C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Running on starting fluid

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Old Aug 24, 2025 | 08:49 PM
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Default Running on starting fluid

OK, I am a carburetor guy, I know nothing about fuel injection. Wires tend to intimidate me.

Here is the situation. I parked the car last winter. I had periodically started i
t with now issues. Then it just stopped starting. It will run on starting fluid. I have power to the fuel pump and it does turn on with the key.

Is there a sensor that will stop the fuel supply to keep the car from staring?

Thank you

stupid guy

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Old Aug 24, 2025 | 09:08 PM
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Welcome to DC! Simple, replace the Hermsdorf modulator and recaibrate the external contabulator (use the metric conversion, adds 20+ hp!), then its job done! Enjoy the ride! Dude
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Old Aug 25, 2025 | 02:41 PM
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Is there more than 1/4 tank of fuel ?
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Old Aug 25, 2025 | 05:19 PM
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Yes, I am curious why you asked that question. When it does get below a quarter of a tank it will stumble like it is running out of gas.

The car is an 1985 with 64,000 miles. It was in storage for 13 years before I bought it. New injectors were installed, fuel tank drained and cleaned, fuel filter replaced and the oil pressure switch relaced. I drove it all last summer and enjoyed finally having a Corvette.

I took it into a shop to have it out on a computer to see why it surges. Once it warms up the rpm wil rise and fall, not lope like a cam or a missfire. They said they could not find anything wrong.

I don't like asking for help but I miss driving the car. I am at the point of switching the fuel system for a carburetor, holley Sniper or terminator systems.

is there a simple solution that I am over looking or should I get rid of the tune port injection?

Thank you for your time.

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Old Aug 25, 2025 | 05:43 PM
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Fist things first, just like if you were having this problem with a carb you need to see if fuel is getting to the engine. This is simple. Just use a fuel pressure gauge and see what it says when you kick the pump on. If the pump is running you should see pressure.
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Old Aug 25, 2025 | 05:55 PM
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Like said put a gauge on it plus or minus 35 PSI in a perfect world it should hold it, next pull a sample from the bottom of the tank to see if water got in.
Get a fuel injection circuit tester (Noid light) see if you have the injector pulse. Tester would flash showing power to injectors
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Old Aug 25, 2025 | 07:59 PM
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Originally Posted by Stupid guy
Yes, I am curious why you asked that question. When it does get below a quarter of a tank it will stumble like it is running out of gas..
I asked because my gauge sender thinks I have more fuel than I do.
Just want to make sure there is gas 🤓
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Old Aug 25, 2025 | 08:06 PM
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Originally Posted by Stupid guy

I took it into a shop to have it out on a computer to see why it surges. Once it warms up the rpm wil rise and fall, not lope like a cam or a missfire. They said they could not find anything wrong.
I would start with looking for a vacuum leak.
The surge could be from the idle air control valve trying to achieve target idle.
As mentioned, your going to want to get a noid light to see if ecm is trying to fire injectors.
The ecm is looking for a reference pulse from distributor, so the problem could be there.
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Old Aug 25, 2025 | 09:42 PM
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Thank you for the areas to look. It will check it out what gas been suggested weekend.

Thanks again for the replies.
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Old Aug 25, 2025 | 11:17 PM
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Originally Posted by Stupid guy
Once it warms up the rpm wil rise and fall, not lope like a cam or a missfire. They said they could not find anything wrong.
I had a similar experience with my '84. You are describing a classic failing coolant temperature sensor. The ECM uses the signal from the CTS to know when the engine is warmed up. In my case the symptoms appeared way before it finally threw a code 15 for bad CTS. Look for it on the front of the intake manifold. In your case there may also be a sensor for the cold start injector.

https://www.corvetteforum.com/forums...-corvette.html

There is the new one way down there all shiny.
There is the new one way down there all shiny.
The new CTS came with a new pigtail because the 40+ year old sensor had a different
The new CTS came with a new pigtail because the 40+ year old sensor had a different "umbrella" style connector.
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Old Aug 25, 2025 | 11:21 PM
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pump running does not mean fuel moving. Check that fuel pressure. If good you got crap in gas or clogged injectors. You mentioned work being done but sometimes on the old cars, repairing other stuff can knock crud loose.
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Old Sep 1, 2025 | 12:01 PM
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Very frustrated now.

This is what has been eliminated.
Fuel pump (new)
Fuel pump sreen (cleaned)
Fuel filter (new)
Oil pressure switch (bypassed)
Fuel pump relay replaced (taken out of running car)
Ecm replaced (taken out of running car)

I have fuel for the first two second and then does not come back on to actually start the car. The car will only start with starting fluid.

What else turns the fuel pump on after the initial prime?

I am just short of either running a jumper wire to turn the fuel pump on manually. This has to be a simple fix from here, what am I missing?

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Old Sep 1, 2025 | 08:19 PM
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Are you sure you bypassed the oil pressure switch and not the oil pressure sender ?
If you bypassed the switch, the pump would run 24/7.
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Old Sep 1, 2025 | 08:29 PM
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I ran a jumper wire to port G under the dash. I could hear when I put power to it so I only applied power when cranking. After I tried that and it didn't work I held power to listen to the pump. It only activates for 2 seconds and then quits.
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Old Sep 1, 2025 | 11:36 PM
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Have you verified that the rail is getting pressurized during those 2 seconds, with gauge or depressing the valve on rail ?

The ecm will energize fuel pump relay for 2 seconds. If it doesn’t see a reference pulse from distributor during cranking,it will stop powering relay.
The ecm will also not fire injectors if it doesn’t see this reference pulse.
Do you have a noid light to test injectors ?


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Old Sep 1, 2025 | 11:42 PM
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I have fuel at the valve on the rail. I do not have a noid tester. I will get one this week.
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Old Sep 8, 2025 | 01:59 PM
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Is your oil pressure switch wired up and functioning ?
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Old Sep 8, 2025 | 02:36 PM
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I am going to remove the wiper motor to check the oil switch. I only have limited time to work on the car so it is a slow process.

I am hoping the oil switch is the problem. Everything else on the list for the for start up procedure has been eliminated.

Hopefully Saturday morning I can hear the car run again.

Thanks
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Old Sep 8, 2025 | 02:58 PM
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Unless I missed it, did you actually put a fuel pressure gauge on to check pressure at prime and watch it during cranking to see pressure once oil pressure is achieved. Just having fuel come out of valve doesn't mean it has adequate pressure to start.
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