Hey guys, new here but not to online forums. anyway like a jackass i've been neglecting my corvette. I've had it for 5 years now and only ever put 10k miles on it.

long story short, I got so deeply involved with my truck the vette took a backseat and almost became forgotten. its been sitting for almost a year and a half now and its time to act. I originally parked it due to the same problem its having now and never messed with it.

Basically I went out to fire it up one day and it started fine but only felt as if it was running on 6-7 cylinders... concerned with this i immediately shut it down and tried to restart it. It did restart but the second time it was worse perhaps running on 4-5 cylinders. I repeated the scenario a 3rd time and then it was barely alive...firing on 1-2-3 cylinders maybe for about 5 seconds then it stalled... after that it never started again.

Recently I tried to get her going again, replaced the battery coil and tried to get her going on ether. On ether it will sputter occasionally and occasionally backfire out the intake but it will not fire not even for a second. all the wiring on the car looks good....

anyone got any ideas for me? i'm not much of a mechanic but i really cant stand to look at the poor car any longer in this condition

Thanks,
Beech

 

Do you have good fuel pressure? Good spark at the plugs? What do the plugs look like? How old is the gas in the car?

 

nasty gas, plugged up injectors

 

Thanks for the quick responses.. the gas is going on 2 years old now

the plugs look fine or at least the driver side ones I pulled. Fuel could very well be the issue but i was thinking even if it didn't get any fuel at all shouldn't it at least run somewhat on ether?


anyone have any info on draining the tank and cleaning the injectors? It would def be a good idea regardless if its the root of the problem or not.


didn't check spark as i didn't have anyone to crank it as i checked and i don't have the tools at the moment to test fuel pressure

 

when the problem originally happened thought the fuel was only about 6 months old...not saying it still couldn't be bad

 

What year is your Vette?

 

It's a 91 coupe 6sp.

I have a sig filled out. Dunno why it's not coming up?

 

There is a way to check spark by yourself. Pull the spark plug boot (#1 or #3 on the driver's side should work), stick a screwdriver in it (make sure it will stay in the boot by itself and is making contact with the metal part in there), then lay the screwdriver on top of the intake, exhaust, etc. with the metal shaft part just an 1/8" or so away from any exposed metal on the engine. While standing outside the car (lights off or in the dark helps), reach in and turn the ignition while watching the screwdriver shaft for spark. It's tricky to get everything in the right position, but can be done.

If you feel up to it, yank the distributor cap and make sure the rotor and cap contacts are clean. I'd also pull a couple of plugs to check their condition. I'd also check the oil and the coolant for cross contamination. If everything so far checks okay, then I'd start in on fuel delivery. Press the schrader valve on the fuel rail with a screwdriver or your finger nail and see if you get a healthy squirt of gas, both right after you turn on the key to prime the system, and then again several minutes later.

 

ok thanks.

fuel aside though, shouldn't it run on ether at least for a few seconds even f it wasn't getting any fuel? long as good spark was present?

 

Ok update, confirmed I have decent spark and fuel pressure. So I added to the half tank of old fuel 5 gal of 93 and a bottle of octane booster + 3 bottles of iso-heat. It will now consistantly fire on ether but then dies out. Anyone have some info on cleaning the injectors?

 

The stock multecs are known for failure. Pull the plenum and install a new set. They can be found cheap at FIC. 200 ish for the whole job.

 

Don't forget to change the fuel filter.

 

Sorry for my ignorance but multecs? The injectors?

 

I you are sure you are getting fire. Get a noild light for about 5 bucks hook onto each injector plug and see if it flickers like it is suppose to when cranking.

 

I'm sure I'm getting spark bUt I'm not sure if the injectors are spraying

 

Get the old fuel out of tank change the filter and get new injectors. Todays gas has a very short shelf-life, also the old injectors don't do well using it. Even more so after sitting for a long time

 

the injectors were replaced on the car in 06... think they should be ok to hold up to the new fuel with ethanol?

anyone know where I can get the Bosch III's locally? i would love to get them from a vendor but im on a pretty good time constraint

 

The fuel when stored in the sealed evaporative controlled tank of the car stays "OK" for quite a while and should be good enough to get going even if it's 2 years old - may not be good enough to get max performance out of and I wouldn't go WOT with it - but it's run-able IMHO - once you get it running then you can drive it and use up the fuel and fill with fresh.

Since you have spark and it now runs well on ether - try priming the engine with some fuel and see if you can get it to run longer by priming the fuel into the throttle body (slowly squirt into say one of the breather hose plugged into the side of the throttle body) - if it runs well then that leads to a definite fuel delivery problem - of which you can rule out pressure (I'm assuming you actually had a gauge on the rail to test pressure and not just a release fuel from the rail and say it's OK as it needs a minimum of 28-30 PSI to start and even have a chance of running from what I recall and any lower it won't have enough fuel to even start - and that's 15+ PSI low from what it should be) A bad fuel pressure regulator, bad pump, or bad pulsator will cause the start/run issues as the pressure will be real low but still have plenty of pressure to spray out when the test port valve is pressed.... A gauge is the only way to verify.

I'd check for injector pulse (NOID Light - parts store may rent them or harbor freight has a set of them which should be OK for occasional use) - or at least the the +12v power to each bank of injectors (the right and left banks are powered off different supplies - if you loose one +12v feed then you'll loose 4 cylinders which may be what happened).

Once you verify that your injectors are getting electrical pulse the only thing really left is to pull the rails off and see if they actually fire fuel and if not - replace them

 

Chances are, the injectors are gummed up with varnish. The same thing happens in carburetors. They can be taken out and professionally cleaned, but I would go ahead and replace them if they are GM Multecs. For less than $200, Jon at Fuel Injection Connection will send you a rebuilt and matched set of Bosch III's, new intake gaskets, and new fuel line o-rings. I highly recommend him. I would recommend that you replace the fuel filter (under the passenger frame rail) while you have the pressure off the system.

This is what I did and now the car runs PERFECTLY.


Mike
'90 'vert

 

FWIW - if you really are in that much of a hurry - the newer 3rd gen design injectors can be had off of some late model applications - just hit up the junkyard with a flow sheet (google injector flow chart or something like that to find one) - check later model ford/lincoln 5.4 L v8's, GM pickup V8's, some dodge/chrysler/jeep 5.9's, etc. Might find what stock applications they were in by searching too...

If you have a late model mustang performance shop in the area they usually will carry the 24lb injectors as they are a great upgrade to the stock 5.0L's 19lb injectors.