Old problem not really solved
Thread Starter
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Laughing Gas
Joined: Aug 2010
Posts: 983
Likes: 49
From: Northern Kentucky
I was trying to figure my next step, aside from a new coil connector. Mine looks to be in very good condition but they are only about $6, so a cheap test.
I wasn't sure whether the coil or the ignition module would be a more likely suspect.
I wasn't sure whether the coil or the ignition module would be a more likely suspect.
Lead Driver
Joined: Nov 2013
Posts: 7,178
Likes: 1,174
+1 on the new coil. Read about my experience here after replacing an old coil that seemed to be working fine:
https://www.ford-trucks.com/forums/1...tion-coil.html
Most times it's tricky to confirm when electrical parts have partially degraded. I used to have a big old SunScope with a screen that could display the coil output pattern under load. As slick as it was for diagnostics, it took up tons of limited garage space. It was easier to just make educated guesses and replace the occasional part.
If the old connector is clean and shows no signs of corrosion or overheat, I'd probably stay with that. Splicing in a new one adds connections that could act up down the road.
https://www.ford-trucks.com/forums/1...tion-coil.html
Most times it's tricky to confirm when electrical parts have partially degraded. I used to have a big old SunScope with a screen that could display the coil output pattern under load. As slick as it was for diagnostics, it took up tons of limited garage space. It was easier to just make educated guesses and replace the occasional part.
If the old connector is clean and shows no signs of corrosion or overheat, I'd probably stay with that. Splicing in a new one adds connections that could act up down the road.
Lead Driver
Joined: Nov 2013
Posts: 7,178
Likes: 1,174
Yes it could, with same basic symptoms as a bad coil. If resistance values check okay on both parts, it's a probability game when deciding which one to change. A coil handles a much higher voltage (more prone to breaking down its insulation) and gets warmer by design, too. Meanwhile, the pickup only handles a weak low voltage signal. Absent any faults specific to the pickup, I'd suspect the coil first.
Laughing Gas
Joined: Apr 2013
Posts: 1,049
Likes: 65
What about your wires? Make sure they're good too.
Now what about your carb? And your fuel filter? If it's misbehaving at 3,000 RPM pulling a hill that takes a lot of gas.
Does it feel like it's running out of gas? If so you have to wonder about dirty fuel filters and low floats.
If it does it worse when the fuel tank is low then that suggests fuel filter. If it cuts out consistently after you've been on the gas for a while then I'd wonder if the floats are low.
Now what about your carb? And your fuel filter? If it's misbehaving at 3,000 RPM pulling a hill that takes a lot of gas.
Does it feel like it's running out of gas? If so you have to wonder about dirty fuel filters and low floats.
If it does it worse when the fuel tank is low then that suggests fuel filter. If it cuts out consistently after you've been on the gas for a while then I'd wonder if the floats are low.
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Thread Starter
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Laughing Gas
Joined: Aug 2010
Posts: 983
Likes: 49
From: Northern Kentucky
Wires don't have many miles on them but a continuity check may be in order. The way it ran with the jumper replacing the resistor makes me think that they are good.
Carb. has been checked twice, floats properly set, power valve looks good, new jets installed and fuel filter changed all since trying to solve this problem.
It actually feels more like the ignition system is breaking down somewhere.
Carb. has been checked twice, floats properly set, power valve looks good, new jets installed and fuel filter changed all since trying to solve this problem.
It actually feels more like the ignition system is breaking down somewhere.
Laughing Gas
Joined: Apr 2013
Posts: 1,049
Likes: 65
Okay, you got the carb covered.
How about your mechanical advance? Pull cap and give the rotor a little twist to verify the mechanical advance isn't binding and is springs back freely. While your in there you can also pull the little felt puck out of the top of the distributor shaft and lube the mechanical advance with a drop or two of oil.
If you have a timing light you can check the mechanical advance by disconnecting the vacuum advance verifying the mechanical advance when you rev the engine.
How about your mechanical advance? Pull cap and give the rotor a little twist to verify the mechanical advance isn't binding and is springs back freely. While your in there you can also pull the little felt puck out of the top of the distributor shaft and lube the mechanical advance with a drop or two of oil.
If you have a timing light you can check the mechanical advance by disconnecting the vacuum advance verifying the mechanical advance when you rev the engine.
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Laughing Gas
Joined: Aug 2010
Posts: 983
Likes: 49
From: Northern Kentucky
Distributor was checked for spring-back and checked OK. Checking mechanical advance will have to wait until I can get my faithful assistant, Mrs. Whisler to work the throttle for me. Can't figure a way to work the throttle, hold the timing light, and watch the advance at the same time.
Installed a new coil today, but it did not solve the problem. The stumbling issue still happens at ~2800 RPM on a steep uphill climb when accelerating. Acceleration on level ground seemed good to about 3200 RPM, where I backed off.
Sitting in the driveway, I decided to rev. it in park to see if things fell apart at some point. Everything is good up to about 3800 RPM, where the same type of stumbling occurs. That is not an RPM range I would spent much time in, but it does show that the fault is not restricted to just a heavy load condition.
I'm frustrated and confused as to where to go next.
Installed a new coil today, but it did not solve the problem. The stumbling issue still happens at ~2800 RPM on a steep uphill climb when accelerating. Acceleration on level ground seemed good to about 3200 RPM, where I backed off.
Sitting in the driveway, I decided to rev. it in park to see if things fell apart at some point. Everything is good up to about 3800 RPM, where the same type of stumbling occurs. That is not an RPM range I would spent much time in, but it does show that the fault is not restricted to just a heavy load condition.
I'm frustrated and confused as to where to go next.
FTE Legend
Joined: Nov 2015
Posts: 30,935
Likes: 4,124
From: Angier, NC
Do you have a tach in the truck or one you can use that will go above 4000?
If you do use it to see if it jumps around. That would point to the electric side.
Can you list (lazy to read back thru it all) again what you have done to try and fix this and the year / motor we are working with. (hint put it in your signature so we know model/year/motor size/trany type)
Dave ----
If you do use it to see if it jumps around. That would point to the electric side.
Can you list (lazy to read back thru it all) again what you have done to try and fix this and the year / motor we are working with. (hint put it in your signature so we know model/year/motor size/trany type)
Dave ----
Lead Driver
Joined: Nov 2013
Posts: 7,178
Likes: 1,174
Sitting in the driveway, I decided to rev. it in park to see if things fell apart at some point. Everything is good up to about 3800 RPM, where the same type of stumbling occurs. That is not an RPM range I would spent much time in, but it does show that the fault is not restricted to just a heavy load condition.
Dave had an excellent idea to watch the tach. If you don't have one permanently installed, you could hook up a dwell/tach used for tune-ups and see what the RPM reading does.
Another thought is to connect a fuel pressure gauge via a tee fitting at the carb inlet. Duplicate the fault and see how the fuel pressure behaves.
EDIT: Limit the time you hold the RPM so high with no load on the engine. That combination is tough on connecting rods and wrist pins.
Thread Starter
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Laughing Gas
Joined: Aug 2010
Posts: 983
Likes: 49
From: Northern Kentucky
I do have a tach and didn't notice any jumping, but wasn't specifically looking for it either.
Didn't want to hold it that high for long.
As to what has been done, I have checked everything in the carb. I could think of or was recommended (float level, accelerator pump, power valve, main jets), tested the fuel pump for supply volume (good), replaced plugs, dist. cap , rotor, ballast resistor & coil, cleaned coil connections, tested vacuum advance and rotor spring-back.
Didn't want to hold it that high for long.
As to what has been done, I have checked everything in the carb. I could think of or was recommended (float level, accelerator pump, power valve, main jets), tested the fuel pump for supply volume (good), replaced plugs, dist. cap , rotor, ballast resistor & coil, cleaned coil connections, tested vacuum advance and rotor spring-back.