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Topic: Starting Quirk 1986 Coupe

in Forum: C4 Engines


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Starting Quirk 1986 Coupe (1/14)
 5/7/11 12:41am
jeffjets55
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Campbell, CA - USA

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.


Joined: 8/6/2009
Posts: 13

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 (2/14)
 5/7/11 7:01am
eddie20890
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lanoka harbor, NJ - USA

Vette(s):
1990 L-98 white/ red/black leather interior targa top auto 1975 L48 blue/black leather interior t tops auto


Joined: 3/22/2009
Posts: 1363

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.



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the dynamic duo


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Starting Quirk 1986 Coupe (3/14)
 5/7/11 10:48am
Adams' Apple
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Duncanville, TX - USA

Vette(s):
1985 Coupe-L98/Auto,Bright Red/Carmine. 1974 Coupe-L48/4speed, Medium Red Metallic/Black Deluxe.


Joined: 3/18/2009
Posts: 2230

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 (4/14)
 5/8/11 6:27pm
The Car Whisperer
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Andover, MA - USA

Vette(s):
1986 Coupe


Joined: 3/22/2009
Posts: 50

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.

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Automatic, Bilsteins - "Mostly Original" otherwise.

Starting Quirk 1986 Coupe (5/14)
 5/11/11 5:49pm
jeffjets55
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Campbell, CA - USA

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.


Joined: 8/6/2009
Posts: 13

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 (6/14)
 5/17/11 11:12am
Drew
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Newnan, GA - USA

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1991 Corvette Arctic White with Black GS style wheels Over 229,000 miles!


Joined: 1/11/2010
Posts: 15

I think the above recommendations are probably the most valid, just don't forget about the fuel filter...
Starting Quirk 1986 Coupe (7/14)
 7/16/11 2:47am
jeffjets55
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Campbell, CA - USA

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.


Joined: 8/6/2009
Posts: 13

[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 (8/14)
 7/16/11 2:53am
jeffjets55
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Campbell, CA - USA

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.


Joined: 8/6/2009
Posts: 13

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 (9/14)
 7/16/11 6:38am
eddie20890
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lanoka harbor, NJ - USA

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1990 L-98 white/ red/black leather interior targa top auto 1975 L48 blue/black leather interior t tops auto


Joined: 3/22/2009
Posts: 1363

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.

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the dynamic duo


c3vr life member #97
Starting Quirk 1986 Coupe (10/14)
 7/17/11 9:48am
jeffjets55
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Campbell, CA - USA

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.


Joined: 8/6/2009
Posts: 13


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.
Starting Quirk 1986 Coupe (11/14)
 7/17/11 12:04pm
eddie20890
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lanoka harbor, NJ - USA

Vette(s):
1990 L-98 white/ red/black leather interior targa top auto 1975 L48 blue/black leather interior t tops auto


Joined: 3/22/2009
Posts: 1363

the number 8 in the vin is for the base model engine which is the L98.  the "9th" injectoer is located on the driver's side runner in between the 2nd and third tube. might just be another injector that only activates when cold, not sure as my 90 does not have one.

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the dynamic duo


c3vr life member #97
Starting Quirk 1986 Coupe (12/14)
 7/20/11 2:53pm
Tpflyer
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Southwick, MA - USA

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1988 35th Anniversary Edition 3,000 miles 2000 Torch Red Convertible 2006 Velocity yellow Z06


Joined: 1/30/2010
Posts: 4

Starting Quirk 1986 Coupe (13/14)
 7/21/11 1:59pm
SAYWHEN
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Joined: 2/26/2011
Posts: 82

[QUOTE=jeffjets55]

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.[/QUOTE]
I don't believe the cold start injector is available any more new. I suspect what you're seeing for sale" cold start switch" is also known as a thermo time switch. This switch contols when and how long the cold start injector is activated depending on temperature. There should be a procedure in your FSM for checking the "cold start" circuit. IMO the thermo time switch gave more trouble then the cold start injector itself--which is likely why the "switch" is still available.
 
OR there are online "tuners" (likely some are vendors here) who can "delete" the need for a cold start injector by reprogramming your ECM making yours much the same as the later L98s. GM stopped using the cold start valve in '89. From "89 and forward all fuel enrichment.... cold through hot start was done by the ECM which monitors the ECT (coolant sensor).
SAYWHEN2011-07-21 11:00:17
Re: Starting Quirk 1986 Coupe (14/14)
 8/12/13 9:26pm
TVaitonis
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Rochester, NY - USA

Vette(s):
1987 Coupe Red and red, Z52


Joined: 8/20/2011
Posts: 60

Thought I'd dust off this old post to find if there's been any new info for harder starting when warm. In the morning I don't think mine cranks over a whole rev and she lights. Great...ready for the day. Then when I leave the office and turn her over there's usually 3 - 5 seconds of cranking and when I release the key she'll catch and stumble to life. Runs just fine after that. Funny how just as I'm thinking of giving the starter a rest like clockwork the engine lights just as I release the key.
I've checked out the cold start thermo switch prices and that's nuts what they get for those. I don't mind spending $15- $20 to try out a hunch but at $130 for the thermo switch, I want to be pretty sure I get good results. I don't see any harm in disconnecting the 9th injector during the warm months. If seems to lead somewhere I might even wire in an under dash switch to enable/disable the cold start circuit. Anybody had a problem with the ignition switch itself that caused symtoms like those?
Just one of the small bugs in my otherwise good '87.

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