General MPI Relay Rapidly clicking open closed 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.

 

[redyute1]

i am having the exact same shit going on right now,but the thing with mine is if i disconnect the battery to let the ecu reset it works good for a few days,and boom clicking again.Drove down to ecmlink ecu tested good i just cant figure this shit out.

 

[AWD_FIEND]

That's weird. By the sound of it perhaps the ECU is at fault for both our issues.

According to my wiring diagram the relay gets B+ from the ignition switch, but it looks like the ecu grounds the relay when it gets signal from the CAS to start the car. That's what closes the MPI to supply voltage to the fuel pump. (Close, see https://www.dsmtuners.com/threads/1g-basic-ecu-mpi-circuit-function.435961/ - Mod)

Maybe my "new" ECU is bad, but I was told it was solid by a supporting vendor who replaced the caps and tested it supposedly. I dont know hopefully someone can shed some light on our situation.

The only other time I've experienced this problem was when the battery voltage was low, but I charged the battery to full capacity to eliminate that possibility.

Also I did check the MPI fuse and made sure there was gas in the tank, just rule out the obvious.

 

[redyute1]

I know i will find it,i even thought about buying an other ecu since i can't get an eprom one from a buddy to try out.Its just been killing me for a couple months now.Still checking stuff so i will post when i have an update

 

[force it in]

Make sure that the positive post on your battery isn't touching your hood. When I bought my car, the battery wasn't bolted down & there was nothing covering the positive terminal. I could see marks on the underside of the hood where it was grounding out. My relay clicking & car stalling problem was cured by bolting down the battery & covering the battery post.

 

[AWD_FIEND]

I have the factory battery box and retainer with a group 51 battery so its no where near the hood, but thanks for the idea I wouldnt have considered that.

Just an update, I tested the MPI Relay and it checks out as expected. Still dont know why the relay is clicking spontaneously but now I'm starting to suspect the ECU as it's responsible for all the grounds for the relay.

That would be great as I just purchased the ECU from a sponsoring vendor who assured me it tested good and the caps are fresh. Just my luck. BTW I hope this post is appropriate for this section, it not could the moderators PLEASE move it instead of deleting it?

 

[twdorris]

A rapid clicking MFI relay really does suggest an ECU problem. If a new ECU is doing the same thing the old ECU did, then there may be something wrong in the car that's killing the ECUs.

You mentioned having purchased the ECU from a sponsoring vendor... I can't find any record of a sale to Mission Viejo, but if the ECU was purchased from us, we will most certainly offer to take a look at the ECU and tell you what's going on, if anything.

[email protected]

Thomas Dorris
ECMTuning, Inc.

 

[AWD_FIEND]

I appreciate your response, but unfortunately I didn't purchase the ECU from you.

The original ECU worked fine until the ISC took it out so I assumed that was the short that ultimately caused the damage. When I installed the new ECU I unplugged the ISC connector expecting that was my only short, but now I'm suspecting I may have another short somewhere else.

I visually inspected the harness and nothing looks frayed, greasy, or damaged. I re-wrapped the harness with fresh loom and tape about a year ago so I cant see any obvious issues, so I guess I'm going to have to test each circuit individually.

Also one thing that makes me suspect the ECU over the harness is that the old ECU never did anything like this. It ran fine then suddenly the car wouldnt start. If I had a short somewhere else that's damaging the ECUs I suspect it would have had the same problem with my old ECU. With this ECU I'm getting spark and fuel, but no injector pulse, my last ECU didn't give fuel, or spark, or injectors.

I don't know just some more info.

 

[yokotabrat]

If you are getting two different symptoms between the old ecu and the new ecu, it sounds like your harness is probably good. As you mentioned at the beginning, the ecu looks for the ignition switch to be on and then it will turn on the mpi relay, so there isn't much to check for.

Even if the caps are replaced, that doesn't guaranty a good rebuild. If the caps leaked at all and that residue wasn't cleaned, it'll still kill the traces over time, in particular the one that controls the mpi relay. Do you have access to another ecu to try?

 

[AWD_FIEND]

Force it in graciously offered to let me try a spare ECU he has but he lives quite a ways away. I took some pics of the board for any clues but I'm haveing trouble getting this old POS computer I'm using to reduce the size so I can upload. I'll post some pics once I get it sorted. Honestly the board looks good, but I've never seen what the electrolytic acid looks like or the subsequent damage it causes so I wouldnt really know.

Here's some pics of the board tell me if you see any telltale signs of unrepaired acid damage, or if the caps look suspect.

 

[yokotabrat]

The board doesn't look too bad. It does look like there was some leakage from the top electrolytic cap. The caps have been replaced, so that's good. It doesn't look especially clean, but maybe it's okay. It's also interesting that it looks like one of the ceramic caps is missing (C38). It's possible the electrolyte leaked toward the white connector which could damage the traces there, but we can't see that from the picture.

I noticed the eprom chip is missing. What chip are you using? Is it a stock chip? Was the chip seated in the socket well when you were trying it in the car?

 

[AWD_FIEND]

Thanks for the evaluation its really helpful as I have no experience with leaking caps.

I'm really pissed I lost the OE ECU because I owned that car since it had 40k miles on it and replace the caps before the ever started leaking. If only I had know about the ISC dangers I could have avoided the trouble.

I'll take a picture of the traces at the white connector and post them tomorrow, but I think you bring up a really important point. Ive never installed an EPROM ECU so I may have overlooked something.

I have no chip, I just installed the ECU as you see it in the photos. Is there supposed to be a chip in the EPROM socket in order for the car to run?

I'd feel like a real idiot if so

 

[twdorris]

Is there supposed to be a chip in the eprom socket in order for the car to run?

Most definitely, yes. That there be your main problem.

It's hard to tell for sure from the photos, but I'm going to suggest you get that caps area "redone" by a reputable shop. I don't like the looks of the pads up near the heat sink and as a previous poster mentioned, it's even missing one of the small SMT caps! That's not a critical component, but leaving it out does bring into question the other work done at the time.

Thomas Dorris
ECMTuning, Inc.

 

[AWD_FIEND]

Most definitely, yes. That there be your main problem.

It's hard to tell for sure from the photos, but I'm going to suggest you get that caps area "redone" by a reputable shop. I don't like the looks of the pads up near the heat sink and as a previous poster mentioned, it's even missing one of the small SMT caps! That's not a critical component, but leaving it out does bring into question the other work done at the time.

Thomas Dorris
ECMTuning, Inc.

Nice. I thought there was a reason this was a good deal. I guess when they advertised a good reconditioned EPROM ECU I shouldn't have assumed it would actually run the car

Well if you were me and seriously broke what would your advice be to get the car running reliably? Should I just go for a Keydiver chip and have the board properly reconditioned at the same time, or try and find a cheap non-eprom ecu, or something else I'm overlooking?

Thanks for all your help BTW your contributions are all really appreciated!

 

[twdorris]

Should I just go for a keydiver and have the board properly reconditioned at the same time, or try and find a cheap non-eprom ecu, or something else I'm overlooking?

That really depends on your needs. If you plan to run a pretty stock setup, then you can just have the ECU cleaned up and a stock EPROM dropped in while you're at it. If you need (or want) some tuning adjustments done at the same time, then drop Keydiver a note. He can do the cleanup and get you a basic chip I'm sure.

Thomas Dorris
ECMTuning, Inc.

 

[AWD_FIEND]

This car is my winter beater so the most it will have is a 14b and 450's plus a MAF Translator II I was about to install, so I dont really need a tuned chip. But I suspect the stock chip and recondition will cost close to what a keydiver will run, and if that's the case I'd rather just get the upgrade. If I'm going to spend money anyways I'd always prefer to upgrade at the same time, which is what took me down the path of investing in an EPROM in the beginning. But if it's significantly cheaper to just refurbish what I have and run the stock chip then that makes better financial sense right now.

Here's some pics I took after reading about Cap damage on your wiki. I can see where there is signs of damage on my board.

It also looks like J109 and R138 are missing or have been removed and there's green traces on R147s pad.

 

[steve]

I'll be happy to make you a stock chip if you don't have someone local that can burn one from the binary on the DSM-ECU yahoo group.

It's sad to see people shipping what was clearly a quick and dirty repair and not even include a stock EPROM. You might want to contact them and ask for the chip since they left you believing you were buying a working ECU. I'm glad to say I don't ship ECU's that look like that out to people and I know that ECMTuning doesn't either.

Without the EPROM the ECU just executes junk in memory which can cause the relays and solenoids to chatter. I'm slightly bothered by the leakage still visible next to where C38 should be. Those two traces are the input from the ignition switch to turn the ECU on and the output to the MPI relay to do so. They eventually will be eaten through and the ECU will stop working.

 

[AWD_FIEND]

Sorry its been a while since I've responded I just moved out of state and have been extremely busy to say the least.

As an update I was able to test the entire harness, and every single circuit checked. Although it took forever and was a pain in the A-- I can finally rule out the wiring and sensors. So I confirmed, with your help, that the problem was the ECU.

Thanks for all your input with this really frustrating situation, it kept me from putting a rag in the gas tank and blowing the car to pieces I was able to speak to the vendor at length and feel satisfied with their position. According to them they got the ECU from a local DSM ECU rebuilder which they have a reliable history with, so they assumed the ECU was intact when they sold it.

They offered a sincere apology and full refund, which works for me. So that makes ECU number 3 for this car (two replacements that were dead on arrival) and now I need another one.

I don't want an EPROM anymore as I've decided to go Haltech to avoid all the reliability issues with Mitsubishis ECUs. If you've got a non-eprom that for sure works let me know, my winter beater is a 92 GSX auto.

Steve, I wish I could've afforded your initial offer way back as I would've avoided all this frustration. Thanks for you help anyway, a really appreciate it.