engine diagnosis ??
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Junior User
Joined: Aug 2011
Posts: 78
Likes: 1
From: College Grove, TN
engine diagnosis ??
I've had my 1966 F100 about 3 months now, so it is all still very new to me. Last week it started running very rough at high RPMs. The alternator light came on before it all started, but then it went back off. It idols great, but above 30MPH is rough.
I've changed the simple stuff, air filter, fuel filters, spark plugs, pcv valve. But it's still not running better. So what do I look at next?
I'm very inexperienced at this so I'm trying to start with simple fixes and work my way up.
I've changed the simple stuff, air filter, fuel filters, spark plugs, pcv valve. But it's still not running better. So what do I look at next?
I'm very inexperienced at this so I'm trying to start with simple fixes and work my way up.
Junior User
Joined: Aug 2011
Posts: 73
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Is it a 6 cyl. or a V8? Stock or aftermarket ignition system? If it still has points and condensor I would start with replacing them and set the dwell or point gap to spec. While the distributor cap is off, check to make sure the inside of the cap is not wet or carbon tracked( small lines of carbon going from one contact to another). Are you sure it is running rough and not a vibration problem? Slip it into neutral at speed and see if the problem is still there. How is the power? Does it seem under powered or does it backfire?
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Junior User
Joined: Aug 2011
Posts: 78
Likes: 1
From: College Grove, TN
It is the 6Cyl with a stock ignition system. It is defenitly not a vibration problem. At low RPMs around 20 MPH power is adequate, but any faster it starts sputtering and jerking around. It has backfired a few times recently.
I've considered puting an after market soild state ignition system in, but that will cost more than points and condensor and it still might not fix the problem.
The truck ran well for the most part, and then these issues started.
I've considered puting an after market soild state ignition system in, but that will cost more than points and condensor and it still might not fix the problem.
The truck ran well for the most part, and then these issues started.
Senior User
Joined: Dec 2010
Posts: 400
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Have you checked the spark plug ''Wires''? did you replace those also?
It sound like a plug wire is Bad? while engine is running at idle in park' pull each plug wire
one at a time and see if any change in engine?
As far as electronic Ignition' I would put a ''Pertronix'' simple to do and cheap!
Replaces your points! Put one on mine and love it!!
It sound like a plug wire is Bad? while engine is running at idle in park' pull each plug wire
one at a time and see if any change in engine?
As far as electronic Ignition' I would put a ''Pertronix'' simple to do and cheap!
Replaces your points! Put one on mine and love it!!
Thread Starter
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Junior User
Joined: Aug 2011
Posts: 78
Likes: 1
From: College Grove, TN
I don't think it is a bad fuel thing, since it ran fine on the same tank earlier.
I didn't change the plug wires, but I'm leaning toward changinf the wires and putting in a Pertronix ignition.
but what exactly do I buy? I see Pertronix I, II, and III. do I need the Flame Thrower ignition coil as well?
I didn't change the plug wires, but I'm leaning toward changinf the wires and putting in a Pertronix ignition.
but what exactly do I buy? I see Pertronix I, II, and III. do I need the Flame Thrower ignition coil as well?
Senior User
Joined: Apr 2011
Posts: 309
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From: Portland, Or
That might fix it but it sounds like it could be something with the carb as well.
To much fuel can cause it to flood and ride rough and back fire as well, do you have a tach; if so what rpm is it at when it starts happening. The more the rpm the more the carb is open.
hard to tell without really seeing or hearing it. Hope this helps.
To much fuel can cause it to flood and ride rough and back fire as well, do you have a tach; if so what rpm is it at when it starts happening. The more the rpm the more the carb is open.
hard to tell without really seeing or hearing it. Hope this helps.
Last edited by Rgd9664; Oct 7, 2011 at 04:52 PM. Reason: spelling lol
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Senior User
Joined: Dec 2010
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jstevens2,
Get the Pertronix 1, make sure you get the one for six cylinder engines as I think it's a
different part# than for a V8. also you might want to check the fuel pump and make sure it's pumping enough fuel into the float bowl, it could be running out of gas when under load and then when at idle the pump fills the float bowl up and idles fine? you should have between 4 and six pounds pressure on the pump. as far as the coil you should be ok with the stock coil but I run a accel coil on my v8..
Get the Pertronix 1, make sure you get the one for six cylinder engines as I think it's a
different part# than for a V8. also you might want to check the fuel pump and make sure it's pumping enough fuel into the float bowl, it could be running out of gas when under load and then when at idle the pump fills the float bowl up and idles fine? you should have between 4 and six pounds pressure on the pump. as far as the coil you should be ok with the stock coil but I run a accel coil on my v8..
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Thread Starter
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Junior User
Joined: Aug 2011
Posts: 78
Likes: 1
From: College Grove, TN
the Pertronix 1 is only $75, so that is a good option. I'm just looking for a simple way to make it run better, nothing high performance is needed. Is there really any need to upgrade the ignition coil?
Elder User
Joined: Oct 2009
Posts: 825
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From: Dallas, Texas
That might fix it but it sounds like it could be something with the cab as well.
To much fuel can cause it to flood and ride rough and back fire as well, do you have a tach; if so what rpm is it at when it starts happening. The more the rpm the more the cab is open.
hard to tell without really seeing or hearing it. Hope this helps.
To much fuel can cause it to flood and ride rough and back fire as well, do you have a tach; if so what rpm is it at when it starts happening. The more the rpm the more the cab is open.
hard to tell without really seeing or hearing it. Hope this helps.
FTE Legend
Joined: Jun 2004
Posts: 32,020
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From: Upstate NY
You can go ahead and get rid of the points if you want but I would definately but a set of wires on it anyways. Sounds like classic bad wire symptoms to me.
Take my advice, I'm not using it!
Take my advice, I'm not using it!
Junior User
Joined: Aug 2011
Posts: 73
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I still don't see that the points and condensor have been replaced or checked. As far as doing this in the most economical way I would start by at least checking the dwell if you have a dwell meter and if not check to see if the points are burned and then set the the point gap and check and set the timing as needed. If this does not do it replace the points, condensor and wires. It sounds like an ignition problem to me but if this does not do it I can give you some ideas on how to check for a lean (not enough fuel) condition.