1986 Ford F-150

Ok, bear with me. I checked and I do have fire at the coil and #1 plug. I have compression, and with #1 piston at top, rotor button is in #1 firing position. I depressed the pressure releif valve on the injector tube and I had good pressure of fuel release.

Per the 2carpros guidelines I attempted to check the injectors for voltage and pulse. I removed #5, it lit the test light on both sides with the ignition on. I removed the remaining injector wires and starting with #4 began the voltage and pulse test. #4 checked ok and I replaced it. #3 lit both sides and I thought I'd found a short, but as I continued to test I discovered that depending on the location of the rotar button the same injector wires that tested bad would test ok, and vice versa. I did hear fuel being injected into the cylinder when they tested ok. Also with all injector wires in place and the ignition on, I checked voltage with a test liight at each injector and both terminal of each injector lit the test light. I discovered the F150 1986 has no knock sensor, nor cam angle sensor, nor crank sensor, so that rules them out. I have already replaced the ignition module, the pickup at the inside bottom of the distributor, and air sensor. Appreciate any help. Hope the info is enough.

Yes, you are helping alot. I feel like I'm making progress. I checked the fuel pressure with a gauge at the injector tube after switching the ignition on/off a few times. I read 38 psi. With the engine turning over, the pressure reads 40psi.

I picked up a noid light kit (never know when I might need one of them again). I unplugged each injector harness one at the time and cranked the engine over then plugged it back up and went to the next one. All pulsed when the engine turned over. I did find the crank sensor on the driver side just above and behind the #7 injector. I'm awaiting your comments before I spend $50 on this sensor.

I removed the upper intake assembly in order to get to the #2 & #3 injectors (this means I have some of the sensors/vacuums disconnected right now. I was going to reinstall all of that, but wanted to see what other tests might be needed. If I need to reinstall, let me know when.

Thanks for all your help. This is kinda fun and has become very personal with me. I really want to solve this.

Johnson094

I will put it all together tomorrow. It rained today. I will replace the temp sensor tomorrow and get back to you and I need info on how to test the throttle sensor. After it sits overnight, when you first attempt to crank, it does seem to want to crank. It doesn't sputter or backfire, but instead of the steady over and over steady pace of turning over, it kind of "stumbles" if you know what I mean. Then it continues just the steady rhythm of turning over. By the way I noticed a post relative to a 1988 F150 with a similar problem and the response was short and sweet: "check the 2 wires on the negative battery post, they are either broken or corroded." Does this ring a bell?

Thanks again for your help and response.

Again, thanks for sticking with me on this. First of all, I replaced the temp sensor, it looked rough anyway. Secondly I checked the gr/Blk wire coming off the ground side of the battery (I cleaned it up, checked the inline fusable link and ohmed it all the way to the fire wall) Somewhere inside the dash it breaks off and connects to 2 terminals on the computer according to my schematic.

Lastly, the TPS, Voltage back probing the green wire with key on engine off (boy that's a good one!) Red approx 3.17 volts. Slowly depressing the throttle it climbe to approx 4 volts then zeros out then climbs to 4.87 volts. You used the term "lifting the throttle" so with key on, throttle depressed, I read 4.17 volts. As I slowly "lift" up on the throttle, the voltage drops to 3.6 volts, then zeros out briefly, the slowly drops back to 3.17 volts.

I haven't pulled any codes as of yet because I couldn't get the truck to a shop. I now have a code sensor for my model. Though I can't provide codes for the engine running, do you want codes just key on? Awaiting your reply, thanks again.

Up at daylight this morning. First I replaced that TPS unit. Then I pulled the codes KOEO (key on engine off) They were 11, 14, 54, 53, 63, 14. One code verifies the faulty TPS doesn't it? I then tried to crank the engine and IT CRANKED FIRST TURN OF THE KEY. I couldn't believe it. I connected up all my intake filter etc. And it was running a little rough, so I pulled out my timing light (hadn't used it since 1974) and the timing was off. I wasn't real sure about the timing so I set it at 10 degrees before top dead center (my code book mentioned this) The engine smoothed out at idle. I switched off the engine and pulled the codes again after warm up. They were: 11, 14 54, 53, 63, 14. I next cleared the codes. After a test drive I pulled the codes KOEO again and got 11, 11, 11, 11. Next I pulled the codes engine running and got: 67, 25, 41, 77, 25. When test driving, when the rpms get high (I don't have a tach, but I would guess about 3500 or so) the engine begins to skip pretty bad. As long as I stay under that point, it's ok. Kinda like the old vacuum advance problem on the old cars.

You just don't know how good I feel at this point. I really do appreciate your help on this. I was reading the code book and I beleive that 25 refers to the knock sensor. That was going to be my next purchase anyway if it didn't crank. Doesn't it figure that the two most expensive sensors are the ones that show bad?

I'll wait to hear back from you on the codes.

Thanks again