1988 Ranger computer test

[Ruger45]

Hello; I need help with this truck . I shut the thing off and then it won't start again . The fuel pumps donot turn on, there is no power to them, the relay is good as are the pumps . there is power to both sides of the relay, switch side.one side is from the ignition switch the other is to the computer. When I bypass the relay the pumps run but I get no pressure. How can I test the computer (ECU) without a reader ? Or is there some thing I'm missing . There was no sign of a problem before I turned it off that last time. Oh yes there is sign of a water leak down that side of the cab under the dash (windshield seal). HELP! Thanks:roll:

 

[MrShorty]

1st question, which engine is this Ranger?

How can I test the computer (ECU) without a reader ?

1st test would be to pull codes, which can be done with a paper clip and a voltmeter. The stickies in the EEC-IV forum will guide you through the test.

When I bypass the relay the pumps run but I get no pressure.

This suggests that you have two problems, one electrical fault in the fuel pump circuit, and a fault that is preventing the system from generating pressure. I would probably work on the electrical fault first.

You say pumps (plural), so I will assume you have a two pump set-up like I had in my BII: a low pressure pump in the tank and a high pressure pump on the frame. Since bypassing the relay seems to make the pumps work, then I would suspect the problem to be in/near the relay. Will the relay close if you ground the fuel pump test lead in the self-test connector?

 

[Ruger45]

"88"ranger comp......

The engine is the 2.9 V6. and the pumps do run when i ground one side of the relay .

 

[MrShorty]

That suggests that the PCM isn't telling the relay to close. Can you use a voltmeter and a wiring diagram to verify that the PCM is grounding (or not) the test lead?