VetteUSA

Here's an update on what's happening.

Firstly, since I already had a new filter on me, and the old one had been on there for quite a while, i decided to replace the fuel filter..Got that all done without too much of a headache. I hooked up the fuel pressure gauge to the valve on the fuel rail.

1. Folowing the shop manual's step-by-step chart, the chart indicates that when the ignition is turned to the "on" position, The fuel pump will activate for about 2 seconds, then stop, and that the fuel pressure should read between 41-47 psi. During the first 2 seconds, the psi read at 47 psi, after stopping, the pressure adjusted itself at a steady 42 psi, just as the chart indicates is supposed to be.
I actually went one step further... i started the car and let it run at idle... the chart indicated that the fuel pressure should drop 3-10 psi when running at idle. It did. The fuel pressure dropped to 38 psi.

2. The next step in the chart said that if pressure is suspected of dropping off during acceleration, cruise or hard cornering, then go to the next chart. Ok, that's the problem i'm having, so i go to the next chart and it says to check for a restricted in line filter or fuel pressure line. Ok, there's no restriction in the filter because i just replaced it. Well, the chart then says if there is not a restriction, then check for A) resstricted fuel pump strainer b) leaking fuel pulse dampener c) wrong fuel pump. And then if those are ok, then D) the fuel pump is faulty.

FYI, after i replaced the fuel filter, i drove the vette around the block. while i was driving in 1st gear, i was giving it some gas, hitting high rpms. Well, right around 3000 / 3500 rpm's the engine suddently just cut off on me... I had no engine power at all. ( It didn't bog down on me at all like before, the engine just completely quit on me. The car was essentially dead until i let off the accelerator, and then I was able to safely drive the car back home hanging under the 2000 rpm mark. Also, please know that the engine does not die on me if I am in "park" and i rev the engine)

Also, For the past few days now, I have been having occasional, intermittent hard starts as well.. the engine will crank but it just doesn't start up. Sometimes if I kept cranking for a while, the engine would eventually start up. OTher times, the vette will start up immediately, just as it should.

So...... what now? sound like a fuel pump problem?

Pete K

Duct tape the guage to the windshield. You need to look at it when it has it's little fit. Then you will be able to tell if it is fuel or other.

yellowlust

Fuel filter on backwards?

Fuel pump.

Ironically it's probably easier to replace the fuel pump.

aminnich

RRT vette

with taping guage to the winshield trick. This should give you some more info.

scranage

FWIW, I can tell you I have seen this exact same behavior in two cars, one mine, and one a friends. Both times it was a fuel pump, and was intermittent as you describe.

The Hobbit

I have seen this a few times , its always been crap blocking the small screen on the intake of the flue pump.
Take the pump out, pull off the filter boot and have a good look at the intake

hope this works for you

Barry

CentralCoaster

I had the same symptoms. Sputtering above 4000 rpm. New fuel pump fixed the problem for me.

Watch that pressure guage while revving the motor.

Demonic85

Everyone says its easy to change the fuel pump on a Vette, but I dont see how, as its in the fuel tank just like most cars. Its like a 3 hour job on my Buick. Wouldnt you have to take the bumper off or something? I'm going to look this up.

teebee

You just remove the "boot" from around the filler neck and the whole thing comes out of the top of the tank.

Square

Silly question:

How much gas is in your tank?

In my 86' if I floor it at or below 1/4 tank it will kill the motor from fuel starvation.

This won't explain your hard start symptom, but I thought I would ask.

Demonic85

Yours dies if it has less than a 1/4 tank??? Thats odd, mine will run just fine, even full throttle until i'm really running low, like a gallon left.

Square

I was told that my tank does not have baffles and that is why it occurs. I am pretty sure it is stock. I have heard of other early C4's having this issue, but I don't know if it was fixed in the later models.

Your profile says you have an 85', do you know if your tank is original?

VetteUSA

Right now it is below 1/4 tank. 4 or so bars. I made a comment to myself that i should get some more gas. But when this problem first occurred, i still had between 1/4 and 1/2 tank left. Even when i've gone below 1/4 before, it's never been a problem.

====================
I'm assuming that removing the fuel pump is as easy as removing that neck boot, removing those 10 or so bolts, and then just lifting it up out of the tank? Is there anything else i may not be aware of before i remove the fuel pump? I'm starting to get low on gas, but i figure that will be better for me since i'll likely need to replace that fuel pump. I'll check the filter screen as well.

VetteUSA

Update: I just finished driving the car around with the gauge hooked up. At the point the car bogs down , the fuel pressure varies rapidly between 40-48 psi. When the car actually dies, the fuel pressure read at a steady 41 psi.

Also, yesterday, when I was having trouble starting the car, one particular attempt caused A lot of white smoke to pour out from the air filter housing.

CentralCoaster

Pull the vaccum hose off the fuel pressure regulator after running the car, see if it's wet or smells like fuel. If the diaphram is torn, the plenum will suck fuel through the vacuum line.

Slalom4me

Maybe so, but put some gas in it anyway. And add a little Gas-line
Anitfreeze (Isopropyl Alcohol) for good measure.

BTW - any change in the level in the rad overflow tank?

.

89vert

I'm thinking out loud here guys, but after seeing the fuel pressure readings he has I'm thinking ignition. How long has it been since you replaced the cap, rotor, plugs and wires? Just a thought.

Pete K

This almost completely rules out a fuel problem. Notice I used the word almost. Hate to eat crow I would shift my focus to ignition at this point, if it were my car.

VetteUSA

I'm way ahead of you... a little while after i last checked the fuel pressure, i went and got some water remover/antifreeze and filled up on gas. I'm not sure how long it's supposed to take effect, but i'll drive my vette for a while and see if it helps to cure anything. The overflow tank was a just a little bit low, but it's still within the hot/cold marks.


The '93 has the Optispark, it doesn't have the traditional cap & rotor. I changed the spark plugs 3 or 4 months ago, but I've never changed the wires.