My 82 Crossfire (Collectors) wont run. Followed book, have no Check Engine Light, all test show it to work. Backprobe pin 20, test light on. Engine cranks, has spark, but has maximum "flooding" fuel pumping into TBI's. Can anyone help me with this one. Live in Australia so have no access to Corvette Wreckers. Is it the ECM, or can anyone help me with a possible simple solution.
By the way, I,m new to the Forum, so gidday to all from the other side of the globe.

 

Welcome to the forum. A few things come to mind concerning your crossfire. I believe that one of the sensors that feeds data to the ECM may have failed. Try the TPS (throttle position sensor) on the rear throttle body, the coolant temperature sensor (located near the water pump) and also the MAP sensor (located on the firewall). The rear throttle body has a fuel pressure regulator built in to it, perhaps that failed? Did your car run well before this no start condition developed?
It seems that a lot of the problems with crossfires comes from a sensor malfunction.
Good luck,
Tom

 

you have spark and you have fuel .sounds like you have to much fuel .my first checks would be the cts sensor and the tps .toms 82 has you going in the right direction.

 

Thanks for the advice, how do I check these, or do you replace and hope for the best. There is only one diagnostic computer in Western Australia, and thats 400 kilometres away.
Alternativly, can I ditch the crossfire in favour for a carby etc. Or does this cause gearbox issues (eg no 4th gear) on the 700R4

 

There are diagnostic procedures for each sensor. I have them for the 81 and hopefully someone with an 82 service manual will chime in.

If you were to convert to a carburetor, you would also have to replace the distributor or you'd lose the advance. Your transmission would still shift into forth gear, but you'd lose the lockup in the torque converter. you can wire this for manual switching though.

 

No special equipment is really needed to check the sensors on an 82. A good volt meter will do just fine. Each sensor has a specified range of voltage, resistance, etc. You just need to check the sensors with the meter.

 

It could be a number of things. These engines are all about air,fuel and temperature.

Try this.

Open the hood. Remove the air cleaner. Plug the one hose that comes from the rear TBI.

Turn the key to one. Listen for the fuel pump to kick in for about 2 seconds. the noise will come from the gas tank. Immediately after you should hear a noise from the injectors. You should see a bust of fuel. its called the prime pulse. turn the key to start. the injectors should spray a perfect cone pattern. The car should start.

As you have said its dumping massive amounts of fuel. Does the fuel dumping stop when you turn the car off? Do the injectors continue to dribble fuel? What do you mean by dumping massive amounts of fuel? is it something else then a cone pattern? When need to figure out why this is.

If you have a vaccum leak the MAP sensor on the rear driverside firewall with the hose to the rear TBI will sense low manifold pressure and tell the ECM to send more fuel. You can check this with a vaccum guage plugged into the rear TBI where the MAP usually plugs in. The minute you unplug the map sensor you should get an engine light on the dash. The engine light will at least tell you the ECM is working at least for this sensor.You should have a constant 19-21 psi. If its less you have a vaccum leak. Usually its the gasket around the plate the TBI's are mounted on. Try tightening down the bolts that hold the TBI plate. also tighten the 4 bolts on each TBI. Where any loose? Do you notice a change in performance when you do this? If the MAP pressure is good move on.

The CTS is at the front of the engine. it tells the ECM what temperature the water in the engine is at. If it thinks the engine is cold it will tell the ECM to send more fuel to raise the idle like a choke would do on a carb car. For the CTS to work you need to have the thermostat in place and the rad must be full. that sensor is right above the thermostat and takes its reading there. If there is no water it will not read, if the water is moving by to fast it will read false. You can also try to unplug the CTS and try starting the car. The ECM should default to something else and the car should run different. If it runs different you should change the CTS. its only about $20. Unplugging the CTS will also cause the engine light to go on.

The TPS tells the ECM if you are idling or are accelerating. If its bad or not adjusted properly it may tell the ECM you are doing 40 mph when in fact you are not. It will confuse the ECM and cause more fuel to be sent. Try unplugging it as well and putting the ECM in limp mode. Again you should have an engine light. Performance should change.

You can clear engine codes by pulling the fuse beside the battery for 30 seconds.

You should also rule out all vaccum leaks. Check those places mentioned above. But also check the hose to the EGR solenoid of the fron TBI. check the Hose and the PCV valve for leaks. I think there is also a hose that goes to the cruise control module as well. Make sure ther are no unplugged holes on the TBI's or TBI plate.

If none of that works there are other things to check. But start here first.

JIm

 

Hi Jim,
Excellent explanation, it should be very helpful.
Regards,
Tom

 

Thanks Tom.

Happy New Year.

I guess your car is a sleep for the winter as well? Only 3 or so months go until this white stuff disappears.

Jim

 

Firstly Jim and Tom, thanks for your response and advice. I have followed your advice in full Jim.

Unplugging the map, CTS and TPS sensors result in no check engine light. Turning key on does give prime pulse, first attempt only, thereafter not, unless battery is discon for 30 secs. Checked all vaccum lines, all good. Cranking motor still no attempt to start. Both TBI's have small fuel leaks, small smear across plate, bolts tight. Both TBI's give a nice fuel spray pattern, which does turn to more narrowed and drect spray when throttle on.
Checked with a company in Perth, no computer repairers in Australia for this model. Only cmputer sales are from the USA.
If neccessary, I may convert to carb, poss Edlebrock airgap manifold, your thoughts.

I look forward to your reply. Regards Richard

 

Like the others have said the coolant temp sensor is what I think is your problem. My connector for that sensor internally shorted causing a problem like your having. Probably why you can't buy the original style one anymore and it's replacement is a new style one at all parts places.

 

Thanks Jeff. When you had this problem, did your check engine light illuminate. Mine will not, its strange as everything else works, just wont start

 

Check all the plug-in connectors and ground connection to the ECM. Perhaps it is not receiving or processing [all] signals nor getting correct voltage. Pin connectors can corrode over time...or work themselves out of contact with their 'mate'. Removing, cleaning and resetting those connectors can sometimes solve such problems.

 

Try disconnecting the elcectical connector to the map sensor. You should get an engine light. You can also try disconnecting the TPS. Again you should get an engine light. Lets figure out if your ECM is working.

When you turn the key to on the engine light should go on and go off after a few seconds.

I assume the fuse beside the ECM is good? Have you also checked the fuses in the panel?

The prime pulse usually only comes once at first start for the day. So that sounds okay.

The TBI fuel leak is of concern. Nothing should come out unless you are cranking the engine or the car is running.

I think you should try changing the CTS as suggested. Its cheap and easy.

The problem with this old technology is the ECM will pick up a bad sensor but can not pick up a weak sensor. I'm still not not sure if your ECM is working. Have you tried to pull any codes from it?

As mentioned also try cleaning the connectors at the ECM. There is a bunch in the firewall as well. follow the wires from the TBI's to where they look like they go through the firewall. There are actually connectors behind that box.

Jim

 

I forgot. The fact that you get a prime pulse suggests the ECM is working to some extent. I would like to here the engine light is coming on though. Work on getting an engine light.

Also look at the wires at the distributor. Any skinned of broken? Especially one the passenger side of the distributor? There are 3 things in there,coil,module and one other(forgot what its called).

Jim

 

no I never got a check engine light immediately. the only other cause besides a bad ecm why this light wouldn't come on is a blown ecm fuse, bad ecm harness engine grounds, or blown check engine light.

however till the motor reaches closed loop which in your case sounds like it dies long before that I believe the ecm ignores any inputs from sensors anyways. when my cfi for some reason wants to die it always pulses the injectors in one long pulse anyways, I believe it to be caused by low engine vacuum and the map sensor seeing it is all. so that could just be a natural thing happening to your car. Look at the cts sensor and see if its connector looks melted in any way.

first I would check all ecm harness to engine block grounds. I am not sure where they are on a vette though.

 

I have a similar NO check engine light (CEL)problem on my 1982 Corvette,
I recently got the car not running and the CEL did not and still does not work.
Car had a no fuel problem, i was all set to replace the ECM but know ECM's rarely go bad, so I kept digging, the hose to my fuel pump was deteriorated and did not look stock,
i replace the hose and then car then started and runs but still no CEL, I have yet to track down why.

I have a High Idle now, just picked up a CTS (coolant temp sensor) I hope that does the trick.

I thought I'd chime in that i too thought my ECM was bad but I got the car running now...

 

Hi,
FYI, just a comment about ECMs rarely going bad. The 82 is peculiar because the ECM is mounted right next to the battery. From what I have been told, the gases venting from the battery can damage the circuit boards and cause the ECM to fail.
Good luck,
Tom

 

i recall reading somewhere a "7747" ECM from 90's camaro/firebird/caprice TBI cars will work if the connectors are changed, those may be easier to come by in Australia, but still check everything else first.

 

Today, I hooked a Snap-On MT2500 scanner up to my 82 Corvette of which the CEL lamp does not work, it read "NO CODES PRESENT",
i deliberately unplugged my MAP sensor to see if the CEL would light, it did not, but the scanner set the code for it, so just because the CEL does not light does not mean the ECM is bad,
try to find a shop with a code scanner.
.