Desperate...I need help?
Thread Starter
Safety Car
Joined: Feb 2003
Posts: 3,848
Likes: 95
From: Springfield MO
Desperate...I need help?
Ok here's the breakdown: with my recent starting problems i've checked and replaced the Fuel pump, fuel filter, Ign. module, and also recently added new plug wires. The car still starts and dies immediately after firing. I am running out of money, time and patience. Can anyone help? :banghead: Thanks for any info.
Le Mans Master
Joined: May 2003
Posts: 5,362
Likes: 3
From: Delray Beach FL
Re: Desperate...I need help? (JJ 86)
What about the coil? I had the coil go out and the car would crank, try to fire and die. My coil then shorted out the ignition control module. Have you checked the cap and rotor? You may have a crack in the cap. These are all inexpensive parts that shouldn't break the bank for ya. :smash:
:cheers:
:cheers:
Thread Starter
Safety Car
Joined: Feb 2003
Posts: 3,848
Likes: 95
From: Springfield MO
Re: Desperate...I need help? (Whitvette)
Thanks for the reply. I haven't thought about the coil or even the cap. Rotor looked good when i put in the module. I'll try to replace these next since it wouldn't hurt. Also the new fuel pump works good as you can hear it running and the pressure is good. If it were the relay would the fuel pump still run? :confused:
Melting Slicks
Joined: Jul 2003
Posts: 2,384
Likes: 124
From: Reno/Sparks Nevada
Re: Desperate...I need help? (JJ 86)
Just a guess, but is it dying when cold or hot. If you have an '86 you should have a cold start injector with a temp sensor on the front of the intake manifold. This sensor sends a temp. signal to the computer to pulse the cold start injector to add fuel during startup. It could be it's not getting enough fuel. I don't think there is a code if the sensor fails or the injector is not adding fuel. I'm still thinking what else could be the problem that doesn't set a code. Obviously, fuel pressure is not monitored by the computer nor is the ignition. Both these areas should be looked at closely for malfunction. :rolleyes:
Team Owner
Joined: Aug 2000
Posts: 40,156
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From: San Pedro CA
Re: Desperate...I need help? (JJ 86)
Thanks for the reply. I haven't thought about the coil or even the cap. Rotor looked good when i put in the module. I'll try to replace these next since it wouldn't hurt. Also the new fuel pump works good as you can hear it running and the pressure is good. If it were the relay would the fuel pump still run? :confused:
the fuel pump relay is wired in parallel with the oil pressure switch. Once the engine gets 4psi reading from the oil pressure switch, it will start, even with a faulty fuel pump relay.
however, if you have a lazy oil pressure switch.... see?
If nothing else, this will make starting hard, cause you won't have fuel pressure as soon as you turn the key. So it is depending on enough fuel in the lines to fire it up long enough to get 4 psi. That will take some karma!
check to make sure the pump is coming on when the key is turned. you will need a friend. someone to turn the key. take the gas cap off and listen carefully. you may want to use a screwdriver as a stethoscope... you can rest the tip of the screwdriver on the tank, and put your ear to the handle. listen for the vibration of a working pump.
good luck!
:cheers:
Melting Slicks
Joined: Jul 2003
Posts: 2,384
Likes: 124
From: Reno/Sparks Nevada
Re: Desperate...I need help? (bogus)
You should be able to hear the pump pressurize the fuel rail and shut off a few seconds later. The relay click and the pressurization is loud enough to be heard with the hood open especially if this is the first start of the day. An assistant is handy for this but if one is not available, you should be able to hear it. Make sure the AC is off or you might hear the clutch instead. A fuel pressure gauge is even better, you can see the pressure rise as the key is turned to on but not to start. As mentioned, during crank mode the oil pressure switch closes allowing current to flow to the fuel pump resulting in delayed starting. I think fuel pump relay function can also be checked at the ALDL connector under the dash, but I think you'll need the factory service manual to check the procedure. :seeya
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From: North Yorkshire, England
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Re: Desperate...I need help? (MrRenoman)
This sensor sends a temp. signal to the computer to pulse the cold start injector to add fuel during startup.
This statement is incorrect regardless of whether you are talking about the Thermo-Time Switch or Coolant Temperature Sensor, both located at the front of the intake. If you are talking about the Cold Start Injector's (CSI's) Thermo-Time switch, there is no connection to the ECM. If you are talking about the Coolant Temperature Sensor (CTS), it does send a temp. signal to the computer, but it has nothing to do with the CSI system. The computer on CSI cars has no control over CSI operation. It gets its power through the Crank Fuse and its control signal from the Thermo-Time Switch. That's all that's involved except wiring.
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Melting Slicks
Joined: Jul 2003
Posts: 2,384
Likes: 124
From: Reno/Sparks Nevada
Re: Desperate...I need help? (Ray Quayle)
Thanks Ray. Ray is correct, I was pulling this info from memory. The sensor is a thermo time switch and is not connected to the ECM. What is still baffling is what is causing his no start. I'm still wondering if the CSI is not functioning properly.
:cheers:
:cheers:
Team Owner
Joined: Jun 2002
Posts: 21,510
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From: On a Wisconsin Death Trip
Re: Desperate...I need help? (MrRenoman)
Quote:
it turned out to be the MAF
The Hobbit is right. The MAF will do this. As for the fuel debate, you shouldbe able to put a fuel pressure gauge on the rail and see if this is your problem. If the car dies and there is still pressure in the rail you're golden there. If it has spark and fuel it should run. Well it runs but it shuts down so something is shutting it down. Check sensors that make the car run at start up such as the MAF. Good luck. :seeya
Check this out: http://forums.corvetteforum.com/zerothread?id=254000
[Modified by loiq, 4:41 PM 8/22/2003]
it turned out to be the MAF
The Hobbit is right. The MAF will do this. As for the fuel debate, you shouldbe able to put a fuel pressure gauge on the rail and see if this is your problem. If the car dies and there is still pressure in the rail you're golden there. If it has spark and fuel it should run. Well it runs but it shuts down so something is shutting it down. Check sensors that make the car run at start up such as the MAF. Good luck. :seeya
Check this out: http://forums.corvetteforum.com/zerothread?id=254000
[Modified by loiq, 4:41 PM 8/22/2003]
Thread Starter
Safety Car
Joined: Feb 2003
Posts: 3,848
Likes: 95
From: Springfield MO
Re: Desperate...I need help? (loiq)
Ok i unpluged the MAF and then tried to start and it would just do the same thing. Nothing changed. Also i don't get a check engine light, so having done this could the MAF still be bad? Also what others sensors make the car run? and finally where is the idle set screw located? Thanks
Thread Starter
Safety Car
Joined: Feb 2003
Posts: 3,848
Likes: 95
From: Springfield MO
Re: Desperate...I need help? (daddvi)
Mass Air Flow. its a sensor that is located between the throttle body and the air filter assembly on 85-89 tpi and also on 94-96 lt1/4 cars. :thumbs:
Melting Slicks
Joined: Jun 2002
Posts: 2,168
Likes: 16
From: Phoenix AZ
Re: Desperate...I need help? (JJ 86)
JJ, check the connector at the MAF relays behind the battery. On my '86 the wire insulation had eroded near the connector and the wires were shorting out, causing what you are describing. It wasn't until it shorted badly enough to set a code 34 that I started lookingat the MAF circuit... :banghead:
Thread Starter
Safety Car
Joined: Feb 2003
Posts: 3,848
Likes: 95
From: Springfield MO
Re: Desperate...I need help? (vetracer)
finally something worked. I replaced the burnoff relay, and power relay. At first tried to start the car it still did the samething. Here's the strange part it would not start until i unplugged the MAF sensor, then it started very rough at first but it ran. So i plugged it back in to see if it would start with it plugged up and it did. Then i get a check engine light. I removed the neg. cable to reset the computer and when i started it up it ran like a charm with no warning lights is it fixed or do i still need to replace the MAF sensor?
It finally runs!! :hurray:
P.S. Thanks to all those who helped, it saved me a ton of $$$$
It finally runs!! :hurray:
P.S. Thanks to all those who helped, it saved me a ton of $$$$
Drifting
Joined: Oct 1999
Posts: 1,722
Likes: 0
From: Gloucester Va
Re: Desperate...I need help? (vetracer)
chances are your MAF is good. The burn off relay is mst likely the problem/was. IF it does not do it's job then the MAF can't do its. It burns off build up from the air that collects on the wire inside the mAF. If this does not happen then the MAF will not function. Just remember one thing the ECM doesn't always set a code fo a problem. And anytime you have a starting problem always check the MAF first. Just unplug it and try to start it. It's so easy/cheap/ and fast. It that doesn't work then move on.
But it's noce to hear you got it runnning again.
But it's noce to hear you got it runnning again.
Thread Starter
Safety Car
Joined: Feb 2003
Posts: 3,848
Likes: 95
From: Springfield MO
Re: Desperate...I need help? (vetracer)
The wiring connectors looked good so i just replaced both sensors and that did it. It feels really good to finally have her back on the road again. Thanks everyone for all your help. :party: