1986 Ford F-150

Tiny
JOHNSON094
  • MEMBER
  • 1986 FORD F-150
  • V8
  • 2WD
  • AUTOMATIC
  • 93,000 MILES
Engine would crank intermittently, but failed after sitting. Have good fire, fuel getting to injector tubes, plugs/wires ok, compression ok. Got to where it would only crank with squirt of ether, now won't even attempt to crank, just turns over until batterry dead. Checked firing order on distributer. Ok. Help.
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Monday, October 6th, 2008 AT 8:49 AM

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Tiny
RACEFAN966
  • EXPERT
If it cranks and won't start then you are missing on of three things. Fuel, spark or air. I am sure you have air coming in so that leaved two, fuel or spark. Now do know what the fuel pressure is when you cranking? Just to make sure you do have spark with out question right? Get back to me with the needed info and we go from there.
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Monday, October 6th, 2008 AT 8:57 AM
Tiny
JOHNSON094
  • MEMBER
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.
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Monday, October 6th, 2008 AT 8:14 PM
Tiny
RACEFAN966
  • EXPERT
Ok test light is not how to test injector's for a novice it is to difficult. Go to you local parts store and buy a noid light. You simple plug them into the injector harness and crank if it flashes all it good it not there is a problem. As for fuel coming out of the valve at the test port tells you have fuel but not how much pressure. It requires about 35 lbs to open the injector. If you have a knock sensor it is at the back of the engine on the block right behind the manifold. But there is no crank or cam sensor. If you can get back to me on the fuel pressure and such. Hope this helps. Let me know where this gets you.
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Monday, October 6th, 2008 AT 10:48 PM
Tiny
JOHNSON094
  • MEMBER
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
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Tuesday, October 7th, 2008 AT 1:09 PM
Tiny
RACEFAN966
  • EXPERT
Ok this is all good so far the fuel injectors are getting there pulse so computer is good and you have spark but is still won't start? Does is try to start and backfire or anything. Oh yea you can put the upper intake back on. Now I do have a question have you checked the TPS (throttle position sensor) or the temp sensor behind the thermostat? If not then get back to me and I will tell how to check them. See if the temp sensor is bad and telling the truck it is like -40 degrees then is will give it so much fuel it won't start or if it does it will richin up and die. So get back to me and we will go from there.
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Wednesday, October 8th, 2008 AT 8:30 PM
Tiny
JOHNSON094
  • MEMBER
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.
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Wednesday, October 8th, 2008 AT 9:37 PM
Tiny
RACEFAN966
  • EXPERT
The wires you are refering to are the grounds for the computer and yes if they are corroded or broken they can cause problems.
Now as for the TPS I figure you know what this is and where it is. So find the green wire it is the reference wire for the computer. Back probe this wire and have a digital volt meter. Now turn the key on engine off and you should read about.8 volts. Now slowly lift the throttle (key on engine off) and it should steadly increase to 4.5 or 5 volt. If there is any blank areas or decrease in voltage as you lift the throttle then it is bad. Let me know how this goes.
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Thursday, October 9th, 2008 AT 9:01 AM
Tiny
JOHNSON094
  • MEMBER
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.
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Thursday, October 9th, 2008 AT 4:33 PM
Tiny
RACEFAN966
  • EXPERT
Ok the TPS with the key on engine off should read.8 volts (throttle closed) now if you slowly press on the throttle to get to wide open the voltage should increase to 4.5 or 5 volt with no gliches inbetween. You said it zeroed out for a second in a couple of spots if this is true the sensor is faulty. If you can pull codes even if it won't run that would be fine I will look them up and see what is important and get back to you on them.
If the TPS is reading 3.7 volts throttle closed this will keep you truck from starting it thinks the throttle is almost wide open when in fact it isn't so it needs to be replaced. It can be no more then.8 volts throttle closed.
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Thursday, October 9th, 2008 AT 9:41 PM
Tiny
JOHNSON094
  • MEMBER
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
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Friday, October 10th, 2008 AT 11:19 AM
Tiny
RACEFAN966
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That is great it is running now. You know where the knock sensor is right? It is on the back of the block just behind the intake on top. I am at work now so when I get home I will check the codes with my repair manual and get back to you on those.
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Saturday, October 11th, 2008 AT 11:01 AM
Tiny
RACEFAN966
  • EXPERT
Code 25 is a test code to turn of all electrical loads nothing to be bothered with on that one.
Code 41 Means what follows will now be the trouble codes so nothing to be bothered with either.
Code 67 is not a code must of counted wrong some how.
Code 77 is not a code either.
OBD 1 computer systems can only reach as high as a code 45.
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Saturday, October 11th, 2008 AT 10:22 PM

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