I'm helping my friend get a 1989 Coupe/Man Trans running, that he bought from his 80 yr old Uncle.

At time of pickup, Uncle tells us he "did some injector and computer work before it stopped running". "Was with a friend showing off grabbed 2nd gear and everything shutdown, hasn't run since."

He thought that was about a year ago, but the last inspection sticker on the car is 2022, so we think it's closer to 3 summers ago.

We get the car to my garage:
Installed new/fully charged battery.

Car cranks, but won't even attempt to fire.
It has spark
It has fuel pressure (45lb cranking)
Pulled plugs and theyblook like they were running rich before it stopped running and are bone dry.

Replaced Fuel Regulator and EGR.

We check the computer Since he claimed something was done to it. As we remove it, one of the harnesses falls off on its own. We snap it in fully and it starts trying to fire, in what I'd describe as a "light cough"

Tested with Noid light and injectors are firing.

We try starting fluid and it fires on what sounds like all 8, then stalls.

Since the gas is from 1-3 years old, we drain the fuel, change the fuel Filter on pass side rail.
No improvement, still intermittent light cough.

Plugs are still dry.

At this point were thinking clogged fuel injectors. I cut the old fuel Filter open and it looked dark brown, no sediment though.

I'm suggesting to replace the unknown injectors with new stock injectors, then if that doesn't fix it, we turn to the ECM/Chip. Not much else left, I don't think?

The one wildcard in all this is the ECM. We're not sure its the correct one for a 1989 Manual Tran. One shop told us the ECU we have is for a 1986.
Current ECU Part# is 16198259 and is a GM Remanufactured ECM

We cant read the entire chip# but its starts with 16072, and we've been told that it should start 16074.

Sorry for the wall of text, but I want to present all we know, if anyone has suggestions or can help? Any suggestions on the proper Injector/Computer/Chip Combo?

 

Long shot, if he was being a little rough on the car at the time could the timing chain have jumped. Yes it would take 1 very tired chain and gear.
But has anyone just put a timing light in or given a little twist, granted the it seems to run on 8 with starting fluid leads towards a Fuel delivery problem

 

Haven't looked at timing yet, mainly because it sounded so good when it fired on starting fluid.

We're waiting on some Delphi FJ10024 Injectors and will swap them late next week. Once we at least get some wet plugs, we'll know the fuel system is working.

I also found a great thread from a few years back explains the ECM Part Numbers and that the ECM in the car is correct for a GM replaced/remanufactured unit. I'm still researching the Chip# however.

 

I would also recommend checking the timing chain, as I've had this happen before on a non-GM vehicle and it took me months to figure out.

Now when it comes to the ECM and doing tests that won't cost anything to give a shot, try to give the harness a shake or shimmy while cranking, making sure to do so in different sections per attempt. If there's a worn or corroded wire somewhere, that'll be a quick way to diagnose it. Also be wary of crunchy wiring, as that could very well indicate the wire shielding has crumbled somewhere and may have shorted out. Putting a multimeter on it would also be handy if you have access to the wiring diagrams.

 

Did you drain the fuel tank?

 

Yes, Drained and replaced fuel filter. Refilled with injector cleaner and 5 gal 93 octane.

Same results. Very weak attempt at starting, plugs are dry.

 

This is one for the dart board but easy to check good or bad...check your closed throttle Throttle Position Sensor voltage.

https://www.corvetteforum.com/forums...when-warm.html

 

Also if you have fuel pressure and the injectors are firing, it dosent mean they are flowing anything.

 

The original injectors are a known common fail. I would be odd for all of them to fail, but if it runs on ether, your problem is clearly fuel delivery. You can test them with a 9v (transistor) battery, but if they're original, they need to go.

 

That's exactly where we're at right now. injectors are the only fuel system component we haven't changed.

I actually just finishing removing them as we have 8 new Delph FJ10024 arriving later this week.

Existing injectors look like they've been tinkered with as someone has removed and numbered them.

 

I'm not sure if these are original or not? Im new to working on C4s. Here's pics of what I just removed. As mentioned earlier, someone engraved them with cylinder number, so Im assuming they're original but were rebuilt somewhere between 1.5 - 3 years ago.

 

Those are original Multecs.

Have you checked for Code 46? The presence of Code 46 indicates that the ECM is not receiving the Fuel Enable signal from the Vehicle Anti Theft System.

 

I have not. I have an OBDII Reader, but I don't know how to check codes on these old ECMs. I was under the impression that if it was a VATS problem, I wouldn't get crank, fuel press or spark?

I'm online researching how to read the codes tonight.

EDIT: It looks like I can read codes with a paperclip, the ignition key and the ability to count to 9?? Does that sound accurate?? LOL

 

If you use the paper clip the light will go in flashes 1 pause 1-2 pause then again 1 pause 1-2 three times, if there's no codes it will pause again and repeat the code 12 (flash pause flash-flash) count the flash. Example code 36 is 3 flash's pause 6 flashs
When all codes are done it will return to code 12 (flash-flash, flash)

 

VATS does not inhibit fuel pump or spark. Only the ECM control of the injectors.

Yes, VATS originally also inhibited cranking, but as these cars approach 40 years old it is best to approach them thinking that previous owners, mechanics and Bubbas may have done things to them. Like bypass the relay, install a resistor bypass, or perhaps even a Signal Generator. Any of these could now be malfunctioning, or maybe a mouse got lucky and chewed the exact wire that carries the FE signal.

In a 1986-1989 there is no indication to the driver that VATS is active and preventing fueling. Only the presence of Code 46. If Code 46 is not there, it is not an active VATS shutdown. Code 46 is not a "stored" code. If 46 is present, the Fuel Enable signal is not.

 

Great info guys!!! I didn't realize how easy reading the codes was. Im going to check for codes tomorrow AM.

Thank You!!

 

UPDATE: She fired and runs smooth!!!
After confirming....
Fuel Pressure
Spark
Injector Pulse at connectors (Noid Light)

We believed we fixed Previous Owners issue, still wouldn't start.

New Fuel/Fuel Filter = Still wouldn't start

New Injectors = Fired right over and runs smooth!!!!

Thank you everyone for your help. Im still going to check for codes, now and again after we get a few miles on her. There's still quite a bit we have to investigate on this project, but so happy we got her heart beating again.

Now off to.....
Brakes
Cap/Rotor/Wires/Plugs
Suspension
Clean and Detail
Weatherstripping ................
LOL

 

Always good to see a happy ending with fuel related problems.

Wish I'd have replaced with Delphis instead of the Bosch ones. The tickity tock Bosch ones annoy me to no end.

With the weatherstrip, whenever you get around to doing it, anything less than Corvette Rubber will likely be a waste of your time and money.