Hello, so ive got a 1989 F250 with the 7.5L 460 EFI. For months now it has been very difficult to start. It will turn over just fine but it wont fire off. Sometimes (very rarely) it will fire off and run good while driving it but when I let it sit and idle it dies and wont start back up again, (turns over but wont fire off) the spark plugs, wires. ignition control module, ignition coil are all new. Its got fuel at the rails(i dont know the PSI). I went through the haynes service manual and did the tests for the ignition control module pins (had me check pin 2,3, and 4) pin 2 and 3 read ~90% of batt voltage(as manual said it should) but pin # 4 read .08V. not sure if thats bad? would like osme information on that cause i cant find any on it. I tested the MAP sensor as well form the manual. the middle wire on the connector read 2.55 volts. so is that an indication that the MAP sensor is bad? any ideas? thanks!

 

Let your computer tell you what it knows;
Engines are easier to diagnose over the internet when all the codes are listed, and in order of test.
KOEO - (O) Self-Test Codes =
KOEO - (C) Continuous Codes =
KOER - (R) Self-Test Codes =
Make sure your A/C, Heat, Radio, etc. are turned off when testing.

 

You should have 5v on the MAP Orange/White wire.
The "Middle" wire, Dg/Lg?, is a frequency measurement when the engine is running.

 

The manual said the same thing about the map needing to be 5V so is that what is keeping it from firing off? i checked codes a while back and it was for TPS voltage being ot low so i checked it and adjusted the TSP idle screw? till i got to .98 volts.

 

Do you have the 5v on the O/W wire?

 

O/W as in off white wire?

 

So, .98 was the Closed Trottle measurement, bid you check the same wire with the Throttle Wide Open?

 

Orange/White stripe...

 

yes .98V was with the throttle closed wide open was at like 4.5V

 

ah ok haha, O/W reads 5V that blue with green stripe is whats reading 2.55v

 

Key on/off/running ?

 

Tested with key off, truck isnt firing off....turns over strong though.

 

And you have 5v on the O/W with the key off ?

 

yes 5V on the O\W wire with key off

 

Off the top ofmy head, seems your EEC Relay is energized when it should not be.