EEC Won't Enable Fuel Pump Relay
Hi guys, I'm new to Broncos, and the forum. I have an 89 5.0L which died on the highway a couple weeks ago. Cranks but no start. Got it towed and have been troubleshooting in my driveway.
I am getting a spark, and with starter fluid sprayed into the intake it'll fire once or twice while cranking but won't start. I've been looking at the fuel system, using many threads on this and other sites to guide my efforts.
I replaced the fuel pump relay because it was badly corroded and looked like a likely culprit. It didn't solve my problem though, and I'm starting to think the problem might be the EEC, and here's why:
-I don't get the expected 1-sec fuel pump prime with key on, or while cranking.
-I've traced this to the tan/LG wire on the fuel pump relay not being grounded by the EEC (pin 22 on the EEC).
-If I ground it myself using the test connection, I can hear the fuel pumps running when I turn the key on, and the fuel rail pressure increases. This means the new FP relay works and that the inertia switch is fine.
-I get good continuity between EEC pin 22 and the T/LG wire at FP relay, as well as EEC pin 8 and the brown wire at the FP relay.
-EEC relay is working and all voltages at the relay are good with key on.
-I think EEC grounds are okay. Pins 49, 20, 40, 60 all have good continuity to ground.
I pulled the EEC and opened it up. No obvious signs of burned or damaged components or broken solder joints, but that doesn't really mean anything.
I'm stumped. As far as I can tell, either the computer is bad or something else is causing the computer to not drive pin 22 to ground to trigger the relay and enable the fuel pumps. Could another sensor or a failed TFI cause this?? Any ideas or suggestions would be much appreciated! Also, I tried starting the Bronco with the self-test connection grounded so I knew the fuel pumps were running, and it still wouldn't start. Seems like if the fuel pump issue is my only problem, it should have started when I did that. Seems incredibly unlikely that the computer would just fry itself driving down the highway, but I can't think of anything else that could be the problem.
It was running fine before this. Just cruising along at 60 and there was a sort of snap noise and the engine died.
Thanks in advance!