Pic of my van (and some issues with spark.....still)

[Tokay]

So here it is in all it's almost-a-rustbucket glory. Someday soon (before summer), this thing will be my go anywhere machine, but for right now, it's a several thousand pound paperweight. Yes, that's a tow sticker on it, but it's only there because I forgot to tell my apartment manager it's mine....

http://a145.ac-images.myspacecdn.com/images01/42/l_5cec19e0aafbd5d952e0d3f9d55776e0.jpg

Anyway, I got around to checking spark BEFORE it reaches the distributor by holding the cable from the coil close to the block (why I didn't think of this before I got the service manual, I'll never know... By the way-- thanks, Nate) and I've discovered that it's only sending spark when I initially turn the key over and when I release the key. The spark that I do get is strong enough to fire the engine up every once in awhile.. not enough to keep it going of course...
I find this quite confusing... Is this a reluctor issue maybe?

I believe someone suggested that before, but I really know very little about that part of the distributor.

Another possibility is a vacuum leak-- when I replaced the carb awhile back, the carb wasn't...precisely correct for my application. It's the carter BBD, but it's much newer and had many more vacuum hose connections that my vehicle just doesn't use. I capped them off, so I'm not sure if that's the problem....Maybe one of the caps isn't fit well or something.....


Anybody have thoughts?

[Dodgevanman]

The starting issue could be a bad ballast resistor. When the key is in the START position, the ballast is bypassed and full voltage goes to the coil and thus the engine starts. When the key is release to the ON position, the ballast kicks in and supplies the coil with a reduced voltage (around 8VDC)...this keeps the coil from burning up. If the ballast resistor is bad then the coil will get zero voltage.

[Tokay]

Checked that....

Turns out the compensating resistor reads as ~2 ohms, with the auxilliary at almost 6. The manual shows them as .5 and 5, respectively.

It's higher than it should be, but the circuit isn't broken yet, at least.
ONe part down, I guess.
I'll update once the new one is in.

[Tokay]

Update - The resistor probably isn't bad, my multimeter is likely off... Or the specs in the book are off. I get the same readings off a new ballast resistor.

Back to searching for vacuum leaks.
Nothing quite as tedious or quite as necessary as replacing rubber hoses....

Double update - I went through the secondary electrical system as described in the manual, but no luck; I didn't find any bad parts. I'm thinking that it's whatever tells the ignition coil when to fire, the name of it escapes me right now.... Heheh... but what else could cause the coil to fire only twice per key turn?

And I'm still bothered by the fact that it hppened right after an oil change... but it also happened right after I replaced the battery and cables...
Oh well. There's only so many components left to check now, so it's but a matter of time.

I miss motorcycle engines....

[Ram4ever]

Hi,

I'm not sure what year van you've got, but you wouldn't happen to have a dual pickup distributor with the Start/Run relay would you? If it's corroded it can cause a great deal of mischief. It lives on the firewall and is switched by a wire from the starter relay.
If the distributor pickup gap is wildly wrong you might see some pretty erratic spark operation - even battery voltage sensitive.

Is this old enough to have an ECU or is it computerized? If it's an ECU, I've triggered the spark by manually moving the reluctor past the pickup while the ignition switch is in the run position. No spark might mean a bad ground - check the various mounting screws.
If it's new enough to have the Hall effect sensor in the distributor it could be bad -they can become really erratic before failing totally.

[Dodgevanman]

It's a '77, so no dual pickup distributor or computer.

There is a pick up module inside the distributor.

Dang I hate electrical gremlins..they're a pain to diagnose sometimes.

[Tokay]

Thanks for chiming in for me there--

Yeah, it's old, and I've only got one pickup gap to set (which I did yesterday).

I think it has to be an issue with the control unit; it tests OK by the book, but all I have is a cheap multimeter, so I'm sure there issues I'm missing there....

I think I'll go grab a control unit from the junkyard, just to see if it makes a difference... For $2, it's cheaper than buying a new one only to find out that's not the issue...