Andy Man

Hello
I'm a new member here ,not really a car guy although i have done almost all my own work on the cars I've owned for the last 50 years.
I wrench because i can,when i was a younger fella i had some cool cars and trucks and never really had the cash to pay others to my work.besides i enjoy turning wrenches.

We/my loving wife and i in an impulsive moment purchased a barely running 88 Chevy Conversion Van back in September we have been having a blast getting it back in shape.

After many long days and lots of rebuilding and replacing I'm still having an issue with the Vans 305 TBI Engine running rich.
Basically I'm to the point where i believe it's got to be the ECM .

The Van Has a 305 V8 with a Turbo 400 The ECM is missing it's stickers with the exception of 86 AMUM,from what i have researched the van should have a 1227747 ECM and the AMUM is the prom designation.

This Van is not intended to ever be our daily driver,it's more of a weekender,day-tripper,camping,fishing recreation type rig with maybe the occasional long run.

I'm no master mechanic and have just the basic understanding of how this TBI is controlled mostly from all the troubleshooting steps I've gone through to get to the point where i can feel confident that I've covered all the bases and I'm left with the ECM as my next challenge.

From what i understand i can try a used Junk Yard ECM from a number of GM trucks as long as it's the 1227747 with the AMUM prom or i can Install my Prom into a used 747 ?
My local Junk Yard has been a real treasure trove,The last jewel was an air control valve when i was chasing vacuum leaks.

The plan it to visit the junk yard in the morning to check if the 2 Vans there have the ECM or maybe the Suburban i salvaged the smog pump air control from will have the right stuff.

My questions are if the salvaged junk yard ECM has been damaged in any way from water etc how can i test it before I plug it into my Van,also do i risk burning out my wires or prom,sensors etc if the junk yard unit is defective.???

I'm in Connecticut does anyone know where i could get the original ECM Tested and or Repaired locally ?

Found a couple of shops where i can send the unit but the idea of shipping it off out of state to test it and then not knowing if it's going to be a repair or a very costly replacement is kinda a gamble for me.
Besides the prices I've been getting were more than what I paid for the Van to start with.

Hence my Junk Yard quest.

Any help or suggestions will be appreciated except that I should just junk the truck,with a few minor exceptions the Vans actually in very nice shape now with no rot and very low original miles for it's age.

Thanks In Advance
Andy Man

RBob

iTrader: (1)

AMUM is for a '88 G10 - G25 van. But with a 700R4 not the TH400.

You can get another '7747 and put that PROM into it.

Get yourself an ALDL cable, laptop and the WinALDL program. With that you can check a lot of items to see what may be going on.

As for the running rich, the coolant temperature sensor (CTS) may be misreporting. The injector o-rings may be leaking. Those of the two most common items to cause an engine to run rich.

Third would be a bad O2 sensor.

RBob.

Andy Man

Hello
Thanks for your response RBob, Replaced the coolant temp sensor last month,re built the TBI and replaced both injectors,swapped out with another TBI still rich,the O2 sensor was first part we replaced before we drove it home when we purchased the van.it was missing.
We have good Vacuum 20 at idle goes to 2 or 3 when wide open right back to 20 averages between 12 and 15 cruising at 45 50 mph ish

We have no solid clue as to what this Van had in it actually when it left the factory ??? all i know is when i looked it up with a 305 and a 3 speed we came up with 1227747 and the only thing the unit still has on it is AMUM.
We don't know if that's what is suppose to be in the Van or not ???

Went to the Junk Yard early this morning,it was brisk here about 8* with 20 mile an hour winds.
Managed to snag some stuff
Got a 1227747 out of a 89 C10 pick up with a 305 TBI and a 3 speed Transmission,looked like a TH350 long tail ?the prom is AMUR
Now we need to find out what what the difference is between the AMUM and AMUR ???? anybody know ???



Got a second unit that looks brand new out of a 91 GMC Van that just came into the yard in the last week .
The fellow that owns the yard told me they drove it in and it ran great.
It has a ECM # 16146299 AWLD now this truck has a 350 with a 700 R4 ??? we need to find out more about this unit as well.
The guy let me take both to try with the understanding I'll bring it back if it isn't the right match for the truck.

The reason i took the ECM from the 91 is my research tells me the 91 Chevy takes a 1227747 so the 16146299 might be an after market number ??? a GMC number ???
I'll start researching that number now ??
Any help will be appreciated.

Great suggestion as to getting hooked up with a lap top.
I'm thinking I may need to go that route eventually to get this puppy fine tuned, it wouldn't hurt my other 2 buggies either We have a 88 Caviler Wagon with 145.000 miles that's "My Puddle Jumper" as we call It runs like a top and gets amazing gas mileage,and the 93 Buick Century Wagon Looks new and runs as good as it looks. 3.8 V6. just turned over 100.000 miles just broken in

We don't own a lap top and i probably wouldn't understand what i was looking at with it connected anyhow,a new learning curve,I'm old but willing to learn new stuff.

As soon as I'm confident that I'll do no harm I'll try the junk yard 1227747 with the AMUR unit and see what happens ???

So do I need to worry about hooking up a different ECM will it burn out sensors wires etc ?????

Numb Fingers Turning Wrenches In CT
Thanks
Andy Man

RBob

iTrader: (1)

AMUR is for a 5.7l with a 700R4. Same for AWLD. The '6299 ECM is not the same as the '7747, but is pin & plug compatible.

> we came up with 1227747 and the only thing the unit still has on it is AMUM.

Should check the PROM itself, it could have been swapped for something else.

RBob.

Andy Man

Hello
Thanks again for your insights RBob !
Pulled the ECM from the truck this morning, upon inspection it does in fact have a AMUM PROM .

I'm just more confused now than i was when we started.

It seems the 88 truck wasn't set up right before we purchased it, or from what i gather if this is the original ECM it was wrong from the git go.??
It would also appear that the 305 C10 3 speed with the AMUR was the wrong set up for that truck ???

Besides running rich the truck ran well and the Turbo 400 Transmission shifted fine,smooth, kicked down and got up and went when floored.
Hows that possible with a ECM and Prom set up for a 700 R4 ???

The 16146299 I'm going to forget about because it does not list a 5.0 as a engine it fits even though when we look up the replacement ECM for the 91 G 20 Van it was in it gives us the 1227747 as the replacement part number .

I'm going to try the Junk Yard 7747 ECM with the AMUM PROM from the questionable original ECM that came in the truck and cross my fingers i guess .

Can you tell me how to find the difference between a AMUM and AMUR PROM ???


I'm also thinking we may want to go and purchase another new O2 sensor as when we purchased the one that's in the truck we went for the "cheap one" that could be our first mistake ???

Wrenching In The Snow Is Therapeutic,At Least That's What I Keep Telling Myself
Thanks Again For All Your Help
Andy Man

RBob

iTrader: (1)

Someone could have done some drivetrain swapping. Or, the ECM died and they just grabbed another and installed it.

Could be the TH400 was swapped in in place of the 700R4. And they didn't use the ECM for the TH400 kickdown. Check for a switch on the throttle linkage to operate the kickdown. That is how GM did it before using the ECM to do it.

RBob.

Andy Man

Hello
Thanks again for your help RBob
Here's an up date ,Swapped the chip components out of the ECM that was in the Van with the AMUM Prom into the Junk Yard 7747 ECM.
Installed that into the truck fired it up,The Van runs pretty much the same as it did with the Original ECM no advantage or notifiable improvement still trowing a #45 code.
At least we know the ECM is working ???


Next I'm going to Try putting the AMUR Prom back into the Junk Yard 7747 and try that in the truck and see if we have any improvement.
It's a dice roll I know.

Ordered a new AC Delco 02 Sensor I'm going to swap that tomorrow as well.

The turbo 400 is original to the truck.
The truck has 60.000 original miles,The Van was parked in a garage for 22 years,the tires had like new tread they were so dry rotted that they disintegrated on the tire machine when we put on the new skins.
The last time it was registered was 98
The exhaust was rotted so bad that it was on the floor under the van from the Y pipe back.

Was careful choosing my donor at the junk yard it was an original 3 speed without overdrive unless maybe they changed the steering column.???
Did some more digging today and found a list of PROM Applications, Didn't include the AMUM but the AMUR was included, just stated the years of C10 and K series trucks no transmission designations.
Did notice they were mostly early years maybe they tweaked the set up to include the later 700R4 ???

Wish i could find more information from General Motors build sheets and such ???

That's It For Today I'll Get Back At It In The Morning And Let You Know How I Make Out.
G20 Sitting Too Long !
Andy Man

Andy Man

Hello
I'm back again just to report the Van is now running like a top.
The replacement ECM Junk Yard 7747 did the trick,after some driving,about 100 miles or so, the system adjusted /tuned itself and started running as it should.
I've been getting really good gas mileage,the van seems to have more power than ever.
Thank you for all your help.I truly appreciate you taking your time to help me.
If you ever need any help with a fishing rod feel free to contact me I'll do my best to help.
88 Chevy Van Running Like A Top !
Andy Man

Fast355

iTrader: (2)

I just pulled apart a 1987 G20 van with the TBI 305 and the 3L80 basically a longtail TH400 with less clutches and a TH350 sized output shaft and 3.08 rear gears. Swapped a 6.0/4L80E into its place.

The TBI ECM ABSOLUTELY controlled the kickdown through a 2nd relay that (looks just like a 2nd fuel pump relay) on the firewall connected to the TCC output of the 7747. This one had a prom of AMUN. This 305 had the air pump on it with federal emissions.