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| Lean burn - wont start https://www.slantsix.org/forum/viewtopic.php?t=28176 |
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| Author: | electricblue [ Tue Apr 01, 2008 8:10 pm ] |
| Post subject: | Lean burn - wont start |
I've been reading the forum for a while, great and active group with great help. Hoping you can shed some light on this. "82 D 150, Lean burn, won't start, acts just like a failed ballast resistor..starts but won't run. I have spark during start, and assume so since there is power to the coil with the ignition key in "run" positon. Strange as it may seem and the opposite of what many of you have done with ignition swaps, I would lilke to keep the truck original, so I am attempting to retain the Lean burn module in the aircleaner. How can i tell if the module is picking up signals from the run pickup coil. I am suspecting that this may be the problem. Also, with many of you replacing lean burn computers, do any of you have one you took off that you would part with? I'll post this parts request on the parts forum later. thanks - electric |
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| Author: | volaredon [ Tue Apr 01, 2008 8:44 pm ] |
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Being a Cali truck I'd bet on the "run" p/u coil being toast. |
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| Author: | Matt Cramer [ Wed Apr 02, 2008 8:04 am ] |
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You can remove the distributor, spin it, and measure the output of the module with an AC voltmeter. It isn't very high at the RPM you can hit by spinning it by hand, somewhere around 0.3 to 0.5 VAC. This will at least let you spot a dead pick-up coil. |
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| Author: | SlantSixDan [ Wed Apr 02, 2008 9:22 am ] |
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Quote: Being a Cali truck I'd bet on the "run" p/u coil being toast.
+1 vote for a dead "run" pickup in the dual-pickup distributor, but could also be a bad ignition switch or wiring fault.
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| Author: | KBB_of_TMC [ Wed Apr 02, 2008 10:01 am ] |
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I really like the idea of keeping it original; so hang in there! You can test the pickup using a screwdriver to make/break the magnetic circuit and generate sparks one at a time, or remove (and ground) the distributor and turn it by hand. You should get good sparks no matter how slowly you turn it. I cobbled together a little magnetic pulser based on a NE555 chip and a the voice coil from an old IDE disk drive that would trigger a magnetic pickup. With the ignition coil running to an adjustible spark gap (from J.C.Whitney), it lets me simulate different RPMs and check the spark with the engine not running. The coil was fragile and eventually broke, so I substituted a magnetic pickup coil from an old aftermarket cruise control that works well too. I'm pretty sure that your pickups use the Hall effect and are not inducttive (like Fords), so I'd expect their output ought to be a clean logic signal whose amplitude is independent of RPM, but I've not actually measured it, and I'd expect they'd require some bias and ground to work properly. I recommend you look for a poor connection somewhere, possibly in the pickup leads. One lean burn system I saw developed a difficult-to-find poor connection right at the main ignition module plug. |
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| Author: | SlantSixDan [ Wed Apr 02, 2008 3:29 pm ] |
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Quote: I really like the idea of keeping it original; so hang in there!
C'mon, you've gotta be kidding me/us/him. The only reason to keep a Lean Burn vehicle original (i.e., to leave the Lean Burn in place instead of putting in a distributor and ignition system that actually work reliably) is if state emissions regulations require it...and even then, you're still much better off putting in a real ignition and leaving the nonfunctional Lean Burn box in place and apparently hooked up to satisfy the visual inspection. Trying to make a new Lean Burn system start and run reliably and properly was almost impossible. Trying to make a 26-year-old Lean Burn system start and run reliably and properly is an utter waste of time, effort, and money. This is a bad system that scarcely ever worked right even when new, plain and simple, end of discussion.Quote: I'm pretty sure that your pickups use the Hall effect
No slant-6 factory ignition system ever used Hall Effect pickups. Always magnetic inductive with reluctor and pickup coil.
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| Author: | wjajr [ Wed Apr 02, 2008 7:18 pm ] |
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After 26 years I can agree that the electronics could be junk. However in the spring of 1976 we ordered a Cordoba with the new for that year 400 cid., 4 bl. lean burn option. That Lean Burn system worked flawlessly delivering 19 mpg on the highway until I sold it six years later with 86,000 miles on the clock, and purchased that rag top K car I still have. Some people had problems with the lean burn because nobody but a competent Chrysler dealer understood how the damn thing worked. Chrysler was the first manufacturer to utilize computers for engine management. Back then the training was not very good at some dealerships, and several yeas passed before all of the dealers were up to speed on computerized controls. The 1973 & 74 models were the worst for drivability, nothing would make them run properly. In those days pollution control devices were just riped out by most mechanics if the car did not run correctly. By 1975 catalytic converters were starting to be used, 1976 computers were added, and automobiles began to run nicely once again. But the tradition of ripping continued when all that was needed was a new sensor, a connection cleaned, or a vacuum hose replaced on a lean burn engine. All that ripping stopped when the feds starting passing out $10,000 fines for tampering with the pollution controls on motor vehicles. |
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| Author: | Aggressive Ted [ Wed Apr 02, 2008 8:04 pm ] |
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electricblue, The two pickups in the distributor can be measured to see if they are working. Test with a multi-meter. Unplug them and check the resistance of the coils. They should be 350 milli-ohms. If they are open, you won't get a value at all. Then replace the bad one. I have had to do this on several rigs. Don't use the cheap $10 after market unit either. Get the good $28.00 one.  The cheap ones may only last a year. 
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| Author: | KBB_of_TMC [ Thu Apr 03, 2008 9:10 am ] |
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Often, at car shows I've seen all original cars rated much higher than nicely modified ones; and while the lean burn may not be a great system, it is historic. Anyway, I believe a Chrysler Hall effect pickup ought to be around 300 ohms, not 0.3 ohms, but I've measured anywhere from 150 to 500 ohms on ones that worked great. |
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| Author: | Aggressive Ted [ Thu Apr 03, 2008 10:11 am ] |
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That's true, had a brain lapse, fade on the ohm rating scale....thanks!
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| Author: | tophat [ Thu Apr 03, 2008 11:21 am ] |
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I happen to have a LeanBurn computer that I will let go cheap. It came with the truck but was not installed, so I have never seen it run. It is out of a 81 225 pickup truck. PM me if you are interested. TopHat |
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| Author: | Matt Cramer [ Thu Apr 03, 2008 11:31 am ] |
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Quote: Often, at car shows I've seen all original cars rated much higher than nicely modified ones; and while the lean burn may not be a great system, it is historic.
For the record, a Lean Burn isn't Hall effect. While K-cars and later Magnum engines used Hall effect sensors, the slant six never did. This would be easier to diagnose if they were, as Hall effect sensors put out a nice on and off signal you can measure with a voltmeter while turning the engine slowly. The Lean Burn is a variable reluctor, a sort of pulse generator that only gives a signal when the distributor is turning.
Anyway, I believe a Chrysler Hall effect pickup ought to be around 300 ohms, not 0.3 ohms, but I've measured anywhere from 150 to 500 ohms on ones that worked great. |
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| Author: | electricblue [ Thu Apr 03, 2008 5:08 pm ] |
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Yes this is a CA truck, and subject to some pretty strict scrutiny when I reregister the truck. I appreciate the tips on checking out the run coil. I had already replaced both pickup coils in the distributor, so I have assumed both are good. I wont have time to check the suggestions out unti the weekend, and can repost my finding then. I'll be reconsidering based on SSD's wise counsel. I do run a risk of it ever running reliably if the computer remains on it. If i do so, I have a spare single pickup electronic distributor. Will I need to drill an extra hole int he carb base plate to get adequate vacuum to pull the vacuum advance, or is there and electronic advance system to do this. Any diagrams or parts lists would be helpful. thanks to all for your advice. |
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| Author: | SlantSixDan [ Fri Apr 04, 2008 1:14 am ] |
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Quote: Often, at car shows I've seen all original cars rated much higher than nicely modified ones; and while the lean burn may not be a great system, it is historic.
You are reaching longer than your arms!  Remember, this what we're talking about is a 1982 Dodge pickup.Quote: Anyway, I believe a Chrysler Hall effect pickup
There are still no Hall Effect pickups in slant-6 distributors.
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| Author: | SlantSixDan [ Fri Apr 04, 2008 1:20 am ] |
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Quote: replaced both pickup coils in the distributor, so I have assumed both are good.
Not necessarily always a good assumption, but you're right; it reduces the odds this is your problem...which means it might be something less convenient (ignition switch) or a great deal harder to diagnose (lean burn computer, wiring).Quote: I have a spare single pickup electronic distributor.
You're most of the way there...!Quote: Will I need to drill an extra hole int he carb base plate to get adequate vacuum to pull the vacuum advance
You will need to swap on a carburetor equipped with distributor vacuum advance provisions. Just drilling a hole won't do it, because the carb isn't equipped with a spark advance port in the inside of the throttle body. Such a port is very precisely located relative to the throttle plate, and trying to make your own will almost certainly give bad results.Be sure and save the carb ID tag from the lean burn carb, in case you might want to swap it onto the replacement carb so anyone who happens to inspect the carburetor sees the right number.  If you have trouble finding a suitable carburetor — don't buy a parts store "remanufactured" or "rebuilt" unit — send me a PM.
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