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Old 11-25-2009, 09:01 PM
64deville 64deville is offline
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84 F150 351W wont fire - Coil Pickup?

I've got a 1984 F150, 351W 2bbl that wont fire. This might be kind of long:

Over the past week sometimes it would take 2 seconds or so of cranking to get it to fire. Today after 2 straight days of rain it wont fire at all. I put my money on a fuel delivery problem but, I know gas is getting to the carb. I sprayed some starting fluid in the carb and still same thing, just cranks, doesn't even try to start. So I pulled the air cleaner housing and I pulled on the throttle linkage, its getting plenty of gas, solid sprays every time. So rule out fuel delivery.

So, now its got to be lack of spark. As far as i know the carb is controlled by a computer under the accelerator pedal in the cab. I don't have the typical Ignition Control Motocraft box bolted to the passenger inner fender with the 2 round wiring plugs hanging off. All the wiring looks fine so I pulled the distributor cap off and cranked it and its getting great spark going to the dist cap (amazing actually). The contacts look fine but I scraped them down with a knife just to be sure.

I'm thinking its something in the distributor like the pickup coil? Its obviously getting spark and I'm pretty sure all of the plugs/plug wires didn't fail at the same time so its got to be something in the distributor right? The suspect is the pickup coil now. From what I know the pickup coil controls the spark to the cylinders at the right time depending on which is firing. I'm guessing when it gets down to the pickup coil, its getting nothing or its not working properly ie. spark at the wrong time.

I've seen parts online from the auto parts places or a new distributor. Before I start throwing parts at the problem, anyone have any suggestions.
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Old 11-25-2009, 09:29 PM
draveling1 draveling1 is offline
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man i have a similar problem with and 86 f-250. mine runs but it acts like its only running on 6 cylinders all the plugs are firing but it really eratic and the motor shakes and has no power. I have the durasapark deal and im thinking its the box thats bad. does yours have the high output coil or the old style? Im thinking im going to get a distributor thats the coil and brain box in one all you need is a hot lead. have you pulled a plug out and checked if it was firing?
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Old 11-25-2009, 09:29 PM
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OK, so, you have spark from the coil to the cap; have you checked at the plugs? Pull a plug
wire and hold it near the engine block while somebody tries to start it, see if it arcs to ground
or not.
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Old 11-26-2009, 07:43 AM
64deville 64deville is offline
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We didn't pull a plug wire and test which would be the obvious next step. That can only go one of two ways though. 1. The plugs are getting spark in which case the pickup coil is working. That would tell me that all the plugs are all of a sudden bad or, they are getting spark but not at the right time. 2. The plugs are not getting spark in which case I would know that either all the plug wires failed or something is wrong inside the distributor.

From my experience the distributor doesn't have a lot inside of it to go wrong. The gear could be broken I guess but i think i would hear a lot grinding around inside the cavity if that was the case. I'm heading out of town today but, on sat i'm going to pull it out and pull the distributor apart.

Will keep you updated.
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Old 11-26-2009, 08:36 AM
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If the pickup coil is bad you mont get spark to the dist.
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Old 11-26-2009, 08:54 AM
64deville 64deville is offline
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I'm getting spark to the distributor cap. I pulled the dist cap off cranked the key and there was plenty of spark getting to the cap. The rotor looks fine so I'm guessing the pickup coil is not working properly.
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Old 11-26-2009, 05:48 PM
FordPickupTrucks FordPickupTrucks is offline
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Have you pulled the spark plugs & checked that they are firing & also where they screw into the cylinder head? That is where the spark goes after it fires the air/fuel if it does not have a good connection( i.e. the grounds) then it will take the shortest route to ground.
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Old 11-27-2009, 09:10 AM
64deville 64deville is offline
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Nope, haven't tired the plugs yet. Will try them before I pull the dist. apart though.
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Old 11-27-2009, 09:45 AM
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Quote:
Originally Posted by 64deville View Post
I'm getting spark to the distributor cap. I pulled the dist cap off cranked the key and there was plenty of spark getting to the cap. The rotor looks fine so I'm guessing the pickup coil is not working properly.
You missed bashby's point completely. If you are getting good spark to the cap, then the pickup coil is working. If the pickup coil were not working you would have no spark even to the cap.

Since you have good spark to the cap, the problem must be "downstream" from there. There are several possibilities (not listed in any particular order)

1) Cracked distributor cap - the cap could have a hairline crack. With the cap off of the distributor, it may look fine. Put the cap back on the distributor and every spark runs down the crack to the distributor body instead of to the plugs.

2) Cracked or otherwise bad rotor - again, you see good spark at the cap with the cap off. Put the cap back on and the spark runs down the cracked rotor to the distributor shaft and not to the plugs.

3) Plug wires - bad insulation or burned up core. Replace.

4) Fouled plugs

Then there is a very unlikely problem - bad timing chain. I had a friend with a 302 that suddenly started running weak. Ran that way for a week or so, then stopped running completely. Had spark, gas, etc., just would not fire. After checking a lot of things, finally found that his timing chain had stretched. It skipped one tooth after which the engine ran weak. Then it skipped another tooth and would not run at all. Since your problem seems to be related to the rain, I would guess this is not your problem.

When you have an ignition that acts up when it rains or is foggy, it is a good bet that you have a bad insulator somewhere (cracked cap, bad plug wires, etc.).
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Old 11-27-2009, 10:29 AM
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To add:
5) Weak coil. You should be able to hold the coil wire close to ground and get a nice blue spark.It should have enough power to jump at least 1/2" to ground
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Old 11-27-2009, 10:30 AM
FordPickupTrucks FordPickupTrucks is offline
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I just know that happened to me on one of my engines is why I mentioned it to you. I hope that you figure it out! Hope Your Thanksgiving was a good one!
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Old 11-28-2009, 03:48 PM
64deville 64deville is offline
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well, here is what we did.

we tested the plug, it was getting very weak spark.

we replaced the cap and rotor. still would not start.

Then we replaced the ignition control unit. on my F150 its the flat style like this one: Ignition Module/Control Unit by BWD - Part CBE24Z - Advance Auto Parts
Still would not start.

So then we determined that maybe the plugs were gas fouled. Pulled them and they all reeked of gas and were black. Replaced the plugs and retested the spark plugs with the tester. Nice blue spark this time but still would not start.

Then figured the cylinders had been washed out with gas so we decided to push it up to the top of the lot and coast/pop start it. Fired up and ran ok but wouldn't idle well. Let it idle with a foot on barely on the accelerator and my friend jiggled the connection going into the ignition control unit. Seemed to improve so I electrical taped it into place because it wants to pop off really easily. Tomorrow going to the junkyard and finding a more solid one. Part of the retaining clip on mine is busted.

So, I guess one problem caused another. Faulty connection to the ignition control module caused gas fouled plugs from repeated starting attempts. At least thats what I'm going with.

Thanks everyone and yes, I probably miss the point in some of the suggestions. Was just certain I knew in my mind how everything worked.
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Old 11-28-2009, 03:48 PM
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