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

94 LT1 Crank No Start

 
Old 04-12-2019, 08:37 PM
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Erik Munoz-Chairez
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Default 94 LT1 Crank No Start

Hello All,

Hoping you can help. Today the car started after sitting for a week and replacing the entire fuel sending unit, there was some black smoke coming out of the exhaust which went away after idling a bit(no more than 10min). Turned the car off then wouldnt turn on again would just crank but not start.

Parts replaced in the two months I've owned it:
Optispark
Spark plugs
Water pump
Serpentine Belt
Idle air control valve
Throttle position sensor
Intake air temp sensor
Fuel sending unit(includes fuel pump)
Previous owner replaced fuel filter, fuel lines, fuel relay, and 30lb fuel injectors, fuel pressure regulator.

Tests I've conducted:
-Fuel pressure is at about 40psi both running and while priming and appears to maintain that pressure.
-there doesnt appear to be any fuel in the vacuum line to the fuel pressure regulator
-did a smoke test to find any vacuum leaks(found small one and fixed)
-injector ohm readings are all reading about 15ohms
-Noid light test, all injector connectors getting power
-spark test, all plugs are getting power
-tested map sensor, placed volt meter on sensor connector and saw voltage go down when pressurized(I believe it's supposed to do this)
-pulled the fuel rail up and primed up the engine to ensure injectors weren't leaking

After all this the engine still will not start. Only seems to start after sitting for a while then doesnt want to start again. Sometimes I get the smell of fuel when cranking the engine.

Please help! Thank you!
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Old 04-12-2019, 08:46 PM
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don hall
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Looks like you have done a pretty thorough job of diagnosis.

You didn't mention if the "check engine" light was on, so I assume it wasn't. You might check for codes, just in case.

I would add a link for codes, but I feel it would be an insult.
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Old 04-12-2019, 08:52 PM
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Erik Munoz-Chairez
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@don hall attempting to pull codes is something I havent done. I'm actually very new to the automotive repair world. No check engine light though. Only light I have on is "service ASR".
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Old 04-12-2019, 08:56 PM
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don hall
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Informative link:

https://www.corvettebuyers.com/c4vettes/codes.htm

Click on upper left "WWW.CORVETTES.COM" for additional info.

Last edited by don hall; 04-12-2019 at 09:01 PM.
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Old 04-12-2019, 09:35 PM
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Maybe a clogged fuel return line? Black smoke is an indication of too much fuel. Hows your air filter look? Maybe an injector is stuck open?
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Old 04-12-2019, 10:22 PM
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Erik Munoz-Chairez
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Originally Posted by thatguy427 View Post
Maybe a clogged fuel return line? Black smoke is an indication of too much fuel. Hows your air filter look? Maybe an injector is stuck open?
I appreciate your response, air filter is new just forgot to list it. Clogged fuel return and injector stuck open are definitely possibilities, any advice on best way to check these?
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Old 04-12-2019, 11:48 PM
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To best way to check for a stuck injector as a home mechanic is to unbolt your fuel rails, pull the injectors from the intake. While everything is hooked up, turn your key to pressurize the system. If one is stuck open it will leak fuel.

To test the return, which if failed I would expect to be due to the fuel pressure regulator, unhook the fuel line closest to the front of the car near the intake, pressurize the system and see if some fuel leaks out.

Going back over your original post, these parts are new/newish... so it would seem unlikely this would be your problem. Why did you replace those parts in the first place? Were you having the same or similar problems? Wait wait, I just read a little slower, you installed 30 lb injectors vs the stock 24 lb... Have you reprogrammed the ECM so it knows how much fuel its pumping? Maybe the larger injectors alone are the problem.
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Old 04-13-2019, 09:14 AM
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don hall
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If you plan on servicing your vette, it is recommended that you invest in CORVETTE FACTORY MANUALS. They are available (new) from many parts and book stores, and HELMS, or eBay (used)
or, from forum members.

Spend a little time researching manuals. Some sneer at the mention of buying a Haynes manual, but it will provide sufficient info for many basic wrenchers. The red GM manuals are preferred, especially for the
wiring diagrams. The white GM manuals are "preliminary data", sufficient info for many..

Last edited by don hall; 04-13-2019 at 09:43 AM.
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Old 04-13-2019, 10:53 AM
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It seems like the fuel system is working, even a leaky injector would not cause it to not to start. When you crank it a lot seems like it's loading up and you will smell fuel.

Just one after thought, does the digital temperature gauge seem to be displaying correctly. Because it governs the A/F in open loop and if (ECT) not working or open it will cause the engine to go very rich very fast so just check that.

It would seem to me it is some sort of spark problem. Did you check for spark when it was not starting? Perhaps the spark is to weak and might be an intermittent problem possible coil or ICM. Check all pin connections for coil, ICM, opti and grounds.

Recently I just had a similar situation on a 70s model GM HEI distributor with a weak coil. I did have spark and it drove me nuts just weak enough spark to have hard starting. Spark tester and all looked close to normal. The coil did have excess resistance in the secondary.
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Old 04-14-2019, 10:08 AM
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Default The Car Drove

Hi All,

Just wanted to give you an update about what happened yesterday. I go to start the car in the afternoon(first time for the day) I got crank no start with black smoke from exhaust. Left for about 2-3hrs. Came back and pressed throttle to floor and cranked. It took a couple turns but it turned on with a bunch of smoke coming out of the exhaust. That smoke eventually went away after idling a bit.

Took her out to drive, drives great, great throttle response, no hesitations, seemed to idle fine at stops. I stopped at my house for about 7-10min and left the car idling, it shut off, but I was able to start it no problem. Drove for hours just around the the area, no problems. Bring it back into the garage and shut it off. Was off for probably 20min, she turned on fine again. Go to get food at a nearby restaurant. Car sat for probably an hour while I ate. Car would not start on normal crank. It would start if i pressed throttle to the floor and cranked it but it would turn on and immediately shut off without idling. I was able to keep it on a bit longer by pressing the throttle but it wouldnt idle. We had to trailer it back. Before we put the car on the trailer, I read something on this forum about disconnecting the MAF sensor if the car wouldnt stay on. That's what I did and lo and behold the car would turn on and stay on. Didnt risk it so I still put the car on the trailer. When the car was back at the garage, it started right up again with the MAF sensor disconnected.

Can the MAF sensor be causing some of these problems that I've been facing?

Thank you!

Last edited by Erik Munoz-Chairez; 04-14-2019 at 10:09 AM. Reason: Title
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Old 04-14-2019, 10:20 AM
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It is one item that keeps tabs on air/fuel ratios.... It would make sense to me.
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Old 04-14-2019, 10:54 AM
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Check to see if there are any codes
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Old 04-14-2019, 03:23 PM
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Originally Posted by pcolt94 View Post
Check to see if there are any codes
Will the codes display on the digital dash? My digital dash has been acting up, only working properly for short periods of time. I will also look into the other spark possibilities you described earlier. Thank you for your help
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Old 04-15-2019, 02:36 PM
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Originally Posted by Erik Munoz-Chairez View Post
Will the codes display on the digital dash? My digital dash has been acting up, only working properly for short periods of time........
It is suggested that you invest in a code reader, many are under $30........ printed display, and ability to erase codes is desirable
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Old 04-16-2019, 10:16 AM
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Originally Posted by don hall View Post
It is suggested that you invest in a code reader, many are under $30........ printed display, and ability to erase codes is desirable
Please offer some suggestions for a code reader. It's hard to find a OBD1 code reader with the OBD2 connector. Price may exceed $30 to find this kind of scanner today.

If the OP cannot read the codes using the on board diagnostics, he may not be able to read the codes with a scanner either. I donít know if he has a dash problem or a CCM communications problem. I would try to find somebody with a OBD1 scanner just to see if it can communicate.
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Old 04-18-2019, 03:38 PM
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Erik Munoz-Chairez
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Hi all, I appreciate the responses. I'm investing in an OBD 1 scanner. My digital dash currently displays all possible light combinations, so my speed looks like all 8s, my fuel looks like it's always full, my reserve indicator is always showing, and my mileage looks like a bunch of 8s and so on. Reading anything in the dash would be difficult until I fix the issue. Fixing that is next on my list.

But for update incase anyone follows this thread later on. I left my MAF unplugged, she turned on yesterday no issues. Drove around for 30min, hesitated once but that's it. Shut her off for about an hour. Turned on again first try. Drove another hour or so without issues, then shut her off. She turned on first try about an hour and a half later. Without checking other codes, the signs seem to point toward the MAF being faulty. I cleaned the MAF with MAF cleaner about a month ago when I changed the TPS, IAC, and Air filter.
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Old 04-18-2019, 03:53 PM
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for dash www.batee.com
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Old 04-19-2019, 01:29 AM
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you got a fuel injector stuck open im sure of it.
pull the fuel rail up tack the 4 bolts out pull the fuel rail up with all injectors and turn key on...ull see what injector is bad
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