Vette won't start...Please help!!!
Thread Starter
Melting Slicks
Joined: Mar 2002
Posts: 2,876
Likes: 764
From: Sligo PA
Vette won't start...Please help!!!
So I'm all finished with my tuned port swap on my 84. I haven't had much time to work on it because I just got a new job. Anyway, so I tried firing it up today. I checked the fuel pressure first. That is my first question. How should I set the pressure on this? I have an adjustable regulator. I put the gage on the test port and turned the key forward and the gage jumped up to 60 psi. Is that normal? I turned it down to about 53psi.
I tried starting it and it cranked over but it didn't even try and start. It has spark. I can tell because I have a clear distributor cap. I checked at the plugs as well and it has lots of spark.
So that leaves the injectors. Any pointers on how to check if the ecu is sending signal to the injectors? I took a volt meter and put the terminals on the ones on an injector connector. (I unplugged all the injectors first) and then turned the key one click forward and it came up as 12V. Same thing on the other side. When you try turning over the engine the voltage at the injector plug drops to 9.5V.
For some reason the injectors aren't working at all. They are all new 30 lb SVO injectors.
Any pointers on where to start looking?
I tried starting it and it cranked over but it didn't even try and start. It has spark. I can tell because I have a clear distributor cap. I checked at the plugs as well and it has lots of spark.
So that leaves the injectors. Any pointers on how to check if the ecu is sending signal to the injectors? I took a volt meter and put the terminals on the ones on an injector connector. (I unplugged all the injectors first) and then turned the key one click forward and it came up as 12V. Same thing on the other side. When you try turning over the engine the voltage at the injector plug drops to 9.5V.
For some reason the injectors aren't working at all. They are all new 30 lb SVO injectors.
Any pointers on where to start looking?
Safety Car
Joined: May 2003
Posts: 4,283
Likes: 0
From: Houston Texas
Re: Vette won't start...Please help!!! (Phobos84)
It wouldn't happen to smell like gas coming out of tailpipe would it? How big is your motor to have put 30# injectors or do you have a supercharger. 24# injectors or usually big enough for heads, intake , exhaust and cam work. If it is a stroker then the 30's might be ok.
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
Re: Vette won't start...Please help!!! (Phobos84)
One wire of the injectors goes to 12v, the other wire goes to the ECM which pulls it to ground for a short duration to spray fuel. Put a low power 12v lamp on the socket to the injector and crank the engine. You should see the 12v lamp pulse on every injector while cranking.
Thread Starter
Melting Slicks
Joined: Mar 2002
Posts: 2,876
Likes: 764
From: Sligo PA
Re: Vette won't start...Please help!!! (jfb)
It's a built up engine but not that big. I used this http://www.rceng.com/technical.htm to figure out that I needed 30 lb injectors. I first bought a set of 24's but that site told me they would be a little small.
Anyway no gas in the exhaust. In fact no gas smell at all. Even after I pulled a spark plug. Didn't smell like gas at all. The one thing I'm really wondering about, as soon as I turn the key one click forward it shows 12V all the time to the injectors. Is it supposed to do that? If so why don't the injectors do something when you give them power?
Also how do you set the fuel pressure. I know it will be different when it's not running then running. Right now I have it as low as I can get it and it is showing 53 psi. The screw on the regulator is hitting on the plenum so I can't go out with it anymore. I guess I might need to get a shorter screw.
Anyway no gas in the exhaust. In fact no gas smell at all. Even after I pulled a spark plug. Didn't smell like gas at all. The one thing I'm really wondering about, as soon as I turn the key one click forward it shows 12V all the time to the injectors. Is it supposed to do that? If so why don't the injectors do something when you give them power?
Also how do you set the fuel pressure. I know it will be different when it's not running then running. Right now I have it as low as I can get it and it is showing 53 psi. The screw on the regulator is hitting on the plenum so I can't go out with it anymore. I guess I might need to get a shorter screw.
Instructor
Joined: Mar 2003
Posts: 185
Likes: 0
From: West Sacramento CA
Re: Vette won't start...Please help!!! (Phobos84)
I don't know about adjusting the pressure for your year, but it is probably the same as an 88. The first thing I have to do to adjust my pressure is hook up the gage of course. Disconnect the hose attached to the fuel pressure regulator because that will definitely affect your adjustment. Turn the screw to forwards or backwards to gain your desired reading and reconnect your hose when you are finished. After connecting the hose your reading will be different but what you see is not the true reading. Kind of like your timing. If you don't disconnect the EST wire you won't get a true timming adjustment for your ignition.
Maybe this will help.
[Modified by ciscokid, 9:57 AM 6/15/2003]
Maybe this will help.
[Modified by ciscokid, 9:57 AM 6/15/2003]
Thread Starter
Melting Slicks
Joined: Mar 2002
Posts: 2,876
Likes: 764
From: Sligo PA
Re: Vette won't start...Please help!!! (ciscokid)
The gas is old but there was very little in the tank. Just enough to read 1 bar on the fuel gage. I put a fresh 5 gallens in it so I don't think thats the problem.
As far as the pressure goes are you talking about after it's running or just with the key turned forward? I know about setting it with the engine running and pulling the hose off. But is it the same wile just priming the fuel pump by turning the key forward?
This all seems very strange to me. It has pleanty of fuel at the rail and lots of spark but the injetors won't fire even with 12 volts going to them. I just don't understand. Could it be posable that every injector I have is bad? That seems so unlikely to me being that they are all new.
As far as the pressure goes are you talking about after it's running or just with the key turned forward? I know about setting it with the engine running and pulling the hose off. But is it the same wile just priming the fuel pump by turning the key forward?
This all seems very strange to me. It has pleanty of fuel at the rail and lots of spark but the injetors won't fire even with 12 volts going to them. I just don't understand. Could it be posable that every injector I have is bad? That seems so unlikely to me being that they are all new.
Pro
Joined: Oct 2001
Posts: 682
Likes: 23
From: loxahatchee fla
Re: Vette won't start...Please help!!! (Phobos84)
ARE YOU TOTALLY SURE YOUR NOT 180 degrees OUT of time on the distributor timing?
gas pressure above 25 psi will work. 38-42psi is correct!
if the TPS is set at about .545 volts and all the other sensors are correct it should fire if the ignition timeings correct, you can always squirt small amounts starter spray (ETHER) into the throttle body bore to test is its getting fuil into the runners but CORRECT IGNITION TIMING not fuel is the likely cause.
heres the correct sensor ranges
http://www.c4vettes.com/sensorinformation.htm
heres the trouble code info to sort it out http://www.c4vettes.com/ecm.htm
gas pressure above 25 psi will work. 38-42psi is correct!
if the TPS is set at about .545 volts and all the other sensors are correct it should fire if the ignition timeings correct, you can always squirt small amounts starter spray (ETHER) into the throttle body bore to test is its getting fuil into the runners but CORRECT IGNITION TIMING not fuel is the likely cause.
heres the correct sensor ranges
http://www.c4vettes.com/sensorinformation.htm
heres the trouble code info to sort it out http://www.c4vettes.com/ecm.htm
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Thread Starter
Melting Slicks
Joined: Mar 2002
Posts: 2,876
Likes: 764
From: Sligo PA
Re: Vette won't start...Please help!!! (grumpyvette)
I will re-check the distributor today. Thanks for the advice. I'm 90% sure it is not 180 out but I will take a look. The thing that bothers me is that after cranking it over and over and then pulling out a spark plug it didn't smell like gas at all. Almost as if the injectors are not firing at all.
Talking about sensers. Funny thing about my TPS sensor. It dosn't have the slots in it to be adjusted. The old crossfire TPS had slots insted of holes so you could just tilt it untill you got the correct voltage. This one has no way to adjust it. Is that the why L-98 TPS stuff is or do I have the wrong thing? Even if the TPS is wrong the engine should still start. This thing isn't even trying to start. It just turns over.
Talking about sensers. Funny thing about my TPS sensor. It dosn't have the slots in it to be adjusted. The old crossfire TPS had slots insted of holes so you could just tilt it untill you got the correct voltage. This one has no way to adjust it. Is that the why L-98 TPS stuff is or do I have the wrong thing? Even if the TPS is wrong the engine should still start. This thing isn't even trying to start. It just turns over.
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
Re: Vette won't start...Please help!!! (Phobos84)
Injectors are a valve that is actuated by a solenoid which opens the valve to allow gasoline to be sprayed into the intake. The ECM is a switch that for a short duration switches one terminal of the injector to ground which applies 12 v across the injector coil and makes the injector spray fuel. You will measure 12v on both terminals of the injector until you begin cranking the engine, and then one injector terminal will stay at 12v and the other terminal will be pulsed to ground by the ECM. A low power 12v lamp across the injector socket will prove that the injector coil is being pulsed by the ECM. It sounds like your injectors are not being pulsed by the ECM. The ECM requires information from the distributor, distributor reference pulses on the purple/white wire from the distributor. Check this wire for pulses when cranking. You don't smell any fuel because your injectors aren't being pulsed. Check your ECM 3 amp fuse with an ohmeter.
[Modified by jfb, 9:56 PM 6/15/2003]
[Modified by jfb, 9:56 PM 6/15/2003]
Race Director
Joined: Feb 1999
Posts: 12,772
Likes: 17
From: Indianapolis IN
Re: Vette won't start...Please help!!! (jfb)
Also, put anoher 5-gallons or more of good gas in, I was surprised at how long the bad gas over rode the good gas.
I drained down to # 2 gallons and put in 12 and it would start and then just not run well. It cant hurt!
I drained down to # 2 gallons and put in 12 and it would start and then just not run well. It cant hurt!
Thread Starter
Melting Slicks
Joined: Mar 2002
Posts: 2,876
Likes: 764
From: Sligo PA
Re: Vette won't start...Please help!!! (LaVidaLoca)
I still can't get the thing running. I pulled the distributor and made sure it was in right. It still won't start. Injectors are not getting any power at all now. I just don't get it. I put a test light in and it never came on. I put an ohm meter on the injector plug and it beeped. Meaning it completed the circuit. Is that supposed to happen? Could I have a short? I'm going to run leads from the fuse box and from the ECM to the injectors and see what happens.
Racer
Joined: Apr 2003
Posts: 260
Likes: 0
From: Palm Bay Fl
Re: Vette won't start...Please help!!! (Phobos84)
I think it would be almost impossible to see a 2-3mS pulse with an incandescent test light.
You can use a stethoscope to listen to see if you can hear the injectors click. Also, on early style TPI setups (or maybe all of them) they had a "cold start" injector to prime the engine with gas before it started. You might try just squirting some gas in your intake to see if it tries to fire.
-Dave C.
You can use a stethoscope to listen to see if you can hear the injectors click. Also, on early style TPI setups (or maybe all of them) they had a "cold start" injector to prime the engine with gas before it started. You might try just squirting some gas in your intake to see if it tries to fire.
-Dave C.
Pro
Joined: Jul 2002
Posts: 729
Likes: 4
From: Yukon OK
Re: Vette won't start...Please help!!! (Dave C. '97 Z28)
I think it would be almost impossible to see a 2-3mS pulse with an incandescent test light.
Regarding the check across the injector. Depending on the setting of your meter this will look like a short because the injector has a coil operated valve. A coil only has a couple of ohms of resistance so unless you have your meter set to the lowest setting you can't tell if it is shorted or not. Also; shorts in inductive (coil) circuits are pretty uncommon, more likely to open than to short.
