scratching my head on this one.. 1991 kodiak no start

[cookie 70]

hello all! i own a 1991 chevy kodiak c70hd with the 6.0l engine.
i am currently experiencing issues with the ecm and PROM.
my check engine light is flashing constantly (code 51?), and i have no start.

the original ecm was toast (ants got in it) and i ordered a refurbished one (after the issue above started), and it still had the same issue.
i then burned a new chip with a factory .bin file and still have the same issue.

any input would be greatly appreciated thanks!!

[steveo]

ensure your grounds are okay by running a jumper from ECM case to vehicle chassis.
if that's no good maybe your burned bin is bad with an incorrect checksum, improperly offset, improperly inserted, something like that

[steveo]

oh and just cause an ECM is refurbished doesn't mean it isn't junk....

[cookie 70]

i will definitely look into all of that whenever i get back to the shop!

[cookie 70]

ensure your grounds are okay by running a jumper from ECM case to vehicle chassis.
if that's no good maybe your burned bin is bad with an incorrect checksum, improperly offset, improperly inserted, something like that

so i ran a jumper from the ECM case to the chassis and no dice.... still no start and still flashing the check engine light..
the bin file i have i found on this thread here- http://www.gearhead-efi.com/Fuel-Injection/showthread.php?1255-1994-GMC-C6000-Topkick-C6H042-6-0-L-V-8-Gas-225-gross-HP-366-cu-in-Engine-ADX

[dave w]

so i ran a jumper from the ECM case to the chassis and no dice.... still no start and still flashing the check engine light..
the bin file i have i found on this thread here- http://www.gearhead-efi.com/Fuel-Injection/showthread.php?1255-1994-GMC-C6000-Topkick-C6H042-6-0-L-V-8-Gas-225-gross-HP-366-cu-in-Engine-ADX

I posted the files in the linked thread, which I personally verified before posting them.

I'm curious what the Noid light testing for the injector wiring revealed?

[cookie 70]

I posted the files in the linked thread, which I personally verified before posting them.

I'm curious what the Noid light testing for the injector wiring revealed?

i am getting no pulse to the injectors, but i do have spark. reckon it might be an offset issue? this is about to drive me crazy..LOL!
:mad1:

[steveo]

no it can't be an offset issue

[cookie 70]

ok so i managed to get pulse to the injectors, but no fuel. fuel pump is running, upon further inspection i found the fuel had turned to some milky color.
keep in mind this isnt too old of fuel (6months) so thats weird. i am now flushing the tank as we speak, and im going to fush the fuel lines.
i managed to get it to bust off by means of pouring fuel in the throttle body, but it still has the flashing service engine soon light.
maybe im on the right path... :innocent2:

[dave w]

When an engine briefly runs after pouring fuel into the throttle body indicates a fuel problem.

Possibly the rapid flashing check engine light is bad chip.

I favor troubleshooting the rapid flashing of the check engine light first, by replacing the current chip with a known good chip.

[cookie 70]

When an engine briefly runs after pouring fuel into the throttle body indicates a fuel problem.

Possibly the rapid flashing check engine light is bad chip.

I favor troubleshooting the rapid flashing of the check engine light first, by replacing the current chip with a known good chip.

the original chip is toast, im using 27FS512 chips (brand new) with the bin you uploaded. im wondering is im missing something, or if i dont have something just right when i burn the chip. :confused:

As far as i know, i have the offsets set right. I'm using BoostedNW chip burning software and Tuner RT to verify everything is right (possibly).
I've become fairly familiar with this software from tuning and playing with my '88 Trans-am Gta, i know it's a different ECM but shouldn't it be the same as far as tuning?


I really do appreciate ya'll taking the time to assist me throught this!

[dave w]

ECM 16147525 Uses a 4K chip, 24 pin. Is this original computer part number and chip for your Topkick?

The 27SF512 chip is a 64K chip, 28 pin. What chip adapter 24 pin to 28 pin is being used?

Possibly the chip is installed backwards?

[cookie 70]

current ECM# 19186079, which i was told was an updated replacement for the 16147525. when purchased that was all i could find in stock.
The adapter i am using is the solder in GM2 adapter ( replacement of the Moates G2 i used in the past) from boosted NW.
Chip is installed in correct orientation because if installed backwards it will kill the chip.

[dave w]

current ECM# 19186079, which i was told was an updated replacement for the 16147525. when purchased that was all i could find in stock.
The adapter i am using is the solder in GM2 adapter ( replacement of the Moates G2 i used in the past) from boosted NW.
Chip is installed in correct orientation because if installed backwards it will kill the chip.

19858
The installation of the GM2 likely OK. The soldering required for the GM2 is basic through hole soldering. An ohm meter can be used to test for solder bridges between pins, which might cause the check engine light to flash.

I'm going to disagree with the statement that the 19186079 is a replacement for 16147525. Form what I can figure out, the 19186079 is for 1989 ~ 1990 Topkick. GM used the same 4K chip for many different computer part numbers, but each computer part number always used a different definition file. I recommend using a .bin file for the 19186079, if the ECM wiring is the same 19186079 vs. 16147525.

[dave w]

Interesting thread:

http://www.gearhead-efi.com/Fuel-Injection/showthread.php?7284-Looking-for-a-ECM-for-a-old-GMC-Topkick&highlight=16147525

[cookie 70]

I'm going to disagree with the statement that the 19186079 is a replacement for 16147525. Form what I can figure out, the 19186079 is for 1989 ~ 1990 Topkick. GM used the same 4K chip for many different computer part numbers, but each computer part number always used a different definition file. I recommend using a .bin file for the 19186079, if the ECM wiring is the same 19186079 vs. 16147525.


What are the main differences?

[dave w]

I'm thinking the main difference between the 19186079 and the 16147525 is obviously the hexadecimal address in the chip and the associated electronics inside the computers.

For example,
1987 ~ 1991 TBI computer 1227747 uses definition $42 vs. the 1992 TBI computer 16146299 uses definition $99; both use the same 4K chip. The programming hexadecimal code is very different $42 vs. $99 and likely different electronics for things like the Injector Drivers, IAC, TPS, Knock Sensor, and others.

It would be a VERT BAD Thing if somehow a 1227747 computer chip was installed into a 16146299 computer and vise - versa.

Basically installing a 16147525 chip into a 19186079 would be considered a VERY BAD Thing too.

[cookie 70]

i see what you mean, i lucked up and finally found the proper ECM from a heavy duty salvage yard up north (im down in the bible belt) and they are gonna ship it in the morning.:jfj:

until then i am going to focus on the other issues and report back ASAP.

[cookie 70]

GOOD NEWS!!!:jfj:

The ECM i ordered from Active Truck Parts came in today, and that fixed the problem! Apparently there is a certain type of ECM for these big trucks '91 and newer.. :doh:
I sent my Driver side Fuel tank off to a local body shop to be cleaned and relined inside while i have the truck down (slight rust inside), so i should have it back next week hopefully.

Very big thanks to Dave W and Steveo for their inputs, comments, and suggestions!:thumbsup:

I sincerely hope that anyone with an issue like or close to mine can benefit from this thread!

[1project2many]

Basic information to help with diagnosis:

The ignition module will fire the coil without a working ECM. Checking for spark while cranking only tells you the coil and pickup coil is working and that the ignition module is partly working.
The ignition module will send a pulse to the ECM for each spark made at the coil.
The ECM will use pulses from the coil to fire fuel injectors.
If you install a noid light at the injector and spark tester on the coil wire you should see noid light blink when spark tester sparks. The "netres" or backup fuel hardware will make this happen even if the calibration in the eprom is bad.

[cookie 70]

Sorry for the delayed response guys... been very busy with work.

so after cleaning the fuel system and having the tank re-lined i now have fuel to the injectors, and i also have spark as well.
The engine will try to start, but instantly stalls. It will try to stay running if i pump the throttle, but it acts like (in my personal opinion) it is not getting enough fuel.
I jumped the starter solenoid to watch the injectors and they have a constant spray.

I have replaced the IAC valve, Coolant temp sensor, TPS, and MAP sensor before the truck started giving me issues. So i have not reason to believe that any of that is the cause.

No codes are being thrown, and i cannot get any useful data from the live reading from my laptop.

[Sledhead2]

I am going to ask / throw a curve ball idea or question.

I remember in the late 80's and early 90's, EFI used the Oil pressure sending unit as a fuel pump shut off. When to truck was started the oil pressure sensor was bypassed for x amount of time. Then when started the oil pressure would tell the computer to keep the power to the fuel pump on.

So I am wondering if, the truck starting and then stalling could be an issue with oil pressure sensor and or wiring.

If the Kodiak, ran this style fuel pump control set up.

[Beaglemaster]

Do you have the correct fuel pressure and volume? Is the ignition timing set properly?

[cookie 70]

So i finally found the last piece of this nightmare... as stated above i didnt have either of the correct fuel pressure or volume. APPARENTLY O'reillys sold me the fuel pump for the
passenger side instead of the driver side... the right pump is out of stock through them, but autozone actually had the right pump. I slapped it in there and BAM she started up just fine! After a little fidgeting with the timing she runs like a top! :rockon:

The part number for the pump O'reillys sales is "E16031" that is for the passenger tank and the output is apparently 3PSI and 15GPH..

The correct pump is a Delphi "CFE0112" rated at 30-40 PSI and 36GPH.

Boy has this surely been a ride, but i hope my mistakes, both costly and frustrating will be of great help to others in the future!

-Cookie70

[Beaglemaster]

Interesting, looks like the passenger pump is used to transfer fuel to the driver's side tank? I couldn't find any info for fuel or ignition specs for this. Glad you figured it out.

[1project2many]

I haven't looked at this thread in a bit but I'm glad you've found a solution. I never thought about getting the wrong pump. The low pressure pump is definitely not going to be enough to run the engine.

That dual tank system is a mess. There's a fuel level module that monitors fuel level in the primary and secondary tanks. The primary tank supplies fuel to the engine. When the primary tank fuel level gets low the module turns on the low pressure transfer pump and moves fuel from the secondary tank to the primary tank. If both tanks are filled at the beginning of a trip this transfer will happen three or four times before the secondary tank is empty.

The mess is that GM connected a single fuel gauge to both primary and secondary fuel tanks in parallel. This configuration makes it so the fuel level is only accurate at full or empty. In between you have some combination of sender readings that may or may not closely represent the total amount of fuel. Worse still, if you fill the secondary tank but not the primary tank, the smaller volume of the secondary tank causes the gauge to read closer to full. A second gauge or a switch to allow one to view fuel level independently would have worked better imo.