7427 install, first impressions

[EagleMark]

Well I got my first 427 from scratch running on the bench today and this seems to be the 427 beginner thread so I have a couple questions.

Does the 427 act differently then the 7747 in that when turned on the check engine light comes on and stays on without a blink?

Does the 427 act differently then the 7747 in that when turned on the fuel pump runs continuously? No prime then off?

That's what mine is doing and I'm not sure if I have something wired wrong?

Check engine light goes off when I spin the distributor and I do have spark, injector firing, IAC moving all looking good but have not hooked up for data yet.

[gregs78cam]

I cannot tell you about my check engine light as I don't have it hooked up, but as far as the fuel pump running there is a parameter for time for fuel pump to run before DRP, I suggest check that to make sure it's not set to something unreasonable. I think mine primes for five seconds. I just remembered I will be driving the Camaro to work tomorrow, I can put the DMM on the CEL wire and see about that in the morning.

[EagleMark]

Cool! Someone may know for sure. But I am used to seeing the flash of check engine light and fuel pump (hanging on wall) turning on, then off till run. So this is all new to me.

I'll be hooking up the AutoProm tonight and starting with one of these manual bin files 1Project2Many gave us earlier. Then get to use the sweet Defs that 93V8S10 built for TP. I'm excited to finally get this far.

Oh yeah there's an update for TunerPro V5 that fixed the data tracing!!! This is like the best day ever!!!

[EagleMark]

In comparing a BMHK OE Manual bin to a BJDR OE Auto bin, the manual has Flag set for Throttle Kicker and the Auto does not!

Haven't looked at the millions of other things in IAC logic but I think starting with a manual bin is going to be much better!

EDIT: WOW! Lots of IAC and other changes from Manual to Auto!!! Although the BMHK I started with was for a 7.4L all I have changed so far is TBI LBS Per HR and Cylinder Volume, unchecked a few flags like EGR, disabled EGR via temp. Should be a good starting point for the new IH engine.

[EagleMark]

I do have a couple questions about the wiring change over diagram. I saw no input for the crank signal (7747 pin C9), I didnt notice this when making the adapter, but when I swapped all the pins into the pcm plugs last night, I had that left over. I figure the pcm doesnt use this? If not I will just remove it from the harness.
Also, the 7747 had two power inputs, B1 and C16. But the 7427 only had one, I'm guessing the other one just gets removed?
And last, are the 7427 pins E14 and F14 inputs or outputs? The diagram shows both of those pins going to the old pin C14. But there is only 1 C14. So do I need to splice into the old C14 wire and add another wire so I can hook one to E14 and the other to F14? Thats what I did on the adapter, I just tied both together and connected it to pin C14

The below information is directly from the notes on Thridgen.org

Old C14 is a 5 Volt Reference and goes to New E14.
Old B1 Battery Volts - goes to New E16
Old C16 Battery Volts - goes to New E13 (Input in place of Brake Switch)

**F14 is not listed in the notes from Thridgen.org.
***1994 Wiring Schematic I have shows F14 as a TPS 5V Reference.
****On the '427 conversions I've done F14 is not wired, nothing going there, not needed for anything!

dave w

There must be a 5 volt reference signal in the 7747 that is tied together IIRC.

I started with an OddBall harness that did not have 7747 or 427 plugs, but did have heated O2? I forget what the ECM was.

But I do have F14 Gray wire to TPS.

Just looked and 7747 does have a 5 volt reference tied from MAP to TPS. That is why a conversion from 7747 does not use F14 but 427 does...
[attachment=0:swes0ow7]747ecm7.jpg[/attachment:swes0ow7]

[Six_Shooter]

No CEL blink and continuous running fuel pump is a sure indication of Limp Home Mode.

[EagleMark]

No CEL blink and continuous running fuel pump is a sure indication of Limp Home Mode.

Well don't know what I did, now running on AutoProm not the origanal chip, but now the fuel pump comes on then off at key on just like a 7747. But the CEL does not blink. CEL goes off and stays off while drill is running the distributor. No error codes set. CEL still does not blink when I go key on? AH! May be the way I have the Test CEL wired I have hanging on the wall, Nope! The light bulb I have wired and hanging on wall blinks with a 7747, but must be to big for 427. I wired in a smaller dash type bulb, instead of a tail light bulb and it blinks when key on! Wierd?

System is running on the bench and I had a High MAP error, forgot the vacuum pump, it went away. Then I got a knock sensor error because I did not have a knock sensor hooked up nor do I have one. So I wired a few resisters in series to measure 4k and that error went away to. I did change a setting I thought was in Scalers but can't find it now? It was VSS not from DRAC or something like that. So with that changed and a 4K resister = no codes!

EDIT: Found the Output speed not from DRAC in Flags 4L80E Tranmission Paremeters. This was unchecked, I checked it and used a 4k resister and no error code set. Have not tested for MPH.

Rewired, tested, emulated and datlogged on the bench and ready to install on the truck!

Thanks for the help!

[EagleMark]

One question on VSS signal? It's the only wire I don't have done. Wiring diagram shows 2 wires from VSSB to PCM at F12 and F13. When not using a VSSB/DRAC what one to use? Or does one go to VSS and one come back?

And I don't see any Park/Neutral switch wire on the 427 wiring diagram? But it's pretty late and I'm wore out...

[JeepsAndGuns]

Wow, yall have been busy posting while I have been asleep

To try and answer a few questions.
When I first installed my 7427 and put the eeprom in backwards, it had a constant cel and the fuel pump stayed running, so it sounds like you were in limp home mode, like mentioned above. Also I coudnt get aldl connection when I had the chip in backwards.
With everything running, yes, my cel flashes just like the old 7747 did when I turn the key on and the fuel pump cycles.

I just checked a 7747 harness I pulled from the junkyard for resale and yes, the 5 volt refrence splits off a few inches from the ecm and then goes to the map and tps. Where the 7427 seperates them.

The BMHK is the same bin I am using, I think its a good bin to start with if your running a manual. Even though its a manual bin (confirmed by a chevy dealer) I still had to change a couple settings in it according to the paramiter comments in the defination. There was one flag called something like enable shift light (or something like that, I dont have my laptop turned on right now) and it disables the auto trans controlls and sets it up for manual. Make sure thats checked, and the comments box says there is a table that has to be set to all 0, and it wasnt. So I changed it. I also went through and turned off every error code for transmission (just to be safe)

six shooter posted up good info in the vss thread. He says the pcm gets both the 40 pulse signal on F12 for trans controlls, and speed signal from the buffer on F13 for other stuff (the diagram I have says fuel cutoff) I used that diagram you have posted on here in another thread and it says to connect A10 to F12, when according to all this, it looks like it should actually be hooked to F13. I have mine hooked to F12. I will try and switch it today and report back with my findings.

[EagleMark]

In re reading the 427 conversion thread, yes it looks like VSS should go to F13.

viewtopic.php?f=9&t=206

[Six_Shooter]

F13 is the wrong pin for the '7747 swap. The F13 pin is the 40 PPR signal, for e-tranny controls.

There is no Park/Nuetral wire on the '7427, since it used "range switches" in the tranny that are 3 connections that tell the PCM exactly what gear the tranny is in. It would come down to ground two of the inputs and switching the 3rd one with park/nuetral IIRC.

[EagleMark]

So is F12 the correct input? The 7747 to 427 conversion writeup says F13... or should I say what do you use for VSS without DRAC/VSSB to input into 427?

[Six_Shooter]

F13 is NOT in anyway shape or form correct for the '7747 to '7427 swap.
F13 is used for tranny controls and needs a 40 PPR input.
F12 is for other functions and uses a 4 PPR input.

[EagleMark]

Is there any paremeter adjustments for VSS coming in F12. I can't find any yet but have read guys change something to use a 2 PPR VSS?

Or just bluntly tell me what VSS I need? I'm getting a headache with all the misinformation I am reading? ...

[JeepsAndGuns]

F13 is NOT in anyway shape or form correct for the '7747 to '7427 swap.
F13 is used for tranny controls and needs a 40 PPR input.
F12 is for other functions and uses a 4 PPR input.

I think I am going to have to disagree with this.
Here are my findings as of today:
I had my speed sensor hooked to pin F12, and it wasnt displaying any speed in the datalog. I changed the setting in the bin for "input not from drac" and tried again. Still nothing, speed was not displaying.
Next I took and swapped my speed sensor wire from F12 over to F13 and tried again. TA-DA! I now have a working speed signal in the datalog! I was thinking it was going to be off, since what I was reading said it should be 4 pulse and not 2 pulse. But I started driving and the speed in the datalog was reading exactly the same as the spedo in my dash.
Now the fuel usage/mpg part of the datalog works, and it also goes into full DFCO. When driving it before, I would watch the injector bpw drop to .49 when I would let off the gas, and decel would work way better than it did with the old 7747. I thought I was in dfco when it dropped to .49, wrong! Now, when I let off the gas, after a second or two, when the computer senses I am slowing down, the bpw drops to 0, full fuel cut off! When it does that, you can feel the decel get even stronger. I really like this PCM! Once you get below a specific rpm, you can actually feel it turn the fuel back on, it does just a little burp/blip when it does. But nothing annoying or anything.

So from my findings today, I can state the following as correct and tested by me:
Speed sensor connects to pin F13, set "input not from drac" and the two pulse vss I got from jtr is working perfectly fine with the 7427.
F12 is the 40 pulse, trans output shaft speed sensor, used for shifting. I think you got the inputs mixed up in your comment posted above.