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F150 5.0 NO SPARK AT PLUGS

G

gbs

Member
I know this is a tractor forum but I have run into a snag and can seem to find an answer else where to the problem with this truck, it is a 1988 f150 5.0 electronic ign. ,TFI system it died about 2 months ago no spark at the coil, module in the dist. went out , installed a rebuilt dist., then 2 weeks ago died again no spark at the coil, voltage at the coil test 10.8 while cranking, the dist. is turning wire to the dist. from the coil shows a definite impulse, replace coil, got spark a coil, spark appeared weak at dist. no spark at plugs, replaced coil wire with 2 different ones no change, replaced dist. cap and rotor still only a weak spark at the plug about every 4th revolution of the engine, replace the coil with another new one no change, every grd. connection I can think of has been cleaned and temporarily grounded with a test led to insure a grd. also installed a test led from the battery to the coil to insure proper voltage no change, what have I missed?????
 
GBS if your only reading 10.8 volts to the distributor, my guess would be either bad battery cables or bad battery. it should read 12.5 to 13.volts if the battery is fully charged. and about 14.5v with the engine running. if it's below 12.5 with the engine running it will most likely be a bad altenator. grab your battery cables and see if they are hard and stiff, have any burn or melted spots on them, next take the cable ends off and clean the posts and connecters. oh and GBS I have ran into brand new batterys that are shorted down to 10 volts or even less.
 
Have you unplugged the plug at the module and cleaned the contacts with contact cleaner?

If so, the cause is likely that the TFI or pickup module has failed in your "rebuilt" distributor. HOPEFULLY, it's warrantied.

Not sure WHY you went with a "rebuilt" distributor, as (typically) they put them together with "recycled" parts, including the modules.

Unless the basic distributor was noticeably worn, I would have simply replaced the TFI and pickup coil modules with quality new ones from Standard Ignition or NAPA/Echlin. Doesn't hurt to get a quote on OEM/Motorcraft units, either.
 
(quoted from post at 06:45:21 02/04/18) I know this is a tractor forum but I have run into a snag and can seem to find an answer else where to the problem with this truck, it is a 1988 f150 5.0 electronic ign. ,TFI system it died about 2 months ago no spark at the coil, module in the dist. went out , installed a rebuilt dist., then 2 weeks ago died again no spark at the coil, voltage at the coil test 10.8 while cranking, the dist. is turning wire to the dist. from the coil shows a definite impulse, replace coil, got spark a coil, spark appeared weak at dist. no spark at plugs, replaced coil wire with 2 different ones no change, replaced dist. cap and rotor still only a weak spark at the plug about every 4th revolution of the engine, replace the coil with another new one no change, every grd. connection I can think of has been cleaned and temporarily grounded with a test led to insure a grd. also installed a test led from the battery to the coil to insure proper voltage no change, what have I missed?????
Click to expand...

Does that dist. have an external module or internal?If ext.it should have dilectric grease between the module and the dist. body.Acts to keep temp.down.Not at all an uncommon failure in that system.
 
the reason I went with a rebuilt unit was I could get one for the cost of the module and drive gear, the last 2 gears I tried to remove were made so brittle that I chipped a tooth removing them, that design of dist. wasn't given much thought as far as repair goes, the voltage I was referring to was at the coil, to insure correct voltage I had another truck hooked to it with jumper cables, the pickup module will cause a test light to blink as it pulses to trigger the coil, is it possible for the module to still be bad causing a weak spark like a bad condenser can, the spark will only jump a 1/4'' gap to a ground at the coil, most of todays systems I worked on will easily produce a spark across a 3/4'' air gap and greater
 
Yes, I suspect a partially-shorted module can still pulse the coil, but "load" it enough to prevent it from "ringing"/producing the proper, HOT spark.

Can you get warranty on the distributor?

Also, it's POSSIBLE a bad (open) resistance spark plug wire can lead to the early demise of an ignition module.

I didn't go back and re-read, so maybe you've replaced the wires, if not, at least "Ohm" them and look for one (or more) with much greater than the others (or "infinite) resistance.

If there's a bad wire(s) that's not dealt with there'll be yet ANOTHER failure, down the road.
 
I just had a similar scenario with a 1985 Dodge, replaced distributor, several pick up modules in the distributor, coils and a few months later lost spark again. I was so frustrated with the amount of money I spent trying to figure out what was wrong with the original ignition system. I just put in an HEI distributor in the truck, it starts faster then ever before. All that was needed was the HEI distributor, new wires and one 12 volt wire to power the distributor. The total cost was 130.00 which includes the shipping. I felt like I gave up on the original ignition but it runs better than ever now. Good luck.
 
(quoted from post at 18:21:55 02/04/18) I just had a similar scenario with a 1985 Dodge, replaced distributor, several pick up modules in the distributor, coils and a few months later lost spark again. I was so frustrated with the amount of money I spent trying to figure out what was wrong with the original ignition system. I just put in an HEI distributor in the truck, it starts faster then ever before. All that was needed was the HEI distributor, new wires and one 12 volt wire to power the distributor. The total cost was 130.00 which includes the shipping. I felt like I gave up on the original ignition but it runs better than ever now. Good luck.
Click to expand...
ood move! Ford's TFI was a disaster. Recalls, lost class action suit, paid for new modules, towing, etc. Just a bad unit.
 
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