Re: Starting problem.. 1989 C4 (jfb)
Wet plugs don't always show up with a leaking injector. When the air/fuel is way too rich, the engine won't start easily. Also, your problem is intermittent and looking ONCE doesn't prove you don't have a leaky injector. And, a leaky injector also doesn't necessarily lower the fuel pressure, so your test by turning on the fuel pump for 5 seconds isn't conclusive. Spend the money and prove beyond the shadow of doubt by actual fuel pressure measurement that your injectors are or are not leaking. Check your initial spark timing, and check each spark plug wire with your timing light to prove that each plug is firing. A vacuum leak will make it hard to start. Measure your manifold vacuum, look for vacuum leaks on ALL of your vacuum lines. Do you have any stored error codes? Check them. What is your TPS (throttle position sensor ) voltage? A stuck EGR valve can cause too low air/fuel ratio during cranking and hard starting. A defective MAF sensor can cause hard starting, try disconnecting it and attempt a start. Put a low power 12v lamp across each injector socket and observe that each is being pulsed when you crank the engine. Let us know what you find. Skip |
Re: Starting problem.. 1989 C4 (SkipI)
Skip, don't feel bad about getting a fuel pressure guage. I know you're probably thinking "I've spent enough money and time on this stupid problem" but believe me, you will find that the guage is actually quite useful for more than just this problem.
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Re: Starting problem.. 1989 C4 (SkipI)
Intermittent hard starting can also be caused by a spark control module. I had that problem and replaced it.
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Re: Starting problem.. 1989 C4 (jfb)
Intermittent hard starting can also be caused by a spark control module. I had that problem and replaced it. |
Re: Starting problem.. 1989 C4 (TheCorvetteKid)
Some auto parts stores can test spark modules, but since you have an intermittent problem, and who knows what the tester is looking for, I would recommend installing a new one since they aren't very expensive. When mine was giving me trouble, about 80% of my starts were long cranks.
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Re: Starting problem.. 1989 C4 (SkipI)
My '89 was a hard start (cold) from the factory. Fuel pressure was normal - An injector balance test was normal (yeah I bought the tool that pulses each injector so you can note the pressure drop on your gauge) - and I replaced a ton of stuff over the years trying to improve it. Finally put in new injectors (Accels) and it fires right up. I even had Rich at Cruzin Performance look at the old ones and he couldn't find anything wrong with them. Go figure.
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Re: Starting problem.. 1989 C4 (jfb)
Some auto parts stores can test spark modules, but since you have an intermittent problem, and who knows what the tester is looking for, I would recommend installing a new one since they aren't very expensive. When mine was giving me trouble, about 80% of my starts were long cranks. Skip |
Re: Starting problem.. 1989 C4 (SkipI)
Yes, I am talking about the module in the distributor that pulses the spark coil.
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Re: Starting problem.. 1989 C4 (SkipI)
I am having a problem with my 89 vette. The engine takes anywhere from 5-8 seconds to start when cranking. Here is what I have done... new plugs, wires, fuel pump relay, dist. cap, rotor, and verified good timing. I have not checked fuel pressure because I don't want to spend $50 for a gage to use only once... instead, I jumpered the fuel pump on and cranked after 5 seconds of fuel pump run... no difference. I placed a timing light on the car and verified I had sparks while cranking... the light flashed fine. So, it is not the fuel pump, nor the spark plugs. I could place a test light on an injector to see if they are working? After it starts it purrs like a kitten all the time. It runs strong and without missing or any other problem. HELP!! Thanks, Skip |
Re: Starting problem.. 1989 C4 (blackvette89)
My 89 had similar cold start problem. I literally went thrugh a starter. after replacing fuel pump, temp sensor (controls air/gas ratio) IAC, relays, the problem was the ECM itself and it threw no codes. I haven't had the problem since! I hope you find it, I know your frustrations. When you replaced your ECM, did you replace the MemCal (the chip) as well? I have a spare ECM for my car, but it doesn't have a MemCal unit - I'm supposed to reuse the one that's in ECM in the car now. [Modified by TheCorvetteKid, 5:47 PM 6/13/2003] |
Re: Starting problem.. 1989 C4 (TheCorvetteKid)
i used my old prom. so far it starts every shot. only problem is my fan only comes on at 236. i've been asking around for input on if this is normal. it used to come on at 228! or so. how bout yours?? :cheers:
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Re: Starting problem.. 1989 C4 (blackvette89)
The factory prom turns on the fan at 228 F. 236 might just be a sensor error.
It looks like you found the problem, the ECM. |
Re: Starting problem.. 1989 C4 (SkipI)
I had asimilar problem on my 89 with an intermittent hard start and failure to start at times. Replaced most of parts mentioned here and finally the ecm. Solved the problem and hasn't missed a lick for over a year. Good luck. You should see if the injectors are being pulsed during the first 5 seconds of cranking but not starting. If not ecm could be the source of your frustration. :)
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Re: Starting problem.. 1989 C4 (jfb)
i bought a low temp sensor on at 200 off at 185 i'm goona see if it does the trick! i'll keeo you posted. just to be sure, this sensor is located on pas side of block?? :cheers:
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Re: Starting problem.. 1989 C4 (blackvette89)
I bought a low temp sensor on at 200 off at 185 i'm goona see if it does the trick! I'll keeo you posted. Just to be sure, this sensor is located on pas side of block?? :cheers: It's funny that you mention this problem actually 'cause my car started doing the same thing. I still haven't tried to swap out my ECM to see if it cures my hard starting problem (I have a few other issues with the car that I am trying to address first) but after I took the heads off to change the headgaskets, I noticed that my fans have also beem coming on later than before. And at the same temps that you mention too. Funny thing is, I've checked my existing temp sensor and it seems fine. Hmmm...makes me wonder what this could be. [Modified by TheCorvetteKid, 12:00 AM 6/15/2003] |
Re: Starting problem.. 1989 C4 (SkipI)
As troubleshooting continues... I have noticed that when I attempt to start the engine and stop cranking before it starts, every time I begin my second attempt, the engine starts immediately. The new ignition module made no difference.
Skip |
Re: Starting problem.. 1989 C4 (SkipI)
As troubleshooting continues... I have noticed that when I attempt to start the engine and stop cranking before it starts, every time I begin my second attempt, the engine starts immediately. The new ignition module made no difference. Skip I guess there's only 2 things it can be: either the oil pressure switch or the ECM. Even though I have a spare ECM at home, I have the valve covers off and the rocker arms out of my car right now so I can't even swap out my ECM just to try; consequently changing the oil pressure switch wouldn't do any good either right now. The oil pressure switch is fairly inexpensive and not too difficult to change (it's right next to the distributor and bolts straight into the top of the engine block). A rebuilt ECM is about $99-$150 from MidAmerica and is a worthwhile thing to have even if your current one is actually OK. Continue with the diagnosis. All us hard-starting '89 owners are watching and waiting... |
Re: Starting problem.. 1989 C4 (SkipI)
If it is annoying enough, maybe a call to Gordon Killebrew is in order.
http://www.gordonkillebrew.com/pages/800737/index.htm |
Re: Starting problem.. 1989 C4 (TheCorvetteKid)
I guess there's only 2 things it can be: either the oil pressure switch or the ECM. Even though I have a spare ECM at home, I have the valve covers off and the rocker arms out of my car right now so I can't even swap out my ECM just to try; consequently changing the oil pressure switch wouldn't do any good either right now. |
Re: Starting problem.. 1989 C4 (SkipI)
I have the same problem also, car is a 88, Just put new motor in and it still is hard to start when hot. when cold it fires instantally. I've put one of the small fuel pressure gauges on and it stays hooked up all the time. It does show a presure drop, so I guess new injectors are in order,
:banghead: :banghead: :banghead: :mad |
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