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Helping a friend out on this one. Car just randomly stopped firing after parking. It will turn over all day. He confirmed good spark but is fuel pump is not turning on. I brought over a scan tool, no engine codes, but does have some airbag codes for impact sensor, ignition voltage low, etc. With scan tool was able to get good cam and crank "on", counts, rpm, and injection pulse etc. Also with the scan took we can manually turn the fuel pump on and off. We looked at wiring diagrams and found that the ecm is responsible for grounding a fuel pump relay coil which sends fused power to the fuel pump. We did research on mitchell for anything that would keep fuel pump from running like a triggered impact sensor or anti theft system, but didn't come up with anything..
That's as far as I got with him, he's going to check for that ground from the ecm. Assuming he is missing that ground from the ecm my thought was to go and check all the basics again. Even with no codes I want to scope the cam and crank signals to look at timing, and then check the ecm main powers and grounds.
Of you can turn the fuel pump on manually with the scanner then that tells me everything in your electric circuit is ok . Can you start it with an alternative fuel source or by manually jumping the relay. What we want to know is if fuel pump is the only thing shut down . In the mean time I'll see if I can find a diagram to be sure there is no safety shut downs other than ecm.
Great thank Ben, forgot to mention that with the fuel pump manually energized the car will still not start. He said he has good spark, I did not confirm. Not with the car now so I can't do any tests but trying to prepare for next time I go out it.
Ok well we need to figure that out too they are likely related . I assume all the fuses have been checked? I don't have time to study the diagram right now but I took a quick glance over it and I don't like it at all! There are 3 fuel control relays it looks like the first 1 is energized by turning the key on the second is energized by the ECM and I didn't catch the 3rd but I seen it is the 1 that actually powers the fuel pump
Yes I only see 2 relays, one is energized from fused power in on or start, sending power to second relay, which is energized by a control ground from the ECM, sending power to the fuel pump.
Yikes, that's a little much Mitsubishi...
I wonder if you're also not getting injector pulse (or spark) considering it doesn't start with the pump energized.
I was thinking along the same lines as Noah about injector pulse. If you find that you have power to the injectors but no control, then I'd wonder if there's some kind of anti-theft problem. Any activity from the dash indicators during cranking? I know that your scan data says there's injection pulse taking place, but I'd suggest backing that up with a test light/noid light/whatever.
Ben you're right about the third fuel relay. On my diagram they're calling it an MFI relay I guess for Multi Port Injection Relay. This one is also grounded by the computer and feeds powers to the ECM and engine sensors.
I was able to get to the car this morning, but haven't figured it out yet. Was able to confirm good spark and injector control. Scoped the crank and cam sensors individually and have good clean square waves. Timing is advanced 5 degrees during cranking per specs so I didn't chase a timing issue quite yet. Was able to see a response on scanner from TPS. The computer is still not grounding the fuel pump relay (- verified at computer connector.), not even at key on. Short of verifying ECM powers and grounds I'm getting close to calling a computer, yet we can still energize fuel pump with the scan tool. BUT even with the fuel pump manually energized it will still not even try to start, which I guess calls for checking fuel pressure and compression. Still no codes. The car uses no immobilizer for anti theft, and I haven't found anything that says an impact sensor would kill fuel delivery. Again she randomly would not start after parking at a gas station.
Oh and the computer from the dealer is $1600, ha, going to look elsewhere of course but I don't think we're ready to call it.! I fell like I need to go back start clean and double check everything.
Ouch computers rarely fail be sure to triple check everything. maybe a (I hate to say it out loud) flow chart cough cough is needed to see what those engineers think you should check
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