Hey guys,
Long time browser of this site (as guest), first time poster. Thanks for all your previous help.

I've got an '88 4.9L that will not start up. Some of the details I can give:
Dome light in the cab comes on.
Head lights come on when you pull the ****.
Radio (aftermarket) DOES NOT come on.
No sounds of fuel pump priming.
Truck makes the annoying warning when key is inserted and turned to on.
No clicks or attempts to turn over when I turn key to start.

1. First thing I checked was battery. Multimeter jumped between 6-12V when tested, so I replaced it after I figured I had a blown cell from winter.
2. Still no start, so I tested with my Mustang's battery. Once again, nothing.
3. Moved over to the starter since I didn't hear clicking, and I replaced that and the solenoid. No luck.
4. Replaced the 3 cables from battery to solenoid, solenoid to starter, and battery to ground. Still no start from key.
5. I did short the starter across the battery, and got the starter to engage and turn, but truck did not start up. I'm presuming no fuel is being sent to the engine based on what I stated earlier about no sounds from fuel pump priming.
6. Tried to short the solenoid across the posts, but all I get is a spark and all power to cab is lost, which I then reset by removing cables from battery terminals and resetting.
7. Replaced the ignition switch just in case that was the culprit. Nothing.
8. Checked the clutch safety switch, and all cables are plugged in and you can hear a 'click' when you press the clutch in, so I'm assuming that's all in order.
9. With the exception of pulling every wire from the steering column to the solenoid, I don't know what else to look for. Maybe a relay, but I have no idea which/where to check for those (I'm not great at using a multimeter on individual connecting pins).


So, a recap of things I've replaced:
Battery
Starter
Solenoid
Cable from battery to solenoid
Cable from solenoid to starter
Cable from battery to ground
Ignition Switch

Any input is greatly appreciated!

Thanks,
bcrone821
1988 F-150 4.9L FI

 

when you turn key to on do you get lights coming on on the instrument cluster?also the fuel pump relay is on the drivers front fender usually cliped into a cover marked fuel pump relay also you said you replaced the ignition switch do you know if the rod attached to the ignition switch is moving when you turn the key?

 

Bolted to the middle of the steering column is the ignition switch.

1st diagram below, bottom left shows the ignition switch terminals.

You should measure 12 volts on the two Yellow wires BATT terminals. They come from the battery and are hot all the time.

It's called fusible link M 16 gauge Black and is connected to the same post the battery positive cable connects to at the starter relay.

If no 12 volts the fusible link is blown.

2nd diagram below shows the fusible.

 

Check fuses.
Change your oil (sludge build up can keep an engine from turning over)
Check distributor/wires/plugs.
Check the fuel pump cut off.
Check your fuel pumps.
Your wiring may be fine, it could just be other things preventing starting.

 

also you can try turning the engine over by hand. use a breaker bar and in the crank pulley center is the crank bolt and try to turn the engine over by hand and turn engine clock wise only>

 

Some great advice above.

Seems like you have two issues:
1) Power to the starter relay (it won't crank, but will if you short the big wires)
2) Power to the fuel pump(s) (it won't start when you crank it by 1 above)

Both of those are easier to get to at the devices than at the switch on the column. Suggest you test voltage at the small signal wire at the relay (solenoid) under the hood while someone else turns the key. Ditto for the main fuel pump underneath on the frame rail.

If you're getting power to the fuel pump, suggest you take a pressure reading on the fuel rail. (EFI, right?)

 

You can test both of these without any equipment. The solenoid will make a clicking sound when engaged and disengaged. If you put your finger on it (DO NOT TOUCH THE WIRES) you should be able to feel the solenoid cycle under your finger when someone moves the key to "START", it'll feel like a little bump, touch ONLY THE PLASTIC CASING!!!! For the fuel pump, it's located under the driver side door, inside the frame rail, it looks like a metal cylinder. When the key it moved to "ON" it'll cycle on and prime the system. You should be able to hear it, it'll be a buzzing sound. You can also touch it and feel it vibrate. However, just because it is engaging and vibrating does not mean it's properly working and priming the system.

 

When I turn the key, no instrument lights come on.

I found two relays near the driver's front fender under a plastic cover. See photos.

Blk/Orn wire was not secured into relay. There was corrosion all about the front of this cable.




Connector that was stuck inside of relay. Note the lack of way to crimp wire to connector.




Starter solenoid connected with all wires. Note the poor condition of the fusible link that feeds behind the red positive cable. This link is also fed from Blk/Orn.

The rod attached to the ignition switch does move when I turn the key.

Tomorrow, I'm going to attempt to solder the Blk/Orn wire to the original connector via a second.

Does anyone know if this Blk/Orn is the culprit?
Considering the poor condition of that wire in the third pic, can I cut that rubber fusible link out and splice in another piece of cable in order to provide a better connection?
If not, can another piece of fusible link wire (assuming there's something significant about what's inside that rubber piece) be purchased from a local auto parts store?

Thanks,
~bcrone821

 

Disconnected the ignition switch from the steering column and checked the multimeter across one of the yellow wires. Grounded the other lead on the bracket holding up the steering column and was reading 10V. Tried the other yellow wire and was also reading 10V. Both were dropping in voltage while taking readings (~9.85V). Repaired the connector to the relay that I mentioned in yesterday's photo post, but still no start.

 

That Fender-mounted relay in your previous post looks after-market.

I would be replacing it with a Motorcraft version when possible. The after-market ones are a complete joke and cause numerous problems.

 

The Yellow wires should read close to battery voltage since it connects directly to the battery positive terminal at the starter solenoid.

The Yellow wires provide the 12 volts for anything that runs off of the ignition switch when in Run, Start and Accessories.

It also provides the 12 volts when in Start to the Red/Light Blue wire at the clutch interlock/neutral safety switch which then goes to the small push on Red/Light Blue wire at the starter solenoid which energizes and battery power is passed to the starter motor.

This is the circuit I believe you should fix first.

Measure the Yellow wire at the ignition switch like you did but use a long piece of wire to the negative battery ground terminal for your black meter probe instead of the steering wheel column. Should read battery voltage. If not you have a problem in the wiring. (Probably blown fusible link).

Also verify how many small black wires connect to the negative battery post.
Should be a Black/White which is ground for the Brake Proportioning valve and a Black/Light Green wire which is ground for the EEC.

Not sure about your wiring colors at the 2 relays on the driver side apron.
One relay is for the fuel pump (the original fuel pump relay was green in color) and the other one is for the EEC. (Original relay was I think Brown in color).

The EEC relay has the following wires at its socket.

White/Light Blue which should have 12 volts when ignition is On.
Black wire is ground
Yellow wire is hot all the time and protected by a fusible link.
Red wire is the output of the relay and provides 12 volts to the fuel injectors, throttle valve air bypass, TAD and TAB solenoids, EGR valve solenoid and also goes to a Red wire on the Fuel pump relay.

Fuel pump relay has the following wires at its socket.

Red wire 12 volts from the EEC Red wire. Hot when the EEC relay closes which should happen when the ignition is On.
Tan/Light Green. This is the wire you can manually ground to turn on the fuel pumps. The EEC normally grounds this wire to turn on the fuel pumps.
Yellow wire is 12 volts and hot all the time.
Brown wire is 12 volts when the EEC turns on the fuel pump relay and 12 volts from the output Brown wire goes to the tank selector switch and powers the fuel pumps.

I don't see a Black/Orange wire in the schematics for a 88 going to either the EEC or Fuel Pump relay like you show.

 

go to this web page it will show step by step diag of your relays
Part 1 -Testing the Ford EEC Power Relay (Brown Relay)
that may very well be the problem.
also check fuse position 16 undeer the dash

 

Oil was changed 800 miles ago. Drained it to check, then poured it back.
Distributor/wires/plugs are all in good condition.
Fuel pump cut off is not popped up.
Fuel pump is not making any noise when I turn key.

 

Sounds like a fuel pump issue then. You can typically pull one at a junk yard for less than $20. I got mine for my '87 for $7.

 

let me get up to date here? are you able to turn the engine over with the starter? Before you go to replacing the fuel pump we need to make sure you are getting power in the correct areas at the appropriate time. also on your starter relay the red wire is coming from your battery correct and what is on the terminal going to the starter the one black cable or is there another wire behind it can not tell from the picture.