Calling Renix gurus...

Does anyone have a circuitry schematic for the RenixII ECU's? Some of the regulators melted and I was just wondering why it happened. Initially, the cat clogged up frying the o2 sensor and melted the first ecu. I d/c the sensor connector and replaced the ecu, and the new one is getting hot and melting some of the plastic voltage regulator connectors. There's four sets of 4 regulators on my ecu...the two sets closest to the big u shaped heat sink melted. Any help would be appreciated.

On my 88' when the ICU went, my connections were melted also. I spliced on new connections and havn't had a problem.

Well none of the wiring seems melted...it's just some of the regulators on the ecu board itself. After cutting the cat off and d/c the o2 sensor...the circuit board is still getting too hot. What could be shorting it out?

The Renix systems manual can be found at the "strokers" egroup (groups.yahoo.com/group/strokers) in the "Files" section - I believe it's called "89FI"-something, or something similar (I changed the name on my copy, so that wouldn't help you.) It's a .pdf file, so you'll need Acrobat to get it open.

As far as internal schematics, I've been looking and haven't had any luck yet. If anyone turns them up, I'd appreciate copies as well - I've gone so far as to run up the company last known to own Renix, and they didn't have anything to offer, either...

5-90

Hey 5-90... not to thread-hijack or anything, but was there any success on the read-the-Renix-datastream project?

Not yet. I've been busy with school and the new job at the campus bookstore, so it's been "back-burnered" for a bit. I'm also waiting to hear back from satan on his approach to individual monitors, as I see no need to reinvent the wheel and looking at them individually will allow me to better understand how to tie them all together.

It's lapsed, but not forgotten...

5-90

Are you sure those are 3 terminal regulators and not the drive transistors for the fuel injectors? I've fixed a few over the years. Never have run across the schematic for the ECU.

I think that they are the drive transistors for the fuel injectors...they are somewhat melted and sometimes I have to fiddle with them to get the truck to start...but once it starts...they get really hot...hot enough to melt the solder contacts on the board. When the first ecu went, I had no injector pulse at all, and the replacement one which is someone melted gets hot. So the question is, what causes them to overload like that and get hot???

Thanks for any help...really stuck here...

Measure the resistance of each of you injectors. Sounds like one or more is shorted. If I remember right they should be in the neighborhood of 16 ohms, but just make sure they are all about the same. Should be a simple fix compared to what you've dealt with so far.

Do you measure injector resistance with ignition on or off, truck running or not running? Thanks.

Resistance is ALWAYS measured on an unpowered circuit - you will want to just DX the drive lead to the injector and measure resistance across the injector terminals. Attempting to measure resistance on a powered circuit will usually result in your meter being boned, unless it's a Fluke or a Beckman Industries "Oops-proof" meter.

I agree with the nominal measurement being 16 ohms or so - I think it's in the Renix manual I pointed you toward in my last post. Did you grab a copy yet?

5-90

Haven't been able to get a copy yet...

Well all of my injectors read 2.6 ohms ...normal, or are they all shorted out?

If the reading is with the wires disconnected and measuring across the two terminals on the injectors, your injectors are hosed and would explain cooking the drivers in the ECU. Actually there is a family of injectors that run the lower resistance. They are not for the Renix system. Are you sure someone hasn't put in the wrong injectors?

Yes, there are two types, and CRASH can fill you in on them better than I can. However, the low resistance would explain cooking the injector drivers - although I think it is possible (but generally unnecessary) to make an adaptive circuit to switch the one to the other.

If the injector readings are consistent (say, withing 10%) of each other, it is likely you have the wrong sort.

I do highly suggest you do a search for "Fuel Injector Information" posted by CRASH - it really was a good thread that can explain both sides of what's going on so you can udnerstand the problem a little better.

Meanwhile, save your nickels for another set of injectors. If you have a spare ECM, any way I can talk you out of it when this is all sorted? I have need of a Renix ECM for some projects I've got going on the test bench...

5-90

actually desperiate times desperiate measures, 4 months ago, 6 leaky injectors, low budget...replaced with 6 from a chrysler mini-van with a 3.? liter motor...looked right and fit right...wrong set?

If memory serves, the two types are "Peak and Hold" and "Saturation" - with the "Saturation" type having the lower reisitance. The "Saturation" type are also used in race engines and such, since they have faster response and can be more accurately controlled for tuning. Again, I'd let CRASH confirm this, as he was the one that posted the original (well-done!) tech article on the subject.

I didn't know that "saturation" type injectors were used in production engines, tho - but I could be wrong.

5-90

5-90, once this is all sorted out...the only ecm that i'll have left has a fried set of injector drivers...if you are still interested...let me know...meanwhile, i'm trying to locate another set of injectors, and possibly an ignition control module...fun, fun, fun...

No problem here - it's going to be a "bench model" and I'll just need basic data on the drivers (if anyone has it) so I can sub for something that will drive an LED indicator.

More than anything else, I need the ability to simulate the control system outside the vehicle, so I can poke and prod and figure out what's going on where. Pressure and temperature signals will be simulated, and so will ignition and fuel system outputs.

BTW - here's an oddity for you. The Renix ignition module is one of the few parts I've ever found that costs less OEMR than aftermarket stock! I think Standard Parts wanted something like $225, while OEMR was about $150 - either case was for the module and coil as a set. Also, the dealer usually has one on the shelf, while you'll have to order the aftermarket (or, I might have a spare somewhereabouts - but I can't make any guarantees as to its suitability as a replacement.)

Why, specifically, are you changing it? Is it an "age" thing, or do you suspect a problem? I can pillage around for my notebooks - I seem to recall devising a workable test some time ago (but the major problem I've found is simply heat - the best test I'd found for that was a hair dryer at idle. Heat the module past normal operating temperature and see if it cuts out.) However, with the divorced mounting, a failed Renix ignition module seems to be rare - and they are MILES tougher than the old Ford DuraSpark modules (and easier to diagnose...)

5-90

Well, the only reason I am thinking that the ignition module might be the problem is because someone told me so...the wierd thing is that it runs fine, just heats up the injector drivers...so I'm inclined to think that the module is fine...if it was suspect, I would expect a miss, or a firing problem...but spark is great...and yea...my injectors are definately hosed...2.3 ohms for a 16 ohm Renix system is not good. Hopefully, that is the only problem??? I'm gonna try and locate some at a boneyard...do they have to be out of a Jeep 4.0, or do they just need to read 16 ohms, bolt up and fit? If anybody has a set, give me a hollar...

Thanks.