ECU Problem?Help

[will90Eclipse]

Does any one know what the little box next to the ecu is used for?? Mine is making a buzzing noise. Its on the right hand side next to the ecu. Sorry I don't have pics.
Thanks Will
1990 Eclipse GS 16V

 

[VerbalKint]

Don't have my Tech CD Here with me. If no one else answeres by the time I get home, I'll look it up and let you know.

 

[huafist]

That's your MPI Relay. To the best of my knowledge, it shouldn't "buzz", just click.

 

[will90Eclipse]

I was looking thru my haynes manual and found the box I was talking about. They call it a EFI fuel control relay, I don't know if those are the same or what. It only clicks when I turn off the car and its real annoying, do you have any idea why it is making this sound??
Will

 

[VerbalKint]

EFI = Electronic Fuel Injection
MPI = Multi Port Injection.

Same thing, two different ways of naming it.

 

[will90Eclipse]

Do you know why it would be clicking like that? Is it a real bad sign?

 

[WS6snake-eater]

Does anyone have a pinout or diagram of what all this modual controls? When I start my car 92 2.0 dohc, it will run fine for about 30 secs. Then this modual will start to click off and on (sounds like a relay), and will cut fuel until the car dies. Once the car cuts off, I have to unplug the modual and plug it back in before it will restart. I have already replaced the modual with a new one from Mitsubishi, but it did not fix the problem. So what all does it control? Obviously the fuel system, but I'm curious as to where it is getting it's input. Perhaps the cam and crank postioning sensors? Any help would be greatly appreciated. I don't want to just start throwing parts at it, if I can help it.

 

[WS6snake-eater]

Do you know why it would be clicking like that? Is it a real bad sign?

Is it clicking while you are driving or just on startup?

 

[DSM Storm]

MPI relay on the DSM cars rarely go, im not saying they are fail proof but the last time I heard one click like a tap dancer was when my friends ECU had some caps leaking all over the main board.

Storm

 

[will90Eclipse]

My ECU was replaced brand new before I bought my car so I don't think it's the ECU. The car makes a clicking sound while it is sitting turned off. The minute you turn the key it stops making the sound. The sound is being transferred thru my EFI fuel control relay. If anyone has had this happen to there car, I could use some idea's on how to fix it.
Thanks Will

 

[DSM Storm]

Your going to need a few things. Test light and wiring diagram will help. Find out what wire keeps triggering the relay and take it from there, it might not even be that there is something triggering it, it might be a bad relay. Let us know.

Storm

 

[WS6snake-eater]

Would a fuel pump that is not keeping up (about to go out), cause the box to click off and on and cut the fuel. My pump is starting to whine pretty loud, and the MPI box will click off and on then cut fuel to the car until it dies. I think the problem is the pump. Can anyone confirm this? Also is the pump in tank or in line? Thanks!

 

[DSM Storm]

Would a fuel pump that is not keeping up (about to go out), cause the box to click off and on and cut the fuel. My pump is starting to whine pretty loud, and the MPI box will click off and on then cut fuel to the car until it dies. I think the problem is the pump. Can anyone confirm this? Also is the pump in tank or in line? Thanks!

The stock pump is intake. Your story does not make sense to me. Your saying that the MPI relay is turning the pump off, then on again, then the car stalls out? FYI a fuel pump will not cause the MPI relay to click. That relay simply turns the pump on or off, not the other way around.

Storm

 

[15poundsoffun]

hey there if you are still having this problem i once had this problem too when my ecu went out the caps. are starting to go or byy now there are gone take it out and look i maybe wrong but it doesnt hurt to look let me know what u find out thanks chris

 

[WS6snake-eater]

I pulled the ECU last night and checked all the caps...Everything in there looks excellent. In fact the ECU looks brand spanking new. After I plugged everything back in the car is running fine. Really weird stuff. Perhaps is was just a loose connection to the ECU? I'll give it a few days and see what happens. Hopefully I will not get stranded on the side of the road again.

 

[WS6snake-eater]

The stock pump is intake. Your story does not make sense to me. Your saying that the MPI relay is turning the pump off, then on again, then the car stalls out? FYI a fuel pump will not cause the MPI relay to click. That relay simply turns the pump on or off, not the other way around.

Storm

Ok I re-read my post and I guess it wasn't too clear. Something (I don't know what) is causing the relay to click off and on. Once it clicks off the fuel pump stops and the car starves out of fuel and dies. I am not sure what all would cause the MPI relay box to trip off and on. I was simply asking if a pump that is not keeping up to the task, would somehow send a signal to the MPI box to turn off the pump. However I see from your post that this is not the case. So what would cause the MPI relay to trip? Thanks.

 

[steve]

So what would cause the MPI relay to trip?

The MPI relay box has two different relays inside. One controls the power to the MPI system the other the power to the fuel pump.

It's possible that you had a bad connection at the ECU harness from dirty/oxidized connectors that was causing the signal keeping the pump running to drop out. If reseating the connector really fixed the problem then that would be my first guess.

The ECU watches the CAS and feedback from the ignition system for signs that the engine has died and it shuts the pump off for safety. It's also possible that the ECU though the engine had stopped and turned off the pump. Again a bad connection at the harness could cause intermittant behavior.

Bad/low voltage to the ECU can cause the ECU to reset over and over causing the MPI relay to buzz.

Capacitor leakage damage can cause all sorts of unusual behavior.

Steve

 

[z3ds]

I'm also having the same problem with my 90 galant GSX. The car starts and runs but the MPI relay kills the engine. The helpful people in galantvr4.org told me that the CAS may not be sending signal/pulses to the ECU. I'm about to check my CAS if it is still good. I will also follow what steve was suggesting to check bad connection within the harness/connectors. i'll post later results

 

[will90Eclipse]

Sorry it took so long to get back to you guys but I have been busy. Anyways ,I had my car checked out at a Chrysler dealership about a week ago and they went and put it on a computer and manually checked the EFI and ECU. They told me that nothing was wrong with the car but it is still making the noise. WTF As to the fuelpump issue my car has never cut out but it does have trouble getting started( i have to turn the keys at least twice).
Will

 

[WS6snake-eater]

I'm giving this a TTT...It's 4 months later and I'm still having the same issue. I ahve not been able to drive the car at all, and have been stuck driving my Z28 instead. Sometimes the car runs fine and other times it just dies. Could a misfire (bad spark plug-possible head gasket leak) cause the MPI relay to cut fuel? I pulled plugs today and found that the nubmer 4 plug has rusted up, indicating a possible head gasket leak. Compression check on all 4 cylinder yeilded good results. I'm just curious if the fouled plug could be sending a misfire, that is getting picked up by the ECM, and in turn cutting out the MPI relay as a safety percaution. ??????????????

 

[steve]

Could a misfire (bad spark plug-possible head gasket leak) cause the MPI relay to cut fuel? I'm just curious if the fouled plug could be sending a misfire, that is getting picked up by the ECM, and in turn cutting out the MPI relay as a safety percaution?

Nope, the ECU doesn't turn the fuel pump off unless it sees the engine stop running. A misfire won't do it.

Steve

 

[WS6snake-eater]

Then it looks like I'm back to the CAS or the ECU...Steve how can I go about sending you the ECU to take a look at? E-mail me @ [email protected] or [email protected]


Thanks,

Matt