Arkyvette

Hi guys. I just brought home my 82 Corvette. The Previous owner said it was running very rich. He has replaced the fuel pump, and claims to have rebuild the throttle bodies and fuel pressure regulator. It ran bad but drove up on the trailer for the trip home. It still sprays way too much fuel and hasnt started since. Now it wont fire at all unless throttle is wide open, and even then it just hits every so often and doesnt really run. So much fuel is coming out that it wont start and the crankcase is full of fuel soaked oil.

I flushed the oil today, checked TPS voltage, ecm fuse, cleaned ECM connectors (ECM was loose in bay and has reman stickers on it) and attempted to get the codes from it. The CEL comes on with key to run but never flashes even with the ALDL jumper installed. The CEL DOES however start flashing codes briefly when cranking the car?! This cant be right.

I then unplugged both injectors and cranked the engine dry. Pulled and cleaned spark plugs, added some fuel to throttle bodies and it does start up and run for a few seconds with injectors unplugged (they dont spray when unplugged, so thats not the issue)
At this point I know there is too much fuel being sprayed in. Can this happen from MAP sensor or Coolant temp sensors alone? I unplugged them and they dont make a difference. I am more concerned about the lack of code reading ability at this point... Please help me not to throw a new intake, carb and vac dizzy on this. I want to keep the fuel injection. Thanks for any help or insight.

hugie82

It sounds like you have a massive plenum leak. If you can see silicon under the plate that the TBI's bolt too, then that means the plenum has never been fix. Gm used silicon from the factory and they all leaked but 25+ years later it will be a really big leak!!!

Felpro makes a nice gasket and its not to hard to replace.

AT-82Collectors

Have you checked the PROM in the ECM for bent pins or a bad connection? If the ECM is not throwing any codes with the engine running that badly then odds are there is a problem in the ECM.

Andy

terry82

i would change the coolant sensor in the front of the intake .that should help with the injectors spraying .then see what you have .

Arkyvette

Thanks for the advise guys. I see a gasket under the TBI plate and everything is nice and tight in that area. It was my first thought as well. I tried with every vac line plugged except for MAP sensor and still no dice. I did not pull the prom chip out, but it has numbers that start with 84 on it. 84 prom? I will pull and clean its contacts as well. I wont be sure im on the right path until the ECM acts as its supposed to. Without that, all other troubleshooting is guesswork. What is the resistance of a normal cold coolant sensor? I can certainly fool the computer with a resistor to eliminate that provided its resistance based. I have plenty of resistors on hand for free. I am also slowly undoing years of redneck on this car. The crank and fuel pump fuses were removed and replaced with jumpers straight to ign source... I replaced with proper fuses, read 12v across them and they didn't blow and everything "works" the same as before. BTW, the CEL does not come on with the ECM unplugged and the injectors no longer spray so its doing something.

LastC3AZ

Have you looked at your fuel pressure ??? with an external regulator you may have to much fuel going in .... check between the TBs .... should be around 15#. would move from there to the regulator in the TB ... may have been over pressured and now doen't work properly ????

Arkyvette

I dont have an external regulator. Only the stock one in one of the TB's that the Previous owner replaced.

Arkyvette

What damage can a backwards prom cause? Im thinking when the previous owner changed the computer, he put the prom in backwards. I dont even know how he got the holder to go that way as its sort of keyed to only go one way. Everything I have seen online suggests the notch goes towards the screw hole. There is even a marking on the board where the number one pin should be.... So. It was in backwards. I reversed it and it made absolutely no difference. Sucks because it was the updated 82 chip and I bet its ruined.

Easy Mike

Have you read the computer for error codes?

Arkyvette

See the first post. Never could get codes. Just get a strobing cel when cranking, and a solid light jumper or not.

Easy Mike

My bad. Didn't catch it with the other items on the list.

Aldo_45030

Injectors? I have a spare OEM ECm if you want to try it? I know the coolant sensor as mentioned before will call fo rmore fuel until warmed up. or possibly a dirty connection in that circuit causing resistance to vary? Do you think he modded the fuel pressure regulator to increase the pressure?
WHat about O2 sensor?

JUst throwing out possibilitys.

Arkyvette

I repaired a bad wire at coolant sensor today. Now the fuel comes out in a lesser pulsing pattern while cranking. I have strong spark but its not consistant. The prom was backwards in mine and I think it was fried. I expect it won't run until I replace prom and possibly ecm. Would o2 sensor cause a no start condition?

Aldo_45030

I dont think so just run crappy.

Arkyvette

IT LIVES! After repairing the coolant temp sensor, I changes the plug wires and it made no difference. Then I pulled the plugs again only this time I changed them. Fired right up. I have never seen plugs that appeared so new foul to the point of not firing at all, but I have now. It runs pretty good too. The cel is still on solid and I'm unable to pull codes. I did drive it around the block and it has plenty of power after a slight bit of hesitation and what felt like the computer learning. Overall in happy. Just gotta figure out my prom/cel issue now. Thanks for the help!

hugie82

That's half the battle won

When you say "cell" your talking about the check engine light....right?

I don't recall a code for a constant light but considering the prom was installed backwards. I would think the prom may have been damaged. since the prior owner installed a new prom did he give you the OEM prom ?

Arkyvette

No he didnt. Im not sure if he did it or the prior, prior owner. However someone did. Apparently the computer still works enough to run the car, but yes the check engine light is on solid all the time, jumper or not. I am going to hunt down a prom either hypertech or original and change it and see what happens.

CDN3g

This is an interesting thread as I have the same "solid" CEL issue with my 82. I replaced the fuel pump with an '85 model which made a huge improvement to the car, but the CEL is on with a fault code of 51. I'll be working on the car this weekend (it's kept out of state) starting by cleaning the ECM connections and attempting to clear the code. If that doesn't work, perhaps I will also need to get a new PROM? If so, who is a reliable source for PROMs? Thanks Chuck

Arkyvette

At least you can get a code. Mine never flashes. Surprisingly the car runs pretty good. I have never driven it with a good prom though, so it might blow my mind when I get one. I think I saw one for around 150 bucks from a vender. Can't remember

Wrecked82

Simple search of Mid America Corvettes yields this:

http://www.mamotorworks.com/corvette...39.9303.609055



Same for Zip Corvettes.

http://corvette-parts.zip-corvette.c...chip&year=1982

I imagine other parts vendors have the chip also.

Finally, have you tried the Hypertech site?

http://www.hypertech.com

The internet is an amazing tool.