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Having major pains with my 81 Ford E-150, 300 straight six with duraspark II setup. I got stranded outside of Hartford, CT trying to get back to New York over the new year. I spent 3 days camped outside of an Autozone trying to sort this one out to no avail. Ended up leaving the van there and coming back up to tow it back here a few weeks later. Basically the motor was rebuilt about 6 months ago, new ignition module and control box put in about a month before the problems started. I drove from Brooklyn to Hartford with absolutely no problems and parked the van in the airport parking lot. was gone for a week and came back started her up....started okay. Drove out and hit the freeway and suddenly started surging big time and back firing. I could get her up to around 30 before she would keep bucking and finally conk out. Got her to the nearest autozone and got to work. had the control box tested there and they said it was alright. checked all vacuum lines and pulled the EGR off and cleaned it out put it back on with a new gasket. Ran the motor off an auxillary gas tank in case the fuel had been contaminated while I was away. Pulled the carb and basically rebuilt it in the parking lot. Reset the timing a billion times. Still to no avail. I went through all hell doing all this in the snow with low funds and no friends for miles. The thing is, practically everything on the motor is new or rebuilt. Now 3 months later I pulled the head off to look for cracks/valve issues. Everything looks good! Havn't magnafluxed but really think the distributor and/or wiring is the culprit. The 300 six has no timing chain and the Duraspark II setup is really simple and straight forward. I've looked for cracks on the distributor and found nothing. Really don't want to put anymore money in to this and on the verge of dumping it but it pains me to lose all that money I've put into it. Please! anyone with any ideas or experience with this. Brooklyn is not the place to have an inoperable vehicle (gotta move it every other day) and I definitley don't have the money to get a mechanic involved. Fuel is good, carb is good...electrical?
I would still suspect the dist pickup module or the ignition module. The ignition module can fail when it heats up, and the autozone tester will not pick this up. And also, aftermarket modules do not have a very good track record for reliability.
You will not be the first person to install "new good" parts that fail.
If it starts and runs ok cold, then do the oven test. Put the Duraspark II Ignition Module in your oven at 250 deg. F for about a half hour or so then quickly put it back on the truck and see if the problem is there immediately after starting. If it is then the module is most likely at fault.
If the module is at fault it doesn't have to do with heat failure. The backfiring kicks in cold or warm at about the same rpm which is like approximately 1/4 throttle (no tach) It's basically acting like the timing is way off...like I said I've set and reset a bazillion times. I don't know too much about the actual operations of a control module....could it somehow be giving the wrong spark signal? Whatever went wrong happened while I was away or immediately after starting the van after a week of sitting. I initially thought there was water in the fuel or worst case the cold had cracked the block or head somehow, the advance on the timing was different with the new control/igntion module installed. I think I'll try to score a new one and see what happens. Ayone know diagnostic procedures for the module operation?
I don't think there is any thing internal to the Duraspark II module that affects timing, unlike later versions with the computer. I'd suspect the pickup coil in the distributor, the vacuum advance unit or an intermittant short or open in the wiring harness.
Backfiring in the exhaust is a sign of raw fuel in the exhaust. This can be caused by the fuel not being burned, because of a weak, intermittent or missing spark on some of the cylinders.
Thanks guys...rebuilt distributor from Autozone is a few dollars more than the pickup so I put an order in for one. Try it out at the end of the week and go through the wiring. Thanks again for the advice, makes me a little more confident in my original thoughts....wish I wouldn't have doubted myself and my compression tester and pulled the head. Got a '49 panel that I'll be towing here sometime next month...my e-150 thats actually been a super dependable work horse for the last few years is gonna donate her innards to the 49, can't wait!