I'm a newbie to the forum but I'm not a newbie to corvettes. I'm a retired industrial maintenance technician and have owned several vettes over the years.

My son has a 92 LT1 that won't start. He had it in storage in his garage for about a year. It was started about once per month. After he re-instated his insurance, it started to occasionally run rough. One day is was good and the next it was rough. After a couple of weeks of this, it would not start at all.

First, I siphoned the fuel tank and replaced with fresh fuel. Still won't start.

Second, since we could not hear the fuel pump, we replaced the pump, sock, and sending unit. Still no start. It does, however, fire on ether.

After purchasing a fuel pressure gauge, we found that we have 42 pounds at the fuel rail. When the gauge is first attached, the pressure builds to the 42 after several cranks. The battery is new and turns over strong. There is no gas smell.

Any ideas would be appreciated.

 

Moved to C4 Tech.

 

I'm as close to an expert in no start problems as you can get with a 92 - I've had them all!

First things first, when you turn the key to on prior to cranking, does fuel pressure go up to 42? The pump should prime the system by just turning the key on. When the key is off, does the pressure stay high, or immediately drop?

Have you checked for spark? I would first check for spark from the coil going to the distributor part of the opti. If you have spark there, check at a plug. If you have spark, your opti is good, so you cn ignore all the people telling you that that's what it is without ever looking. If you don't have spark, that doesn't necessarily mean the opti is bad.

What does the security light do when you try to start it? Has any portion of the VATS been disabled? There are two parts to it - a starter disable (the commonly disabled part) and an injector disable (has to be chipped out of the ECM).

You say it fires on ether, does that mean it will start up and run and idle, or just fire and then sputter out when the ether has burned off. If the latter, that would lead me down a path of "likely fuel delivery problem".

 

Sure do appreciate the help.

When the ignition is turned on without cranking, the pressure goes to 30. After two or three cranks (engine turnovers) the pressure builds to 45. There is no leakage when the ignition is turned off.

We haven't checked for spark because I assumed that since it fires on ether, it would have spark. It sputters and dies when the ether runs out.

The security light comes on when you try to start. It's throwing a 43 error code which is the knock sensor I think. That makes sense to me because the fuel pump died and leaned the fuel mixture on it's way to death.
Can the error code disables the injectors?

 

I can't say for sure, but I would not think it would. In my car I had sporadic no starts due to the vats chip disabling my injectors. It would typically start when I tried it again, which made me think it was heat related. Turned out it would start again because the 5 minute security lock out would expire.

When you turn the key to on with the doors shut, if the security light is on or flashing that is a problem, and injectors will be disabled.

I ended up buying a kit from pcm of NC that was a piggyback to the PCM that allowed for a custom chip with vats turned off. Never had the issue again.

 

We disconnected the battery and left the ECM without power for several hours. After re-connecting, It still wouldn't fire. I had the fuel pressure gauge on it and noticed that the initial pressure (ignition on but not cranked) was only 25 pounds. We're going to try a new fuel filter and if that's not the problem, we'll replace the pressure regulator. I'll let you know how it turns out.

 

If the problem is VATS (security system), then it won't even crank.

It's normal for it to build pressure slowly enough, that you don't reach pressure/spec before the pump shuts of, during "key on". If you're getting 40+ PSI while cranking, that is better than good enough to start it.

I think this is the problem:
Combine that with this:
....add up to ME, as strong indicators that you've got plugged, or not firing injectors. I'd guess "plugged". I would focus my efforts there. I would remove the fuel rail w/injectors intact, place them in bottles or over rags, then crank and see which ones are actually dispensing fuel.

 

Thanks for your time and knowledge.
My son and I are gonna do some studying up, and as soon as we figure out how to do what you've suggested, we'll give 'er a try. We plan to get back to it on Saturday and we'll let you know how it turns out.

 

It's super easy on an LT1. Unless I'm forgettting something, it's only 4 bolts that hold the fuel rails down, with the injectors. Remove the beauty covers (they just snap up/off), then the fuel rails and bolts are apparent (see pic below). Remove them, then gently pry the rail w/injectors, up and out of/off of the intake. There are clips that secure each injector to the rail, so they'll come out of the intake, w/the rails.




Then, in the interest of "fire safety", place something under them to catch the fuel, crank and see what's happening. On your '92, 4 injectors on one side should fire, then the other side, back and forth twice per revolution of the crank. It should be super obvious which are firing, and which are "piddling", or not doing anything.

I did this test on an L98 a while back (much harder to do, than an LT1), and 5 of the 8 injectors were plugged. That car wouldn't start either.


.

 

VATS has a starter kill AND injector kill. I'm not sure if there's a way to have a fault where only injectors are disabled. It was possible on mine because at first the starter kill was disabled before I disabled my injector disable.

 

Yeah. Mine had the same problem (wouldn't start) so like a genius, I jumped the start enable relay. Then it would crank...but I only complicated my diagnosis by doing that.

 

Thanks again for the info.
We're gonna pull the rails with injectors and see what we've got this Saturday.

 

We pulled the rails and injectors this past weekend. Someone has been in there before and left a cobbled mess. The injector retaining clips that secure the injectors to the fuel rails are missing. Two of the eight are still on the rail because they are between the pressure regulator bracket and the schrader valve and they won't easily slide off. The two that are still there can't be used because the groove that's machined in the barrel of the injectors is not machined all the way around and they are 90 degrees away from where they need to be in order for the clip to engage. The injector can't be turned because of the electrical connector and the rail itself.

We seated the injectors as far as they would go into the rails. We then secured sandwich baggies to each pair of injectors with rubber bands. When the fuel pressure reached a certain point, it would pop one of the injectors out of the rail. This would happen before the motor had a chance to turn over. So, we couldn't check for fuel spray.

At this point, we thought that we would replace the injectors with some that came with new retaining clips. We thought that we could do this for under a $100. What we found on the internet was 15 or 20 different kinds of injectors ranging from almost $1000 to $50 for the set of 8. They not only had the wide price range, but also had various ratings as far as flow rates and/or operating poundage. So, we decided to put it back together since we didn't know what injectors were the ones to purchase.

When we went back together, we discovered that these injectors are too short by approximately 1/4 to 3/8 of an inch. When they are fully seated into the rail, the bottom o'rings are fully visible at the top of the holes where the injectors go into the intake. This is with the rails bolted down tight and solid. If you pull the injector down and fully seat it in the intake, it will completely separate from the fuel rail. My son says that the Haynes manual says that they should be fully seated on both ends. He also tells be that the stock injectors for this motor are 25 pound injectors.

We haven't been able to find any info as to the overall length of the injector. We have a local motorhead who's a good source of knowledge, but he's on a cruise ship somewhere in the Bahamas.

So, we are looking for knowledge.

 

As a post script, my son has owned this car for 8 or 9 or 10 years. He's lived at his current residence for 7 years and owned the car for some time at his prior residence.

Anyway, this motor has run good for a long time even with the apparently wrong injectors.

Also, this problem started with a "knock sensor" error and a dead fuel pump.

 

Get 25 pound Bosch 3 style injectors .you can get them fairly easily either from FIC or even Amazon or eBay. I got mine for eBay, the guy rebuilds them and flow test them. They were inexpensive too, under 100 bucks for them all. Very happy with them.

My old injectors were fine, it was part of an overhaul for the whole fueling system.

 

Thanks again for the info. We'll check 'em out.
We're having trouble finding dimensional information for the injectors that are for sale out there.
The ones that we have are too short and we'd like to verify that any that we buy as replacements are longer, top to bottom, than what we are replacing.
If you still have one of the injectors that you replaced, it would sure help to know what it measures in length.