My 7427 Fuel Injection thread

[mineral co]

Things got screwed up last weekend and I didn't get to do any boneyard scrounging while in Denver, but I did get to do some today, more locally, in Alamosa. (70 miles away is "local" around here.)

On a side note, this was kind of the truck's shake-down run since getting it going again. The oil pressure gauge likes to meander around but, other than that, no problems.

Scads of trucks, most all with engines missing and harnesses cut at the firewall. And, curiously, most all had the glove box area of the dash ripped apart. Hmm. And, hardly a PCM in sight.

It took most of the afternoon, but I did find a truck that had a 7427 PCM! Again, the harness was cut close to the firewall, but there is enough there to at least power the unit up and see if it will talk (once I get the Moates stuff to do that with). At 15 minutes before closing time I found a second truck that had an in-place 7427, and what looks to be a complete harness and engine, minus the TB injectors. I grabbed the PCM (just in case!), and will go back for the harness and TB during the week.

I grabbed two of the cut-short PCM harnesses from different trucks (PCM to, and through, the firewall). Having an extra sounded like a good idea (and they were cheap since they had been cut short).

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It is my intent to document the full process of doing a 7427 from the ground up. There seems little point in starting with a 7747 and then modifying it later. I have to contend with substantial altitude changes around here locally, ranging from 7,100 feet around Alamosa to over 13,000 on some of the trails. If you make a trip to Denver than add another 2,000 feet. Make a trip to the beach and, well, you get the point.

I now know that the 7427 is capable of supporting a MAF sensor (with the correct version of hacked code), and I think that is the best solution to dealing with these wild swings in altitude.

As seems to be the case with anybody just starting to learn this stuff, my feeling is that there is a ton of information out there, but it isn't cohesive, it's frequently confusing or contradictory, it's periodically out of date and, sometimes, it's just flat wrong.

And I'm one of those people that tracks details when I'm trying to educate myself, and when the details don't line up, I cannot assume I now know something. Words that are misspelled are somewhat annoying, but when the misspell changes the meaning of the word, the reader isn't going to be getting an education, he's going to be getting confused! Information that is presented out-of-order has the same result. I could go on ad-naseum. . .

I hold myself to the same standard. If somebody is confused by what I write, or if it is incomplete, please say so and I'll do my best to fix it!

I do much better with new topics once I have put my hands on some part of it. Today's activities went very far to relieve some of the stress and confusion about this whole thing. I knew what I was looking for (a PCM with a tag number that ended in 7427), but I wasn't even sure exactly where to look to find the PCM on a truck. I had read that it was under the dash, but the undersides of dashes are usually dark and scary places when you have to find something specific. I also had no idea what the orientation of the tag would be relative to where I might be viewing from. Having never seen one in person, would I even know it was the PCM if I couldn't see that tag?

As it turns out, this is not a tough problem. In the trucks, the PCM is located to the right of the bottom-right corner of the glove box. If you remove the glove box enclosure (four small hex head screws) the PCM is in plain sight, and the tag is right there where you can easily see it. Whew, what a relief! I thought I was going to be laying on the floor of the truck, on my back, reaching into neitherlands over my head that I couldn't actually see.

Next anxiety attack: now what do I have to do to get this thing out? (More nightmares of using little easily-dropped tools, turning a dozen screws one-sixth of a turn at a time, none of which are visible.) Once again, this turns out to be about as simple as it can get. Disconnect the two PCM header connectors and two other, unrelated connectors in the same harness and then push the PCM unit UP at each of the two friction retainers. These friction retainers are located only on the left (visible) side of the unit. The unit's right side profile fits into a bracket, and once the two friction retainers are disconnected, the unit is completely free from its mounting and can be removed via the open glove box. Done! What I feared would take hours, I could now do in about three minutes.

[Insert photo of PCM on tray]

Okay, so, next I need a harness. Whadaya know? There is a firewall connector that the harness passes through. Nobody ever mentioned a firewall connector in anything I read prior to going to the boneyard. Every truck that I looked at there, regardless of ECM/PCM type, had a firewall connector of some sort. Leave the connector connected and just remove the two small hex head screws from the engine compartment side and pull the connector off the firewall. The hole in the firewall is more than large enough for the PCM connectors (and the other two unrelated connectors) to pass through. Those two screws' heads are some oddball size. A 6 mm and a 1/4" wrench are too small and a 7 mm wrench is too large (but still works). Perhaps the heads are some strange number like 9/32".

That's as far as I can go right now. Once I get back down there and pull that full harness off that one particular truck, I'll be able to add more detail on collecting all this stuff.

Now, I did see a couple of other things that got my attention. The most important was the big, five-position terminal block screwed to the engine side of the firewall. There are going to be several things that will need a power source on my truck, and I've been struggling with this for a few weeks. I don't want to have fifteen ring lugs on the battery side of the starter solenoid, and I wouldn't want to run all those wires that far anyway.

These terminal blocks use 8 mm (~5/16") studs and are shrouded along the top side. They have holes for mounting screws on both ends. They are very heavy duty, and look like a factory OEM part (and they are!), and can be put where appropriate so that multiple large hot wires aren't running all over the place under the hood. I snagged three of them.

I also grabbed a few relays with weatherpack connectors, plus I found a few single-fuse fuse holders that are attached to the firewall. I really like this as there are circuits that need to be fused, but I don't want to be running wires back and forth inside the truck, or use those silly in-line fuse holders like you see in use for radios, etc. These fuse-holder are screwed to the firewall, so will make for a much nicer look under the hood.

And one other thing, I found two 8625 PCMs at the bone yard. These also use red and blue connectors like the 7427, and are on the same vintage of truck as the 7427. Just what are these 8625s?

Also, what is the difference between the BJYK and BJYL PCM versions that I picked up? I'm hoping that one of them is the $0D version as that seems to be the right one for what I want to do.

[babywag]

Try to find a G-van harness. they are nice and longer than truck harness.

Don't worry about what BJyy or BBJxx is it really doesn't matter, once you modify or adapt the memcal you can use whatever poison you pick.

Personally if I was to do another one, I'd just start w/ 7427 + OD MAF.
I would also have bought a moates ostrich emulator right off the bat.

If you hit any snags, just post up.

[Bill usn-1]

Also, what is the difference between the BJYK and BJYL PCM versions that I picked up?

Both are 1995 5.7/4l60e from C/Ks
The difference is just the rear end gear ratio.
3.08/3.42 vs 3.42/3.73

[mineral co]

From gearhead-efi.com:

7427 BJYK = '95 C-K Truck 5.7 TBI, 4l60e with 3.08 or 3.42 gears.BIN
7427 BJYL = 350 TBI, 700r4

I'll keep looking for additional (lack of) confirmation/confusion.

[tgreese]

You asked about the 8625 - Google search for "8625 PCM" gives this -

http://www.fullsizechevy.com/forum/gene ... 5-pcm.html

Apparently used on S10s. Post says that it can be a viable alternative to the 7427.

[mineral co]

I had seen that the 8625 was used on S10s but, apparently, it was used on some of the 5.7 engines in the larger trucks as well, if the emperical evidence of two in this boneyard can be trusted. So far, I haven't seen anything out there on the 'net that acknowledges this though. It is stated repeatedly, though, that the 8625 will run 7427 $0D code just fine. I did see one comment that implied that the 8625 may have some number fewer inputs.

Just more information (and questions!) to be clarified at some point in the future!

[Bill usn-1]

The 8625 was the early TBI PCM, note it was used in 93. The 7427 and 6395 came out in 94. There are some minor difference internally but I have interchanged codes between them without noticing any change if how they operate. You may want to verify that 700r4 info. These are PCMs-powertrain control modules used for control of the engine and electronic control transmissions. If you review the code you will see there are scalers for the 700r4 but the $0D and $0E were primarily used for the 4l60e and 4l80e trans.

$E6 16168625 93 C/K Truck, Van, 4.3L, 5.0L & 5.7L 27C512


$0D 16196395 or 16197427 94 - 95 C/K Truck, Van, S-10 LN2 (16168505), 4.3L, 5.7L & 7.4L 27C512


$0DA 16196395 or 16197427 94 - 95 Truck, Van, 4.3L L35 CPI 27C512


$0E 16196395 or16197427 94 C/K Truck, Van, 5.7L & 7.4L (HD) 27C512


$31 16197427 or 16156930 95 C/K Truck, Van, 5.7L & 7.4L (HD) 95 - 96 Hummer H1 (Gas) 27C512


$8C 16245358 16197427 95 C/K Truck, Van, 4.3L 94 S/T Trucks, L35 4.3L 27C512


$63 16197427 96 - 97 C/K Truck, L05 EXPORT ONLY 27C512

[mineral co]

I went back to the bone yard yesterday and pulled the majority of the harness off the truck that had the complete 7427 PCM. This truck did not have a complete TB assembly, but I did find a dirty but uncorroded complete TB assembly off a '92.

All the Moates stuff will be here tomorrow, as well as a TB rebuild kit and remanufactured distributor.

I'll start pulling the harness apart this evening.

This brings me to the wideband O2 sensor and Air/Fuel gauge. I have read several negative comments about the Bosch O2 sensors, but the majority of wide band A/F gauges use a Bosch LSU 4.2 sensor. Is this included in the group of sensors that people don't like? Or, are those negative comments restricted to the narrow band sensors?

Also, for closed loop operation, the PCM requires either a real, or simulated, NB O2 signal, doesn't it? Are folks using two O2 sensors (NB for PCM and WB for gauge) or is there a WB system that also provides an appropriate NB signal for the PCM? I need to get a WB gauge here very soon in order to tune the system.

As much as possible, I would like to keep all the instruments in the truck the same, i.e. manufacturer and style. The only way I've seen to do this is to go with somebody like Auto-Meter, but their description of their A/F gauge is somewhat out of the ordinary:

http://www.autometer.com/cat_gaugedetai ... 4063&sid=4

This unit does provide an analog output that can be used for logging, but is limited to 0-4 volts, representing 10:1 through 18:1 ratios. Other manufacturer's gauges use this exact same O2 sensor, but offer a wider A/F range output.

This also raises the question of how the logger reads and presents this data. Does it have some user configurable conversation to output something meaningful?

Thanks for all assistance!

[JeepsAndGuns]

Use a heated NB for the pcm, dont try and use a simulated NB output from a WB, it never really works right. I kept getting a o2 sensor code when I tried it.
I have the innovate MTX-L. I have one in my cherokee and my YJ. They work great.

[mineral co]

Okay, so that means you have two O2 sensors in your exhaust?

Which NB are you using?

[JeepsAndGuns]

Yes, I have two o2 sensors.
For the NB, I am using one for a truck like the 7427 came out of.
Looked it up, I am using a ACdelco ASF74

[mineral co]

Having a little trouble. . .

I've got the Moates APU1 and TunerPro RT is installed. TP seems to be working with the APU1. However, I'm not getting any data out of the 7427 (as far as I can tell).

The PCM and harness and a couple of sensors are laying on the floor. I have the ALDL cable connector from Moates connected by three pins to the PCM (A: gnd, B: diag, M: data).

Under "Preferences/Data Acquisition & Logging" in TP, I can specify either "Use plug-in" or "AutoProm/MAFTPro". I don't know which of these is right since neither choice matches what I could find in any online-instructions.

More relevant perhaps is that TP's instructions say that "and running the ALDL tool within TunerPro RT" after connecting the ALDL cable. Where the heck is this done?

This has been most aggravating. None of the on-line documentation accurately reflects what the program actually looks like. Even Moates' references where to find and/or do stuff in TP don't match up. I suspect that a lot of this is documentation that has not kept up with the program, but it sure is hard on somebody that isn't already familiar with the program.

I have no way to tell, at this point, if the PCM box is even alive. Is there any way to tell this if you can't get data out of the ALDL port?

If somebody could get me over this ALDL hurdle, I would surely appreciate it!

[babywag]

Does it show a connected status on the bottom of tunerpro app?

What .xdf & .adx files are you using? Wrong ones will cause all sorts of mayhem.
What version of Tunerpro?
Since you have an Autoprom that is the setting in TunerPro to use.

Autoprom switches set correctly for 8192 baud?

[mineral co]

Somewhere along the line I stumbled across some success. When not emulating, I can get data on the ALDL port. I think this was due to having replaced the FTDI driver with an older version.

I have the BJYL-$0D-5.7-Auto.bin, 0D_TPV5_v250.xdf, and A217_0D_v250.adx files. TP ver 5, build 5.00.8144.00

Right now (working ALDL), the "Data Aquisition & Logging" is set to "Use Plug-In", not "AutoProm/MAFTPro". The plug-in is "TunerPro Data Acquisition I/O Interface". This is configured as "Standard Serial" and "{COM1}".

When working, the outer switch on the APU1 is "out" as opposed to "in". This corresponds to the Moates instructions for only logging. Before calling it a night, I did try a few times to get data while emulating, but was not successfull. In this case, the only change was to move that same switch to the "in" position, initialize emulation, load the bin file, start emulation, cycle power on the PCM, verify the ram contents for the bin file and then try to read data. No luck with that.

I assume there has to be a very specific sequence of events to get emulation to work, and get any data. It would be too easy to get something out of sequence and have the PCM hang rather than work. At this point, I have no way to tell if the PCM is running under emulation or not.

The "inner" switch on the APU1 is "out" (open) which is what I believe is supposed to be the configuration for the 7427. Since I am getting data, I am of the opinion that this has been verified as correct, along with my pin selection for the loose ALDL wires (A: gnd, B: diag, M:data).

All comments and advise are welcome!

Thanks,

Chris

[babywag]

For emulation you need to change the "code mask ID" in your bin from OD to AA using TunerPro.

Without changing it your PCM will be unhappy and error out.

[mineral co]

Baby steps.

Okay, so with the Data Acquisition and Logging changed to AutoProm and the Mask ID set to AA, and starting the data collection, TP does say "connected" and the rate is close to 15 Hz.

But all the gauges show at (or very close) to zero.

This is not something that I recall having seen mentioned in any write-up.

---------------------
Edit:

It occurs to me that simply being "connected" may only mean that the APU1 is returning data. Is it possible that the PCM is still off in la-la land? I need some way to know if the PCM is actually running.

---------------------
Edit:

I now know this is the case. I can leave the PCM disconnected before starting TP and the APU1 and TP will still show that it is emulating and connected. What the heck is this? I'm a bit PO'ed. I've followed their (vague, contradictory, incomplete, out-dated) instructions and I've spent the money they asked for.

[babywag]

Assuming your doing a bench test by reading your posts...

#1 You need to have an SES light hooked up.
What does it do when you apply power & ground to the appropriate wires?
Can you jumper the correct wires/pins to get it to return codes/blink?

You're using mostly "clean" power for this like from a car battery?
A battery charger or AC>DC converter isn't going to cut it, they're usually way to "dirty".

[mineral co]

Thanks for responding.

This has been a most aggravating exercise. If I ran my business like this, well, I wouldn't have a business for long.

I haven't hooked up an SES light because I don't know if it is an active high or an active low signal.

However. . .

Again, dumb luck has found me. Just out of a need to do something, I was looking through a lot of the .bin data and it all just looked like trash. Nobody would have actually run such on a real engine. So, remembering what you had written last night about the wrong files causing all sorts of trouble, I decided to see if I could find a .bin with data that made more sense. I found a BJYK file and loaded it. What do you know? Numbers that looked reasonable.

And, surprise surprise, now it will log data during emulation.

----------------------

I guess I knew I was taking a chance going straight to a JY 7427 with no prior knowledge of any of this stuff. Presumably, if I had started with the 7747, I could have relied heavily on the scads of information out there to get up and running more easily. Had a I just had an operating vehicle that had a 7427 I could have skipped all the worry about the wiring as I could have assumed it was good.

The other thing that is true is that an earlier ECM would have been much easier to get the PROM out of. Normally, I would just read the existing PROM and use that as the initial .bin file. As you know, the memcal in the 7427 is built in such a way that removing the PROM is not a good idea unless you like trouble (I'm sure that's why Moates built the adaptor the way he did).

Anyway, I've spent the last two days fighting with this stuff, and it really has been a hair-pulling exercise. It just shouldn't take that long to get new equipment up and running. But, I suppose, in the grand scheme of things, that memory will fade and I can get onto the more fun stuff. It has been a very steep learning curve over the last several weeks, and that sort of thing generally incurs some cuts and bruises along the way. But, I'm getting there. That Jeep is going to be FI'ed, some how, some way.

I really appreciate the willingness to help out with the problems! I'm sure there will be more, but I think the toughest ones are out of the way.

Again, thanks!

Chris

[babywag]

Lots of info to absorb
And yes it's a steep curve.

SES wire from PCM is a ground.
Hook a hot in run wire to light of your choice and the pcm SES wire to the other side.
Simple and done.

If you search via google tons of threads/info/wiring diagrams etc.
You must have a good wiring diagram or you're just spinning your wheels.

Just about everyone that takes the plunge says the same thing and has a few issues along the way.
It's worth it.

[mineral co]

I'll get the SES function hooked up and see what happens.

I did find a pretty good 7427 wiring diagram. It details all the sensor, injector, fuel pump relay, ESC/ignition, and EGR wiring. Most all of the wire colors were a match as well. The only two issues on it is that the swithed DC+ does not match my harness, and it doesn't show which power rail the SES light is connected to. All in all, not bad.

I was watching some youtube videos on setting up TunerPro RT last night, and one of them reminded me of what the more-likely initial data problem was. In a previous post I said that I thought that replacing the FTDI driver was the likely fix of the problem, but there was also in issue with the com port number. The initial driver install exercise did assign COM3 (as indicated as correct and desireable by both Moates and TP), but TP only showed COM1 as an option in the configuration. I ultimately went back into the Windows Device Manager and changed the driver's configuration to use COM1 rather than COM3.

Watching that video, the presenter was having trouble with the same thing. He finally said "just use whatever TunerPro shows as available". Of course, this doesn't actually work if TP doesn't display the actual, available com ports.