I replaced my ignitor a while back with the standard GM HEI module running to my stock coil w/ a 1000 ohm resistor and it generally runs fine. The issue is that it sometimes takes a really long time to start when it's cold out. Today is the coldest it's seen since I did the conversion and the trend hit bottom--the truck won't start.

When I was researching the process I swear I ran across someone talking about that issue and how they addressed it but I have no idea where I found it. Does anyone know what the deal is with this issue?

 

Year/Engine? Where in the circuit do you have the resistor?

You do not need the resistor with the GM HEI Module, as far as the ignition system itself is concerned. My '78 20R runs with a stock type coil, Standard Motor Products UC12. Any resistor in the + or - line to the coil is just cutting down voltage to the coil. It's not necessary & if that's the case, you are actually not getting all the coil power you could be.

I think the confusion may come from an article I saw a while back on the GM HEI Module conversion, specific to Toyota. I recall that they had put a 1000 OHM resistor inline with the wire from the - terminal of the coil that then went to their stock in-dash Tachometer. Apparently the stock Tach wouldn't work right without the resistor in-line. I'll hunt around the web a bit to see if I can find that posting. Meanwhile, try running a direct line from the "C" terminal on the Module to the - terminal on the coil & see if she wants to start for you.

 

1983 with a 22R, desmogged.

1000 ohm resistor inline with the yellow wire per the standard instructions. Apparently it's there precisely to reduce voltage and save wear on parts. It's bypassed during starting, though.

Here is a diagram showing it on the 1980: https://i0.wp.com/wiringforums.com/w...tion.gif?ssl=1

I don't know that this diagram is actually a 1980, though, since it depicts an emissions control computer. As far as I know, that wasn't a thing in 1980.

Anyway, I don't see any reference to a resistor in my 1983 FSM wiring diagram so I guess they changed the setup. The coils are different, after all.

 

I've removed the 1000 ohm resistor and it still won't start. Diagnosis continues.

 

Have you confirmed that a lack of spark is the problem?

 

Jake, that's a damned good question. I did verify that the carb was shooting fuel but I haven't checked for spark from the coil lead yet. I based my assumption off the general feel I have for no-spark hard starts and that it has gotten steadily worse as temps drop and only happens when the truck is cold. I'll make that check, though.

Check is made. No spark from the ignition coil lead. It could be total coincidence but it sure seems like it's temperature related.

 

I've found that my coil is not within Toyota spec's for resistance.

Primary Spec: 0.8 - 1.1 ohm
Mine: 1.6 ohm

Secondary Spec: 10.7 - 14.5 k
Mine: 9.45 k

When I was first undertaking the swap, though, I bought a replacement Toyota coil and it wasn't even within specs, brand new, so I don't know that this is really an issue for the stock system.

However, other posts on this swap indicate that the GM module is designed for a 0.5 ohm resistance on the coil's primary and I'm 3x that so I do suspect that as the issue. And If cold temperatures drive up the resistance/impedance further somehow, that could explain the intermittence.

 

Later this same day, after sitting in the sun with the hood up for a while, the truck started fairly easily. Not like normal but almost.

 

Your ignition coil is out of spec, and in 2 different ways. Out of spec/high Primary resistance is often causes the Module to not work, and can actually "break" the module internally. I know because I've been through this before with a cheap ignition coil that developed high Primary resistance within 6 months of use, and blew up 3 brand new quality modules in a row. 1.6 Ohns is too high, as the HEI Modules usually like Primary resistance to be 1 Ohm or less. That's what they were designed to work with.

I also say the coil is out of spec a second way because the baseline "stock" readings you posted do not agree with the info I have from FSM's on what the coils values should be. Here are the specs I have on file:

Primary Resistance:
20R (1975-79)-1.3-1.7
20R (1980)-0.5-0.6
22R (1981)-0.8-1.0
22R (1982-88)-0.4-0.5
22R-E (1984-85)-0.8-1.1
22R-E and 22R-TE (1986-88)-0.5-0.7

Secondary Resistance:
20R (1975-79)-6500-10,500
20R (1980)-11,500-15,500
22R (1981)-11,500-15,500
22R (1982-88)-8500-11,500
22R-E (1984-85)-10,700-14,500
22R-E and 22R-TE (1986-88)-11,400-15,600

According to that, looks like you have a coil intended for a 84-85 22R-E instead, with double the primary resistance that your 83 is supposed to have. That 0.8 to 1.1 Ohms spec doesn't leave the Module with a lot of "wiggle room" if anything happens to raise the Primary resistance

I'd also suspect the coil at this point due to the failure (or working) in a given temperature range. When I was dealing with the cheap coil before, the engine would crank & not start after being shut down from full temp, and would only restart after allowing things to cool off for 10 to 20 minutes. What was happening is that several wires in the Primary were broken and as the coil heated up, the wire ends would pull away from each other. When it cooled down, the ends would close up & "reconnect". This is a classic sign of a failing or failed ignition coil. You just happen to have it happening in reverse, with it not wanting to work when cold. As a test when cold, you could try heating the coil up with a hair dryer on high for a few minutes & see if it starts. Personally I'd just pull the coil and the HEI Module & take them to a parts store for testing (which many do for free). I'd also get the correct coil for your truck.

The only other thing it might be is an out of spec pickup coil in the distributor. If old & fatigued from many heating/cooling cycles, these can also sometimes develop breaks in their coil wire. Correct resistance spec for your '83 is 130 to 180 Ohms. Also check the Air Gap between a Vane on the Reluctor Ring when lined up with the direct center of the coils face, Spec for this gap is .008" to 0.16". I have mine set at .012", right in the middle.

 

Thanks for your input. I don't know what's up but this morning I measured my coil again and got 0.6 ohm and 8.86 kohm. And yet it won't start. I did try hitting it with a heat gun for a bit anyway but that didn't get me started.

Reverified that the accelerator pump jets are spraying healthily.

I might just submit to parts-throwing and get a GM coil to match the module. Although I guess it could be that this module is bad, too.

UPDATE: A few hours later, just like yesterday, after it has sat in the sun a while it starts right up. What the hell??

 

I'd just take the coil & module & get them tested, easiest way to find out for sure. And don't forget testing the distributor pickup coil.

 

I have a spare good Toyota coil. My ignitor turned out to be my problem so I replaced that and the coil with a set up from FAST.

Can anybody tell my why a company with as well known a name as Crane would replace it with FAST? Yes Fuel, Air, Spark, Timing. But still.

 

I think I may have figured this hard starting issue out. I should probably wait to do more testing but I'm too excited about my success!

Today I experienced the same won't-start-when-it's-cold-out problem and went back to scrounging though the various threads on this ignition swap that I've already seen a hundred times.

Then I found this blog: http://joeynovak.com/blog/diy/79-toy...ct-on-voltage/

Very interesting bit of information, that the GM ignition module expects a much higher voltage than the Toyota module. So I figured I should check my reluctor gap and make sure it's allowing the hottest signal possible to be generated. Mine was set at something over 0.008 and under 0.016--probably about 0.010. So I reset it to 0.006, which is a bit under the Toyota minimum spec but seems wide enough to avoid trouble. Buttoned it all back up and the truck fired right up! After cranking and cranking to no avail earlier in the day. I assume cold weather simply widens the gap through mechanical contraction. I'll have to see if 0.006 will work in hot weather when that season comes back around.

I will wait and see if the problem comes back in the immediate future or not to verify my success and report back.

 

I'm glad to hear you got the truck to start and run, however...... Did you test the pickup coil for resistance as I earlier suggested? (See last paragraph of previous post) If not, narrowing the gap could just be making up for a problem in the coil. Making the gap smaller to make for a "hotter signal" may be just enough to overcome a resistance problem in the coil from wear & fatigue, and it wouldn't be a long term solution. Also, thermal expansion & contraction shouldn't change the gap very much if at all. The valve lash on these engines only changes a max of 2 thousandths of an inch (.002) from cold to hot, and those parts get a ton more heat than the pickup coil does, so they expand more. However on a fatigued coil, possibly with a few broken wires in it, thermal expansion or contraction could cause some of those broken wires to "connect" or "disconnect". Given that you were experiencing this problem based on temperature, I'd strongly suspect this.

Get out the Ohm Meter & test the pickup coil, both cold and hot. That way you can be sure instead of assuming. I am running the GM module & the stock Toyota pickup coil, and have my reluctor gap set at .012", right in the middle of the stock spec, and it starts & runs fine at any temperature. Also, my pickup coil is new, inside an A1 Cardone rebuilt distributor.

 

13Swords, I appreciate your continued logical analyses. Yes, testing the distributor resistance was a step I took early on in my initial diagnosis and it was spot on. That was a cold test. At that time I ran through all the FSM steps to arrive at the conclusion that the stock igniter was bad. I suppose I ought to put the multimeter back on it and jiggle the wires to check for poor connections but if it were really just a poor connection, it seems like the bouncing around that occurs during driving (and we all know about how these trucks bounce) would yield stuttering or cutting out but it doesn't at all.

I'm happy to report that this morning, which was just as cold as yesterday morning, the truck fired right up and hot restarts with satisfying alacrity. I'm not closing the book on the matter yet, though, so I'll wait and see what the long term behavior is. I'll admit that I don't really get what's going on. If the distributor signal to the GM igniter is "weak" due to the mismatch of parts, it would make sense to me that the issue would manifest not just at startup but at all times, as the temp of the engine shouldn't necessarily affect the signal strength. And yet it's only ever been a starting issue.

 

Following up on this. It's two weeks since I reduced the air gap in the distributor and I haven't had a single hard starting issue since then. I'm calling it solved and settled.

 

Thanks for the update & glad to hear it's working OK. Did you ever get a good look at the connecting wire from the pickup coil to the module? The one in my '78 was in sad shape & also measured some resistance. That less than 3 foot run of cabling/wires was measuring 0.4 ohms resistance; it should be zero or close to zero. That resistance could be causing signal loss to the module too.

I swapped in some new 2 conductor, 22 gauge shielded security/alarm cable & it works great. Been running on that for over 2 years with no problems. ! was able to find & buy it "by the foot" at Home depot for about 30 cents a foot (6 foot minimum = $1.80 plus sales tax). The foil shielding inside the insulation keeps any interference from messing with the pickup coils signal to the module, and compared with the old cable, looks like a direct replacement. Of course you'll have to terminate the new cable with new connectors.