1989 4.9l 5 speed manual. Went through the diagnostics in the Haynes manual: grounded Data Link Connector (DLC) fuel pump terminal - no pump noise. Made sure inertia switch was in 'run' position (pushed down). Checked for power to external fuel pump - no power. Went on to the 'circuit and component checks': Fuel pump relay - 12volts to relay pole #2; harness from FP relay #1 to EEC #22 good; power from FP relay to EEC #22 good; power in at FP relay #4; harness from FP relay #3 to inertia switch good; power from FP relay to inertia switch good.
Here's where I need your feedback: the next check say : FP relay #3 to ground - when key is turn to 'run' position, the manual says: "Circuit should briefly complete (1 to 2 seconds) immediately after key is turned to RUN." This test failed. Manual says: "Possible EEC failure". OUCH!
I pulled the EEC and sent it to SIA Electronics to have them check it and (hopefully!) repair it. I have had good luck with them in the past with my 4Runner EEC. So I'm just wondering if any of you have run down a similar problem? How often do the EEC units fail in these trucks? Did I miss something. I tried to be extremely methodical in my diagnosis, but I'm sure I could miss something. Any and all comments welcome!

 

The EEC typically is very reliable. Their weak link if you can call it that is old age. There are three electrolytic capacitors on the pc board that eventually fail and fuel system problems can occur. A visual examination will show the suspect capacitors buldged out and/or leaking onto the pc board. If you have soldering skills, it's not a big job to change these out. If one goes, change all of them.

 

Read these pages & follow the relevant links on them:

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Thanks to raski and Steve83. Wish I had not been in such a hurry to send it off for repairs! I'll have to wait and see if SIA can fix it. Next time I won't be in such a hurry and I'll wait to hear from the forum first. Looks like a fix I could handle. I'll let you know how it goes once I get the EEC back.

One other thing: the Haynes manual said to make sure relays and fuse are good before going too far in diagnosis. I confirmed that the relays are OK (EEC and FP), however I don't see a fuse for the fuel pump. Perhaps there isn't one on the 1989? Or is there another fuse block somewhere else?

 

'89 trucks have only 1 fuse block; the circuit protection for the fuel pump is a fusible link wire, but I'm not sure of the location. It might be near the starter relay, or near the FP relay.

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