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I recently had a local shop do a tune-up. They replaced the distributor while they were there. Now it will crank and crank and only starts the moment key is turned to run position. It's like no spark while cranking. It seems I should be able to unplug the connector at the distributor and test for cranking voltage, and run voltage. But I don't know which plugs are supposed to have 12 volts. It always started very quickly before this. Thanks in advance for any light anyone can shed on this.
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« Last post by VileZambonie on April 15, 2024, 04:06:16 PM »
Make sure you ohm the pickup coil before replacing the module.
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« Last post by VileZambonie on April 15, 2024, 04:04:52 PM »
The HEI/EST is used on models with Computer Command Control (C-3) or Electronic Fuel Injection systems. The system utilizes a distributor similar to the unit used with conventional HEI systems that has been modified to allow spark advance to be controlled by the fuel control system Electronic Control Module (ECM). Modifications to the distributor include a revised ignition module, with additional terminals to receive signals from the ECM, and the elimination of the conventional centrifugal and vacuum advance mechanisms. In addition, some models use a Hall effect switch mounted above the pickup coil in the distributor to provide a reference pulse to the ECM. The ignition coil on HEI/EST systems is mounted either integral with the distributor, Fig. 1, or remotely mounted, Fig. 2, depending upon engine and application.
Primary current switching in the HEI/EST system is performed by the ignition module based on reference pulses from the pickup coil as in conventional HEI systems. However, all spark timing changes in the HEI/EST system are performed electronically by the Electronic Control Module (ECM). The ECM monitors information from various engine and vehicle sensors, determines the correct spark timing and signals the distributor to change timing as necessary. An EST bypass circuit is incorporated into the ignition module to allow ignition in case of ECM failure and to allow base timing adjustment.
On some HEI-EST systems, Electronic Spark Control (ESC) is used to retard ignition timing when detonation occurs. The ESC system consists of a knock sensor, distributor module and controller. The knock sensor is an accelerometer or magneto-strictive device, mounted on the engine block. It detects the presence and intensity of detonation by vibration characteristics of the engine. The sensor's output is an electrical signal which is sent to the controller. The controller is a hard-wired signal processor and amplifier which operates from 6 to 16 volts. The ESC controller processes the sensor signal into a command signal to the distributor to adjust spark timing. This is a continuous process monitoring and controlling detonation.
When detonation is detected the spark advance command is delayed, providing the level of retard required. The spark is retarded for 20 seconds, then the spark control returns to EST. The amount of retard is determined by the controller based on the severity of detonation. A failure of the sensor would allow no retard, while controller failure would be indicated by no ignition, no retard or full retard.
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« Last post by Chevygold on April 15, 2024, 02:54:38 PM »
So I won this MSD 8362 Distributor Street Fire on fleabay for £89 needs the ICM replaced which I happen to have so figers crossed it all goes according to plan, I could do with a stroke of good luck for a change, got a set of plugs on order as I broke 2 getting them out, the joys of headers!
Will update once it's all back together.
Graham
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« Last post by KamperBob on April 14, 2024, 08:08:15 PM »
More updates:
#3 dash progress is inching forward. The gauge cluster is mostly working now. New speedometer expected this week. Fan blows but vibrates so inspect/clean soon. Meanwhile, ducts sourced and reconstructed. Vacuum controls still need attention to select vents. AC will stay disconnected until that service makes my list. It's still cool in SoCal high desert so no hurry. Yet.
#5 wheels also progressing. I decided against 33" 16.5x12.5 wheels. Too big. Not enough front clearance. Got some deep dish Dodge rims that center nicely after 1.5" bolt on spacers. New stock size LT235/85-16 tires on order.
#6 issue is steering. Slop probably from blown boot on main link from the pitman arm. Hopefully tear into that this week.
It's exciting to see the old truck has good bones. Moreover, how serviceable it is, especially by an amateur mechanic.
PS- sorry; non diesel engine issues off topic for this channel...
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« Last post by Chevygold on April 14, 2024, 04:09:57 PM »
Hi BD, it was a definate 11 degrees consistently repeatable, timing chain is quiet and timing is dead steady so I can only assume advance is made in the ICM hence the extra connections.
Been looking at replacement units and Amazon have one at a good price with good reviews, Voltstorm, also a Proform from a UK supplier I've used before but that's about a third more. Still looking but not many options, current exchange rates make buying from the USA less attractive :-(
Graham
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« Last post by bd on April 14, 2024, 12:32:59 PM »
Graham, your earlier narrative regarding ignition timing advance increasing to 11 BTDC at 3,500 RPM caught my attention.
@ Vile:
Do you know whether an ESC distributor module has a built-in timing curve? I've never had reason to question this until now and assumed that timing was strictly dictated by external input from the ECM, modified by the ESC module. If my assumption is true, why is ignition timing advancing with no ESC module connected to the distributor? Although one might expect a worn timing chain to retard timing, I wonder if validating the timing chain condition while waiting for a replacement distributor is prudent.
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« Last post by Chevygold on April 14, 2024, 10:12:58 AM »
And another
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« Last post by Chevygold on April 14, 2024, 10:11:12 AM »
Here's a couple of pictures of what I've got, no weights, 7 pin ignition control module and no provision for a vacuum unit so looks like I'm in the market for a new distributor, wish I'd pulled it sooner now! Any suggestions and any to avoid?
Thanks
Graham
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« Last post by VileZambonie on April 14, 2024, 07:12:21 AM »
Electronic Spark Control. ESC Distributors are to be used with an ECM, Knock Sensor, Vacuum controls and are for retarding the ignition timing if spark knock is detected. What you have is an anti-performance distributor.
You want a standard HEI vacuum advance V8 distributor.
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