it.

2) No pumping at the fuel pump. Ended up taking apart the pump, cleaning it out, putting it back together and it works fine now.

3) A full week of trying to figure out the ignition problem.

4) Now, tonight, after finally getting it going, I decide to take it around the block to see what happens. Do a couple of laps around the block, definately needs the timing fine tuned! Then, it dies! Now what!

Out of gas!

Sheesh!

But it's running, so I can finally get some rest.

Thanks everyone!
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Old 02-18-2007, 05:43 PM
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Doc here,

DUDE!!! You Have had ONE Crappy week!!!!!!!

I don't know if the other thread helped you, But for future referance..on Static timing...

Cylinder #1 , top dead center, BOTH intake and Exhaust Valves DEAD closed, Timing marks aligned...IF you have this, Mechanical timing is correct..(the crank and cam are right AND you are on #1 Cylinder TDC) If you have this, and the marks don't line up , suspect the crank pulley if it is a replacement, or the TC cover if it is a replacement.The timing still should be good.

NEXT check the position of the rotor...It should point to #1 Plug tower, Traditionally at the 6 to 7 O'clock position on the cap. If not , reset the dizzy to that position, Line up the oil pump shaft, and slowly drop the dizzy in, watch as it seats, the rotor will turn as much as a tower width, note the distance, withdraw the dizzy, and move the rotor BACK that amount and install the Dizzy. This will bring it DEAD on #1 Tower..be sure you have about 15 or 20 degrees of advance/retard clearance before you bolt it up..

Using that procedure It should fire on the first crank EVERY time!!

Next time you pull the mill..after you get it out, engine NOT disturbed, install the dizzy back in, and leave it in until you reinstall the engine, this way, if it gets turned while it's out it won't get out of time..

Well, Good to hear it's up and roaring..

Keep us posted!

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Old 02-18-2007, 06:38 PM
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Thanks, yeah, it was quite a week!

But it is running, although not quite roaring.

The timing is still off, I think. It starts, and runs, but not quite like it did before. That the timing is off is not surprising, since it has not been set in any real manner.

I've tried turning the distributor to a few different positions, but I haven't found the right timing yet.

Any thoughts on how to do that? Keeping in mind I don't have any timing marks on the balancer or the flywheel! I've read about people timing by ear, but I must be deaf, because I can't hear any difference in the way the engine runs at idle when I move the distributor.
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Old 02-18-2007, 06:42 PM
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Doc here,

What's it Idling at ?

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Old 02-18-2007, 06:50 PM
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Doc Here,

Be sure it is warm, Choke wide open, and Idle about 650 RPM for Manual, 950 for automatic, Vacuum Advance Disconnected and Plugged...

With the advance unit approx in the center of it's travel, turn it clockwise, It should slow and , if far enough, sputter..and die or backfire. then rotate it counter clockwise and it will speed up until it gets to a point it won't speed up any more (overadvanced..) back it down about half the distance from center, and that should be ballpark.

Next get a Vacuum gauge out, and put it on a manifold source. start the car and advance / retard the Dizzy until you get max Vacuum. That should be correct.

Doc
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