The Top DSM Community on the Web

For 1990-1999 Mitsubishi Eclipse, Eagle Talon, Plymouth Laser, and Galant VR-4 Owners. Log in to remove most ads.

Please Support STM Tuned
Please Support STM Tuned

1G 92 Talon Main Relay - AEM ECU no signal to fuel pump even with new Main Relay

This site may earn a commission from merchant
affiliate links, including eBay, Amazon, and others.

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

nkosi

15+ Year Contributor
321
3
May 17, 2004
montreal, QC_Canada
I need some help with trying to figure out on my 92 talon tsi awd why when i turn on the the ignition key to run without starting the car i cant get the fuel pump to prime and run after the car is started . Here is how it went down and what i have done so far , i was driving the car home from the drag strip(didn't race the car) got off the highway the car was idling perfect at the traffic light. The light change to green i start moving then the engine was just wanting to die like its getting no fuel so i let go of the throttle and it dies immediately. While my gf calling the road side people i doing some trouble shooting to save my self a tow charge, i start by turning the key from off to run position and i don't hear the fuel pump priming as usual, so i check the relay of the fuel pump re-wire and that's working fine. Next i re-wire the pumps to direct battery power and the are working fine , i attempt to start the car and it fires up and starts to run with the pumps directly wired to power but not smooth and my AEM wide band gauge confirms it with readings 10.9-10.00 so its running rich but its running and i drive the car home which was about a 5 minute drive from where the car stalled. So thinking about what happen and how the car started running with the fuel pumps to direct power i came ti the conclusion the Main Relay needs to be replaced and i order one. I got the relay today and install it in the car and still i get no priming of the fuel pump when the key is at run before start, i try to start the car anyway and it starts but runs for about 10 secs and then dies no matter how much i step on the throttle. So i start checking all parts starting with Msd ignition box ,the coils , the transistor and the Main Relay itself and i hear it going on and of but still no fuel pump priming or running when the car is started. Next thing i do is check the wires going to and from the main relay to the ecu and they all seen to be working properly, Then with my tester light grounded i check a white/red wire at the Main Relay and at input 56 of the ecu and the fuel pump starts to run from the ground it gets from the tester light.

Now i lost as to what is going on with the car this has never happened before and everything seems to be working as they are supposed to but the car continues to start and run only for about 10-15 seconds and then it dies out. Again i wire the fuel pumps to direct power from the battery and start the car and it runs but not smooth with the Wide Band gauge saying rich at idle and when i press the throttle the wide band goes to 15-17. Is there a relay or fuse i need to change or there is something i didn't check please let me know any DSM wise man or anyone that had this problem and found the culprit thats causing the fuel pump not to prime and run continually when the car is started . Need some help badly on this one fella's .
 
How is the wiring to the fuel sender in the trunk, is it ok, wiring could be a issue somewhere with a old car, mpi relay fuel pump relay, trying to read it all.
 
Hey man thanks for the reply , See that's the thing i don't know where the fuel pump relay is on the car and the chilton service manual i have doesn't give much info on any of the relays i had a hard time even finding any info in that manual about the main relay and the wiring diagrams. can you tell me where it is and there is a block of relays up under the dash that i cant find in the manual to identify what relays they are and what they control.
 
Also if you could tell me where all the grounds are located for the ECU and main relay that would be most appreciated ,I forgot to mention im using AEM EMS not the stock ECU and could i have damaged the ECU with the fuel pumps wired directly to the battery.
 
As i mentioned i the first thread when i was testing the wires to the main relay and wires to the EMS to make sure they were getting power, there was a white/red wire(input 56 at the ECU) and it is connected to the main relay same color, when i touch it with the testing light grounded the fuel pumps start to work with the key on the run position so i think the wiring in the car is still in tack and it says to me there might be a bad ground wire somewhere.
 
After doing a little bit of searching and reading and the test a performed so far on the car im thinking my ignition switch and steering lock where the key goes to start the car is finish cause everything works as normal but when i turn the key to on before start i dont hear the fuel pump priming cause the ECU and main relay is not getting the signal from the ignition switch, i will do some testing when i get to the garage to confirm this but if anyone ahs any thoughts let me know.
 
On all 1g's and 2g turbos the ECU only turns the fuel pump on when it sees CAS pulses which means the engine must be rotating and the key on (MPI relay on and ECU powered up). So just turning the key on w/o the engine rotating won't do it.
 
On all 1g's and 2g turbos the ECU only turns the fuel pump on when it sees CAS pulses which means the engine must be rotating and the key on (MPI relay on and ECU powered up). So just turning the key on w/o the engine rotating won't do it.


Hey man , I was trying to start the car also and it fires right up but dies out after about 10 seconds of starting, but when i start the car with the fuel pumps wired directly to the battery the cars runs without stalling out and runs really rich on the wide band idling it says 10.0 -10.9 and when i give throttle the reading on the wide band jumps to 15.9-16.9 leans out.

I tested all the wires going to the Main Relay/fuel pump relay and the AEM EMS all seems to be functioning as they should and when the car is running before it dies out i hear the fuel pumps running and then they stop , I'm thinking its the ignition switch itself that broke cause everything seems to working im going to test the wires from the Ignition switch to the Main Relay and EMS and see it there is power to all parties.
 
From the sound of things, you may want to send in your aem and have it tested/serviced. If your map, and iat sensors are logging normal, a problem with the ecu would cause the tune to shift, and the fuel pump to have issues. Running power directly to the fuel pump should never change the tune.
 
From the sound of things, you may want to send in your aem and have it tested/serviced. If your map, and iat sensors are logging normal, a problem with the ecu would cause the tune to shift, and the fuel pump to have issues. Running power directly to the fuel pump should never change the tune.

Thats the thing sir the AEM Ems was brand new last year when i put it in the car and had it tuned, I only drove the car about 2000 kms since then i cant see the ECU having a problem. What do you think about the Ignition switch not sending the signal to the Main Relay pin 3 and ECU pin 110. When i start the car the signal to ECU pin 108 from the ignition switch is working cause before the car dies i hear the fuel pumps running and then they stop and the car dies.
 
The only common factor between a fuel pump running, and a very different change in tune is the ecu.

If you think the ignition switch is the issue, try bypassing it. I have actually seen bad ignitions in these cars, but that wouldn't explain the change in tune. However it is a dsm, and two simultaneous, unrelated failures aren't out of the question.

Also, do you have a turbo timer?
 
The only common factor between a fuel pump running, and a very different change in tune is the ecu.

If you think the ignition switch is the issue, try bypassing it. I have actually seen bad ignitions in these cars, but that wouldn't explain the change in tune. However it is a dsm, and two simultaneous, unrelated failures aren't out of the question.

Also, do you have a turbo timer?

Yes i have a turbo timer on the car, I'm thinking because of the non signal from the ignition switch to sensors/main relay and the ECU pin 110 is not receiving the ignition switch signal with the fuel pumps wired directly to the battery this is causing the ECU to act weird.
 
Yes i have a turbo timer on the car, I'm thinking because of the non signal from the ignition switch to sensors/main relay and the ECU pin 110 is not receiving the ignition switch signal with the fuel pumps wired directly to the battery this is causing the ECU to act weird.
First off, I'd remove the turbo timer. It's just another part in the chain that can be simplified for diagnostic purposes.
 
You Nkosi Im having the exact same problem that your having with AEM EMS on the Fuel pump MPI Relay side no power from the signal wire.. Have you solved this problem?
 
My situation is. i can pull the cover from the MPI and manually hold the relay closed and the car will run fine.. but i cant get AEM to do dick... never once had this problem.. i have pulled the motor million times ad replaced it without any problems from AEM or Grounds or what not..
 
So after messing with the wiring and just moving the cables around i reconnected the mpi and i got signal to the pump side and its working correctly.. original problem is solved... but now it dont start the mpi Fuse blew and now theres no power from pin 102 pin 107 but if i manually hold the relay closed it will start and run like shit,. like the injectors are flooding.
 
You Nkosi Im having the exact same problem that your having with AEM EMS on the Fuel pump MPI Relay side no power from the signal wire.. Have you solved this problem?

What i did was sent the AEm EMS in for service and they said everything was good and returned the ecu to me ...i still have to try the newly repaired AEM EMS in the car and see if it primes the pumps as it should and if i have the same problem im just going to get the EMS series 2 for my car.[DOUBLEPOST=1417628623][/DOUBLEPOST]
Sounds like a bad or loose ground wire somewhere.

I haved checked all ground wires in the car and they are all clean and properly connected to the body ... my car is very low miles so all the wires are in excellent shape.
 
Man. I've been having same issue.
Except mine runs. But all of a sudden the priming won't occur.

I used the ecm link function to turn on fuel pumps and set pressure. Now they won't turn on anymore with that function. Then they quit working. Re-wired the relay and bam works. Still won't turn on with Ecm link

But the car runs.

So I'm sitting here on my bucket watching. Good luck man.
 
I know this thread is old, but I am experiencing this exact same problem to the T. I have an AEM, if I ground the fuel pump control (red and white wire) pin at the main relay the fuel pump primes. Now out of no where the starter won't even engage. I have run all of the exact same tests as the OP and everything tests out except grounding the fuel pump coil in the main relay.

I am going to test the starter circuit tomorrow. I feel like this has to be the ignition switch or the AEM at this point, but I don't know. It is being a pain. I will report back when I figure this out, but thought i'd see if anyone else has seen this or maybe somehow the OP figured it out.
 
Based on what I've read here, the only common part is that your AEM is having problems. Lots of problems with the AEM's blowing transistors/drivers over time if you dig around, more so that the factory ECU's. The two issues may not be related.

With factory wiring there's isn't something the ECU can do that keeps the starter from engaging. I don't know if the AEM changes that somehow but assume it doesn't. The starter signal chain is simple unless you have an original anti-theft or aftermarket alarm/turbo timer.

Start at one one of the chain or the other and work back. Either from the ignition switch or from the starter solenoid. On manual cars disconnecting the clutch safety switch bypasses it's operation and is one step of diagnosing the problem.
 
Based on what I've read here, the only common part is that your AEM is having problems. Lots of problems with the AEM's blowing transistors/drivers over time if you dig around, more so that the factory ECU's. The two issues may not be related.

With factory wiring there's isn't something the ECU can do that keeps the starter from engaging. I don't know if the AEM changes that somehow but assume it doesn't. The starter signal chain is simple unless you have an original anti-theft or aftermarket alarm/turbo timer.

Start at one one of the chain or the other and work back. Either from the ignition switch or from the starter solenoid. On manual cars disconnecting the clutch safety switch bypasses it's operation and is one step of diagnosing the problem.

Thanks for the input. I have had the clutch safety switch disconnected all along so i'm good there. I am going to test the starter circuit this afternoon...I have the dash half way out for other reasons so I have access to everything right now. I agree they are unrelated issues and I confirmed the AEM doesn't change anything with the starter circuit.

Luckily, there is a company that refreshes AEM v1s that popped up out of nowhere. They have good ratings and warranty their work so I'm probably going to have it sent in to be bench tested and repaired if they find anything. I would just switch to Link or Haltech but it was making good power and there's not an AWD dyno within 5 hours of where I live so it would be best if I could reload the cal file and go from there.
 
Support Vendors who Support the DSM Community
Boosted Fabrication ECM Tuning ExtremePSI Fuel Injector Clinic Innovation Products Jacks Transmissions JNZ Tuning Kiggly Racing Morrison Fabrications MyMitsubishiStore.com RixRacing RockAuto RTM Racing STM Tuned

Latest posts

Build Thread Updates

Vendor Updates

Latest Classifieds

Back
Top