'92 F150 quit running on the highway. Won't start.
My truck suddenly quit running last night while on the interstate. I was doing 75 mph, running fine and without any warning it just quit. Once on the side of the road, I popped the hood and I could smell something was hot. I looked at the pre-converter (I believe that is what it is. It's the first exhaust canister that the 2 exhaust pipes off the inline 6 go into) and it was cherry red. I let it cool down and while it would crank, it would not start. So I had it towed to my house. Today I hooked up a fuel pressure gauge to the fuel rail and after cranking it for a while, I registered 55 lbs on the gauge. My Ford manual says 40 lbs in one place and in another it says 55 lbs so it appears that I have adequate fuel pressure. Next I pulled a sparkplug and grounded the sparkplug body and had my boy crank the engine. I did not see any spark. So it appears I have spark issues. Can anyone tell me what I should check next (maybe something 9 times out of 10 that it is on these year Ford F150's) and how to do the check. Any advice would be appreciated. Here's some facts on my truck: 1992 F150/4.9L/auto trans/2WD/145K miles. It's been a great dependable truck and I maintain it well.
On a side note, I'm thinking the red hot preconverter may have been glowing because when the sparkplugs quit receiving spark, raw fuel got dumped into the preconverter causing the red glowing. At least thats what I hope caused it because I don't want to face replacing the cats right now, LOL. Anyway, any advice would be appreciated on the no start situation.
The first thing that comes to mind is the ignition module. On my '85 (RIP) it seemed like I put a new one on every year. On my '85 the module was on the distributor and they failed due to heat issues. Yours may be different. Either way, find it and take it to Autobone or similar place and have it tested. Then replace it even if they find it is good.
Hope this helps. And if I am completely out in left field on this, at least I bumped you to the top of the list.....
You might pull off the SPOUT plug and see if you have spark then. If you do, them it could be the computer or its power fuse/relay etc (EEC power).
If not, I agree that the TFI ignition module is a likely suspect.
If you have to replace it:
- screw heads are 7/32 ( I think) which ARE 5.5 mm. You also have to find a thin socket to fit in there.
- make sure that you put the thermal grease on the back of the new module -- you should get a little dab with it.
- On some of them, one of the screws is grounded -- or so I've heard.
Otherwise check the usual suspects, pickup in the distrib and the coil.
My last '93 Lightning intermittently lit up the converters like that and spit and sputtered then would die. After swapping in several parts (I had a complete Lightning to pull parts from) it turned out to be a bad PIP in the distributor. The PIP feeds the ICM, so it's a crap shoot for either one. If yours is 100% dead the ICM is easily removed and taken to be tested.
I have always wondered if I placed my DVM on the Hertz(frequency) scale, then cranked the motor over while monitoring the PIP output if it would read some sort of frequency. In theory it should because the PIP is a square wave output to the ICM and PCM. The faster the cam cranks, the faster the pulses, therefore the higher the frequency. Too lazy to go out in the garage and test that theory right now, and the temperature is dropping.
You can put the test light on the TACH wire in coil plug (tan wire with a yellow stripe) and it should flash as the engine cranks. If it flashes you know the PIP, ICM and computer are more than likely OK. You also more than likely have spark.
If the PIP is good it should put out 4-6 VAC on the PIP wire.
You can also check to see if the injectors are firing while cranking.
If the injectors are firing the PIP sensor is good, if not then it is the ICM, coil or the computer.
As ford2go said above you can pull the SPOUT shorting bar out or unplug the computer and if spark returns then you know you have a bad computer or the ignition wiring is grounded.
Check at the coil for power on both small wires with a test light by back probe to see if the coil has continuity and that the coil plug is good. This is done with the key on and both should light the test light.
Today I replaced the original TFI module with a new one from NAPA. I then tried starting the truck and while it spins over very nicely, it will not start. So I then checked for spark by pulling the #3 plug and with the ignition wire on it, I grounded the plug body to the block. I had my boy crank the engine but there was no spark. After learning from one of the above posters that Autozone can test the TFI module, I took the original Motocraft TFI module to them. He tested it and said that it read OK while cold. But once his machine heated it up, it read bad. I also had him test my coil. He stated that it's a so-so test because it only tests the coil while it is cold. Anyway, my coil tested in range on the primary and tested under range (low) on the secondary. So he felt that my coil was OK. When I got home, I pulled the dist cap and had my boy crank the motor. The rotor rotates as it should. I also grabbed it as suggested above and tried to manually rotate it to see if the drive gear had come off, but it would not rotate, so it appears that I am OK there. I opened the main fuse box in the engine compartment and every fuse was OK. I also did the same with the fuses under the steering column and they were all OK. I may remove the new NAPA TFI module that I installed today and take it to Autozone and have them test it? I suppose I could have gotten a bad one but I would think thats unlikely. Anyway, thats where I am right now.
This evening I read the above responses and have a couple of questions.
What is the SPOUT shorting bar?
What is a PIP? Is it the pick-up coil that is in the distributor?
SPOUT is that little plastic block you remove to test or set timing, I forget what it stands for but it removes the computer control of the timing. Its really just a connecter and pulling it out opens the circuit.
and yes, PIP is the profile ignition pickup, if i remember right, in the distributor.
edit - you might want to verify voltages at the coil. I had my wiring corrode open once.
It's most likely the PIP in the distributor. The distributor must be removed and disassembled to replaced the PIP. Make sure you take the proper steps BEFORE removing the distributor, so you can get the distributor installed in correct time, close enough to start so you can fine tune it with a timing light. I would make one more test before removing the distributor, make sure you have power to one of the small connecters on the coil with the ignition switch turned ON.
Last edited by 88n94; 11-25-2009 at 03:00 AM.
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