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Topic: Starting Quirk 1986 Coupe

in Forum: C4 Engines


Starting Quirk 1986 Coupe

Posted: 5/6/11 9:41pm Message 1 of 14
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Campbell, CA - USA
Joined: 8/6/2009
Posts: 13
Vette(s): I own one 1986 C4 coupe in like new condition with 30k miles. I own a second C4 convertable with 100k miles I am restoring.
I have a 1986 Coupe in cherry condition with only 30K.  I recently broke down about 100 miles from home and had to have he car towed to a GM dealership. The problem was found to be the fuel pump which was replaced. 
The first start of the day the engine turns over and starts right up normally.  The car runs beautifully and strong with no hesitation.  It has a weird quirk however.  After every drive when the car needs to be started again it always starts but the turnover time takes longer than the first start of the day up until it sometimes takes 10-15 seconds of the engine turning over before it starts.  It always starts though.  Any member have any ideas what could be causing these longer engine turnovers before it starts? 



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Starting Quirk 1986 Coupe

Posted: 5/7/11 4:01am Message 2 of 14
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lanoka harbor, NJ - USA
Joined: 3/22/2009
Posts: 1363
Vette(s): 1990 L-98 white/ red/black leather interior targa top auto 1975 L48 blue/black leather interior t tops auto

strange as it may seem maybe there is a problem with the fuel pump that was installed. i can imagine what t cost to have gm do it and if the problem wasn't there before i would take it back to them.






















the dynamic duo


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Starting Quirk 1986 Coupe

Posted: 5/7/11 7:48am Message 3 of 14
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Duncanville, TX - USA
Joined: 3/18/2009
Posts: 2248
Vette(s): 1985 Coupe-L98/Auto,Bright Red/Carmine. 1974 Coupe-L48/4speed, Medium Red Metallic/Black Deluxe.
Perhaps there is a problem with the fuel pump relay. If the relay doesn't close, or the contacts aren't allowing enough voltage across, the pump will not run until the oil pressure comes up. It's a redundant system. If the oil pressure goes below a specified pressure, it turns the fuel pump off, keeping you from driving the car with no oil pressure. My '85 suffers from the same malady....I'm just too lazy to fix it, since it does always start after a few seconds. I'm just not sure if my issue is with the pump relay, or the oil pressure sender unit.
It's just another idea that could be checked.



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Starting Quirk 1986 Coupe

Posted: 5/8/11 3:27pm Message 4 of 14
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Andover, MA - USA
Joined: 3/22/2009
Posts: 50
Vette(s): 1986 Coupe
I had this very same issue a few years back.  Would start fine when it sat overnight, but hard to start again afterwards that day.  I had recenetly changed the spark plugs at that time and noticed that one was wet, not with oil but with gasoline.  Immediately thought it was a leaky fuel injector.  I soon after replaced the injectors and no more problem starting.  Starts up immediately and also runs stronger now.  Sometimes the fuel injectors build up varnish on the pintle and do not close all the way, reulting in a gas leak into the intake runner.  If your 1986 has the original fuel injectors this could very well be the problem.  There is also a ninth injector on the 1986, that's the "Cold Start Valve".  That could be leaking, or the sensor that allows it to open when cold may be malfunctioning and allowing it to open when it shouldn't or possibly not allowing it to open if needed, like when the engine may be warm but not warm enough to start without the extra fuel it injects.  Kind of like a choke on a carburator.  Hope this helps you find the problem.  Let us know how it works out.


1986 "Bright Red" COUPE - Aluminum Heads,
Sport Seats, Bose, Ultra-Flo Exhaust,

Automatic, Bilsteins - "Mostly Original" otherwise.

Starting Quirk 1986 Coupe

Posted: 5/11/11 2:49pm Message 5 of 14
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Campbell, CA - USA
Joined: 8/6/2009
Posts: 13
Vette(s): I own one 1986 C4 coupe in like new condition with 30k miles. I own a second C4 convertable with 100k miles I am restoring.
Thanks to you all for your suggestions.  I think I will start by installing new injectors and spark plugs. If that doesn't work then I'll look at the fuel pump relay.  I don't think it has anything to do with the oil pressure though but maybe.
Regards,
Jeffjets55



Starting Quirk 1986 Coupe

Posted: 5/17/11 8:12am Message 6 of 14
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Newnan, GA - USA
Joined: 1/11/2010
Posts: 15
Vette(s): 1991 Corvette Arctic White with Black GS style wheels Over 229,000 miles!
I think the above recommendations are probably the most valid, just don't forget about the fuel filter...


Starting Quirk 1986 Coupe

Posted: 7/15/11 11:47pm Message 7 of 14
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Campbell, CA - USA
Joined: 8/6/2009
Posts: 13
Vette(s): I own one 1986 C4 coupe in like new condition with 30k miles. I own a second C4 convertable with 100k miles I am restoring.
[QUOTE=The Car Whisperer]I had this very same issue a few years back.  Would start fine when it sat overnight, but hard to start again afterwards that day.  I had recenetly changed the spark plugs at that time and noticed that one was wet, not with oil but with gasoline.  Immediately thought it was a leaky fuel injector.  I soon after replaced the injectors and no more problem starting.  Starts up immediately and also runs stronger now.  Sometimes the fuel injectors build up varnish on the pintle and do not close all the way, reulting in a gas leak into the intake runner.  If your 1986 has the original fuel injectors this could very well be the problem.  There is also a ninth injector on the 1986, that's the "Cold Start Valve".  That could be leaking, or the sensor that allows it to open when cold may be malfunctioning and allowing it to open when it shouldn't or possibly not allowing it to open if needed, like when the engine may be warm but not warm enough to start without the extra fuel it injects.  Kind of like a choke on a carburator.  Hope this helps you find the problem.  Let us know how it works out.[/QUOTE]


Starting Quirk 1986 Coupe

Posted: 7/15/11 11:53pm Message 8 of 14
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Campbell, CA - USA
Joined: 8/6/2009
Posts: 13
Vette(s): I own one 1986 C4 coupe in like new condition with 30k miles. I own a second C4 convertable with 100k miles I am restoring.

I am finally getting around to address this problem and am going to buy new spark plugs, the injectors and the "cold start valve" from Ecklers. Is the cold start valve really a switch as Excklers calls it?  Would you be inclined to buy the 24 lbs/hr or the 30 lbs/hr injectors? I do appreciate the advice you have given me so far.




Starting Quirk 1986 Coupe

Posted: 7/16/11 3:38am Message 9 of 14
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lanoka harbor, NJ - USA
Joined: 3/22/2009
Posts: 1363
Vette(s): 1990 L-98 white/ red/black leather interior targa top auto 1975 L48 blue/black leather interior t tops auto
i would get the injectors that the car calls for. my 90 calls for 22# injectors and i installed 24#. was told after a while that eventually it would burn out catalytic converter. besides that the computer can make adjustments at an idle for the extra fuel but at higher speeds it cant adjust it as fast and you wind up using more gas which these days means a lot of money wasted. the only way i can think of to get around that problem would be to have the computer updated with the higher pound injectors.




















the dynamic duo


c3vr life member #97

Starting Quirk 1986 Coupe

Posted: 7/17/11 6:48am Message 10 of 14
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Campbell, CA - USA
Joined: 8/6/2009
Posts: 13
Vette(s): I own one 1986 C4 coupe in like new condition with 30k miles. I own a second C4 convertable with 100k miles I am restoring.

Yes, I just bought a set of new 22 psi Borsch injectors on Ebay. FYI, the seller said look the VIN. If the eighth digit is an 8 the 22 psi injector will be the exact replacement required and matches the OEM injector. I'm having a hard time finding the ninth injector you refer to as the cold start injector. Is it a switch?  i found a cold start switch. Is this what I need? I also bought an upgraded fuel filter too.


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