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Topic: 90 Vette won't start

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90 Vette won't start (1/25)
10/4/11 11:01am

vette2100
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Spring Grove, PA - USA

Vette(s):
1992 Black Rose Coupe

Joined: 7/25/2011
Posts: 18

Got fuel pressure 42 lbs. at rail, got spark to multiple plugs and air still wont start, could it be the ignition module or coil even though there is spark, my 92 had spark but was told not enough, turn out i had to change good ole Optispark do 90 vettes reqiure the same amount of spark to fire up

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Vette2100

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Re: 90 Vette won't start (2/25)
10/4/11 1:19pm

Adams' Apple
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Duncanville, TX - USA

Vette(s):
1985 Coupe-L98/Auto,Bright Red/Carmine. 1974 Coupe-L48/4speed, Medium Red Metallic/Black Deluxe.

Joined: 3/18/2009
Posts: 2230

Gotta have spark, fuel, and air, at the right TIME.
You do need a good spark to fire off an engine. Have you checked your plugs for correct gap, fouling, or other problems?

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Re: 90 Vette won't start (3/25)
10/4/11 4:12pm

SAYWHEN
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vette2100 said: Got fuel pressure 42 lbs. at rail, got spark to multiple plugs and air still wont start, could it be the ignition module or coil even though there is spark, my 92 had spark but was told not enough, turn out i had to change good ole Optispark do 90 vettes reqiure the same amount of spark to fire up

How 'bout some more details. Did it cut off going down the road? OR One morning wouldn't start after being driven the previuos day ? Has any work been done on it recently and now it won't start? What do the plugs look like ? Wet or dry?

Since you have spark I'd try some starting fluid in the throttle body. If it runs w/starting fluid i'd use a noid light to check for pulse at the injectors while cranking since you have fuel pressure.

If it won't start w/starting fluid i'd guess spark is to weak to start (coil maybe??) I say this under the assumption that nothing has been done to change spark timing such as loosening or removing the distributor recently.

Re: 90 Vette won't start (4/25)
10/4/11 4:14pm

vette2100
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Spring Grove, PA - USA

Vette(s):
1992 Black Rose Coupe

Joined: 7/25/2011
Posts: 18

Yeah plugs are good the car started ran for ten seconds then shut off, thats what my problem was with 92, had spark but not enough thats what i am wondering could it be the ignition module or if thay was no good would i get no spark at all

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Vette2100

Re: 90 Vette won't start (5/25)
10/4/11 4:25pm

SAYWHEN
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When the ign. modules fail you would loose spark. Once again starting fluid would check the entire ignition system....so to speak

Re: 90 Vette won't start (6/25)
10/4/11 5:39pm

vette2100
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Spring Grove, PA - USA

Vette(s):
1992 Black Rose Coupe

Joined: 7/25/2011
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tried starting fluid fires n thats it so i guess its getting spark, i have heard that if even one injector is bad the car wont start

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Vette2100

Re: 90 Vette won't start (7/25)
10/4/11 5:40pm

vette2100
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Spring Grove, PA - USA

Vette(s):
1992 Black Rose Coupe

Joined: 7/25/2011
Posts: 18

nothing was done car arn fine then went to start it one day and it ran for ten seconds and shut off, wont start now

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Re: 90 Vette won't start (8/25)
10/4/11 7:01pm

eddie20890
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lanoka harbor, NJ - USA

Vette(s):
1990 L-98 white/ red/black leather interior targa top auto 1975 L48 blue/black leather interior t tops auto

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could it be the fuel pump relay?

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Re: 90 Vette won't start (9/25)
10/4/11 7:06pm

SAYWHEN
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vette2100 said: tried starting fluid fires n thats it so i guess its getting spark, i have heard that if even one injector is bad the car wont start

Yours pulses 4 injectors at one time (what some call batch fired)...the ECM has 2 injector drivers each driver running 4 injectors..so if one injector is bad the "driver" won't operate any of the 4 on that circuit. If you have a VOM check the resistance on each injector I think they should read around 16 ohms..that may vary a little depending on your meter. The point is the readings of all should be close to the same. if you have one reading 3-4 ohms or one reading 48 ohms those injectors are bad and all should be replaced. If the readings are good you're back again IMO to checking for pulse at the injector connectors w/a noid light Thumbs Up

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Re: 90 Vette won't start (10/25)
10/4/11 8:45pm

vette2100
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Spring Grove, PA - USA

Vette(s):
1992 Black Rose Coupe

Joined: 7/25/2011
Posts: 18

Alright thanks ill give that a go tomorrow morning and let you know what I come up with, nothing like spending vacation days working on other peoples car huh?Really would like to get this running the weather finally got nice around here perfect for cruising Got mine running perfect and cant go, Thanks again

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Vette2100

Re: 90 Vette won't start (11/25)
10/4/11 8:46pm

vette2100
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Spring Grove, PA - USA

Vette(s):
1992 Black Rose Coupe

Joined: 7/25/2011
Posts: 18

I dont think it could be that, I got pressure at fuel rail, or can it still be the relay

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Vette2100

Re: 90 Vette won't start (12/25)
10/5/11 2:06pm

vette2100
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Spring Grove, PA - USA

Vette(s):
1992 Black Rose Coupe

Joined: 7/25/2011
Posts: 18

checked injectors with noid light all are good went and changed ignition module still didnt start i sprayed starting fluid it fired up then shut off, so i have to be getting spark it just seems thst its not getting fuel, check all fuses they are ok im at a lose now

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Vette2100

Re: 90 Vette won't start (13/25)
10/5/11 5:23pm

SAYWHEN
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vette2100 said: checked injectors with noid light all are good went and changed ignition module still didnt start i sprayed starting fluid it fired up then shut off, so i have to be getting spark it just seems thst its not getting fuel, check all fuses they are ok im at a lose now

If you checked all the injectors one by one with a ohm meter and got good/even readings
...then checked with a noid light and it blinks/pulses while cranking...it starts with starting fluid.

Then IMO one of 2 things either all the injectors are stuck/plugged and/or blocked and fuel can't pass thru ( I wouldn't think that would be very likely) OR... IMO more likely what the injectors are spraying may not be good fuel...water maybe??

i wouldn't think a bad cold start(if the '90 L98s used a cold start valve..I'm not sure) would create you issue since it doesn't continue to run after the starting fluid it should continue to run on the main 8 injectors after starting although poorly until warm.

It's also possible the ECT is so far out of range( the ECT may be sending bad info to the ECM ??) that it won't start. If you have a FSM there is a chart with resistance readings for the ECT depending on the actual temperature. I'm getting way too long winded LOL

LOL

If it was me I'd take a fuel sample in a clear jar and be sure you don't see any separation
after it sits (water) and be sure it looks and smells like gas my 2 cents

Re: 90 Vette won't start (14/25)
10/5/11 10:36pm

Adams' Apple
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Duncanville, TX - USA

Vette(s):
1985 Coupe-L98/Auto,Bright Red/Carmine. 1974 Coupe-L48/4speed, Medium Red Metallic/Black Deluxe.

Joined: 3/18/2009
Posts: 2230

The coolant temp sensor is a valid point. Needs to be checked, for sure. Another thing that just popped into me haid is the TPS(throttle position sensor). If it is out of whack, it the ECM could be in "clear flood" mode, killing the fuel supply while cranking. You can unplug the TPS and crank it to see if it will start like that. If it does, the TPS is the problem.
Weird that you say you have fuel pressure, and the infectors are firing. Are you showing that 42 lbs pressure while cranking, or just key on?

|UPDATED|10/5/2011 7:36:24 PM (AZT)|/UPDATED|

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Re: 90 Vette won't start (15/25)
10/6/11 9:57am

vette2100
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Spring Grove, PA - USA

Vette(s):
1992 Black Rose Coupe

Joined: 7/25/2011
Posts: 18

42 lbs while cranking checked it three times gonna check thr TPS today , the pressure is at fuel rail

|UPDATED|10/6/2011 6:57:58 AM (AZT)|/UPDATED|

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Re: 90 Vette won't start (16/25)
10/6/11 1:25pm

Adams' Apple
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Duncanville, TX - USA

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1985 Coupe-L98/Auto,Bright Red/Carmine. 1974 Coupe-L48/4speed, Medium Red Metallic/Black Deluxe.

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Posts: 2230

Something stinks in Denmark.....got good fuel pressure, infectors firing, plugs sparkin....I assume the plugs are all sparkin? I think I'd have to get a spark tester and see how much energy the coil/ign is actually getting to the plugs, at this point....sure seems like it's gonna be an ignition issue somehow.

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Re: 90 Vette won't start (17/25)
10/6/11 5:17pm

vette2100
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Spring Grove, PA - USA

Vette(s):
1992 Black Rose Coupe

Joined: 7/25/2011
Posts: 18

That was my next step after that I have no idea i am gonna test coil and if its good guess it will have to go to shop. Thanks

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Re: 90 Vette won't start (18/25)
10/6/11 10:37pm

Adams' Apple
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Duncanville, TX - USA

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1985 Coupe-L98/Auto,Bright Red/Carmine. 1974 Coupe-L48/4speed, Medium Red Metallic/Black Deluxe.

Joined: 3/18/2009
Posts: 2230

Imma gonna back up a bit, and ask...have you actually checked each individual infector for resistance? You could have ONE infector that is shorted, or close to it, and it would kill all of the infectors on that side of the engine, making it hard to start, or not start at all. Unplugging them to use the noid light would show them to be getting a signal to fire, but once plugged back in, it would again kill the circuit.
I mention this because my '85 had ONE bad infector(shorted), and it absolutely would not start. I'm sure if the rest of them weren't derty from age, it may have had an easier go at it, but still....

|UPDATED|10/6/2011 7:37:52 PM (AZT)|/UPDATED|

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Re: 90 Vette won't start (19/25)
10/7/11 9:31am

vette2100
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Spring Grove, PA - USA

Vette(s):
1992 Black Rose Coupe

Joined: 7/25/2011
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yup, checked each injector, all are good, ihave no idea what to do next. This is what if done so far, injectors, fuel pump , fuel filter, ignition module and coil. The only thing that i can think of now is, is the ecm bad? i guess a Gm shop would have a way to test it, so maybe that will be next step

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Re: 90 Vette won't start (20/25)
10/7/11 1:03pm

SAYWHEN
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vette2100 said: yup, checked each injector, all are good, ihave no idea what to do next. This is what if done so far, injectors, fuel pump , fuel filter, ignition module and coil. The only thing that i can think of now is, is the ecm bad? i guess a Gm shop would have a way to test it, so maybe that will be next step

What resistance readings did you get on each injector ? Was it 15-16 ohms ? When you checked while cranking engine with a noid light plugged into the injector harness...the light flasnes while cranking...correct ?

Re: 90 Vette won't start (21/25)
10/7/11 8:25pm

vette2100
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Spring Grove, PA - USA

Vette(s):
1992 Black Rose Coupe

Joined: 7/25/2011
Posts: 18

finally got it running thanks everyone i put another coil in it this morning and it fired up

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Re: 90 Vette won't start (22/25)
10/7/11 10:41pm

Adams' Apple
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Duncanville, TX - USA

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1985 Coupe-L98/Auto,Bright Red/Carmine. 1974 Coupe-L48/4speed, Medium Red Metallic/Black Deluxe.

Joined: 3/18/2009
Posts: 2230

Glad ya got it runnin again! Sux when new stuff don't work, but it happens all the time....

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Re: 90 Vette won't start (23/25)
10/7/11 10:53pm

eddie20890
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lanoka harbor, NJ - USA

Vette(s):
1990 L-98 white/ red/black leather interior targa top auto 1975 L48 blue/black leather interior t tops auto

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just another question....is there any codes stored in the memory. i saw no mention of you checking for any.

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Re: 90 Vette won't start (24/25)
10/8/11 7:06am

SAYWHEN
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Glad to hear you got her goin' ! Big smile

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Re: 90 Vette (25/25)
6/19/14 1:01pm

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Check the pressure regulated , you could pull injector out to check spray . Pinch off return line and see if regulator hold pressure .

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