Got a 87 f150 4x4 ,5spd. 4.9 300 I6.

Had no spark when I got it, only had 1 wire to coil hot , when key was on.
Fixed a ground wire on negative batt cable, one wire was hot with key on, the other wire gets hot when cranking. ( yellow / green wire and solid Grey wire to coil )
Fuel pump constantly runs when key is on.
I had swapped ignition coil, cranked it the motor over and it popped 2x then nothing. Now both wires going to coil pack are hot with key on and when cranking , both are hot at same time , with key on , and when pushing push button while cranking.


Previous owner rigged it up to where a push button is used to crank the motor .

I'm thinking I definitely need to replace coil pack.

should I leave the push button deal alone , or will it be okay ? I just want to see if the motor will run before I spend a lot on this truck.

I got a Haynes manual , a multi meter, I spent a week studying wiring diagrams, I'm not 100% sure , but I swear , there is a green / yellow wire coming from wiring harness that is not on diagram. There is a yellow / green wire that has a black square thing on it , it goes to coil pack plug, then there's another yellow / green wire coming from icm on distributor to coil pack. Previous owner has it soldered to the green wire with yellow strip that runs from pin 4 , that goes to the coil pack.

 

Common symptom of a bad computer. Or the PO wired the pump to Key On hot circuit. Given your symptoms I suspect the former.

Disconnect the computer, see if you get spark. If so, you have a bad computer. Some have stated removing the SPOUT plug effectively disconnects the computer, but I have my own opinions. You can try the easy route by removing the SPOUT and check for spark. If no spark, then completely disconnect the computer.

 

I removed the pcm, opened it up, it looks perfectly fine . With it removed , I now have spark at the plugs. I hook it back up, no spark. Remove it , now I have spark again.

I have fuel pressure at fuel rail, the fuel pumps constantly run , even when the key is off.

I still have to use the push button to crank the motor. I have checked for broken wires , can't find any.


I guess I am going to order a new pcm , and possibly a new ignition switch.

 

I hope the new computer solves the no spark issue, it should. As far as the fuel pump running constantly, that sounds like another hack to make the truck run.

 

FWIW the junkyard is a great place for computers. even though theyre 20+ years old, most of the trucks out there with OEM computers will never have a problem in their entire lives. lots of good, high quality computers out there in the JY's. id rather have (2) used computers for 15 a pop than 1 aftermarket comp for hundreds.

 

I found out that the yellow wire to the eec relay had no power , I tested pin 53 & 37 at the pcm plug for power, there was nothing.

I ran a hot wire to the eec relay , and now I have power at pins 53 & 37. I re installed the pcm , and now I have spark at the plugs.

I'm guessing the pcm wasn't getting power. Well now the pcm has power , it's hooked up , I now have spark at the plugs , and the truck still won't run , won't run on starter fluid, no pops bangs or coughs.

Fuel pumps Still runs constantly, I think it is a Jerry rigged circuit , I have to unplug a wire from the Jerry rigged fuel pump relay .

 

The yellow wire gets its power from a fuse link at the starter relay on the passenger fender on the relays battery side.

If the fuel pumps were running with no power to the eec relay then the fuel pump relay was bypassed. The pcm would have no control over the fuel pumps wired like this.

The fuel pumps running all the time the key is on with the fuel pump relay bypassed would have no effect on the running of the engine.
But this would bring up a safety fire hazard as the fuel pumps would not shut off if there was a wreck and the engine died.
I am guessing the fuel shut off switch is also bypassed.

 

Yes , the inertia switch is bypassed. It looks like the plug going to it is melted , the inertia switch iitself is broken. Previous owner had the wires taped together to bypass it. Even with the wires disconnected , the fuel pumps run.

Pretty sure the fuel pump relay is bypassed like you said . I got a wiring diagram and multi meter , I'm going to dig around and see what I can find.

As far as having spark and still no start , I'd assume the coil is bad , I used my test meter to test it , if I had done it right , it failed the secondary test I believe, so come pay day , I get a new coil.

 

Okay , I now have spark with computer hooked up, I have fuel pressure at rail, I had to run hot wire to eec relay ( yellow wire has no power)

I installed a new ignition coil, sprayed starting fluid in intake , cranked it and no start. It has a funny smell , puffing white or blue smoke from intake. Cranked it again and it made a loud bang, fire came out of intake.

I rotated crank pulley to TDC according to Haynes manual , removed distributor cap , and the root was pointing to number 5 plug not number 1. I assume this means the distributor was 180* off ? I removed the distributor and re installed it to where the rotor was pointing to plug #1 when the cap is put on.

I got it all put together, and now the battery is junk, so won't know if that was the problem until I get a new one.

I did manage to give the truck a $15 rustoleum rattle can paint job to hide the fugly green bay packers paint job !
Now it looks like a halfway normal truck!

 

Truck runs now . I have to turn distributor clockwise to start it , once it starts it revs up, backfires out tail pipe , have to rotate distributor counter clockwise to get it to where it's not "knocking " or idling fast.

The engine dies when I remove a battery cable ( found 2 wires with fuse able links ran to one fish eye connector hanging on fender that I assume gets mounted to starter relay)

Fuel pump still runs constant & no power to yellow wire at eec relay , still won't start with key and I have no working headlights , tail lights , Hazzard or brake lights, no dash lights. I should be able to figure it all out within the next week when I have time.

Anyway it runs and moves under it's own power. Couldn't find 5th gear , but every other gear works. Brake pedal sinks , but the wheels lock up and leave skid marks.

 

Note that you have to pull the SPOUT out and set the timing to 10deg BTDC with a timing light to time the engine. Then of course put the SPOUT back in to use the truck.

 

well i had someone time the motor, he said its not at exactly 10 deg. motor starts up , idles high for a few seconds , sort of makes a popping / gurgling sound out of the tail pipe, then the idle smooths out and runs great.

new problem : no power to anything . i turn key on, gauges work, battery light comes on . there is no power to the fuse box , everything is dead. there for now , i have a single hot wire ran to eec relay and fuel pump relay to power them. i have no lights, interior or exterior, no radio , heater, brake lights, nothing. i still have to cross starter solenoid to start crank it.

i can tell you that the red wire to the s terminal on solenoid is "burned" , i stripped the wire to replace the plug and the copper wire is black.

all the fuseable links look good , but have not tested continuity yet.

any tips on where to start after fuseable links are checked ?

 

i didnt check the date on this before butting in but for those not very familiar with the 4.9 when timing it dont use the timing marks on the timing gear cover. Use the large bolted on plate on the block under the alt at about the 10 o clock position of facing the harmonic balancer. The large v cut is 10 deg.

 

Where are you located, Our JY, the vultures are there within hours of a new truck showing up and taking just the ECU and MAF. If you are lucking to find an ECU, it will cost you $45 Min.

 

I was just about to say the same thing. If you use the timing gear marks on most 4.9s you'll be screwed. They made it fun. If you are into yoga you won't have any probs. On my 90 all I have to do is get under it. 340lbs of frailty. Then use mirrors