Wid

Hey fellow Yota Lovers, I'm back with yet another annoying running problem.

My 79 Pickup with the factory 20r has been acting up again. It runs perfectly fine without any problems until it reaches operating temperature (according to the gauge) but then it stalls under any load, or when I rev it, the truck will stall when I let off the accelerator, cut out and start itself back up. It idles perfectly when this happens, and gives no warning signs (that I can see, feel, or hear) It kind of sucks because I have almost been t-boned twice now.

Things you should know.

100% stock 20r Block, head, exhaust, and Intake manifold.
Weber 32/36 New as of 6 months ago.
New spark plugs, Wires, Distributor, Cap, Rotor 6 months ago
New Fuel Filter, and pump 6 months ago
NO Vacuum Leaks.
Verified very nice blue spark on each cylinder
Emptied the tank, no moisture or debris
Fresh oil change
The entire Ignition system has been replaced.
New Coil
New ICM
I even wired the coil directly to the battery just to make sure there was 12 volts. No difference.....

I'm doing a compression test in about a half hour. I will post my results immediately.

I'll be around all day to answer questions, and test your suggestions.

I have had a somewhat similar problem in the past but exactly. It ended up being an improperly wired ICM ( Ignition Control Module ) But there isn't a single change with that. I'll be going through my wiring and redoing all connectors today, and will let you guys know what I find. And connectors would not explain the fact that it only happens at Operating temp.

OH! I almost forgot to mention, I have been using the GM Toyota Ignition bypass method. But I'm using the factory coil. Which has tested perfectly, and works better than the Duralast crap I bought. One word to the wise, buy the extended warranty guys. God forbid your fuel pump fails after a year and you can't get a new one for free. But the fuel pump is working great. I even temporarily unplugged the Oil Sender to make the fuel pump stay on permanently, and its definitely working great.

Hope to hear some good ideas, as I have to move out on the 31st and will be completely screwed if I don't have this solved.

Wid

Well, I went to do my compression test this morning, and I tested at 150psi across all cylinders. Not 1psi difference between a single one of them. Just as I assumed. BUT. On the #4 cylinder I found this...

Wid

Putting new plugs in right now, just got back from the parts store. I will post back with my results.

enigmaT120

I never saw that before. Was it eroded away somehow or broken off?

Wid

I really have no clue. There could have been a stress crack before I even put them in. But honestly all four looked to be in good shape considering the last one... Nice even tan burn. Maybe slightly rich but overall I've seen much worse.

A little bit of an update, I had a brand new distributor in my garage and I put that on last night in the dark and hooked up a timing light to get it to 8 degrees BTDC, and it was actually running great! Better than before but I probably just had it out of tune slightly.

Unfortunately, this solved nothing. Literally everything in my ignition system is brand new. I'm so stumped. The spark cuts out when it stalls, I don't believe this to be fuel related. The fuel pump is operating flawlessly.

I'll follow up with the video in a few minutes, just have to upload it first.

gillesdetrail

iTrader: (1)

So just to be clear you are saying your that when the problem occurs you have no spark? Can you test your ignition switch at that moment?

Wid

Yes that is exactly what is happening. It cannot handle a single bit of load or spark will momentarily stop, and then start again. I am going upstairs to post the videos so you guys can see what's going on a little better.

Wid

So this link here, will bring you to my youtube video of the truck idling before it reaches operating temp. There are no ignition issues present. Idle is stable, but there was a slight lag on throttle response when I first attempt to rev the engine.


Now this video, shows the spark issue I am having after the truck reaches operating temp. Ignore the light stopping at the end. My ground for the timing light fell off the battery.


And lastly, I installed another new distributor and timed it to where it ran best by my ear, and although probably not ideal, the truck ran the best I've ever seen until it reached operating temp again. Now the problem is consistent at idle. Surging and stalling without me touching the throttle whatsoever.


Let me know what you guys think.

kawazx636

iTrader: (3)

I think that I'd be a little more concerned about where the ceramic is that came off the spark plug. That can't be good for your cylinder walls.

As for your problem, Have you checked the resistence on your wires?

kawazx636

iTrader: (3)

And is your battery and alternator putting out enough amperage to run your ignition set up? Try hooking up jumper cables to it from another vehicle (like a fullsize truck) and see if you still get the same problem.

Wid

Thanks for the reply kawazx636,

Not too worried about the porcelain at the moment. Based purely on the burn pattern on the broken part, it seems I have already put a lot of miles on it, and let it idle quite a bit the way it is. So I guess with the great compression in all four cylinders, I think I'll rest easy for now.

As for checking the resistance on all my wires, I will go down to the garage and take those readings and then some. Be back soon with an update.

Wid

And to answer your question about output, there was no difference with my 12v charging system hooked up to it, and my alternator is putting out 13.4 roughly

Wid

Tested a few things, my results were

#1 Plug Wire - 3.9k
#2 Plug Wire - 7.4k
#3 Plug Wire - 7.1k
#4 Plug Wire - 9.9k
Primary Coil Winding - 1.7 ohms
Secondary Coil Winding - 13.5k
Coil High Tension Lead - 17.8k
Distributor Signal Wires - 179 ohms
Resistor Wire (From the Ignition) - 12.1V

Wid

All of those readings are within factory recommendations. BUT, I found a decent amount of corrosion on the inside of the boots at the distributor cap. I replaced it with my old Bosch cap, that barely had any miles on it. And went for a test drive. I think I ran out of gas but I am not sure. My fuel pump started whining, but the truck continued to run. It may have just not cleared out the lines yet, but who knows. I'll check in the morning. I may as well just drain the tank and see how much is in there just to be sure, and if there is a lot and it's whining, I'm just going to take the bed off and replace the pump tomorrow. This is the last part I'm buying on a whim.

This is just the truck after a (what I consider) perfect tune, at operating temp after the cap was replaced.

Wid

One thing I forgot to mention is that all tests on the plug wires were done from the plug side through the cap to the posts. Same with the high tension coil lead.

kawazx636

iTrader: (3)

Perhaps you should eliminate the fuel tank variable and run the fuel supply out of a gas can just to test it. If you are running on a low tank or no fuel then there is no telling what you might be sucking up. All of my vehicles are re-fueled at 1/4 tank and I have never had fuel issues - although my wife's Camry has the worst invention ever; the fabulous "Distance Until Empty" feature... I've caught her a couple times with less than 5 miles left on the tank and gave her a stern talkin' to! In theory, that would be less than a 1/6 of a gallon of gas for a vehicle that gets 30mpg.

gillesdetrail

iTrader: (1)

I imagine you have checked all grounds?

Wid

So I woke up this morning and started the truck. And the alternator wasn't charging the system. It had 12.4 volts right at the beginning, and slowly dropped until it was at 11.9 volts. The stalling began right after.

So I hooked it up to my shop charger and set it to 12v High, the voltage at the battery raised to 13.4 volts. And yep, you guessed it Sherlock... It ran flawlessly.

So I figured, eh what the hell, I sure do love buying new parts I can't afford, and bought an alternator. Put it in, and it was working great at first. Steadily holding at 13.4-13.6 volts. No change after 20 minutes at idle. So I took it out for a drive. Ran great! Drove even better. Until I had to turn on my headlights. The damn thing gave me a warning backfire because the voltage was low and wasn't igniting all the fuel, and then sure enough it stalls out. Back to its normal ways. I turn off the headlights and let it idle. It charges itself back to 13.2v and I hop in and it drives, but the headlights bring it back to 12.5-12.6 and it starts stalling again. Go figure.

Now I am thinking its gotta be a shorts somewhere, a shot ground, or it's my voltage regulator. I honestly have no clue but maybe you guys have another idea as to why it's doing this still.

With the headlights on, and the truck running, I unplugged the voltage regulator, the voltage immediately drops to low 12's. Plug it back in and it's at 12.6 volts. I'm stumped here guys. Should I try out a new regulator in the morning and return it if it acts up still? Or do you suspect a wiring gremlin?

I'm tired of pushing my truck with a fractured ankle. I'm wearing a damn walking boot pissing people off cause I'm getting stuck at intersections all damn night. I'm tired, and really close to burning this ˟˟˟˟ing truck to the ground. I just love it so much...

Any suggestions would be appreciated, and I'm pretty damn sure it's safe to say this problem is clearly electrical...

gillesdetrail

iTrader: (1)

I don't think you can buy an electronic piece like a voltage regulator and return it. I am no electrical expert but I would check and rebuild the grounds from the motor mount to the frame, mine acted really weird yesterday when I was cranking it with it not properly secured, I would also check the wire from the alternator to the battery, but I'm sure you already did, keep us posted on the problem!

Wid

Well I haven't even rolled out of bed yet, but I will check up on my grounds again. Hell they're all original so I should replace them anyways.

Now yesterday when I was fidgeting with the wiring to the regulator I noticed the voltage changing, I'm thinking it's either a bad plug or some wiring near the alt. wiring might be a headache but I'm actually pretty good at it. Depending on what I find as i work my way through the harness, I might just make myself a new one. Just pull the old one out unwrap it, label everything and just start duplicating it wire by wire. Could be fun lol… and I can get wire spools pretty cheap.

I'll keep you guys posted, I'm unwrapping my whole harness and redoing my grounds today. One at a time then rechecking of course.

Later!