I'm by no means an expert at car repair and most definitely inexperienced on corvettes, but I can usually get the job done with the research. Unfortunately I'm stuck and don't know where the next most likely issue is.

I have a 1990 L98

I was mid-driving and the engine just died. All the electronics are fine and kept working.

Since then I've checked just about everything that I could think to check. I have gas and spark, but no fire in the engine. The starter is cranking but the engine never catches and continues on. I get spark at the distributor and the plug. And I get gas on the rails, but I don't know the pressure(the schrader valve) which means I should get the engine to at least turn over and run or at least try to run but it doesn't. I have not noticed any decrease in performance recently. I didn't see anything overheating or have any problems in general. Once in a while I would get a bad start where it would take a couple of starts or a little throttle to keep the engine running, but I always attributed it to the heat since on a cool morning or during the night it would start right up (Texas/Arizona heat).

Any help or pointers would help.

 

Pull the error codes, this can tell you exactly where the problem is.
Engines need hot spark and spark at the right time, fuel and air and in the correct ratio and cylinder compression in order to start and continue to run. Check spark timing with a timing light while cranking. Bring a grounded wire close to an unplugged spark plug wire boot while cranking, you should see a snappy at least 1/2" spark. Measure the fuel pressure, it should be 35-42 psi and it should hold up for 1/2 hour with the ignition off or you have leaky injector/s or defective check valve in the fuel pressure regulator. Use a noid light on each cylinder bank injectors. You should see pulsing during cranking. You can make your own noid light with an LED (light emitting diode) and a series 680 ohm resistor, connection polarity must be correct for it to work. Use starting fluid and if the engine starts, you have a fuel delivery problem. Last, measure cylinder compression. Your gasoline must be water free, you can get a test for water at a parts store.

 

You need to check the fuel pressure. I take it stabbing the gas doesn't help matters? It'll crank all day and give you nothing if the fuel is just sitting in the line w/ no pressure, nothing will make it through your injectors.

Give it some starting fluid and see if it tries to get up and go. If you don't get anywhere with starting fluid or a pressure gauge, then we need to start talking about your spark timing.

 

I would not use starting fluid I have seen several engines wasted by this proper testing will give you the resulys to get yourcar running. buy a fuel pressure gauge with what you describe this would be the first test I did

 

Cheap and easy to check, resistance on your injectors with a voltmeter.

Press in the clip on each injector-connector, and pull the connector at the same time.

Set a voltmeter at 200 ohm or higher, put the leads on em, and see what results you get.

Check em both cold and warm.

You should get something like 14 ohm to 17 ohm on each.

If one is below 10-11 ohm, that one most likely is dead.

Take a look at the sticky´s on this tech-forum by FIC injectors and you will know what I mean.

If a certain number of injectors fail (3 or 4?), it won´t start.

You could have some of em going south.

 

There is definitely pressure in the fuel lines. opening the shrader valve sprays a lot of gas. I don't have a tool to measure off that valve at the moment...

since I finally got some tools I've now replaced the spark plugs for giggles, and noticed that the ends seem to have oil on it somehow... I'm now looking into the head gasket as the culprit.

stupidly enough I don't have anything that I can short the pins with to get the codes off the car. I don't have anything like a paper clip lying around anywhere.

getting the stuff together to start with starting fluid. any tell-tale ways to figure out if the gasket went? I wasn't getting any smoke out the tailpipe.

 

"All the electronics are fine and kept working." Obviously incorrect. You must follow the advice already posted, otherwise . . . .


Jake

 

got something to short it... started the car... it flashed 1 and c12, then 1 with --- and then 4 with --- and finally to 1.0 with nothing at the bottom where the --- were. To my understanding that means there is no saved issues in the car. so there's that.

Edit:
The reason that I was thinking Head Gasket is because there's a very faint smell of gas on the oil dipstick and oil was on the spark plug...

 

If it´s a 90, you probably haven´t shorted the right pins.
It´s the 2 top right pins on the ALDL, then you turn on ign. without starting, the coolingfan will kick in as well.

In the info center with all the lights (over the radio) there should be an orange (service engine soon) light starting to flash.

It will flash each code 3 times, starting with 12, 1 flash followed by a pause, then followed by 2 flashes, again followed by a pause, and showing the same code again.

To test if the ECM is communicating with the different sensors, you can do the following.

Ignition off, remove the short from the ALDL pins, disconnect the connector from the TPS (small black box on the opposite side of the throttle linkage at the Throttle Body).

Now, turn on the ignition and wait until the SES light comes up (could take a half minute).

When it does, turn off ignition, then turn on ignition, read the codes by shorting the A and B pins at the ALDL.

You should get code 12 (3 times) and at least code 22 (3 times), if nothing else is stored you should get code 12 again (3 times).

If you get those codes, the ECM is working correct at least.

Now you only have to disconnect, and connect the minus cable at the battery to get rid of the stored codes.

 

I followed "Sequenced Code Recovery - 1990 through 1993:" at this link
http://www.corvettebuyers.com/c4vettes/codes.htm
I'll try the a-b pins later if you want but I think they're the same test aren't they, just different way to display the codes?

 

The one you performed, gives the CCM codes in the speedo display, by shorting A-G.

To show the ECM codes, you short pins A-B.

Not exactly the same thing.

Or someone else can chime in with an explanation.

 

Also, it's important to turn the ignition on but NOT start the car. That would put it in field test mode.

 

Still getting 12 over and over again.

 

Checked injectors resistance yet?

 

You're right. Depending on which two pins are jumpered you access different modules. Either CCM or PCM.

Jake