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Topic: Just a quick question...

in Forum: C4 Engines


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Just a quick question... (1/5)
 8/20/13 9:47pm
hafferf
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Columbia City, OR - USA

Vette(s):
1988 35th Anniversary Edition Corvette Coupe


Joined: 6/30/2013
Posts: 23

Howdy Folks!!...;
   Just a quickie... I've been slow but sure getting my 35th Anniversary up to speed. I just finished getting the tranny flushed a couple weeks ago, and the engine put back in time, as well as repairing the AC.  We're replacing the Fuel Pressure Regulator the 1st of the month. Somebody Bubu'd the valve by putting a bolt in it to try and regulate the pressure. It seems that she had set for a spell... and was told to get out and drive it and it would smooth out. But she's hard to start at temp. Cold she fires up instantly, but If I drive her till she's warmed up, you have to give her some accelerator to get her running. Then she runs OK. Could this be remedied by the new FPR valve? And no, we never found a vacuum leak.
    I've been asked if I'm going to do any Mods... I think probably not. My days of loud pipes and accessories to get the Babes are looooong over. I was after all, a child of th' "60's". I have something a little out of norm, and I think I'll leave her the way she was intended.
 
Thanks Folks for any replies
Fast Freddie


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USMC 64-67 RVN I Corps "66"
"Democracy is two wolves and a lamb voting on what to have for lunch. Liberty is a well-armed lamb contesting the vote."
Attributed to , Benjamin Franklin, 1759
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Re: Just a quick question... (2/5)
 8/21/13 7:33am
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

Hard start when hot can usually be caused by leaky injectors, but it your regulator is creating too much pressure, that could also create too much fuel getting thru the injectors. Go ahead and fix the regulator, and see if that helps with the hot start issue. IF it doesn't, then you may need to dig a little deeper, and see if the injectors are leaking.

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Re: Just a quick question... (3/5)
 8/21/13 10:15am
davep85c4
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Joined: 4/4/2009
Posts: 254

A fuel pressure regulator "with a bolt in it" is an adjustable fuel pressure regulator. Nothing wrong with them ( except they won't pass visual emissions inspection in California) if they are adjusted correctly. These AFPR's are often installed in conjunction with and aftermarket "chip" or PROM in the ECM. In order to achieve the desired performance gains, higher fuel pressure results in more fuel delivery, even if the injector is at maximum duration "on time".

Have you opened your ECM and inspected the PROM for a label? Stock GM PROMS have a 4-letter code on them. Aftermarket usually have the name of the supplier.  Some of your miladies may be arising from less-than optimum programing.

As far as determining whether a proper balance of fuel pressure, injector function, fuel delivery (pump), and O2 sensor feedback exists, drive and log it over various conditions. Look at BLM, or Long Term fuel trim on the scanner or log program. The 'perfect' center is 128. (128 is digitally in the middle of 1-255 which is the max value for an 8-bit binary number) A BLM that is less than 128 indicates the system is removing fuel (running rich) and a BLM greater than 128 indicates the system is adding fuel (running lean). Generally, BLM's will be within +/- less than 5 counts from 128.

If BLM varies too far rich or lean, over certain period of time, the Trouble Codes 44 (Lean) and Code 45 (Rich) are set, and the MIL is turned on during the time the problem exists.

Check your prom. Check the fuel pressure and compare to factory spec. Observe your BLM's.
Re: Just a quick question... (4/5)
 8/21/13 9:21pm
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

if the pressure is set too high, it will not start correctly when at running temp. i installed an adjustable regulator on my 90 and by mistake had set the pressure to high. went to store and when i got back in car it wouldn't start. let it cool down and when i came back to get the car it started right up.

when i got the car home, i found my mistake and reset pressure to the correct setting and haven't had a problem since.


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Re: Just a quick question... (5/5)
 8/22/13 1:17pm
hafferf
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Columbia City, OR - USA

Vette(s):
1988 35th Anniversary Edition Corvette Coupe


Joined: 6/30/2013
Posts: 23

Thank you all for your replies.
    That bolt in the FPR is not stock. As far as I know, 1988 did not have an adjustable FPR. and you can readily see that this bolt (and it hits the bottom of the plenum) is canted. Chevrolet (my local dealer) concurs, hence, I just ordered the FPR and gaskets from my favorite (well... one of them) internet Dealer. Now.... if I could just make my Targa Top Shade stay up where it belongs... and not droop down...;>(((  I may never get her to idle smoothly... I notice that a little rough idle is the norm for a lot of these C-4's (according to the various forums, this is a common problem).
    Again, thanks for the help... Thank goodness for these forums and members that will pitch in and try to help..Hug
Drive On!!...
Fast Freddie


______________
 
USMC 64-67 RVN I Corps "66"
"Democracy is two wolves and a lamb voting on what to have for lunch. Liberty is a well-armed lamb contesting the vote."
Attributed to , Benjamin Franklin, 1759
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