Hard Cold Start-Up... - Team Camaro Tech
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post #1 of 24 (permalink) Old Sep 4th, 00, 07:25 AM Thread Starter
 
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Hey all. I'm having a problem with my '89 L98 IROC. For quite a while now, the motor will turn over when I crank it, but it won't start for a good 10-15 seconds or so. If I crank it for a couple of seconds, stop, and then try again, it usually starts right up. But this is mostly only when it's cold. There is no smoke when it starts up, and it runs great once it's started.

That would lead me to believe that there's an oil pressure problem, but the oil gauge looks good when I turn the key. It Seems to build up normally and won't start even with good pressure - according to the in-car gauge.

Timing is set to 6 BDC, plugs are Bosch Platinums, the pick-up coil and ignition coil have both been replaced in the last year or so, and the wires are brand new. I haven't had a chance to get a hold of a fuel pressure gauge, so I'm not sure where I sit with that.

If anyone has any suggestions, I would greatly appreciate them. Thank you for your time. - John '89 L98
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post #2 of 24 (permalink) Old Sep 4th, 00, 10:42 AM
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You're on the right track now. I'd replace the fuel filter. Very easily done, takes longer to jack up the car. Precaution when changing filter is the orings at the end of the fuel lines. If they're damaged, they'll leak. So give them a good inspection.

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post #3 of 24 (permalink) Old Sep 4th, 00, 04:04 PM
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Does the fuel pump run like it should when you turn on the key? Something to check if so - a lot of these FI cars have a thing in the tank hooked to the fuel pump called a Pulsator. Has a diaphragm in it to smooth out fuel flow. This can get a hole or split in it and you lose fuel pressure. Takes a while to build up and bleeds off fast. Need to check the fuel pressure. An old AC gauge will hook up to the pressure tap on the fuel rail.
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post #4 of 24 (permalink) Old Sep 4th, 00, 05:47 PM
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John, Some of those cars had a 9th injector that was used for start-up and for cold enrichment and it is in the lower part of the intake that is bolted to the engine. I'm not sure what year that they were in, but they did get clogged. Does your engine have an extra fuel line that goes to the back of the engine?

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post #5 of 24 (permalink) Old Sep 4th, 00, 05:52 PM
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some cars had a seprate oil presuer sending unit for the computer
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post #6 of 24 (permalink) Old Sep 4th, 00, 06:07 PM
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I had an 89 IROC it had no cold start injector.
Be shure when you try to start the engine to first turn the key to on, then pause, count to four, then try to start.
The fuel pump is turned on by the computer for about three seconds to pressurize the system. If you try to start too soon you are just cranking with no fuel going into the engine because minimum injector firing pressure has not been reached yet.
If you don't hear the fuel pump run, there is a problem.
And keep your foot off the gas pedal of course.
David

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post #7 of 24 (permalink) Old Sep 4th, 00, 06:59 PM
 
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Your fuel pump should operate for 2 seconds when the ignition is turned on.
You can check if it does by having some one turn the key on while you're back near the tank and listen for it or if you have a test light connect it between the fuel pump test terminal and ground. The fuel pump test terminal on your ALDL connector under the instrument panel should be the lower left most terminal as you look at it.
If you don't hear the pump or have no light for 2 seconds, suspect the fuel pump relay.
If the fuel pump relay goes bad the fuel pump will be energized through an oil pressure switch. This means the engine has to be cranked till oil pressure builds enough to close the switch and turn the pump on, 10-15 seconds of cranking sounds a little long although even if the relay was bad.
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post #8 of 24 (permalink) Old Sep 5th, 00, 12:07 PM Thread Starter
 
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All right... Thanks to everyone for the replies so far, I guess I should add a little more to my story. I replaced the fuel pump (and filter) about 6 months ago because I honestly thought that was the problem. It wasn't.

When the key is turned just prior to cranking, I can hear the fuel pump running for its usual 2-3 seconds, although it can sometimes take up to 7-8 seconds. No matter how long I wait after the system pressurizes and before cranking, it does the same thing.

So... I don't think it's the fuel pump, I'm certain it's not the fuel pump relay, (although the symptoms are similar to what a faultly relay would result in), and because GM did away with the 9th injector prior to '89, it can't be the problem. Any other suggestions? Thanks again. - John '89 L98
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post #9 of 24 (permalink) Old Sep 5th, 00, 01:00 PM
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Okay, so once the engine starts, while it's in open loop operation, the engine idles good.

How does it run once the engine goes into closed loop (operating temp)?? Do you notice any bogging when you floor it?? Erratic idle (hunting)??

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post #10 of 24 (permalink) Old Sep 5th, 00, 08:46 PM Thread Starter
 
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The engine runs fine once it starts. It doesn't matter if it's in open or closed mode. In fact, I just took it out to Cedar Point last week. Everything, as usual, was fine - except for the hard starting. - John '89 L98
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post #11 of 24 (permalink) Old Sep 6th, 00, 12:41 PM
 
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I had a similar problem with my 86. I replaced the in-tank fuel pump and it cured the problem. Turns out the pump wasn't holding pressure.

Good luck.....
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post #12 of 24 (permalink) Old Sep 7th, 00, 05:15 PM
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John, can you have someone hook a scan tool to it while it is cool to check to see if the temp sensor is telling the computer that the engine is cold? If the sensor is telling the computer it is warm, it will be hard to start cause it will be lean.

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post #13 of 24 (permalink) Old Sep 8th, 00, 12:56 PM Thread Starter
 
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That's a good idea, Chev. I check out as soon as I get back to the garage, which should be tomorrow morning. I'll let you know what happens. In the mean time, any other suggestions? Thanks again. - John '89 L98
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post #14 of 24 (permalink) Old Sep 9th, 00, 04:23 PM Thread Starter
 
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All right... I didn't get a chance to check out the temp sending unit, but I did get my hands on a way to check fuel pressure. Here's what I have:

When I turn the key, pressure is immediately up to 48PSI while the fuel pump is running. While I'm cranking, pressure sets at around 40PSI, and as soon as I shut the car off, pressure starts to quickly drop off.

It takes 8 seconds for it to drop to 30PSI, 15 seconds for it to drop to 20PSI, 33 seconds for it to reach 15PSI, and 58 seconds for it to get down to 10PSI.

It seems a little quick, if you ask me - especially for a new fuel pump, but I'm not sure this is where my problem lies. I say this because I can try to start the car while pressure is anywhere between 50 and 40PSI, and I get no start until I let up and try again.

Argh... Any ideas? Thanks again. - John '89 L98
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post #15 of 24 (permalink) Old Sep 9th, 00, 06:12 PM
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did you ever change the regulator on it?it might be pushing it straight through. i cant remeber it has been a couple of years since i went to school for cars butt it could be loading the lines with air when you shut it off and let it sit ...if you shut it off will it start right back up? if so i would look at the regulator. you should be able to change the fuel pressure with a vacume pump on the regulator and reading the guage on the fuel rail

[This message has been edited by DEVIL'S LAKE (edited 09-09-2000).]

[This message has been edited by DEVIL'S LAKE (edited 09-09-2000).]
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