I just got a 1985 Corvette with 101k miles.. Ive noticed 1. When the car is warm and i go to shut it off sometimes it i have to crank it over longer in before she will start.. Im not sure what is causing that... 2. When the car is running sitting still there is a clapping sound coming from, sounds like mid car, but goes away while im driving or when i give it gas. The guy said it started doing that when he got the starter replaced.. Im not sure what it could be..

Any advice or suggestions are greatly appreciated.. Thanks.

 

1) Get a fuel pressure gauge. Many parts stores will loan one to you, or purchase one. Check the fuel pressure by hooking up the gauge to the Schrader valve on the passenger side of the fuel rail. There should be a cap on this valve. When you remove the cap it will look like a tire valve. Attach the gauge here. Then turn on the key (don't start the car) and watch the gauge. The pressure should build to about 39-42 pounds and hold. If the pressure drops to zero quickly, then the check valve in the fuel pump is bad. Replace the pump, If this is not the case.....get back to us.

2) Need additional information. Automatic or manual? Guessing automatic. If an automatic, remove the cover over the converter area and check the three bolts holding the converter to the flex plate.

 

it is automatic, and Ill be doing that this weekend seen how im going to my buddies to put it on a 2 post lift

 

My 85 would only just show 30 psi when it had the standard fuel pressure regulator, i put an adjustable one on cause the vette loves around 45 psi.

Even so it ran fine at 30 psi remember the 85 has 24lb injectors standard.

When you have the fuel pressure gauge, check how quickly the pressure drops, one or more of the injectors may be leaking.

For the car to start and run as it should all sensors should show correct, and idle screw not be messed with without going thru the base idle setup.

 

Im new to all this Corvette stuff. This is my First Corvette. so Im learning as I go

 

Welcome to the Forum. PM sent to you.

 

Welcome to the madness


That's the way to get some work done!

 

Well Filled her up with 93 and put Lucas Injector cleaner in it today. Rough idle is gone, Still having the starting issue to where it takes longer cranking over before she will start. Fuel pressure is good, at an idle its at 33-34PSI. with just key on with the car off its at 38. Found out the Flex plate was tapping the start ever so slightly, Shimmed it today that went away. but there is still a noise that is pretty loud that sounds like a flex plate noise. Pull the inspection cover check the torque converter bolts, they were tight. Then was turning over the engine by hand inspecting the Flex plate, Found a 1/8 crack in it going towards the crank. Which is the cause of the noise. So the transmission is coming out next weekend and new Flex plate is going in. Also going to do a Fuel filter while the tranny is out.



Also found out im going to need a new rear tire... 271$ a tire.

 

If the tires are stock size, $271 per tire sounds pretty high. Might want to check out www.discounttire.com. I've gotten to the point where I buy tires for both Vettes and the Honda turd car from them, I've always gotten great service and the prices are good. Hopefully there will be one in your area (no, I don't work for them, I'm just a typical broke Vette lover).
Mark

 

If you're charged $271.00 for just one tire, be sure to have a cigarette afterwards because you just got f-cked! Seriously....you can get them for a whole lot less. Maybe $110.00 to $160.00 tires can be found unless you are looking for something special.

 

My 85 used to require a lot of cranking after being shut off for ten to fifteen minutes when it was fully warmed up. New injectors eliminated the problem.

 

I just picked up a set of Stock rims and Brand new tires with less than 200 miles on them for 300$ today untill i get new tires for my 17's

 

I got a long crank from my 85....it was bad oil/valve leaking on cylinder 3, 5, wild crazy compression numbers all over the cylinders, and 98-100psi on cylinder #8. It has since stopped moving(the whole car), and an L31-R is on the way

Seriously tho, age and not using something is just as bad as driving it too much. I should have pressure tested earlier, and the cylinders leaking that much oil just isn't good either.

115k, time, flat tappets.

 

My 85 requires alot of cranking if I don't override the injectors.

I should say, the first start of the day is fine, and normal... but any time after that, I automatically put the gas peddle all the way down and crank and soon as it catches.... I lift (as to not over rev). Put the peddle down turns off the injectors so they are not flooding the car.

 

I fought this one for many years and was not happy about it. two fixes for me. I had a couple of leaking injectors - replaced all. the second problem is that my fuel pressure was not holding to spec after shut off. After a complete search and change out of the entire fuel system, i found it was a ruptured fuel pulsator damper - it's just upstream of the fuel pump (note the troubleshooting manuals dont mention this thing as a potential pressure issue source). You can replace this little piece with straight fuel hose - pressure problem now solved and my hard starts when warm are now much much better. hope this helps.

 

An 85 in good tune should start very quickly hot or cold, even the old 350 which i removed to fit my new 383 had 170,000 miles on her.
I could barely hear the starter engage before the started was almost instant start

Perhaps you need to tune her check plugs and check the ignition lead resistance. Fit a new fuel filter and do a base idle setup, check the throttle position sensor (0.54 volts dc measured at top and middle wires) also check you get 4.5 volts dc or at least 3.5 volts at wide open throttle.

If the idle screw has been adjusted, without the correct base idle setup that can affect starting and idle.

How to adjust base idle.


First thing to do is disconnect and re-connect your battery (or the ECM connector plug near the battery)
the ecm will detect faults and make adjustments to try and rectify them. ie retard timing.

Set your car to a base idle (as per my shop manual)
when hot.

Connect a paper clip, to your diagnostic terminal under your dash connect to terminal A and B (the top right two pins).
Turn on ignition but don't run the engine.
wait at least 30 seconds and then remove the idle air valve connector (IAC) (the square plug) then turn of ignition and unplug the paperclip.
Now remove the timing connector a single wire near the fuel pump relay.
Start your vette and set the idle speed to 400 rpm in neutral (auto trans) 450 rpm (manual trans) then check your throttle position sensor,
the top two wires it should be set to 0.54volts dc, also confirm with engine off that the tps rises to 4.5 volts at full throttle or at least 3.5vdc.
Turn of the ignition and reconnect the iac valve connector and timing connecter and start your vette.
it should go to 1200 rpm then drop slowly to 600 rpm, take the car for a 15 minute drive with the usual stop lights.
It is normal for a little hunting while the ecm relearns.
All should settle after 15 to 30 mins normal driving and have a stable idle.
Of course any vacuum leaks fouled plugs can affect the correct base idle.

Good luck.

 

Hi guys, I'm looking at a tired '85 today and I'm sure this info will be very helpful if I buy it. Thank you guys, one and all.

 

For the hard starting folks there is a fuel temp sensor on the front of the engine, check and clean or change it. It could cause the problem too. My 85 starts when the key is put to run any time(167000) so something is out of wack.

 

I've had my 1985 for 28 years, it's always started when I turn the key but I've always done the maintenance and upkeep also.

 

I have had my 1985 since 1992. Always starts quick. Never engauge the start function until after I hear the fuel relay click off.