northoak

13Swords

Good idea on testing the coil & igniter hot, will be interested to hear the results. At this point, & after going back though all of your posts to double check things, I'd think it's either the igniter or the idle circuit in the carb. The no spark when hot for 20 minutes, then spark coming back indicates either the coil or igniter. Since we know the coil is new & in spec, that leaves the igniter. If you replace the Igniter & still have the problem, it has to be the carb, likely the idle circuit. Up to me, I'd clean out the idle circuit the way I described before first. Only costs a can of carb cleaner & some time. Igniter is going to cost a lot more than that. If you address both those things & it still does it, I will be near stumped.

If it is the Igniter, what could be likely is that your previous bad coil has damaged 1 or more of the igniter driver transistors. This is usually due to a shorted primary winding in the coil (sometimes the secondary) causing feedback in the igniter's triggering circuit & frying the transistor(s). The Igniter basically is the on/off switch for your coil. Same would go for high primary resistance. I went through 3 ignition modules on mine before I got my crappy quality coil problem figured out. The bad coil would keep frying them. Thank gawd I modded mine to use the GM HEI Module; they are dead cheap compared to the stock style Toyota Igniter ($20 vs $300).

I do not recommend the GM HEI Module mod for your truck as it will not pass Cali Smog. I'd get that Igniter fully tested at a parts store as well to make sure it's the problem. They have equipment that can stress test it.

It is possible for the Igniter to fail when hot & then be functional when cold, or even to just be barely working when hot. I had the same problem with my coil issue. Started & ran ok cold, run got worse as it went on, shut off engine, crank & crank w/no spark or start. Had to let it sit for 20 to 30 minutes then it would start up. In my case the secondary part of the coil was the problem. There were shorts in the coil windings (wires), but not bad enough to keep it from making spark energy when cold. Once it got some heat, the copper wires inside expanded & cause more shorting, & reduced how much energy could get out of the coil. Enough to keep running, but not enough to start it. Also, hot wires conduct less electricity (higher resistance when hot). This is normally not a problem, unless the metal in the wire is old, fatigued from use & has been carrying a fair amount of current.

And speaking of cost, the OEM stock style Igniter is no longer available from Toyota, but Standard make one of very good quality. Standard Intermotor Part # LX 796. Direct replacement, plug and play with the correct connectors. Only problem is that the normal retail on it is about $300. I did some shopping for you on this in case you'll need to get a new one. The parts stores are at full retail (O'Reillys, Auto Zone about $310, not stocked, special order only). Ebay seems to be between $250 & $300. Rock Auto & Summit both have it for about $240 (free shipping from Summit). I also found 1 on Amazon for $191.45 + free shipping:

You can try the junkyard part route for a used one if you want, they are usually $50 to $100, but they don't guarantee them usually, & no telling how much wear, tear & use they have on them.

The only other thing I can think of is the distributor pickup coil. It's very rare but it might be heat affected, which would raise the resistance in it, causing some loss of triggering signal when hot. For the record, I've never come across this. That coil doesn't carry much current at all (like the milliamp range, very small) so fatigue shouldn't be a factor with it. You can of course check it with a meter for resistance, cold or hot. The spec I have for it is 140 to 180 Ohms (cold).

There is also the air gap spec for the distributor pickup coil that you can check. With one of the "vanes" on the rotor centered on the coil, the gap spec should be .008" to .016". If the gap is too tight or small, the metal could expand & cause a short, I suppose, but again I've never heard of this happening. I run mine at .012". A steel feeler gauge can give you a false gap "feel" when checking it if you aren't careful (the coil has a magnet in it). Most recommend you use a brass feeler gauge but I just use a standard business card (.014" thick) or a dollar bill folded in three layers (dollar bill paper is .004" x 3 layers = .012").

Pickup Coil adjustment instructions/info here: https://www.autozone.com/repairguide...0c1528004fb0f#

Sorry to hear about the ATM leak. I'd suspect the pan gasket is petrified (stiff) from age. It shrinks over time leaving the bolts a bit loose. Wouldn't be a bad idea to get a filter & gasket kit for it & replace that stuff, plus fresh ATM fluid when you get it done. Filter/gasket kits are around $10-$20 for good ones. Torque spec on auto trans pan bolts is the same as the engine oil pan, 8 foot pounds (do not exceed!). 15 foot pounds on the drain plug, if it has one. You can also take one of the un-broken bolts to the hardware store & have them match it up for you; cheap & it works. Just let em know it's metric. Got ideas on how to get the broken one out?

northoak

Thanks again for all the help! I ended up dropping the AT pan, welding the stripped bolt shut, and drilling/re tapping that broken stud because I couldn't get it out. Not the best solution if I need to change that AT fluid again but oh well. I think my electrical problems stemmed from the battery I was using. When my bad voltage regulator gave me charging issues my battery died. When that happened I threw a deep cycle battery I have in there to get to the store. I put the new regulator in and the charging issues wen't away but I forgot to put my regular battery back in. I think the fact that deep cycle batteries charge at a slower rate may have been causing my electrical problems. Can't be sure but I put my old car battery back in.

I 'm confident at this point that it is a fuel delivery issue as you suspect.

The problem has been getting progressively worse and last night the truck wouldn't start at all. The fuel in the sight glass was definitely less that half way full. It turned over fine but wouldn't start. I tried tapping the carb a bunch to see if the float needle was stuck to no avail. I also tried taking the fuel cap off. We pushed it into a parking space and went to bed. The weird thing is that It started first try this morning. I was able to drive about a mile back home but the bucking/misfire issue continued and I image they would progress again into eventually dying and not being able to start if I had kept going. The sight glass once again is less than full.

here is my list of things to try:
Replace fuel lines
spray out lines and charcoal canister with air compressor (if i can find one to borrow)
Spay out idle passages in carb
replace fuel filter agian even though its only a couple months old

My idle cut circuit has always clicked when I plug in the connector with the ignition on so i believe it is functioning well.

If anyone things of other things to add to my list please chime in! happy new year y'all.

northoak

13Swords

This is gonnea be another long one; lots of explaining stuff below. Don't say I didn't warn ya so grab a drink & settle in.

Don't get discouraged, you are doing the things you need to be doing & besides, every procedure you do should get you closer to getting it working right. Let's take it in order.

Your AT pan. A creative solution & as long as it works & doesn't leak, OK.

I don't think the deep cycle battery would give you the problems you described. The only real difference in deep cycle batteries is that they are designed to discharge up to half of their capacity before being recharged. Using one in a constant charge system like a car or truck shouldn't bother it any. I do think your bad old voltage regulator may have damaged your old battery. How old is it? It's a fairly common occurrence, especially in charging systems that use a separate voltage regulator like our trucks. So your old battery might be causing you problems as well. The only way to know for sure is to have it completely load tested. That would reveal any internal damage that you can't see or any function that isn't normal. Again, most parts places will load test a battery for you for free.

Before going any further I have to remind you that you are working on a 35 year old vehicle. It's been my experience that with older vehicles, there is often more than 1 thing going wrong/not working right at the same time. This can make diagnosis & fixing frustrating & difficult, but not impossible. It's just a matter of chasing things down system by system, being logical about it & having the correct info.

Your problem may be a fuel issue, but not so fast. The sight glass is how much less than half? Just a bit? or more like 1/4 full? There is a big difference between the 2 in how the carb works. Did you check sight glass with the truck level on the ground, not tipped to front or back? Previously you reported that the fuel level was exactly half way in the sight glass. Are you sure you're checking that sight glass the right way? The truck has to be on level ground & you have to get your eye dead level with the sight glass. This was a mistake I made myself. I also thought the level was too low, until I stuffed my head down into the engine bay in front of the carb to look at it straight on. In my case it was an optical illusion making it look too low, because of the angle of view.

Yes, it could still be a fuel issue, but the things you have said that you have done kinda narrows it down a bunch. Tapping on the fuel bowl to see if it's a sticky needle valve is a good idea. It must be flowing at least some fuel as you were able to drive it a mile (even with the bucking) & still showed some fuel level once you got it home.

IF there is a problem here (& there may not be) it may be a possible partial blockage under the needle seat valve or in the valve itself. This could be some of those tiny rubber particles from the insides of the old fuel lines I mentioned before. The fuel filter may not catch all of these & they could build up just below the needle valve, as that is a natural point of restriction. I personally doubt this is happening, due to the carb being 6 months old or so & being a fresh rebuild. National has been doing this a long time, & uses quality stuff in their rebuilds, so I'd doubt your float valve was defective. Not a lot there to get messed up. Also, float height does not just get messed up on it's own; it take s a human agency to do that & if no one has had the carb top off since you've had it, there is no way that float is going to change it's height on it's own. Also, since you went ahead with the idle passage cleaning, that should have gotten out any particles below the needle valve seat, & washed out any particles from the valve itself. All that should be clear now.

You changed the rubber lines; just the front ones? What about the ones near the tank? I know they are a pain but they have to be done, for no other reason than to eliminate a possible source of trouble, & because they are old.

Good job on the Idle Circuit cleaning, & the rest of the clean out procedure you did. If all those things are confirmed clear (good airflow with the compressed air) we don't have to worry about those.

Now the more serious problem - your distributor pickup coil. First, let me say, GREAT JOB on testing it under various condition & great reporting of what you found. All of that information is very helpful. You may have found a major source, if not the source of the trouble. An explanation...

By ANY of the readings you quote, that pickup coil is bad. There are 2 things going on here; first, the wild readings. Most likely you have lost some of the insulation on the wire in the coil. This a a long continuous wire wrapped around a magnetic core. Normally, whatever electrical signal that is generated is supposed to travel the full length of the wire. This wire is usually insulated by an enamel coating, which can break down over time due to engine heat (gets brittle & flakes/falls off), from vibration, & eventually metal fatigue from age plus those factors. This missing insulation allows some of the wire "turns" to touch each other & cause a small "short'. if you have several or more of these shorts, the voltage "jumps" across the shorts, so the voltage is nor travelling the way it was designed to. As the coil picks up engine heat it expands, which can shift those small loops of wire, sometimes shorting, sometimes not. This would account for the various readings you got. It's also like I explained about a bad ignition coil, with the heat driving up the resistance to a point where the electricity just can't get past it. The engine heat will make it progressively worse.

Second & most important, are the high resistance readings. The FSM sounds right on with the 130-190 Ohms spec. 190 Ohms resistance is the highest spec you could measure & still call the coil "good". 320 Ohms reading when it "died" is double the average "normal" reading.
That means you are losing at least half of your signal voltage, possibly more, resulting in a weak signal (or sometimes missing signal) to the Igniter. To make matters worse, your distributor pickup coil (signal generator) does NOT work off of your 12 volt system; it generates it's own voltage, which is a much smaller voltage, probably something along the lines of 3 volts & maybe 200-300 milliamps (0.2-0.3 Amps of current) normally. Given such lower voltage & amperage, anything that "cuts it down" like high resistance is a BIG cut in voltage & current.

What's all this mean? It means that what signal you are getting out of the pickup coil is weak, probably inconsistent & sometimes no signal at all on some "pulses". It's not signaling the Igniter to switch the coil on & off on a regular, even basis. This causes an erratic no spark condition, like a misfire. It's a random misfire at that too, across all 4 cylinders, since the single coil drives all four spark plugs.

Given that your distributor may be original (35 years old), it wouldn't be uncommon to have parts in it failing by now or for wear in it causing you other problems down the road. You could also still have some problems with the vacuum or mechanical advance mechanisms. The rubber diaphragm in the vac advance might be pretty stiff by now. There is also gear & shaft wear, bearing wear, etc. all of which can mess with your engine timing.

Solution? You could replace just the pickup coil with a new one & hope for the best, but at minimum that's going to cost at least $50 for just the pickup coil, & you still might be left with worn out parts or other problems in the distributor. As far as I know, the parts stores do not test distributors, as that takes some expensive equipment, & these days many cars & trucks use a distributor-less ignition system. You could also try a junkyard distributor, but again, you don't know how it was used or if it also has internal wear. I don't recommend it.

I think a re-manufactured (rebuilt) or new distributor is in order.

Rock Auto has 2 available, 1 reman'ed & 1 new, & neither has a core charge so you wouldn't have to hassle with sending back your old part. Link here:
https://www.rockauto.com/en/catalog/...stributor,7108

The reman'ed is $54 + ship & has a 1 year warranty. The new one is $77 + ship, has a Limited Lifetime Warranty & even comes with a new cap & rotor (free spares! ) Either would be fine; A1 Cardone has been rebuilding parts for a long time & they do a good job of it. Auto Zone & O'Reillys both have these parts available, but they'd have to order them in as well (not stocked) & the prices are double or more! They might also want to charge you core charge ($30 or more) & for the shipping, which makes no sense to me. Here's the O'Reilly link for reference:
https://www.oreillyauto.com/shop/b/i.../toyota/pickup

It's not too hard to change out a distributor on these engines & your FSM should have the procedure in it. If you follow that to the letter it will work fine. You may have to adjust the timing afterwards but the adjustment will be small. If I could do it (& I did do it on mine) you can do it too.

There is also a good video on Youtube about how to change the distributor by a user called "WheeliePete." Link here:
So I recommend the rebuilt or new distributor ($25 extra for new would be my choice). Again, that would be one more thing you knew was correct & you could stop chasing. You said you tested the Igniter & it was in spec, so it's likely working ok. It's just not getting the signal it needs.

northoak

Hello and thank you once again. I was able to take the coil from the new signal generator I bought that did not fit and put it on the mount for my old coil. The result is interesting. The replacement listed everywhere however has a resistance of 205 ohms new and thus is out of spec? I put it in and set the air gap and redid my timing. The strange thing is that my timing doesn't change whether i disconnect and plug the lines to my vacuum advance or not. Could this been a sign of the diapharm being bad as you suggested? I tried 5 btdc and it runs rough. I then tried 12 before with the lines connected and its better. My bogging in the low rpms wen't away but it sputters as if it is starved for gas and misfires at times when the rpms are high. I'm thinking this hacked pickup coil is still not giving it the proper spark it wants.

I order a new distributor like you suggested and will report back! I'm surprised the whole distributor doesn't cost much more than a new pickup coil and cap. Wish I new that when i bought both, oh well. Hopefully this solves my problem! Thank you for walking me though this truck chaos. ps. that video is great and easy to follow. here is a pic of the beast I've been struggling with. Its definitely a little banged up.

13Swords

You are most welcome, I am always glad to try to help & hopefully let people have the benefit of whatever knowledge I might have gained.

I did see your other post about trying to replace the pickup coil with a new one. The size difference I just cannot fathom. You would think that someone doing an aftermarket part would at least make sure the thing would fit, work & be the original spec. Weird. 205 Ohms new is out of spec. I can only guess that someone didn't do the math correctly in figuring out just how much wire was supposed to be wound on there. Wire normally has resistance per foot, how much depending on the wire gauge (thickness/thinness) It's probably 38 Gauge @ 2.16 Ohms per foot, with close to 100 feet wound on there; that's close to 205 Ohms. Oh well.

Spark advance explanation. if you already know this stuff skip ahead. You generally want the spark to happen just a few degrees before top dead center. This helps make use of the full power of the combustion on the "power stroke". The combustion speed of the fuel/air mix is constant, but the engine speed isn't during driving. The faster an engine turns, the faster the piston moves. The engine timing has to advance when the spark happens in order for the combustion to coincide with the correct position of the piston. Otherwise the combustion will be happening too late, past top dead center, once the piston is already moving down on the power stroke. This is a loss of power.

In essence, you have 2 timing advances in a distributor, vacuum advance & mechanical advance. Vac advance works on engine vacuum, which should rise past a certain base level once some throttle is given to the engine. Once an engine gets to a certain speed, vacuum actually drops off. Plugging the vac advance line during timing efforts is done to make sure that the vac advance doesn't come into play when setting timing at idle. To the best of my understanding, the vac advance gives you timing advance on initial throttle. Anything past about 1500 RPM the mechanical advance should take over. The mechanical advance operates like a centrifuge. The faster the distributor spins the more the timing is advanced. The further out it throws the advance weights, which are attached to a lever, & the further it advances the timing, until it reaches it's limit of travel. The springs on the weights are there to make sure the weights retract when the engine slows down (engine rotation speed, not vehicle speed). The springs also act as a dampener.

All of this is why I wanted you to look into the distributor to make sure the springs were still there, & to put a few drops of light oil on the weight pivot points. Missing or weak springs, or weights that bind up on the pivots will all affect your timing advance adversely.

Disconnecting the vac advance isn't really a good test of it. The only way to truly test a vacuum advance is with a vacuum pump & gauge setup. With the cap off you can see the rod coming from the vac advance. With a few pulls on the vac pump, the rod should move. If it takes more than 2 pumps before moving, or more than 2 pumps & moves very slowly, the diaphragm inside is stiff. If 2 or 3 pumps the rod moves but then starts to go back to it's starting position, the diaphragm is leaking. If the rod doesn't move at all the diaphragm is ruptured & not holding vacuum. You can do a leak-down test on it using the gauge. Put vacuum on it & check the gauge. Leave it hooked up & check back in a few minutes. If no change to gauge it's holding vacuum. If the gauge reading dropped, it's leaking.

Timing. Most engines will seem to run better with some extra initial advance (changing base timing from 5 degrees to 12 for example), especially at idle. However there is a limit to this. The more advanced the initial timing is, the more advanced the later timing will be at speed (RPMS higher than idle). This could cause the spark to advance too far at speed, causing the exact symptoms you are now describing. It could even cause engine damage over time.

The hacked pickup coil is obviously working, as now your idle & low rpms are good. If the hacked coil was still a problem, it would be a problem at all speeds (like your original pickup coil). It's more likely that the distributor has internal problems like weak springs, sticky advance weights, worn bushings or shaft, etc. I plonk for the mechanical advance being the problem, since it has no effect at idle speed, but does at higher RPMS. This makes sense, so the new distributor is the way to go & should solve a majority if not all of the problem. Just make sure you follow the correct procedure for install. That video was a godsend to me as I did not have a FSM to reference at the time I did mine.

That truck isn't banged up; it has "life scars" & "character creases". Cool dog too.

northoak

SOLVED!!!!!!!!!

Looks like the multimeter does not lie. My new distributor came in the mail a few days ago and the pickup coil read a resistance of 189. Literally 1 ohm away from being out of spec but so far its all good. I installed the distributor as per the video 13Swords posted above and it fired right up. I used the timing light to get things at 5 before tdc with the advance plugged. The bucking surging under load/acceleration is gone and the sputtering in the high rpms like it is starved for fuel seems to have gone away. It no longer dies when the truck warms up. Truck is running better than it ever has since I bought it. I haven't gotten on the highway yet but all is going well in town as of yesterday! Hopefully I don't come crawling back to this thread next time I go on a longer drive...

If anyone having similar problems comes across this thread I'd recommenced checking that your pickup coil resistance is within the fsm spec of 130-190 ohms. If its out of spec replace it or get a new distributor from rockauto for about 80 bucks. If it dies or stuggles when in warms up, check the pickup coil resistance when the symptoms are showing. THIS IS IMPORTANT because mine tested ok when cold but out spec when warm. ps the pickup coil is the two wire plug off the distributor :-)

13Swords: I can't thank you enough for walking me through the two and a half week process of tracking this problem down! I honestly wouldn't have figured it out with you. Hats off to you from Oakland. :-)

13Swords

Those wild variations in the meter readings you took on the pickup coil was a pretty good signpost to the problem. Even under heat stress a coil in decent repair shouldn't "wander around" that much in resistance. There has to be some wire fatigue or breakage or both going on in your old part. I still also think your old distributor was on the verge of being completely worn out. "Slop" in the parts from wear can cause the headaches you've had with trying to track this down. Told ya it would be worth it in the end. Nothing like working on something, fixing it & having it respond & improve. I'd suspect most of your troubles are over for the moment. You may still have some little things to do but then again, everyone who plays with old vehicles knows this from experience.

If you could, please come back & post what results you get on a highway test, I'm very interested to hear details.

Again, you are most welcome to the help, but I'm only going to take something less than half credit. YOU did all the work & some of the "puzzling out" yourself, so you get the lion's share of credit. You would have figured it out eventually even without me; it just might have taken a bit longer. I don't mind doing this because I couldn't find any help in fixing my truck. I had to do most of the figuring out myself, and without the specific FSM! No $ to buy the overpriced originals available on Ebay, & no PDF copies on the web anywhere I only got some help through these boards on Yotatech, so now I give back when I can.

Good work sir. Hoping to hear back about the highway test.

Tincanmuffler

I've been having almost the exact same thing happen to me on my 81! Hesitation leading to stall sometimes. Any luck with a solution? I've replaced just about everything besides the intake manifold and did an emissions delete when I put the weber on.

13Swords

In Northoak's case, it appears to have been a worn out distributor, likely a problem with the advance mechanism. Have you replaced that yet? Can you give a complete list of what parts you have replaced? As for the Weber was it new or used?

Tincanmuffler

Thanks for the reply swords! I've replaced: Distributor and cap, cat converter, exhaust, fuel lines, new weber, fuel filter, fuel pump, spark plugs and lines, thermostat, coil. I dropped the fuel tank and ended up finding a ball of old fuel hose in it. It's been a pretty wild ride so far haha! I've actually replaced the carb several times at this point and had the problem persist. The reason I dropped the fuel tank was because I had a fast clogging filter issue and kept losing pressure.

13Swords

New distributor, gotcha. Got the timing set right @ 5 BTDC?

I assume that the carb is a Weber 32/36? Do you have the electric choke power wire hooked up to keyed (ignition) power? And that you have the stock or stock type aftermarket in-tank electric fuel pump? If so, it may be that your fuel pressure is too high for the Weber. The stock in-tank electric pump is rated for 4.5 PSI minimum to 9 PSI max. The Weber carb is notorious for not liking higher fuel pressure, so the pump may be somewhat overwhelming your needle & seat & is pushing too much gas into the float bowl, causing a slight flooding/rich issue. The Weber 32/36 has a recommended fuel pressure of 2.5 to 3 PSI. Anything much beyond 3 PSI & they start having trouble working correctly. This is a commonly known issue.

The usual way to solve this is with an adjustable fuel pressure regulator. I've seen something like this work:

https://www.holley.com/products/fuel...ors/parts/9710

The regulator installs inline of your fuel supply line. I personally recommend it be installed after (past) the fuel filter.