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MFI/MPI Relay

kahl23

Proven Member
1,094
11
May 10, 2004
Wellesley, Massachusetts
I know a lot of guys are trying to find the MFI/MPI relay, here's where it is and what it looks like on a 95 GSX.
 

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kahl23

Proven Member
1,094
11
May 10, 2004
Wellesley, Massachusetts
In case you were wondering, that last picture shows the two mounting holes for the relay. They're located behind the center console side panel (passenger's side) below the radio.
 

steve

DSM Wiseman
13,807
888
Feb 3, 2002
Boulder, Colorado
Testing the relay is a matter of applying power to the coil winding and making sure the contacts close. Inside the metal box are two relays, one for the MPI power and one for the fuel pump power. The fuel pump relay has two coil windings and energising either should close the contacts.

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This is the circuit for an 1G automatic car taken from the 1G tech manual. The manual cars have the starter relay and clutch safety switch replacing the AT Inhibitor switch for providing power to the second fuel pump coil to activate the pump while cranking the engine.

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Applying +12v to pin 10 and the ground (-battery) connection to pin 8 should make 12v show up at pins 4 and 5. Same deal for pin 3 and 7 causing 12v to show at pin 2. Applying 12v across pins 9 and 6 will cause continuity between pins 3 and 2. (on relays with the second input)

I haven't looked at the 2G wiring to see if the 95's still use the second input of if they use a different MPI relay. The later 2Gs don't, they use two individual relays.

Steve
 

luv2rallye

DSM Wiseman
7,976
846
Jun 7, 2003
Minneapolis, Minnesota
I haven't looked at the 2G wiring to see if the 9's still use the second input of if they use a different MPI relay. The later 2Gs don't, they use two individual relays.

Steve
I show the 95 still has both relays in the same unit but the FP relay now has only 1 coil (1 input). The 96-99 all have separate relay units.
 

phillabaum03

Proven Member
851
3
Nov 28, 2005
sharpsville, Pennsylvania
im not getting any power to my fuel pump either, took me days to think to see if these cars have fuel pump relays or fuses, im gonna try a friends and see if the car starts!! wish me luck fellas
 

DSMunknown

Proven Member
4,110
36
Sep 16, 2004
Worcester, Massachusetts
Make sure your pump is working correct as well (or first). I had problems with my pump during on. I hooked up an alternative power source to see if it was activating properly. Turned out that it was seizing up on me. Replaced it with an Evo 8 pump and all was well.
 

phillabaum03

Proven Member
851
3
Nov 28, 2005
sharpsville, Pennsylvania
thats what i thought at first, swapped them out numerous times now, is there a way to check these?/test
 

white_dsm

Proven Member
230
0
Feb 9, 2008
Plains, Texas
^

First test:
Have a friend untwist the gas cap and listen inside while you turn the key to the on position, if your friend hears whirling your fuel pump is working. If not go to step 2.

Step two:
Test to see if you're getting voltage at the pump. This can be done under the hood next to the battery. Get a jumper wire from the positive side of the battery onto the fuel pump check terminal. Get your buddy to listen again while you do this, If you still don't hear whirring the fuel pump relay or it's control circuit is faulty.


Step 3:
Check for voltage at the proper pins on the EFI contorl relay, the one in the pic posted above. If voltage is present go to step 4.

Step 4:
Check for voltage at the fuel pump electrical connector, since you done swapped fuel pumps already you should know what the connector looks like. If there's voltage replace the pump, if not there's your problem.
 

kkenui

Probationary Member
4
0
Jun 8, 2009
Wailuku, Hawaii
I acquired a 1991 Mitsubishi Eclipse that was not running for over a year due to the MFI/MPI relay not in the car.

When I got the car, they said the part was ordered, and that I just needed to go pick it up, but that was over a year ago, and the shop had already sent it back, and does not keep record of what it was. The old relay that came out of the car is missing, as the previous owner does not have it anymore.

I did some searching online, and found this wonderful website. I then took the numbers that I found on this site:

E8T08474 (from Picture),

MR224159 - After July 05
MR161519 - Before July 05

and actually had to call a Mitsubishi dealership before ANYONE could help me find the relay. They were able to send me a MPI/MFI relay, but I am not sure it is the correct one for my car. The numbers stamped on the top are: E8T07071. Is this the correct relay?

I plugged this relay in, changed the spark plugs and spark plug wires, put in 5 gal of new gas (cause it was sitting for over a year), and installed a new battery. The starter turned the engine, but the car would not start, and it did not seem to "turn over."

Anyone have any ideas? Do I have the correct part? Any help would be GREATLY Appreciated!

Thanks in advance!

VIN: 4A3CS54U7ME033181
Year/Make/Model: 1991 Mitsubishi Eclipse GS
Body Style: Hatchback 2 Dr
Engine Type: 2.0L L4 FI
 

meyer795

Probationary Member
17
1
Mar 28, 2007
Minneapolis, Minnesota
Hello,

First of all thanks Steve for all the pics and time you have taken to help your anonymous cohorts.

I checked my 1990 talon TSI for voltage coming to pins 3, 9, and 10 and I found that 3 and 9 have 12 volts.
Pin 9 does not get any voltage. I do not have the automatic tranny so I am not sure which sensor to check next? Your drawing is obviously for an auto... any thoughts would be appreciated... Thanks !!


Best Regards,
Jesse:banghead:
 

yokotabrat

Proven Member
480
34
Mar 11, 2004
Longmont, Colorado
Which pins have 12V? In one sentence you say 3 and 9 do have 12V, but the other says pin 9 doesn't. :) Assuming you are looking to see where pin 9 on the mpi relay goes, on a M/T car, it goes to the starter relay. You should only see 12V there when the car is cranking. The more important question is what do you see for voltage on pins 7 & 8 of the mpi relay when you are trying to start the car?
 

steve

DSM Wiseman
13,807
888
Feb 3, 2002
Boulder, Colorado
Any thoughts would be appreciated.

Depends on what your trying to solve. (Please tell us)

If the problem is the fuel pump then the output on pin 2 is important and you would be looking at pins 3, 7, and 9 to figure it out.
If the problem is your not getting power to the MPI circuit then the output on 4 and 5 is key and you would look at pin 10 and 8 for clues.

As Bert points out pin 9 only has 12v on it when the car is cranking. Assuming the car starts the ECU will pull pin 7 low to keep the pump running.
 

meyer795

Probationary Member
17
1
Mar 28, 2007
Minneapolis, Minnesota
Which pins have 12V? In one sentence you say 3 and 9 do have 12V, but the other says pin 9 doesn't. :) Assuming you are looking to see where pin 9 on the mpi relay goes, on a M/T car, it goes to the starter relay. You should only see 12V there when the car is cranking. The more important question is what do you see for voltage on pins 7 & 8 of the mpi relay when you are trying to start the car?

I confused the pins in my last post sorry. The pin 9 has no voltage which sounds like its supposed to. If I understand correctly, I need to test whether the voltage gets through the MPI relay while the key is on. I am new with the DMM, so I am wondering: do you just plug it in and shove the point of the electrode in the back of the connector?

The car seems to be getting fuel (fuel pump whines and inlet pulses) but has no spark and no ECU boot. I fried the shit out of my ECU beyond cap replacement, and I got a matching one from a guy of craigslist. I opened the replacement and it doesn't look or smell fried. After putting the new one in I noticed its not booting, but the MPI does click... I will try to check the MPI relay across my battery this afternoon.

I'm gonna go out there right now and start shoving the DMM into the backside of the wire connector and see what happens.

Thanks for your responses guys!!!
 

steve

DSM Wiseman
13,807
888
Feb 3, 2002
Boulder, Colorado
The car seems to be getting fuel (fuel pump whines and inlet pulses) but has no spark and no ECU boot. I fried the shit out of my ECU beyond cap replacement, and I got a matching one from a guy of craigslist. I opened the replacement and it doesn't look or smell fried. After putting the new one in I noticed its not booting, but the MPI does click... I will try to check the MPI relay across my battery this afternoon.

Sounds like the fuel pump side of the relay works so you should focus on the MPI side.
Since pin 10 has 12v all the time just go to the ECU connector with the ECU disconnected and ground pin 63 (or 66) and see if that turns on power to pins 102 and 107.

It's common for leakage to damage the traces controlling the activation of the MPI relay.
If grounding the pin turns the power on then you know the problem is the ECU and not the relay. (which would be the first place I would have been looking since I've yet to see a bad MPI relay but lots of bad ECUs)
 

meyer795

Probationary Member
17
1
Mar 28, 2007
Minneapolis, Minnesota
Sounds like the fuel pump side of the relay works so you should focus on the MPI side.
Since pin 10 has 12v all the time just go to the ECU connector with the ECU disconnected and ground pin 63 (or 66) and see if that turns on power to pins 102 and 107.

It's common for leakage to damage the traces controlling the activation of the MPI relay.
If grounding the pin turns the power on then you know the problem is the ECU and not the relay. (which would be the first place I would have been looking since I've yet to see a bad MPI relay but lots of bad ECUs)

Alright, I did that. Just in case i did it wrong heres what I did...

Shoved a little wire into #63 and bent it down to touch the middle steel area. Then I shove the voltmeter into 102 and 107 while grounding the other end. 0 volts. Bad MPI then?
 

meyer795

Probationary Member
17
1
Mar 28, 2007
Minneapolis, Minnesota
i forgot to mention I turned the key and still nothing.. I was rough on it while i took it out so I'm wondering if the wiring between the two is the problem. I could test it across the battery by using some wire right?
 

steve

DSM Wiseman
13,807
888
Feb 3, 2002
Boulder, Colorado
I could test it across the battery by using some wire right?

Yes, just like I said in post 5.
So what color wire went to the pin you grounded. Since the ECU was disconnected the ignition switch isn't involved. It's normally the input to the ECU to turn on the MPI relay but there is circuitry between the two.
 
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