Runs Nice for a Few Min. Then Rough, Then Kills...

[FastWoman]

^^^ That's my understanding too, Captain. I suspect the pump was made to run with EITHER sign of life because...

--- otherwise you wouldn't be able to start your car after an oil change if going on oil pressure only.

--- otherwise your engine would die if your alternator failed, leaving you stranded, if going on alternator output only.

Personally, I think a better system would be one that monitors the ignition and runs the fuel pump as long as the ignition system is putting out sparks. It could be contained in the ECU. But that's just me.

[Zed Head]

I saw the post three weeks ago but figured the OP and anyone else looking had enough focus on those two items to go look themselves. Who knows, we could all be wrong, the discussion is just a starting point.

And I'd like to have written from knowledge acquired having gone through the wiring diagrams and figuring out what all the relays are doing but the reality is I came across the attached chart in the FSM. It takes some study since the oil switch description is kind of counter-intuitive. The oil switch "open" is what actuates the relay and the pump, not closed. Still much easier than the wiring diagram.

[Captain Obvious]

Yeah, that's the chart from EF-16. That chart clearly indicates that the intention is that the engine will run with alternator output OR oil pressure.

Using the chart you referenced, in conjunction with another chart on page EF-36 and the wiring diagrams, I think I was able to figure out what all of the involved switches and relays do under the different conditions.

And you're right... It's a counter-intuitive, convoluted, screwy system. I should really document the system before I forget again.

[Captain Obvious]

Personally, I think a better system would be one that monitors the ignition and runs the fuel pump as long as the ignition system is putting out sparks.

I agree. With the current system, I think they swung too far in the "unsafe" direction. If my current understanding is correct, once the ignition switch is in ON or START, you could completely disconnect the oil pressure switch and the alternator connector and the fuel pump will run.

The sense of the failsafe detection is wrong. OPEN is not failsafe...

[Zed Head]

I've seen this pointed out somewhere else on the internet, that there is a flaw in the logic. Maybe a link from atlanticz.

Found it - http://atlanticz.ca/zclub/techtips/fuelpump/moreinfo.htm

Edited November 14, 2013 by Zed Head

[Captain Obvious]

Thanks for linking to that doc. I had previously gone poking around the Atlanticz site and found the fuel pump page that linked to the doc you found, but that's where I stopped.

That document mirrors my understanding completely (or more accurately, my understanding mirrors that doc, since it was here first!). I was one mouse click away!

Lesson? When you don't know, check the Atlantic Z Car Club first, and if you still can't figure it out, then study the FSM.