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Hey guys. Just got home from a day in the bush. truck ran great on the way there. 1hr on highway (100 kmh) about half way through the 4x trip i noticed when i gassed it to go around a corner it sounded odd below 2800 rpm by odd I mean its seems and feels smooth up to there then gets the miss, doesnt knock just seems to have a dead cylinder?

limped home at 70 km/h under 2k rpm and parked it an hour ago. I am gunna go and pull the plugs and see what they look like, but what else should I look for. I didnt take in water and i wasnt pushing it either.
Motor has about 2200 km on it, bought it from s&J engines in spokane washington, reman block w/ some head work done, chevy valves and a moderate cam.

thanks for any insite

I could get a video too i guess of the sound...
 

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Discussion Starter #2
here's a video . it doesnt really offer much to the sound but you can see the rpm drop even though I can get the engine to come up.

Notced some oil residue around the PCV as well. there has often been some but it looks more noticible tonight. As far as a misfire goes, i squirted some water on each header pipe and all steam off right away, considering the idle quality is fiine im going to rule out a cylinder that has no spark
https://www.youtube.com/watch?v=SMq98z_zrZM
 

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When coil is out i don't think the truck will even start. My ignition stopped working last night I hit the coil a few times! Started. Idk if coil would effect you problem. I had 3 cylinders down last month but it would still run 75 mph without the 3.
 

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I could be way off just sharing personal experience. Mine is fuel ejected which might change the symptoms possibly.
 

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Too many variables. Time to start eliminating some. Kind of sounds like a loss of spark energy to me, but honestly it is way too hard to know from my chair. I would start by reading the plugs and taking a vacuum reading and then a compression test. This will tell you enough to get a better idea of direction and general engine health.
Also, look for grounding out plug wires, bad EGR, cracked or bad distributor cap etc. You could have a bad spark plug, so depending on the last time you changed them, it might not hurt to do a complete tune up.
On these older trucks, it is a good idea to carry spare parts. Two parts I highly recommend are a coil and an ignition module. If you are inclined to throw a few parts at the problem, I would swap in a known good coil and then a module if that doesn't fix it you have spares...

Don't rule out fuel pump or carb issues.
Like I said, a lot of variables.
 

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Discussion Starter #8
Ill run a compression test once i get all my plugs out tonight. No egr, ill go over the cap. My coil reads 1.4 ohm on primary and 9400 (9.4kohm) on secondary, which from what i read is ok i have a spare, known to be working ignition module aswell. Maybe ill plug it in first be fore i take anything apart
 

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Ill run a compression test once i get all my plugs out tonight. No egr, ill go over the cap. My coil reads 1.4 ohm on primary and 9400 (9.4kohm) on secondary, which from what i read is ok i have a spare, known to be working ignition module aswell. Maybe ill plug it in first be fore i take anything apart
I've seen plenty of coils read fine when cold. They can change as they heat up. The more load you put on them, the hotter they get. In fact, too large a gap of your plugs will increase spark energy. This puts more of a load on the coil which equates to heat. Ford went to a larger cap diameter so they could run a larger gap plug thus increasing the spark energy. The larger cap was to space out the terminals inside so they wouldn't cross fire by arcing. This was about the time they switched to the E-coils also IIRC. It can handle the increase of energy better than the round canister coil. There were other differences, but this is the basics of it. Reading the plugs will show you a lot. It is often a much overlooked part of diagnosing engine loss of power scenarios.
Sorry for the rant. This discussion brings back many almost forgotten lessons.
 

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Discussion Starter #10
Hey reading all this is what i like.. Learning time. Ill have the plugs out in an hour, compression test. I tested the wires and thier fine. I have 2 coils here my buddy gave me but they are the square style... Can i rig it up to work?
 

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Discussion Starter #11
here's some shots of my plugs. All WERE gaped at .044 when I installed them but i re checked and now they were quite a bit tighter. wierd?

Im no spark plug reader so what do you guys think? Ill put em back in and try my spare ignition module to see. if that's no different then Im going to get it hot tomorrow night and pull plugs for compression test and also check fuel pressure... Had peeps over for dinner and ran out of time.






I will also note that my cap/rotor and Dist are about 2 months old.
cap inside

 

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Cap looks serviceable. Might hit those terminals with some sandpaper though. Glad to see they are brass terminals. I never use aluminum caps.
The pictures of the plugs are a bit dark, but from two of the plugs I can see they are wet looking. The majority of them do look as if they are running cold. Perhaps a second opinion here from others, but that is what I see. This could be because you pulled them from the engine without it being to full temperature when shut down. Can you shed some light here?
Post back after you swap coils please. Also clean your engine grounds. I like each head to have a separate ground.
 

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Discussion Starter #14
Progress report.... All plug wires check out on resistance testing
- Cleaned engine grounds
- Re gaped plugs, installed back to normal condition (original cap,coil,wires etc.)
Started it up and the same issue was present.
- Changed to spare coil, same issue. Tried second spare same issue.
- Re installed original coil, and also put inline fuel pressure gauge.

Here's where it gets weird.
When I started it my ignition got stuck in the crank position (this has happened once or twice before in the past 4 months) so I back the key to off, still cranking/running etc, I have to cycle it a few times to get the starter to disengage. After that it has NO PROBLEM i could bring it up smooth and slow or hard and fast through the rpm range and there's no problem just like it should be. so i hop out and look at the fuel pressure gauge, Its holding at 6 psi. I then hand rev it and its good once, PSI stayed at 6. Hand revved again and the problem came back and got wierd at 2500 rpm up, missing sort of thing...

I was sure I had a spare ignition module, blue wire seal one but I have no idea where it ended up. That's all I couldn't try out.

My first thought was something clogged in 3 inches of fuel hose from filter to carb but then the problem came back.

On the stuck ignition note, I read about a ballast resistor. I dont know what it does or where it is. should I be checking this?
 

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tried something else and when I looked at the fuel gauge it was 1.5 psi... would it even idle lol? I guess my first cost will be a pump, go electric or replace mechanical?
Sounds like you are on the right track. Erratic fuel pressure can drive you nuts.

As for the ballast resistor. In the older days, it was a ceramic blok that mounted on the firewall or inner fender. Then it became a wire with a specific resistance that was also a specific length. It usually has a cloth like brownish or tan cover on it, and the wire is stiffer than the normal braided wires of same gauge.
It's purpose is to limit current to the coil in the run position for better cooling, but gets bypassed in the start position. This is for easier starts. Some coils will be stamped "internal resistor". I guess that means you could bypass the resistor wire and not overheat the coil at low rpm's. Perhaps that is only for older points ignition systems IDK.
 

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Discussion Starter #17
Replaced fuel pump and have a steady, 6.5 psi throughout the rpm range and flow that is correct to the volumes in the manual. Still have the stutter... Luckily while at the parts shop i grabbed a new module aswell just in case. Plugged er in and GOOD TO GO very happy to have solved that one so thanks for the pointers yo.
 

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Replaced fuel pump and have a steady, 6.5 psi throughout the rpm range and flow that is correct to the volumes in the manual. Still have the stutter... Luckily while at the parts shop i grabbed a new module aswell just in case. Plugged er in and GOOD TO GO very happy to have solved that one so thanks for the pointers yo.
Nice job!
Keep the old module so you can gut it out and use it for a heat sink in case you want to convert to a GM boomerang four pin style module for a little bit more durability.

 
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