MPI Relay Clicking Rapidly Please Help

[AWD_FIEND]

Ive been diagnosing a recurring no start condition that first began with a failed fuel pump, which then turned into a fried ECU, that's now manifesting in my MPI relay rapidly clicking open/closed when key is in run and start position! The car still wont start and I'm at my wits end. I'll try and give you the total history in hopes anyone can offer some insights. Going back the starter spins and engine turns over but initially the fuel pump wasnt priming. I bench tested the MPI relay it checked out, then I tested the FP and it was toast. So I replaced it but the car still didnt start. Suspected the ECU, pulled it and sure enough it was toast. ISC motor burned it good and destroyed the board. I installed a new ECU, and it still doesnt start and the MPI relay was rapidly clicking on off. Then it suddenly stopped clicking all together and the fuel pump isnt priming again. I'm going to bench test the MPI again maybe it fried but any suggestions as to what else I can check would be appreciated. Oh BTW I disconnected the ISC connector to keep it from frying my new ecu, dont think that would cause a no run though.

 

[Boosted3s]

Sounds like another bad ecu. Was Your replacement ecu reman or used.

 

[AWD_FIEND]

Supposedly it was Reman according to the vendor but I havent opened the case to confirm. I'm going to test my harness now to make sure there isnt another random short somewhere else that's damaging the ECUs. But my old ECU never did this, and this ECU is giving me spark where the old one didnt so I'm suspecting the wiring is fine. I'll find out. Any other possibilities?

 

[1998gstmaniac]

I'm fighting the same problem with the shop car. Injectors not pulsing at all but I was getting fuel pressure and spark. The only way i can get it to start is to hook up a jumper box, let it sit for a little, floor the car and it will start up but the main relays clicking constantly. Even switched out the relays with other but same problem. Check and see if your injectors are pulsing at all. For a while I was switching out ecu's to see if it was that but it didnt make a difference. Let me know if you find out anything....

 

[ilco187]

the mfi/mpi relay has 2 relays inside it, one is for the injectors and the other for the fuel pump, have you tried another relay, also have you tried this thread for help http://www.dsmtuners.com/forums/newbie-forum/263224-mfi-mpi-relay.html

 

[Lofty]

Clicking would imply the relay is bad. Have someone try to start it, and go in the engine bay, and put your hand over the relays and figure out which one is clicking. Usually a bad ECU won't do that. I think I answered a question prior to yours a while ago, and it turned out to be a bad MPI relay. But just keep us posted.

 

[LKWTSI]

Clicking would imply the relay is bad. Have someone try to start it, and go in the engine bay, and put your hand over the relays and figure out which one is clicking. Usually a bad ECU won't do that. I think I answered a question prior to yours a while ago, and it turned out to be a bad MPI relay. But just keep us posted.

My MPI relay is behind the radio stack next to the ECU. Did I miss something.

 

[steve]

Clicking would imply the relay is bad. Have someone try to start it, and go in the engine bay, and put your hand over the relays and figure out which one is clicking. Usually a bad ECU won't do that. I think I answered a question prior to yours a while ago, and it turned out to be a bad MPI relay. But just keep us posted.

It could be a simple as a dead battery, the low voltage isn't enough to keep the relay activated or the ECU running.

A ECU that is running junk will also cause the relays and solenoids to chatter since the processor is basicly bouncing off the walls. Bad ECU or bad/missing EPROM is the usual cause.

And yes, the MPI relay is mounted on the passenger side console support, not in the engine bay.

 

[GooeyGus]

My car did this a few days ago after I popped in a different EEPROM chip. I swapped the other one back in and it's running again. Although, before I put the other EEPROM back in, I touched up A LOT of connections on the ECU board. SO I really dont know if my spare EEPROM chip is bad, or if the socket job was a bit iffy to begin with.

The main thing that will help you, check the codes while the problem is happening. If you just get a steady voltage (no pulsed, just steady 12V from the connector) then there is a problem in your ECU. Also, if your check engine light is on, you know that the ECU is getting power. So if the light is on, you at least know it's the fuel pump 'side' of the MPI relay (mine was).