Dead as a doornail, no clue.

B

bruss01

Member
My 1978 345 Scout was running just fine until recently and suddenly stopped yesterday. Let me describe the circumstances leading up to the event.

Bought the Scout 1 year ago yesterday. Most of the time it sits idle getting various tinkering on incidental things and occasionally running an errand. The fuel and oil pressure gauges have never worked in my history with this vehicle. It's been driven on some long highway trips (my commute to work on the freeway 40 mins, a run to stockton, two round trips to Grass Valley). It passed the stringent CA emissions test with flying colors.

It stopped on the highway being driven home from Grass Valley (I was not driving at the time so I do not have details). It also stopped on my wife running an errand. No fuel was getting to the carb, so I replaced the fuel filter. Still no gas, so I replaced the fuel pump. After the new fuel pump, it seemed to run fine.

Saturday I changed the oil. I used a good quality 10w-40 oil and a new filter. It May be just a tad over-filled (I thought I rememberd it being an 8 qt sump so I put in 7 qts and called it good, intending to top up as needed). Well, the dipstick is reading a bit high, maybe 1 quart over full I'm guessing. Didn't think that should be a problem.

Vehicle started and ran fine out front of the house, idled a minute or so to get oil up in the filter and passages. No problem. Then later I took it out to run a quick errand. Got three blocks from the house to a stop light, and pulling away from the light suddenly the engine stumbled and ran badly for about half a block and then died completely. No amount of coaxing could get it started again. I had my wife run down with a bit of fuel, just on the off chance the new fuel pump turned out to be a factory dud. Trickled a little stream into the carb while she turned over the engine. Nope, that didn't make a difference. Had to tow it home.

This morning I pulled a spark plug, thinking maybe if the valve seals or piston rings were shot I would find a wet, oil-soaked plug. Nope, it's dry and looking like a spark plug ought to.

Any suggestions on what the likely culprit might be, or things to check?
 
Robert kenney said:
first I recommend verifying spark as it sounds an awful like ignition related.
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Thank you Robert... It occurred to me that the timing between the oil change and the <kaput> May be strictly coincidental. I will go out and pull the center wire from the distributor and see if I can see/hear the spark arcing.
 
Robert kenney said:
first I recommend verifying spark as it sounds an awful like ignition related.
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Spark at the (hotter, aftermarket) coil seems steady. Pulled one of the plug wires off at the distributor and it seemed a lot less steady. Checking the book to see what to check next. Visual inspection of wires, cap & rotor turned up nothing unexpected.
 
Sorry if you have already posted what your setup is somewhere else but could you give us the specifics.

Have you tried to start is since having it go "kaput" like say a day or so later? You could squirt a bit of fuel down the carb and see if it pops. You are indicating that you see spark at the plugs. If it is a blue/white spark you should get something.
 
Robert kenney said:
sorry if you have already posted what your setup is somewhere else but could you give us the specifics.
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Bone stock 345, except for the hotter coil and an upgrade 12si alternator in place of the stock 10si.

Robert kenney said:
have you tried to start is since having it go "kaput" like say a day or so later? You could squirt a bit of fuel down the carb and see if it pops. you are indicating that you see spark at the plugs. if it is a blue/white spark you should get something.
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Yes, I tried starting it later that night and again the next morning. Not even a "pop". There is definitely spark between the center wire and the coil. I was having a much harder time seeing/hearing spark between the cap and the plug wire I randomly chose. I'm replacing the cap/rotor just to eliminate them as suspects in the investigation. Never had one go bad on me all at once like that, but there's a first time for everything I suppose.

Just to clarify, didn't pull a plug wire at the plug... I pulled it at the cap because I can see better there. (don't have a garage). I saw/heard spark clearly at the coil/wire. Not so much at the plug wire (did definitely see/hear one, couple more not so sure, definitely not strong like the coil). That makes me wonder about cap & rotor. We'll see if the new one's make any difference, should have them and weather permitting try them tonight.
 
I think Robert was wanting more specifics about your other components such as distributor model, coil model etc. When was the coil replaced in relation to this recent chain of events and why? Do you still have the coil that you replaced? Maybe swap it back on and see what happens? Like Robert, I think this is ignition related, but as a rule out, have you looked down into the carb while actuating the throttle linkage by hand to verify that the carb is delivering fuel down the gullet?
 
scoutboy74 said:
I think Robert was wanting more specifics about your other components such as distributor model, coil model etc. When was the coil replaced in relation to this recent chain of events and why? Do you still have the coil that you replaced? Maybe swap it back on and see what happens? Like Robert, I think this is ignition related, but as a rule out, have you looked down into the carb while actuating the throttle linkage by hand to verify that the carb is delivering fuel down the gullet?
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Scoutboy -

I'll try and answer your questions as best I can, seeing how I am not present with the vehicle right now (at work).

As far as I know, the vehicle is low in miles, high in years - bone stock 1978 IH Scout with 80k miles. Coil was replaced in July/August last year, worked great all this time. Old unit looked tired and I had been recommended to up the juice and overgap the plugs to .50 from .35 (standard) and again this has worked flawlessly all this time. My concern at that point was putting out a good profile for the emissions test and the new coil and plugs were what I considered "cheap insurance".

Distributor is the model with the male prongs sticking up (like the end of a spark plug). Couldn't tell you any more than that. The rotor is the narrow kind, not the full round kind. Don't know anything more about the rest of the ignition system, but as far as I am aware it is all stock, likely origninal.

Carb was completely rebuilt by me using a kit around the same time as the new coil came aboard... July/September last year. Worked perfectly all this time. Passed emissions with flying colors. I actually poured a trickle of fuel down the carb with the engine turning, no dice. Does not appear to be fuel starvation.

The curious thing is that it went from running perfectly to stumble-stumble-cough-sputter-fail in the space of about 30 seconds, maybe less. And hasn't uttered a *pop* since. That's just veird.
 
Prestolite distributor: I recommend the napa cap & rotor, highest quality that they carry with copper contacts. Don't but the cheap parts here.

.050 is too much gap for your plugs, imo. .035 is fine.

The rotor has a resistor built into it, looks like a small black box, take off the cap and do a resistance check to it. It could easily be bad.
 
1975ih200 said:
prestolite distributor: I recommend the napa cap & rotor, highest quality that they carry with copper contacts. Don't but the cheap parts here.

.050 is too much gap for your plugs, imo. .035 is fine.

The rotor has a resistor built into it, looks like a small black box, take off the cap and do a resistance check to it. It could easily be bad.
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Did not know that about the rotor! Thanks, good info. If this resistor has suddenly gone bad it would help explain the symptoms I'm getting, so the new rotor I'm putting in tonight May solve the issue. If that does it, I May need to have a few to keep in the glovebox. Is there an "emergency workaround" to this issue, such as an improvised bypass of the resistor?

Re: plug gap. - I have been told many people run them up to .070, sweet spot is supposedly .050. Not arguing that .035 can't work, obviously, but to a point "more is better". Or so I've been told. The reasoning being that IH didn't feel the need to have a bigger gap which would require a better coil, because emissions or fuel economy weren't really seen as big issues back then. Plus materials were't as good (at least without investing a good bit more money) back then and saving money on the assembly line could either be passed on to the consumer or pocketed by the mfr.
 
bruss01 said:
re: plug gap. - I have been told many people run them up to .070, sweet spot is supposedly .050. Not arguing that .035 can't work, obviously, but to a point "more is better". Or so I've been told. The reasoning being that IH didn't feel the need to have a bigger gap which would require a better coil, because emissions or fuel economy weren't really seen as big issues back then. Plus materials were't as good (at least without investing a good bit more money) back then and saving money on the assembly line could either be passed on to the consumer or pocketed by the mfr.
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You've been grossly misinformed on this subject. Don't feel bad. You're far from the only one. Lot's of bad information out there being regurgitated and spewed about.

The electrodes on spark plugs are delicate. Overgapping can weaken them to the point that they can break off. According to michael mayben, who ought to know, there is never a reason to exceed a spark plug gap of .045 on an IH produced engine even if it is running electronic ignition and a capacitive discharge (cd) box. These engines can only make use of so much electric current. In almost every case, a good oe coil more than meets these needs. Ignition coil condition cannot be properly assessed by a visual inspection of the canister either. There is a methodology involved which requires taking measurements with fairly sensitive diagnostic equipment.
 
Don't ever gap a conventional tip sparkplug to a gap any greater than 0.045"!!!!!!

We've stated this same thing here on this forum over and over. The various spark plugs used in these conventional ignition designs do not have a side electrode designed and implemented for a gap of more than 0.045" or they will most likely break off during operation at some point.

Whoever advised this kind of spark plug gap stuff to you is fulla shit! A gap like that is totally useless on these vehicles no matter what ignition system you are running. People that talk crap like that don't have a clue as to what they are doing or how this stuff works.

And, we have no idea what your entire ignition system setup actually is.

You must check for proper spark at the sparkplug gap, that is all that really counts at this point. If no spark (or very weak), then you work your way backwards through the system.

Only a prestolite distributor uses a rotor with an internal resistance element. The Holley/IH and the delco distributors do not use a resistive element rotor.
 
X2 with scoutboy and michael. Think of it this way, you said you think you have a weak spark at the dizzy to the plugs with a gap that wide the spark can't make the gap. I have seen it on my Chevy, plug gap got wide enough (just from mileage) it would not run very quickly! And that just normal use and lack of maintenance.
I neglect my Chevy but not my Scout:thumbsup:

ron
 
Ok, I appreciate all the good feedback and advice.

And I surely do not wish to argue with people who obviously know their stuff...

But I do want to point out that the vehicle, with this setup, has been running great (often starting up with hardly a single turn of the crank) for months now, and the plug I inspected looked great, classic "book" appearance for a good spark plug. Also passed a stringent emisisons test set like that. Would not expect that if it were set "so wrong it has to fail" as indicated by the seeming admant certainty expressed above. Maybe there's part of that I'm just not getting. Such as why a slightly larger spark gap would break off an electrode. Maybe someone can explain that part a little more.

Also, I didn't understand if I was being recommended to remove all the plugs, regap to .045 and reinstall, or simply never flex the electrode to the degree necessary to reach .050 (in other words, damage done, leave it alone, you'll know better next time). Or if I was being recommended to take the plugs out, throw them away and buy new ones. Kind of hard to justify the expense if the vehicle is otherwise running ok (which admittedly it is not at this very moment, but has been for a year and plugs do not seem to be the issue for the current state afaik, pending further investigation).

The reason I came on here and asked was because I panicked, thinking that somehow the oil change had messed up the engine in a serious way (timing chain or some deep engine malady) as in, I don't know what the po was running for oil, he could have had the crankcase full of stp for all I know. I didn't really think "ignition" at first because there was no reason to at that point, after all, I hadn't done anything to the ignition system recently. I guess things just fail when they're gonna, and timing doesn't have anything to do with it. Sometimes coincidence is just coincidence.

Let me get my head back under the hood tonight, try the new cap/rotor, and check a few of the things that have been mentioned, and then touch back with further developments.

Thanks again everyone.
 
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Ok, photos are worth 1k words, so here's a few thousand word's worth...

1978 345 Scout ignition pics

Is this enough to assess what is present?

It looks like a petronix? Prestolite? P-something maybe. Distributor cap.

There is a flat *something* on the rotor. Is that the resistor mentioned? How long are these supposed to last? Is there an ohm value that should measure out as? If you look close (not sure how well this shows in the pics) it seems to be eroded around the rivets holding the flat something down. Could this be a problem? Is there a way to test this? Is that just considered normal appearance after a few k miles, or an indicator of trouble brewing?

As you can see, the terminals are all brass, as recommended here.

The auto shop messed up and gave me the wrong replacement rotor. Correct part is inbound and should be here tomorrow.

You should be able to see the engine and even some of the factory and emissions labels... Hope that removes any ambiguity about "what he has under the hood". The coil is an msd blaster, good quality name brand, not some off-the-rack at k-mart pos.

Maybe the photos will stir some thoughts?
 
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Another question....

If it turns out the resistor in the rotor is bad... And the new one runs ok...

I am thinking (dreading) the day I am off on a solo adventure, up in the mountains, beyond cell phone range... Hearing on the radio that a huge storm is coming in and I jump in the truck... Only to find a repeat of this scenario. Sudden winter storms here in the mountains in mid-late autumn are not unheard of and they can be deadly and people have gotten stranded. Obviously, one tries to avoid those situations but life is life and things happen.

My question... Is it possible to bypass the bad resistor on the rotor and simply make a solid connection in it's place? If I did that to a bad rotor and kept it in the glovebox as a just-in-case emergency measure, would that work? I guess I am asking if that resistor is just there to keep the radio noise down or if it actually performs some crucial engine function.
 
If it were me and I was worried about it, I would just throw another new rotor in the glove/tool box. I don't think they go bad that often, but it can leave you stranded as you well know.
Normally plugs, cap, and rotor and possibly plug wires are changed on some sort of tune up schedule so it gets changed before they go bad.
Ron
 
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ronmc1954 said:
if it were me and I was worried about it, I would just throw another new rotor in the glove/tool box. I don't think they go bad that often, but it can leave you stranded as you well know.
Normally plugs, cap, and rotor and possibly plug wires are changed on some sort of tune up schedule so it gets changed before they go bad.
Ron
Click to expand...

I think that's a terrific idea and one I plan to implement. I still think it's a valid question, though, for the sake of understanding what goes on under the hood. It's mind-blowing to think that a tiny resistor which May not be an essential part of the engine's function could bring the whole show to a halt. I'm interested in knowing if that resistor's function is essential or just a nicety to keep radio interference down to a dull roar. I suppose I could just do it and see if the truck runs... But would rather hear from some of the resident experts here before just going off and doing it. If these parts become unavailable at some point in my lifetime, it would be nice to have the option to solder in a copper wire and "keep on truckin" after the last real replacement parts have bitten the dust.
 
Its a prestolite distributor. The item in depicted in image 31 of your album is not a gold box. It's a throttle deceleration module. Emissions shnizz.

I don't like the looks of that one wire connected to your coil. Not the red one. The other one with the hideous bare strands showing. I'd snip that garbage terminal off and crimp on a new ring terminal at least. Just a house keeping thing.
 
I would advise against that, you have a prestolite dizzy which is electronic ignition bypassing that resistor May burn out your ingition module. Then your cost just went up a heck of alot more than just an extra rotor.
I don't know if it would or not but I would not risk it.
Imho

ron
 
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