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  #1  
Old 09-28-2010, 05:40 PM
csouther csouther is offline
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68 F250 w/ 360 and C6 strange misfire HELP!

So I have been battling various issues with my 1968 F250 camper special since I began this project. Here is a list of the new parts on it:

New gas tank and lines
rebuilt carb
fuel pump and filters
converted to electronic distributor
coil
alternator
voltage regulator
ignition switch
vacuum advance and vacuum lines
spark plugs and plug wires

Here's the problem...The engine will start and idle just fine with two exceptions.
1 - When put into gear it will sparatically misfire and die. It doesn't do this consistently not related to being hot or cold
2 - If you turn the headlights on it will start to misfire and die.

I don't know if it is normal for these trucks but if when idleing you pull the ground cable off the battery (to get it to run just off of the alternator) it will runn very poorly and die. The battery reads 15v when idling. Whats a good way to test the alternator output?

I think my problem is electrical but I can't see why with everything that is new it still does this. The timing is set to 14 deg BTC (with vacuum adv. disconnected) and goes up to 18 with it connected. The vacuum adv. is connected to manifold vacuum (distribution block with the tranny line on it).

So there you go you master detectives, figure it out and help a fellow Ford Truck guy keep it form the scrap yard.
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  #2  
Old 09-28-2010, 09:55 PM
tuktukme tuktukme is offline
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Is your dist vac line connected to the manifold, I believe YES, alternatly change it to the carb port for the dist.
Verify that your ignition wires are indeed cleanly connected to the starter solinoid. A coroded connection will result is ir-regular ignition.
I have been going thru this delima for 5 years with no-one being able to offer input to the problem. I guess this was the first on and I have now taken care of the problem.
Good luck
Let me know if you may need anything else.
Roy
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  #3  
Old 09-28-2010, 11:21 PM
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Well the issue seems to be voltage. 15 volts at idle is not good it should be no more than 13.8-14.4 max. make sure you have good connections at the alternator and at the regulator. Also when you switched over to the electronic distributor did you upgrade the coil? Or the wiring? The stock wiring has a inline resistor in it to drop voltage to the coil to 7 volts this is good for points systems but not for electronic. What is the voltage at the coil with it running? And as mentioned above vacuum advance should be connected to the carb not the manifold.
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Old 09-29-2010, 03:02 PM
csouther csouther is offline
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I'll move the vacuum advance to ported vacuum but I still don't understand why these trucks are setup like that. Isn't the whole point of a vacuum advance to help smooth out the idle by advancing it at higher (manifold) vacuum so when you step on the gas (little to no manifold vacuum) the timing will drop back down to where you set it initially?

What should be my initial and total advance with the vacuum advance on be? I believe I'm right around 15 deg init. and some 30-35 deg total after 3000 rpm.

The voltage at the battery at idle could very well be 14.4, not 15. I had a crappy analog meter when I read it. I'll get my digital one and recheck it and the voltage at the coil. I replaced the coil when I went electronic dist. with an original replacement one that is supposed to be used with the existing resistor (built into wiring harness?). Should I bypass the built in resistor to get the full voltage to the coil? If so is there an easy way to do it without tearing the harness apart?

I'll also clean the starter solenoid terminals and connections to be sure. Thanks for all the tips guys. It is much appreciated. I'll let you know who wins!
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  #5  
Old 09-29-2010, 06:02 PM
tuktukme tuktukme is offline
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FE ARE THE BOSS

Believe me the FE engine is the BOSS, you just got to get it running right. In ref to your ? about the advace adj, there is a allen head screw in the advance, screw it in all the way NOT TIGHT, then back it out 3 1/2 turns. hOWEVER THE OLD ONES REQUIRE SHIMMING IT.This will get you into position. I tricked one out that would advance, hit passing gear and 4 bbl all at the same time, she would breka loose and go squirrely @ 55. Thats a rush !!!.
1/4 was very fast. I could take off and in town before my tires (front ) reached the oposing cross walk I would be at 60 mph. Oh by the way, I still got 19mpg.
Unless I was to pedal to the metal ...!!!!
Your dist ignit ion wire should read 13.8 volts, when running. No varry in that.
Take care
Roy
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  #6  
Old 09-29-2010, 06:03 PM
tuktukme tuktukme is offline
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Quote:
Originally Posted by ford390gashog View Post
Well the issue seems to be voltage. 15 volts at idle is not good it should be no more than 13.8-14.4 max. make sure you have good connections at the alternator and at the regulator. Also when you switched over to the electronic distributor did you upgrade the coil? Or the wiring? The stock wiring has a inline resistor in it to drop voltage to the coil to 7 volts this is good for points systems but not for electronic. What is the voltage at the coil with it running? And as mentioned above vacuum advance should be connected to the carb not the manifold.
WHERE IS THE RESISTOR HIDDEN !!!!!!
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Old 09-29-2010, 08:35 PM
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So i checked the voltage across the coil and to the coil. It seems as though there is only about 5v across it and 12+ supply to it (testing the ign wire and ground). The electronic ign is also getting the same 12+v to it.

I started pulling plug wires from the dist. cap while it was running to see if I could find if it was missing only on one cylinder and not a random one. After each one i noticed a drop in rpm and a rise when put back but on all but one cylinder. Its the number 7 cylinder and you can hear it missing in the exhaust on that side.

I tried to set the timing to 10 deg btc but it ran poorly and would lagg when you open the throttle up. I kept advancing it and turning the idle screw on the carb down until it didn't hesitate as much . I thought that i confirmed the marks on the harmonic balancer to be accurate but maybe i was wrong. It idles and doesn't lag at 25 deg btc. The vacuum (manifold) is at 18 mmhg at this point.

What does it sound like now?
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  #8  
Old 09-30-2010, 03:30 AM
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Quote:
Originally Posted by tuktukme View Post
WHERE IS THE RESISTOR HIDDEN !!!!!!
As original:

D7AZ12250A .. Resistor Wire, Ignition Coil-Use with DuraSpark Electronic Ignition (Motorcraft DY213)

49" long / 1.30-1.40 ohms resistance / Color coded Red w/Green stripes / #16 gauge wire.
----------------------------------------------------------------------------------------
COLF12250A .. Resistor Wire-Ignition Coil-Used without DuraSpark Electronic Ignition (Motorcaft DY37)

61.49" long / 1.30-1.40 ohms resistance / Color coded Pink / #20 gauge wire.
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  #9  
Old 09-30-2010, 11:42 AM
csouther csouther is offline
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So should my truck have both wires and only one is used? Or will I need to run a new wire from the ignition switch?

Also, I found it to have 12+ volts on the wire going to the coil but only a 4-5V across the coil terminals. Whats up with that?
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  #10  
Old 09-30-2010, 01:34 PM
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I'm not using duraspark but an accell points eliminator kit. Sorry if I caused any confusion.
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  #11  
Old 09-30-2010, 10:58 PM
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When I put a duraspark in my '69 w/ a 390 I bought a coil that said it has internal resistance and no external ballast resistor needed. I bypassed the resistor wire and ran full voltage to the coil. I also am running timing at 8btdc and using ported vacuum.
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  #12  
Old 09-30-2010, 11:28 PM
csouther csouther is offline
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That is good info and all but I don't have a duraspark setup in my truck. I have an accell conversion kit with a factory replacement coil that says to use the resistor wire.
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  #13  
Old 10-17-2010, 06:46 PM
csouther csouther is offline
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Figured out some things....

So after testing the ignition (everything!). I decided to double check the timing and the harmonic balancer marks for accuracy while I was at it. It HB hasn't spun and the marks are correct. I am at 12 BTDC with vacuum advance plugged into switched vacuum port on carb. I get about 35 deg total after 2500 rpm.

While I had all the plugs out i decided to do a compression check on all the cylinders. I know which one(s) it is missing on so what I found makes sense. I got the following PSI readings with a good snapon guage.

1 - 110
2 - 120
3 -100
4 - 95
5 - 110
6 - 86
7 - 66
8 - 106

I knew the # 7 was misfiring because I could pull the spark plug and hear very little change but is 86 Psi enough you think?

This engine sat for a long time and when the guy i bought it from tried to get it ready to sell he fond slacky tar all over the inside from old gas and cheap lead additives. He told me he had to pull the valve cover and tap all the valves directly with a punch to free them up because they were glues shut and would bend the pushrods when he tried to turn it over. I double checked all the rods for straightness and replaced one or two but the compression is still 66 psi.

What could be the cause of the low compression? Any suggestions on how to fix this low compression issue without the obvious " rebuild the engine" answer would be awesome!!!
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  #14  
Old 02-02-2014, 05:45 PM
tuktukme tuktukme is offline
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Its been a while ---- missed you guys, my truck is now fine, its been a long hard road.
I converted to electronic as in a 74, and allot of new changes.
Now I have a holley 2300 runs great after rebuild, so what size jets should I have.
1967 352 electronic ign, recent rebuilt heads, and 2 barrel intake fomoco original !
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Old 02-03-2014, 10:20 AM
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Quote:
Originally Posted by tuktukme View Post
Its been a while ---- missed you guys, my truck is now fine, its been a long hard road.
I converted to electronic as in a 74, and allot of new changes.
Now I have a holley 2300 runs great after rebuild, so what size jets should I have.
1967 352 electronic ign, recent rebuilt heads, and 2 barrel intake fomoco original !
This kind of depends on how it's running with what jets are in it now.

1. you really need to read your spark plugs color.
If black carbon fouled reduce size 2-3 smaller.
If whitish go bigger. I think #62 were like standard jetting for those 2barrels

Dual exhaust and or headers adds to the engine running leaner, a long with hotter ign systems plus any boring of the cyl.
Plus a bad vac. advance sucks air that can add to it running leaner also.

Many guys make this mistake when doing a rebuild of there engine trying to run a out of the box carb with stock jetting and it runs lean.
This is where dialing or tuning in the carb too ones motor.

Ps, I have a good number of extra Holley jets in many sizes if your in need of some.
orich
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Old 02-03-2014, 10:20 AM
 
 
 
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