I just picked up a 91' f-150 with a 5.0 liter engine in it. Previous owner said it was running and shut down abruptly, cranks over fine. Checked for spark, none! changed distributer, rotor, and coil. Distributer looked terrible. Still no spark. Question #2. The battery terminal power. When it is connected to the battery the fuel pump kicks on while the ignition power is off, that shouldn't happen until the ignition power is turned on right? Previous owner stated that if he left the battery connected the battery would be drained to nothing .could the fuel pump relay be stuck?

thanks for any guidance
Nathan

 

computer is suspect if fuel pump stays on when not running.

 

First check the wiring under the EEC Power relay and the fuel pump relay sockets.
Then check for power at both sides of the coil with a test light with the key on.
If you have power on both small wires unplug the computer and see if spark returns while cranking.
If still on spark replace the TFI module (ICM).
Still no spark replace the distributor or the PIP sensor inside of it.
Right.
Yes it sounds like the Fuel Pump Relay is stuck, start by replacing it.
Or someone has wired around the relay and put a switch somewhere.

 

I checked to see if I had spark coming out of coil, have none. Unhooked the computer also. could it possibly be a EEC Power relay?

 

The EEC Power relay does not supply power to the Ignition system. The power for the Ignition system comes from the Ignition switch low on the steering column.

The EEC Power relay can stop the fuel pumps from running (no power to the fuel pump relay coil) but it can not keep them running alone (it would need help from a bad fuel pump relay or computer).

If you do not have a test light to do the above test buy one or make one.

 

Finally found my test light,power on both sides of the coil. Unhooked the computer and still no spark. Gonna try replacing the TFI module tomorrow.

 

I don't think it's as simple as "power or no power" at the coil, your supposed to check if the test light flashes or not at the coil TACH while cranking over the engine. If flashing then move on to test the coil resistance but the problem is probably the coil itself. If light doesn't flash but comes on and is bright, then the trouble is in the primary circuit and you have to check the resistance in the ICM and Tach. If the light is dim or doesn't come on then you should check ICM, PIP sensor and SPOUT signal (PCM).

 

It does not sound like you read this thread and what he has replaced.
He has already replaced the coil and the distributor (PIP sensor).
As far as the SPOUT and PIP yes a grounded SPOUT and PIP wire in the wiring or PCM can stop spark but we have not got that far yet. We will check them by unplugging the PCM to see if it is stopping the spark. Then check those wires if the spark has not returned at that point.
The only item he has not replaced is the ICM (TIF Module) and that may very well be the problem.
But we need to find out if he has "power or no power" at the coil first.
As far as the flashing test light at the coil if he has power on both sides of the coil and he has no spark then we know that a test light will not be flashing there.


When someone asks for help on here you do not know how much he knows about a Ignition System and you have to find out what he has done, what he is working on and try to lead him through it step by step and not jump over some step. This is why I do not like any sticky's at the top of a Forum.
It sounds like you are reading out of a book on Ignition Trouble Shooting, I do not find them helpful.
How bright is bright, different test lights will be brighter and some dimmer. My Snap-On test light is very dim when hooked to a 12 Volt battery and my three K-D Test lights is about half way between my Snap-On and my no-name test light that is very bright.

I am not sure what you mean by checking the resistance in the Tach. Can you give an explanation on that one.

 

Hey Subford, your right I'm reading from my manual and those are the very first steps in diagnosing ignition troubles. I think the main point in what I wrote is if the test light is constant or flashing. As for brightness of said light, I would say dim is relative to each light but if you know how bright your test light is normally...anything less then normal would be dim.

Step 16 in my manual says....

Unplug the wiring harness connector from the ignition module and unplug the ignition coil wire harness. Inspect for damage, dirt or corrosion.

17. Check resistance from coil harness connector terminal TACH (coil negative) to module harness connector pin 2. Measurment should be less than 5 ohms. If greater, service open circuit in harness and perform general ignition tests.

18. Check resistance between coil harness connector terminal TACH to ground. Measurement should be greater than 10,000 ohms. If the resistance is lower, repair the short in the harness. Perform general ignition tests.

19. Check for stray voltage at module harness connector pin 2. No voltage should be indicated. If voltage is indicated service short to power in harness and perform general ignition tests.

Hope that helps...

 

All right, finally got the ICM changed and it had spark. Hooked the computer back up and it fired right up and purred like a kitten. Thanks for all the help and getting me pointed in the right direction.

Still have a problem with the fuel pump though,
I replace the fuel relay. The fuel pump still comes on with the key in the off position, when the battery cable is hooked up to the battery. Also noticed that when turning the key to the on position the fuel pump turns on. which is normal. But (with the truck not running) you turn the key to the off position (from the ON position) the fuel pump kicks back on again! Has me stumped , any ideas?

 

When you turn the key off you drop out the PCM Power relay.
With the Power relay dropped out you cut power to the computer and the fuel pump relays coil.
With no power to the fuel pump relays coil the fuel pump relay will drop out turning power off to the fuel pumps.

Does the Power relay click each time the key is turned on and off?



/

 

Just checked it and it clicks when the key is turned on and it clicks when you turn the key off also