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1G Simple Fuel Pump Rewire became a problem

turbotom

15+ Year Contributor
102
6
Sep 27, 2003
New Bedford, Massachusetts
1GB 92 Eagle Talon TSI AWD
Stock block with 272 cams
ECMLink V3
B16G
FMIC
FIC 660s

So this was supposed to be simple thing that had been covered hundred times but for some reason my car has to be difficult 🤦🏻‍♂️

I finish the rewire and in ECMLink I activated the fuel pump. The fuel pump sounds a lot better vs before where it sounding like it was struggling to keep up and I feel my inconsistent idle change is due to the fuel pump with weak voltage.

I went to start the car, won't start 🤷🏻‍♂️🤬. Check spark (coils, cas, plugs, transistor checks out 👍🏻), so I decided to reconnect the black/white wire together with out relay and the car starts right up 😲. I said to myself, this doesn't make sense. What am I'm missing?

The relay is a BOSCH 40a and has 85, 86, 87, 87a and 30. Only thing I could think of is the middle prong not being used (87a) and maybe has to be connected to a existing prong that being used 🤷🏻‍♂️

I'm stumped, what you think guys? What am I'm missing here 🤔


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AWD-Tony

Supporting Member
6,796
3,683
Sep 11, 2017
Cincinnati, Ohio
On a 5 pin relay, the output is switched from 87a to 87 when energized. Sounds like a bad relay to me if it’s wired correctly. You can double check with a volt meter or test light.

Post 30 - should always see 12v+
Post 85 - should always see ground
Post 86 - the input signal wire. Simply test voltage at this wire using link. Only 12v+ when pump is turned on. This is the trigger wire to turn on the relay. I used the stock fp wire here.
Post 87 - should see 12v+ Only when pump is turned on/pin 86 energizes.
Post 87a - should always see 12v* until pump is turned on (then 0 volts).

There’s no reason to run a 5 pin relay when rewiring a fp but it should still work.
 
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turbotom

15+ Year Contributor
102
6
Sep 27, 2003
New Bedford, Massachusetts
Updates:
Ok so I have some time today to mess with the car, I put in a 4 pole relay, no luck (won't run).
Connect the factory wires back together, (runs) 🤷🏻‍♂️
I activated pump to always stay "On ALWAYS " on Link with relay, (won't run).
Put factory wire back again (runs) WTF 🤬
Now here is the funny part, leave it factory (no relay) but activated the pump on "ON ALWAYS" on Link, car won't run 😡 Makes no sense 🤯
 

AWD-Tony

Supporting Member
6,796
3,683
Sep 11, 2017
Cincinnati, Ohio
Check the connections and the wires for the relay. Grab a multimeter.

First I’d check voltage at the factory wire with pump turned on in link and also check with it off. Then check ground. Can you post a pic of how it’s wired and which wire goes where?

If everything checks out, jump 30 & 86. Maybe you have a intermittent problem with the stock power wire to the pump. Possibly mpi issue

 

turbotom

15+ Year Contributor
102
6
Sep 27, 2003
New Bedford, Massachusetts
Check the connections and the wires for the relay. Grab a multimeter.

First I’d check voltage at the factory wire with pump turned on in link and also check with it off. Then check ground. Can you post a pic of how it’s wired and which wire goes where?

If everything checks out, jump 30 & 86. Maybe you have a intermittent problem with the stock power wire to the pump. Possibly mpi issue

From the harness I'm getting battery voltage 11.9-12.4v with the car off. While running 13.7-14.0v without the rewire, and I can the same with the rewire but not running because it won't run with the rewire hooked up.

Far as how it's hooked up:
30- constant 12v right to the battery
85- Ground
86- signal wire from harness
87- to the fuel pump
When I hook up the rewire the pump works and comes on strong no problems with that, but the car will not start up and run. I wired the pump straight to the battery, car will not start up and run. If I reconnect the black/white wire car starts right up and runs. I even activated the fuel pump to stay on on Link v3 and the car dies. Go try to start it up, will not run hesitate like the coolant temp sensor is no good reading -40 on the Link which is not the case because it's working. The car will only run with that black/white wire from the harness is connected. I'm stumped, never had a DSM do this to me 🤦🏻‍♂️
 

AWD-Tony

Supporting Member
6,796
3,683
Sep 11, 2017
Cincinnati, Ohio
Have you confirmed that the wire to 85 is actually grounded?

From the harness I'm getting battery voltage 11.9-12.4v with the car off.

I assume this is with the key in on position without starting the engine and pump on in link?

Can you post a pic?
 

1990TSIAWDTALON

Moderator
9,673
5,508
Nov 14, 2013
Independence, Kansas
I have never heard of this or had this issue with any car, so I am following along to see what becomes of it and if I can come up with any test, I will chime in.
Good luck Tom, super weird.
 

luv2rallye

DSM Wiseman
8,393
1,169
Jun 7, 2003
Minneapolis, Minnesota
I think your problem is without the black/white wire connected, ECU pin 13 (fuel pump control sense) now doesn't see power to the fuel pump, so it won't allow ignition when trying to start. You need to wire the black/white to the wire that now goes to the fuel pump on your new relay and cut the black/green (pin 2) on the old fuel pump/MPI relay (note the black/white becomes is a black/green on it) so it doesn't cause problems. Note the fuel pump relay and MPI relay are both in the same unit so you can't just remove that relay.
 
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