shootnstarz

Just got an 89 in September and from day one it was hard to start after it sat for several hours/overnight. After it's run it starts right up instantly.

I have already replaced the fuel pump with a Delphi and the fuel pressure regulator with one from Summit.

While not quite as bad it still take some cranking in the mornings even after I turn on the key and let the pressure build up.

Another issue I assume is related is tank pressure. When I remove the gas cap there's always a ton of air pressure in the tank that comes hissing out. This is my first Corvette but I don't think that's normal.

Any opinions?

Rick

joe paco

unless you used a fuel pressure gage you can not be certain what is happening. if you turn key ON, are you sure the fuel pump is running for 2 seconds? if it is, we can't be sure that pressure is up to 36-42 psi.
if you don't verify the fuel pump running with key on, it is possible that the pump relay is not working, meaning that the pump is running from the oil pressure switch, which will make a longer crank time, 6 seconds or more. Another possibility is that an injector is leaking fuel over time.
not sure about the gas cap but I think it is normal.

John A. Marker

You need to put a pressure gauge on the fuel rail and turn on the key and watch what happens to the pressure reading.

DUB

HOPEFULLY you have a vented fuel cap...that allows air in but not out....and if you are getting super high pressure blowing out...I would be looking at your vapor line from the fuel tank to the charcoal canister/purge area in front of the drivers wheel. I have encountered so many that have got plugged or split due to people over filling the fuel tank and fuel being drawn in this line...and moisture added to it...when it froze...the line burst....OR WORSE YET...is that it is plugged up...which is more common (for me)...thus NOT allowing the fuel tank to have the vapors pulled from it....thus causing excessive pressure when the cap is removed.

I AGREE withe the past 2 posts...you need to verify your fuel pressure when you turn the key on...and it need to HOLD also....and NOT drop immediately...or ti is best if it does not drop instantly.

DUB

shootnstarz

Thanks for the info guys.

Is the tank vent line the one that comes out of the sending unit top and runs up the left side of the car? The other two run up the right side from what I can see.

Rick

DUB

Rick,
YES...the small hose that goes to the left ( drivers side) and connects to the brass 'T' fitting...then that 'T' fitting connects to a hose that goes to a steel line that goes to another rubber hose ( if my memory serves me correctly) and then that steel line runs along the underside/bottom rocker area on the drivers side and comes up by the cross member behind the radiator....then a hose connects to another steel line that goes to the charcoal canister area.

I have made these lines and installed then and they are NO FUN...but can be done.

DUB

shootnstarz

Thanks DUB, much appreciate it.

Rick

shootnstarz

So what exactly is it that keep the fuel rails pressurized when the engine is off? There must be some kind of check valve or something in the pipeline from the tank to the rail.

Rick

John A. Marker

In the fuel pump, there is a check valve that will hold the pressure for an extended period of time. If you put a fuel pressure gauge onto the rail and turn on the key, it should build pressure to about 36-39 pounds. It should slowly drop pressure over the next 12 hours. I tested my once and it dropped about 3 pounds or so per hour. If the pressure drops instantly it could be that the check valve in the pump is bad. If you installed the pump using the existing pulsator, the line may have partially come off the pulsator allowing fuel to flow back into the tank before it ever gets to the check valve.


••••• TESTING FOR LOSS OF FUEL PRESSURE

... Here are the sure fail tests for the fuel system to save you time and money.. Take a fuel pressure gauge attach it to the Schrader valve.. Turn the key on and off a few times to build up the pressure in the system... If you are having starting trouble the pressure will probably drop as soon as it hits 38 or 40 and the pump turns off it will probably leak back to zero within a few minutes. Ok now right after you prime the system pinch off the return line near the tank if the pressure drop stops it is a bad fuel pressure regulator.... Next pinch off the feed line if the pressure holds then the leak is before the point where you pinched the line IE fuel pump check valve..hole in the metal line on the sending unit caused by it rubbing on the inside of the tank you should visibly be able to see this if you pull the pump and the sending unit...(this was my problem) or the pulse dampener which is the piece between the pump and metal line on the sending unit.. the diaphragm tears.. and last if you pinch both the feed and return line near the tank and the leak down of the pressure continues then a fuel injector is your problem.. This is the GM test.. saves time and money..
•• disconnect the vacuum line from fuel pressure regulator

shootnstarz

Thanks John, I'm going to get a gauge and tackle it this weekend. Got down to 20 here in Florida this morning so I won't be going outside any time soon.

Rick

ghoastrider1

Often overlooked system

puufgone

Any results from this past weekend, and if so did it help any ?

David

shootnstarz

I didn't get a chance to delve into it yet. I did turn on the key and let the pump run for it's few seconds then checked the rails, zero fuel pressure. It takes a good 3-4 seconds of cranking to start so somehow the entire line has to be repressurized before it starts.

The fuel injectors, fuel pressure regulator and fuel pump w/submersible fuel line (not cheap) have all been replaced in the last 2 months. The car was doing this before the new parts so I missed something somewhere.

There is no gas smell at anytime so I'm pretty sure it's leaking back into the tank. Sure hate to lay out $50 for a test gauge I'll probably use once but it's the only way.

Rick

Cliff Harris

Sounds like your fuel pump relay is not working.

Are you sure you're getting fuel pump is running when the ignition is first turned on? Either listen for it or measure the pressure on the rails. I have heard that you can borrow a fuel pressure gauge from AutoZone...

shootnstarz

Yes, I can hear the pump run for about 2 seconds but there's still no fuel at the rails.

I did already replace the relay, forgot to mention that.

I bought a test gauge yesterday from O'reillys. The last 3 times I've been in Autozone there's been no one behind the counter, including yesterday.

Today is rain all day so I won't be doing it until tomorrow or Saturday.

What in the fuel sending unit besides the pump and it's attaching hose could leak pressure down?

Rick

shootnstarz

Here's the results from yesterday's test.

1. Cold car, key on, fuel pump runs for 2 seconds, zero pressure at rails.

2. Key on, crank car, pressure jumps to 70 - 80 lbs instantly, car starts after 3-4 seconds. Pressure constant 40lbs when running at idle.

3. Key/engine off, pressure drops to zero in less than 30 seconds.

4. With engine recently run, key on, pressure jumps to 40 then bleeds down to zero, starts normally.

5. Removed sending unit, tested check valve w/40lbs of air. Kept 40lbs for 15 minutes with zero loss in pressure.

6. Reinstalled sending unit, attached spare fuel hose with gauge to high pressure fuel line outlet, energized fuel pump, pumped fuel for 2 seconds but with hose pinched off still zero pressure until first crank.

7. Tested by pinching off return fuel line while turning off engine. Twice zero pressure, twice 80lbs and held with no drop. I think if I waited a split second before clamping the pressure dropped, if I caught it just at stop the pressure held firm at 80. No fuel or fuel smell is present in the regulator vacuum line.

I can't imagine where the fuel is going when I shut off the engine. It makes no sign of smoke starting anytime, no gas smell ever, all the fueling parts are new, pump, relay, regulator, injectors. Only the filter hasn't been changed by me but that wouldn't account for the rapid drop in pressure.

This one has me stumped. I have also noticed when the fuel level starts getting low, less than a quarter the car will bog down during rapid acceleration, like the fuel's not getting to the engine. Not sure it that's normal but I don't like it.

I have acquired a service manual, I'll study up on it and see if I've missed anything.

Rick