I've had my truck for 10 years now but i never noticed until now that my distributor has an electronic spark advance pigtail coming out of it that it not connected, and never was. I have no "orange computer" or anything, and my Holley 1945 carb has nothing on the spark advance vacuum port and i think it never did. ...

All these years later, should i bother to change it to a vacuum advance distributor, and hook up the vacuum advance?

Have i been wasting fuel all this time?

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'87 D150 Slant-6 A904 with wooden cap

Well, i guess i do have a computer after all... in the driver's side front quarter panel. Ooops. Still my spark advance has been unconnected for who knows how long.

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'87 D150 Slant-6 A904 with wooden cap

Someone probably disconnected it for a reason. The "computer" probably took a dive and this was a stop gap measure to get it running.

Yes, I'd retrofit HEI on there with an earlier electronic ignition distributor. If memory serves those distributors have neither vacuum or mechanical advance. You've been loosing power and mpg if you were just running with base advance all this time.

Edit: Wait a sec, if the distributor was completely disconnected, there's no way your motor would run at all. I believe some of those distributors had two pickups, maybe one is connected and the other isn't?

This distributor has a two-conductor connector that had been disconnected for many years apparently. The distributor has no vacuum port, so as i am learning about this i concluded that it's an electronic spark advance, but it was disconnected.

Otherwise, the distributor is connected -- to the six spark wires and the main wire from the coil.

So my guess was that it was working like normal but didn't have any spark advance going on.

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'87 D150 Slant-6 A904 with wooden cap

I meant the smaller gauge wires, not the sparkplug wires. The distributor, through the small gauge wires, should be connected to the coil if it was points, the computer if it was esc, or a module if it was electronic ignition.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

I still want to know how the motors running if the distributor pickup is disconnected.

Could be he has this didtributor http://www.cardone.com/Products/Product ... 691&p=rock

Dave

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86 Miser 170,000+
2 1/4" exhaust
Holley 1920 #55
HEI MSD BLaster 2
17.8 mpg

Dave, That's what I suggested above, the dual pickup distributor. But apparently the OP only found a single connector.

Wasn't there a version of ESC that used a single pickup and another that used a second pickup? Who knows what would happen if that system only had one pickup hooked up. Or perhaps the OP has a single pickup system in which someone threw in a dual pickup distributor, explaining the second danging connector.

It can't

Pull the cap and take us a picture.

Rick

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2 Mopars come with Spark plug tubes. One is a world class, racing machine. The other is a 426 CI. boat anchor!

12.70 @ 104.6

Here is the distributor cap:




Here is the connector that is newly connected:

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'87 D150 Slant-6 A904 with wooden cap

First- Dan is right. The cheapest, fastest, easiest, most reliable, best, most MPG beneficial, most performance beneficial, cure to this issue to swap in an HEI ignition system. Just do it.

Second, if you REALLY want to try and futz around with the ignition system on your truck, you MIGHT be able to improve how your truck runs by resurrecting the lena burn system, but it likely won;t happen.

You truck is a 1987 truck. This means it absolutely had a lean burn system that almost certainly originally controlled both the timing and the carburetor. From what you describe in this thread and the pictures and questions you posted HERE, it sounds like someone has disabled and partially removed portions of the lean burn system on your truck. I know you are missing the idle stop solenoid that also was the curb idle speed screw. It sounds like someone has disabled the vacuum advance provision of the lean burn systems well.

In a lean burn system, the computer (in your case the one mounted on the driver's side fender) controlled the timing. It required a source of constant manifold vacuum to be allied to the vacuum transducer on the side of the computer. There is a port on the carb that sees full manifold vacuum all the time. There is supposed to be a hose that runs from that port on the carb to the vacuum transducer on the computer. If that hose is missing, the computer will default to limp mode and the timing will be static and not advance. If that hose is hooked up to a vacuum source other than full manifold vacuum, the computer will change the timing incorrectly.

The distributor has a "start" and a "run" pickup. As the names imply, the pickups operate at different times- one when the engine is starting, one when the engine is running. I would have to go back and reread the lean burn section of my factory service manual, but if I remember correctly the start pickup retards the timing during starting and the run pickup correlates to the timing as is set using the timing tab. Someone has been in your truck and messed with things, so I suppose it is possible they hacked and spliced the ignition system to remove the wires that are supposed to go to one of the pickups in order to get the truck to start and run. You will need to get a factory service manual for your truck and spend some time tracing wires using the wiring diagram if you want to try and get the ignition system sorted out.

It looks to me like someone jammed the two prong "run" pickup lead onto the three prong "start pickup" plug. That is pretty amazing in and of itself. Try plugging the two prong distributor plugs together and the three prong plugs together.

Verify tha tthe vacuum transducer holds a vacuum and run a hose from the correct port on the carb to the lena burn computer. The port is called the "ESA signal tube":



That may or may not be the correct carburetor for a 1987 slant six. It appears that the mixture solenoid and the bowl vent solenoid electronics are missing. Could be that someone swapped carbs. Could be that your truck was built with a lean burn system, that controlled only the ignition and not the carb.

But, at the end of the day, rather than waste your time trying to save the lean burn system, your resources are much better spent converting to HEI.

I am curious- what are your base timing and idle speed set to?

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Casually looking for a Clifford hyperpak intake for cheap.

I appear to have a rebuilt Holley 1945.

I do think that the vacuum hose for the ESA is routed correctly to the computer, although i haven't check the connection to the transducer, and i don't know if the computer works either.

That connector that you're commenting on, i just connected that a couple days ago and it seems to have made no difference in the way the engine runs.

I am beginning to understand that my truck has been greatly modified. All these years i had no idea that it was the case.

I also learned that all distributors have at least one wire to send the signal to the coil to make the spark, is that correct?

And then, if there is a vacuum based advance then it also has a vacuum port to connect to the carb's OSAC port, or if it has electronic advance then the computer makes an electronic signal based on the readings from the carb's ESA signal port.

I have two questions:

1. Does the ESA signal port work the same as the OSAC port? Are these just different names for the same port depending on whether the truck uses a computer and and electrical signal to the distributor, or a vacuum line?

2. Could i install a different distributor, one that uses vacuum-based spark advance, and get spark advance working?

Thank you for your advice.

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'87 D150 Slant-6 A904 with wooden cap

Here it is with cover off.
You are right, there's a two-conductor cable that was already plugged in before. Does that contain the spark advance signal from the computer as well as a signal to the coil for timing?

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'87 D150 Slant-6 A904 with wooden cap

Points distributors have one wire that goes to the coil and a vacuum advance pod. Electronic ignition distributors have teo wires that go the ignition control module and have a vacuum advance pod on the side. Lean burn distributors have four wires ( like yours) and no vacuum advance pod.
No. The OSAC port provides no vacuum with the throttle closed an full manifold vacuum as soon as the throttle opens. The ESA signal port provides full manifold vacuum all the time. The ports function differently and are NOT interchangeable. A distributor vacuum advance must use an OSAC port and the computer MUST use an ESA signal port.
Yes, provided you also install an ignition sustem other than the lean burn computer.

For now, connect the distributor plugs to theconnections on the wiring harness correctly. Disconnect the hose that goes to thebOSAC port on the carb. Cap the port on the carb. Run a new hose from the transducer on the computer to the vacuum tree on the #6 intake runner. This MIGHT get your timing advance working again.

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Casually looking for a Clifford hyperpak intake for cheap.