kiwivetten

im trying to help a friend of a friend get his corvette running. currently it starts, splutters and dies. cooling fan runs full time and relays are clicking on and off under the bonnet. I tried to scan it with my Tech1 but it couldnt get any data from the computer. it had apparently had computer repairs in the past so i decided to buy a new ecu. bought the 85 ecu off ebay and when I went to fit it the ecu was different. it was manufactured in October 1985 but has the later 1986 ecu. I cant see any obvious wiring loom changes though which I would have thought I would have seen with the upgrade. what other changes should i look for to see if it has been upgraded or is it possible late 1985 cars had the new 86 ecu?

WVZR-1

With a build date of 10/85 the car would actually be an '86.

Always use the VIN as an identifier. The 10th digit of your VIN I'd think would be G - an '85 would have been an F. A couple of other identifiers would be the presence of ABS and also a CHMSL on the hatch lid.

Also I believe you need the PIN E adapter for the Tech1 TA02149 Do you have that? I'll confirm the requirement and post back a confirmation.You do need adapter A Vetronix equivalent would be 02001244 I believe.

rblakeney

I experienced this behavior on my 89. The eprom carrier for the chip has slightly warped and not fully seating in the ecu socket. I placed a piece of cardboard between the eprom and its cover plate. Problem solved for now but I am going to look for a more permanent solution.

kiwivetten

Great info guys. I dont have an adaptor but just jumped on Ebay and bought one. I will also check seating of the eprom.

thanks!

Pwnage1337

I would check to make sure its the right ECM first and foremost. The 85 was a unique year using the 870 ECM, later years used the 165 ECM.

They are absolutely not interchangeable, the 85 being the only year to use the 870 along with the burnoff module instead of the burnoff relays for the MAF as used in 86 forward

WVZR-1

Checking the VIN revealed what?

rblakeney

I stumbled upon this issue when I left the ECU plugged in while on the car floor. I could literally cycle the radiator fans on and off by gently pressing the eprom.

kiwivetten

will get back around to see the car tomorrow ( other side of town) and will check VIN and also seating of Prom and let you know what I find

WVZR-1

Since you're going to the effort to reseat the PROM - while you have the PROM visible make a note of the information on the label that's visible through one of the windows of the PROM 'blue' cover. Maybe a snapshot and post it. If there's a label on the ECM get the information from it also.

What 'cartridge' are you using on your Tech1? MASS STORAGE or something other than that?

kiwivetten

re-seated prom/connector, no difference. 10th digit of the VIN is a G so its an 86.

Prom says Delco BUC 1724 and computer is a 1227165.

Yes Im using a mass storage in my Tech1.

Im thinking my next step is a new ECU, any other thoughts before I do this?

rblakeney

To be clear, removing and reseating the eprom carrier may not exhibit the problem. With the eprom inserted into the ECU and the ECU plugged into the car, turn on the ignition (do not start the car). Gently pressing on the eprom may turn on the fans or may shut them off. Other wonkey behavior may show. If this happens, then it's a good chance the eprom carrier is warped.

kiwivetten

yep, I tried it exactly as you described. Had ignition on and gently applied pressure to top of ECU carrier then slightly wiggled each way etc but it didnt tie in with fan coming on and off from time to time. As the computer has already been out for repairs in the past I think a new ECU would be best bet

WVZR-1

Buy 'nothing' until you complete diagnostics!!

Does your friend have the FSM (Factory Service Manual) for this car?

3D-Aircrew

You may be chasing your tail on the ECM.

Something you can check easily is the Fuel Pressure Regulator. Pull the vacuum line just after you shut it off. If it is dripping fuel then it's bad. I have had it happen twice on my car (1986). It will do exact;y as you described with no codes.

rblakeney

OK, just to make sure we are talking the same thing, here's a pic. It's not the ECU connector but the actual slot for the chip.

kiwivetten

I have a paper copy of the FSM for a 1986 corvette. I also have a tech1 but waiting for correct adaptor to arrive

kiwivetten

yep we are on the same page - realise its not the connector to the ecu wiring harness

kiwivetten

Good info, thanks for that, will give it a crack next time I see the car. Here in New Zealand Corvettes are rare and mechanics that know anything about them even rarer. I seem to get contacted by people with issues in theirs even though I really dont have the time noting that I dont fix cars for a living but word has just got around that I know a bit about them!

kiwivetten

The reason I didnt think it would be fuel is that this wouldnt cause the radiator fan to run all the time and for relays to be turning on and off all the time under the bonnet. Im guessing you didnt get these symptoms?

WVZR-1

Sounds as if you've got things somewhat under control.

Do you have the '86 FSM complete including the wiring schematics?

You're correct of course that the FPR isn't/can't influence the symptoms you mentioned. A check of the fuel pressure goes along with basic diagnostics and it seems I believe you understand that.

Judging from the PROM ID this is an AT with 'cast iron' heads. An issue with the PROM isn't out of the question. A PROM issue could result in a 'no data' when using even the adapter and a Tech1.

When do you expect the adapter?