Sorry, searched and read everything. 90 F250 351 ran fine, parked it, now won't start. Cranks but won't fire. Pulled one plug, I see no spark. Replaced coil, still no spark. Check for fuel pump, I hear it, on both tanks, saw gas shoot out when the hose was disconnected from the filter and ignition was turned on. Replaced cap, getting new rotor right now. Replaced ignition switch because it was working, but needed jiggling to make the ABS light stay off. Read about TFi, not sure what that is or where it is. Throw me a bone please, thanks.

The TFI will cause it not to fire. It stands for Thick Film Ignition. It is mounted on the side of the distributor, and takes a $5 tool to remove the torx (?) (I think they are torx, I just have the tools, never really looked at it) screws that hold it on

If you replace the distributor replace the TFI as well.....they USUALLY go hand-in-hand about going out. And besides....it's better to be safe than sorry.

Thanks for that. So who can tell me what would cause the coil to NOT spark? I'm trying to trace backwards from the coil, because I don't see a spark comming from it.

Pull all the plugs and try to fire it in the dark to see if its completely jumped time if so it might be the distributor, my guess anyhow, or posibly a timing chain but you would have valves ratting on that note.

that's good stuff, thanks. Dizzy is around 150 or so, so maybe all is not lost.

TFI module - get a thin wall 5.5 mm socket to change it - it controls the spark and the fuel timing -
check for power to the coil - should be very close to battery voltage. ( it has to have power if not check the EEC relay )
check for signal - use a test light - hook to power and probe the neg side of the coil and crank - should blink - if not

without testing every wire / etc. --


replace the TFI - on the side of the distributor has 7 wires ( i think ) going into it

replace the tfi - not the whole dist. - cheaper -

make sure you have the 5.5mm socket to do it tho.:D

the tfi is also called a module, its very common for them to fail on fords. cheap ones are under $30 good ones are $80+. theres nothing wrong with the distrubter on your truck.

the tfi is also called a module, its very common for them to fail on fords. cheap ones are under $30 good ones are $80+. theres nothing wrong with the distrubter on your truck.

carry a spare. they will break whenever they feel like it.

I believe you can actually convert to a fender mounted TFI (they came in later year trucks). They have a big heat sink around them which keeps them cooler, the main reason why the stop working (excess heat). I think you have to change dizzy's and make/get a harness from a salvage yard.

Also, make sure you put some heat-sink compound between the module and the dizzy. IIRC, it use the dizzy as a heat sink.

ok, I'm getting a tfi right now. I took the old one off and opened it, it has a window that pops off with a screwdriver. The "thick film" or jelly stuff looked good. I found that a condensor on the side of the coil had a few strands of the wire broken, getting a new one of those too. If this doesn't fix the rig, I don't know what to do. I pulled all the plugs, one of them seems really caked with black stuff, all the rest looked grey and good. After all the cranking, should my spark plugs look wet with gas? I don't see any gas on the plugs. How can check for fuel getting to the plugs? It's an old rig and the motor needs a rebuild but I couldn't see why it cranks but won't fire, at least a cough or a hickup. I'll post back when I try the new tfi and condensor, and thanks again for the help folks.

try priming the engine with some fuel or starting fluid. start with the whole getting spark first though.

Check the oil for any gas in it if there is some change it.

the tfi module helps control injector timing - so if its not working - no fuel - check to make sure you have voltage to the injectors - should be the same as the battery when the key is on

is sounds as though its not getting any signal from the dizzy that the engine is turning over, if it has a tach, look at that while cranking, if its not moving, the trigger in the dizzy is what I would point my finger at. Check to make sure the plug from the dizzy to the wiring harness isn't all corroded up or a small animal hasn't chewed through some wires.

Also, not sure if yours has an inertia switch or not but check to make sure the red button is pressed down. I haven't looked at the wiring diagrams to see what exactly it kills, whether it's the fuel pump, crank signal, injector hot wire, or what.

the inertia switch only affects power to the fuel pump - fuel pump relay to inertia switch then, fuel pump - nothing else

Also, not sure if yours has an inertia switch or not but check to make sure the red button is pressed down. I haven't looked at the wiring diagrams to see what exactly it kills, whether it's the fuel pump, crank signal, injector hot wire, or what.

that would be the fuel pump:laughing:

oh - and if the tach is not working - a tfi module can affect that to - as all wiring from the pick up / dist must run through the tfi module

Well, put the TFI on and...It runs! I fawked up the timing by pulling the dist. out to try and change that piece the TFI mod. plugs into. But the rig starts, so now I'm waiting for my neighbor to come by with a timing light. When I pulled the dist. out, I think I got it back in a tooth off or more, not sure on that yet. But anyhoo, thanks for the help folks, beers all around.:beer:

Ok, got the timing set, 10 degrees before top dead center. Truck runs like crap. Won't idle, give it gas and it backfires out the exhaust. Removed the spout (little plug in goody off of the tfi wiring harness), and the truck runs good. Anyone understand why this would be?

did you set the timing with the pill out ? are you sure the dist is in right

Make sure you remove the spout connector THEN time the engine. If not it will run like ass.

Yes, set the timing with the spout out. Put the pill in, and it runs horrible then stalls. Drove the truck today, it idles good(with the pill out), but under load it pings and has little power. Checked the engine code (jumpered between the diagnostic plug and the overide wire), it flashes an 11, which means no codes. I don't know the cause yet, but it seems like timing is the issue. After putting in the new tfi modual, it starts. Pull the spout out, and it idles well. I manual advanced the dist., and it runs better. I think we are getting there, but still the rig that ran great a week ago is not back to the way it should be. Thinking about getting a new computer for it next. I hate to throw parts at it trying to chase down the problem. ANyone else got an idea? If you need more specific info, let me know. I know alot more about this Ford now then I did a week ago, more then I wanted to know.:confused:

timing chain & gears. most of the gears have plastic teeth. it may be worth looking into. seen a bunch of them get slack, and run like shit...

I thought that too, so I put a socket and breaker bar on the crank shaft nut, and there is about a 1/4 inch of play when the nut is turned while watching to see if the rotor turns. Does that sound like too much? I don't see a corelation between that being the cause, and the truck not starting until after the tfi was replaced. But, I can always try to replace the chain and gears I guess. Sounds like alot of work, I'll read up on it. Thanks again.

You know, the more I think about it, the more I'm leaning towards rebuilding the engine in this rig. Anyone have a suggestion what rebuild kit I should buy?