1988 F-150 302 XLT

Guys,
I purchased a new battery, in which I installed the terminals backwards. It was dark out, and I am stupid I guess. Anyway, it burned the 14 ga fusable link between the solenoid and alternator. I fixed that and also installed a new alternator. When I turn the ignition, all seems well, including the fuel pumps coming on, however it will not turn over. I can jump the solenoid and it will turn over but will not crank.

Any suggestions? What else did I destroy?

 

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Sounds like the coil for the starter solenoid is open.

At the starter relay/solenoid there should be a Red/Light Blue wire. Use an ohm meter and measure from that post to the negative of the battery. Should measure about 3 ohms.

With the ignition switch in Start position, you should measure 12 volts on this wire. If you do, and the starter doesn't engage, the coil for the relay may be open.

You can also try disconnecting the plug at the TFI module and see if the engine will crank. If it does, the TFI module is bad.

 

Is the TFI module the small black box near the air filter, beside the diagnostic test plugs? If so, it makes a click when I turn the ignition....normal???.....I'll try unplugging it.

 

No, those are your Fuel Pump and EEC relay's. The TFI module is mounted on the distributor below the cap and housing. Long, flat and 6 pin connector attached to it.

 

Unhooked the TFI module, no go. Even tried to jump across the solenoid and notta. Now with the TFI connected, when I jump the solenoid, all goes black. Wiggle the positive lead on the battery and have power once again. Jump across again and black again. Guess my solenoid has now bit the dust? Any other ideas?

Thanks from Mississippi.

 

When you say you wiggle the positive lead, is the connection loose or is the whole post in the battery moving? If the post is moving, I would get another battery before that thing shorts out and you have a big BANG.

 

Now I'm confused. You have a new battery but can wiggle the positive post and power comes back.

You said you jumped the solenoid and the engine turns over but will not crank? (Do you mean the engine turns over but won't start)?

Here's how the starter circuit works.

12 volts for the ignition switch comes from Fuse Link M which is a 16ga Black wire attached to one of the lugs at the starter solenoid. The battery red cable also attaches to the same lug. A large wire attached to the other large lug of the starter solenoid goes direct to the starter motor.

When you turn the key to Start, 12 volts goes thru the ignition switch and thru the Clutch interlock switch (manual trans.) or thru the Neutral safety switch (auto trans) then to the Red/Light Blue wire at the starter solenoid.

The 12 volts activates the solenoid coil. The solenoid closes and 12 volts is applied to the starter motor.

I don't think the fusible link is blown because you said when you turn the key to run the fuel pump runs and everthing appears normal.

At the same time you turn the key to Start, the same 12 volts is applied to the TFI module. So if the TFI module was damaged because of the reverse connection of the battery terminals, it could cause problems on the starter circuit. That's why I suggested you disconnect the TFI module to see if the starter motor cranks the engine.

Many auto part stores like Autozone will test the TFI module for free.

 

When I say wiggle the battery cable, I mean wiggle the connector that attaches to the post. I'm getting 12v from the battery on the dash display. A day or so ago, I could jump across the solenoid and it would turn over, but not start. Now when I jump across, all goes black until I wiggle the battery lead. From what you are telling me, I need to check the v at the starter. The TFI module does not change the situation whether connected or not, same results.

 

Then I would check your battery post connection to make sure it's good. Also, when you wiggle it make sure the post is not moving where the post enters the battery. If you can wiggle it and get power the lose it when you try to start, you have a bad connection at the battery. It's not making good contact somehow. If that post moves in the battery case, you need to replace the battery ASAP.

 

Now we are getting somewhere. I put a new solenoid in, and now she is turning over but will not start. I'm going to check for fire in the plug this evening. I pulled a plug yesterday, and it was bone dry, even after numerous attempts to crank it. This truck has been sitting for a year in my garage, so I'm not sure what else could be wrong. Can you put fuel in the intake on a FI vehicle without damaging anything? If so, will it serve as a primer or am I wasting my time?What steps would a pro mechanic take to resolve issues?

 

Yes you can shoot a small amount of starter fluid or gasoline into the intake. Manually hold open the throttle blade before you inject the starter fluid or gasoline. Make sure you reconnect the air filter plumbing. If you don't and the engine backfires you could have a fire on your hands.

Take the TFI module to an auto parts store like Autozone or Advance Auto Parts. They will test it for free. If the TFI module is bad you most likely will not have spark. It could have been damaged by the reversal of the battery cables.
(The ECM could also be damaged).

Also I think if there is no reference signal from the TFI module to the ECM, the ECM will not pulse the injectors.

 

I'm still at it, and no go.

Just for review, I've replaced a bad alternator and solenoid, plus a new battery. Still wasn't getting fire to the plugs, so I tested the TFI and it was bad so I replaced it. Now I'm getting a spark, but still will not crank. This truck has been sitting in my garage for 1 year without being cranked. Any suggestions before I call in a mechanic would be appreciated. I can hear the fuel pump relays clicking on, but the engine just turns over and over without starting up.



Thanks in advance