Bought a 93 about a month ago and it started and ran fine. Still does, but if it sits a couple days it starts hard, basically 1st time you turn the key, nothing, 2nd time it will start then stall, 3rd time it will start idle rough, but eventually keep running. After that in the course of a day it will start on first crank.
So my plan was to give it a day or so and see if it still has fuel pressure, if not I'm guessing that it has a fuel pump not holding pressue.
My question is, how much fuel pressure should it have after 24 to 48 hours. My 2nd question is, do you think my dignosis is correct or could there be other issues?

 

FP readings after that much time will be very low. It should not matter. What is important is what it reads when you turn the key on and for 20min after you turn it off. The system is not "fuel tight". It should be ~40+- 3 or 4 when you turn the key on. turn it off and see what happens then. It will " leak down" over time but should not do it in 1/2 hr.

When was the fuel filter last changed? That would be my first thought as it is part of scheduled maintenance. If your pressure holds and is correct then make sure the IAC passage is clear. You did not mention if when it is hard starting if you feather it to keep it running or not.

Come back after getting your FP and leak down done and post what you find.

 

yes.. Check the Fuel Pressure Regulator and what fuel pressure reading you have with just the key on, starting and running.. on shutdown and after a while, there will be some blead down of the pressure. I would think that it would zero after a few hours (?), let alone a day or two. If it leaks down any quicker.. could be a regulator or leaky injectors.

But I would also go about doing the the whole 9 yards as far as checking everything.. almost a major tune up.. Clean and Check everything is what I do when I buy any used car (new ones too LOL).

- This being a early LT1.. Check the Distributor and it compones. Maybe upgrade it, (i'm not a LT1 guys..(I have Gen I and III's) but someone can fill you in on them or research on the subject).
- Maybe a weak Coil (not likely, but check anyway).
- Check for vacuum leak around the Throttle Body back and into the Intake area, hoses and other lines. Gaskets
- Check that the Fuel Injectors are ok and not leaking, O-Rings on the injector and fuel rail.
- Carbon in the Throttle Body, IAC and intake passages. (maybe Seaform the engine and Intake system?)
- Check the TPS voltage and setting.
- Clean the MAF.
- Check for loose wires on the harness
- correct heat range of the spark plugs

Could be over kill.. but it is a good way to make sure everyhting is in good running order and safe.

Good luck.. keep us posted on what you find !

 

Okay, went and checked FP about 41 with key on and with motor running. After sitting about 40 mins, still at 40. So I guess I can rule out fuel pump.
To answer your questions. PO gave me paperwork for a tune-up done last fall, but I don't see a fuel filter on it so I guess that's next. Also I'll clean out the IAC passage and see if that helps.
Yes the car does require a little feathering when it first starts. Auto Xray is showing no codes stored, check engine light is not on.
This is a recent problem as when I bought the car it would start and run fine after setting a week. At frist I thought it might be the old gas as it was on reserve when this started. Filled up with BP ultimate and it was there again today.
But right now I have to run down to my local Chevy dealer as when I took off one of the vacuum lines on the intake to reach the schrader valve a little cannister like thing, cone shaped about 3/4 x 3/4, one of the plastic ends just fell apart.
I'll keep you guys updated, I'll pick up a fuel filter too.

 

Sounds like a bad/ plugged IAC to me. You can get that cannister thing in the "Help" section at any parts store. It is for the HVAC and is a check valve. Very common for those to break.

 

Local Chevy store had one. 5.00. Now I'm going to do a serch and find proper way to clean IAC Valve and passage.

Thanks so much for your help!!

 

Thats the spirit.

Hopefully that is all it is.

 

The whole Throttle body is very simple to reubuild and clean.. $6.00 for a rebuild kit, which is just a few gaskets and o-rings..

You can use some Seaform Deep Creep spray (or some other cleaner, tho Seaform is designed or lossen and remove Carbon) to soak the Throttle body passage to the IAC.

I just took mime apart, soaked all of the parts in a gallon can of Carb Cleaner and then re-assembled it with the new gaskets...