Blowing MPI Fuse... HELP!

[RU2SLOW?]

So I'm at my wits' end here folks, and I was hoping all of you could give me a huge hand in possibly diagnosing this problem. I replaced my stock 1G intake mani with a JM Fab unit 2 months ago and did some other minor mods in the process. I removed my charcoal cannister, replaced my Optima Redtop battery with a lightweight Odyssey unit (with JM Fab install kit), deleted all of my unnecessary vacuum lines, swapped my stock throttle cable for a non-cc unit, replaced my 650cc injectors with 850cc, and relocated my coil pack. The coil pack is now mounted on the back side of my block with the plug inlets facing upward toward the intake mani. I made the bracket out of aluminum diamond plate, and placed a few pieces of a thick rubber between the new bracket and the coil pack to help pad it. I put emphasis on this one mod because it's the only one that I've done that isn't quite straight forward. Also, the TPS would not fit back on properly with the new mani so I had to put it on with the plug facing the battery rather than the driver side- checked readings in DSMLink after install and all seems to be working fine. So once these modifications were done I started my car and it ran well, drove it around a bit and all seemed to be functioning fine. However it started to rain while I was out, and after getting on it through first and second gears in the rain the car just died, rpms dropped, and DSMLink could not locate my ecu. Come to find out the MPI fuse was blown on the 3-fuse bock located on the 1G battery. I replaced the fuse, tried to start the car and it blew out immediately again.

I removed the CAS as soon as I got the car towed home, tested it off of the car, and it seemed to be in functioning order. I also pulled my ecu and checked it for any noticable signs of being blown with none evident. Installed the ecu in a friend's 90 AWD Talon and the car ran fine. So after allowing anything that potentially got wet to dry I tried starting the car again a few days later. The car started right up surprisingly and ran for a good 5 minutes with what I would describe as a rough idle (holding high at approx 1500-2000 rpm but NO CELs- possibly because the CAS needed to be re-adjusted after removal). I tried to give the car a small amount of gas on the pedal and POP! The fuse blows again. I replaced the fuse and tried to start it again, only to blow yet another MPI fuse. Sooo to make a very long story short the car now refuses to start and these fuses continue to fry. What could this possibly be due to?

I'm pulling my hair out here DSMers, so any help you can offer would be extremely appreciated. I've done some research on the MPI relay blowing over time, but could find nothing suggesting that the MPI fuse would blow if this were to happen. I also am having a very difficult time tracing what component on the MPI circuit would cause this to take place if it were to malfunction, or making sense of any mod that I may have performed that could provoke this problem. Thanks in advance for any advice, tips, suggestions you all can offer.

 

[RU2SLOW?]

I also just wanted to add a link to some pics that I took of the mods I performed as I explained above. Sometimes it's a bit difficult to explain certain things, and I also thought this may help out if anyone could see anything that didn't look right.

http://community.webshots.com/album/523823807PChrwA

Please feel free to ask any questions that I haven't touched on but may help out as well.

 

[just2asian]

what all is done to the car? do you have a bigger fuel pump on the car? I ask this because I had a buddy who used to blow his MPI fuse all the time and we couldn't figure out why, then one day he decided to rewire the fuel pump with a rewire kit and the fuse just stopped blowing, not sure if it was a coincidence or if it was actually the reason.

 

[RU2SLOW?]

what all is done to the car? do you have a bigger fuel pump on the car? I ask this because I had a buddy who used to blow his MPI fuse all the time and we couldn't figure out why, then one day he decided to rewire the fuel pump with a rewire kit and the fuse just stopped blowing, not sure if it was a coincidence or if it was actually the reason.

The car does have a Walbro 190lph fuel pump on it, but it has been rewired with a relay and an inline fuse. The inline fuse for the pump has been checked routinely since all of these problems began and it is fine.

Aside from the rewired fuel pump, the car also has the following for fuel-related mods:
-FIC 850cc injectors
-2G MAS
-DSMLink

 

[RU2SLOW?]

Where's all the wisemen??? I can't be the first person to experience this... any ideas at all?

 

[Gs Dewd]

Have you tried grounding the coilpack bracket you made? I believe the bracket is where the coil packs pick up there ground. So try that.

 

[RU2SLOW?]

GS DEWD- Thanks for your reply. I actually had that on my checklist of things to do today before I stepped into the garage. I did, however, locate my problem earlier today and was able to fix it as well.

After drawing a blank from my searches and post here I decided to venture over to good ol' DSMSource to see if I could get any insight. After researching for a little while I found a post that explained how over time the wires going to the O2 sensor located right before the O2 plug (found connected to 2 clips on the side of the block right under the water neck) tend to go bad over time. The protective cover on the wires peels back and wires become exposed, often shorting out on any metal around them or, as in my case, shorting out on themselves. Unplugged my O2 connector to find a bit of a mess, and after a little bit of wiring and reconnecting wires my problem was fixed!!

So just to try to offer help to anyone who may have this problem in the future- especially since this is a somewhat common problem on 1Gs as I've come to find- I'll share my checklist in order of most frequent occurrences to try and locate the cause of a blown MPI fuse. As always, feel free to add to this list if I miss something...

1. Check O2 wiring at the plug harness
2. Check your grounds for anything related to the MPI circuit (CAS, fuel injectors, O2 sensor, coil pack, etc). Particularly if you've had to rewire or relocate anything related to these componenets- ie. relocating your coil pack after a SMIM install.
3. If you have rewired your fuel pump, double check that the relay has not gone bad and caused the fuse to blow.
4. Use a test light/voltmeter to trace any faulty connections in the MPI circuit, such as revealed injector wires, CAS wiring, and in a worst case scenario wiring related to your MPI circuit near and in your ECU harness.

Attached is a pic I took of the culprit of my headaches...

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[Spyder4g64]

& when you go to replace your bad wires on the front o2 plug, make sure to label ALL of them far back enough, so you dont cover them in electrical tape and accidently remove all of the markings..

 

[RU2SLOW?]

& when you go to replace your bad wires on the front o2 plug, make sure to label ALL of them far back enough, so you dont cover them in electrical tape and accidently remove all of the markings..

BTW- Why's your profile still say N/T Spyder???? Hmmmmmmm... you lie like a rug!

 

[Gs Dewd]

Glad to here you got it straight.

 

[Spyder4g64]

BTW- Why's your profile still say N/T Spyder???? Hmmmmmmm... you lie like a rug!

It is an N/T Spyder. Wanna see the VIN or the registration?