FD_James

iTrader: (9)

I recently had an overheat event with the car - pretty sure it was a massive air bubble or a stuck thermostat - my thermostat test proved it didn't work very well.

More interesting though was that when I went to check on the car ten minutes later, I was noticing that my aftermarket thermostat and the OEM one were saying very different things. So, I decided to plug in my commander to see what the computer was seeing. While I was doing that, I suddenly started smelling fuel wafting through the vents. I ran around the other side of the car to grab my fire extinguisher and noticed raw fuel vapour coming out the tail pipe (car was off but key on to keep fans going). At this point I also noticed fuel pouring out on the ground. I assumed the heat had cooked a fuel injection line and it had started leaking somewhere on top of the block near the fuel rail.

I had the car towed home and the next day began pulling it apart to figure out where my bad fuel line was - turns out, no fuel on top of the block and all the lines looked and felt great.

I did a key on and I could hear fuel flowing which is expected but it was louder than usual. After a minute or two, I could see fuel bubbling up through the LIM!!! The injectors were dumping fuel into the engine. So now I'm suspecting one or more leaking or stuck open injectors - as a result of the hot engine event. So I rigged up some extra fuel line, pulled all the connectors off and did a key on - nope, all the injectors stayed closed and not a single drop of fuel was leaked. Next I suspected a short somewhere and started testing all the wires to/from the injectors for both voltage and continuity - that all checked out too. Lastly, I pulled the computer and opened it up - near the main grounds I could see some "heat treatment" on the board and around one of the chips I could also see some brown from the resin being heated up. What I don't know is if someone re-soldered some cracked cold joints or if it's from some other event.

I also noticed that my commander won't turn on. I've checked continuity from all the pins on the Power FC to the board - they all check out, no shorts or open circuits. I've also checked continuity end to end on the controller cables - no issues.

I hooked everything back up - same issue. Fuel pump does what it's supposed to and pressures the system and the injectors dump fuel into the runners forever - until all the fuel pressure is gone.

Has anyone seen this before? I want to make sure before I go buy a new Power FC. I want to make sure I'm not overlooking anything.

I've also checked all the fuses. My circuit opening relay was making weird noises but I think that's because the battery was dead - it seems fine now and that controls the fuel pump - not the injectors.

DaleClark

iTrader: (55)

Yeah, sounds like the PFC. You may be able to fix it but with both the injector driver issue and the commander not coming on there may be multiple failures, could be better just to get a new one.

Dale

FD_James

iTrader: (9)

Thanks Dale - that's what I figured but reassuring to hear it from someone else. Looks like I'll be posting a "Wanted Ad"

Cheers,

Sean

jza80

iTrader: (32)

You might want to consider buying a new pfc, you will know it’s history (brand new, no possible issues from anything that might have occurred in the past, etc.) also it will come with the better display which is a huge upgrade. Just a thought...

billyboy

Only pfc equipped car I worked on where the drivers fried, had no fuel. Short in the emissions harness after a fire killed them.

Have you checked the harnesses in the wheel wells - lots of gremlins lurk there! Hard to tell what mods you have, if it's stockish on injectors, a standard ecu should let it start and run. I'd probably look at another ecu type anyway if it is dead as a door nail.....unless the tune has been saved or the only expertise available locally is for apexi.

cr-rex

iTrader: (114)

it can be fixed....

https://www.rx7club.com/power-fc-for...rvice-1138676/

contact him and he can take care of it

FD_James

iTrader: (9)

What was weird to me is it happened along with an engine overheat - literally while the car was cooking. I've pulled the harness since then, checked continuity end to end on the injector connections which are the ones giving me issues, and then re-wrapped - problem persists. I've tested for shorts on those wires and there are non - no open circuits either except for when there should be i.e. connectors NOT plugged into the ECU.

I don't have a spare ECU to test with. I actually bought the PFC because the old ECU was giving me issues.

Any other idea? I'm open - I do think it's weird that the PFC would choose then to roast itself but like I said - the board has some areas that look like they got hot - bubbled resin etc.

Sean

FD_James

iTrader: (9)

Thanks I'll have a look!

FD_James

iTrader: (9)

Appreciate the feedback - it's a valid point.

Cheers,

Sean

scotty305

iTrader: (2)

Two dead ECUs suggests a pretty serious wiring problem, like 12V getting onto a 0-5V sensor signal, or 12V shorted directly to one of the ECU's ground pins, or 12V shorted onto the ECU's 5V sensor reference wire. I would put the stock ECU back and disconnect as many sensors and plugs in the engine bay as you can reach. Ideally, the ECU should only be getting power and ground. Use the factory service manual to find which pins those are. Then use your multimeter and a back-probe tool (basically a long thin needle that can reach in the back of the plastic connector to touch the metal pin inside) to check the voltage on all the pins. Cross-reference the chart in the factory service manual which will show what voltage those pins should have with the key off and key on. If you don't find anything unusual, try plugging sensors in one at a time and measure the related pin voltages on the ECU.

Or you can fly blind and simply replace all the harnesses that connect to the ECU, unfortunately there are a few different ones so this could be expensive and time-consuming. If you're nearby a shop that is very good with wiring and electronics, it may be cheaper to pay them to diagnose & fix the specific problem.

FD_James

iTrader: (9)

So - the old ECU wasn't cooked - but I did an Auto to Manual swap and the car never ran right after that - lots of issues with hesitation. I "think" it was actually because I had the TPS in the incorrect spot but I'll never know since I got rid of that ECU a long time ago. I also didn't have any issues with the PFC - ran like a champ for a year.

What's weird is that whatever happend to my PFC happened in conjunction with the car overheating - that's what cause the injectors to get stuck wide open - as I've mentioned above, I've double checked all of the injector wires and they are not shorting. That said, I take your point that another short elsewhere in the harness could have cooked the PFC with the side effect being that there is now a short across the internal injector circuit - and so that is a symptom rather than a cause.

I'll do what you say and start testing all the other power/ground connections and work my way forward - sounds tedious but necessary. Car is now off the road for the winter anyway so no big deal.

Thanks for all of the help!

FD_James

iTrader: (9)

Just to update this and likely close it out:

I opened up the PFC and could see it had overheated inside. I sent it to Brandon at Rotary Performance in Texas and he was able to confirm that it was the injector driver circuit and was then able to repair it for me. Took almost no time to get it done. My working theory is that the hot injectors actually got physically stuck open and drew too much current for too long across the board in the PFC and caused the circuit to burn out - I can't really think of any other way to tie the two events together.

Hope that helps someone.

Sean

FD_James

iTrader: (9)

Confirmed a unhappy injector last night - I finally pulled the plug off of it and had a look and it looks pretty melty - the injector is running OK according to my PFC but it's definitely going to need either servicing or replacing.