snb73

Just rebuilt the engine and it has the correct new fuel pump from Zip. I have good (4-6lbs) at idle. When I back down the driveway to road test, after 20 feet of a normal takeoff, pressure drops to zero and the vette stalls. Has anyone had this problem before.

I e-mailed Lars about this yesterday, he suggested I check fuel pressure. This seems to be the culprit, but what is causing it? Did I just get a defective pump?


Here's what happened yesterday:

I installed a rebuilt L-82, comp XE268, hooker super comps, and TFS 23*
64cc, and 1.6 ratio rollers. It fired up fine and ran for the initial 20
minute break in period at 2500 rpm. I changed the oil and filterand it ran
fine. No road test yet. I set the timing to 36 degrees, as per your
tutorial. Idle is a little rough, and timing moves a bit at idle. When I rev
it, it seems like the engine takes too long to get back to idle.

When I first road tested it, I went about 1-2 miles and it sputtered and
died. I let it site for approximately 5 minutes, then it fired up for 15
seconds and died. The longer I let it sit, the longer it would stay running;
10 minutes/30 seconds. I took off the air filter and looked into the carb as
I manipulated the throttle. After about two or three full pumps, no more
fuel was squirting.

I checked the fuel filter, it wasnt clogged. Then I removed the fuel line
attached a bottle and turned the engine over. After approximately 3
revolutions, I got about a cup of fuel in the bottle. Fuel pump seems ok. I
reconnected the fuel line, it still wouldnt run. I gave it a little fuel
"charge" through the float vent and it ran like normal. I am assuming I have
a float level problem or something else is not letting the fuel into the
bowl.

Like I said, it will idle all day long. But once I get on it and start using
the fuel in the bowl, it doesn't seem to be replenished.

I also get surging just off idle while cruising, 30mph at 1200-1400 rpm in
second


Here's what went on today:

I borrowed a fuel pressure guage today. I'm getting between 4-5 pounds of pressure, 3-4 at idle and 5-6 above 1500. The vacuum advance is hooked up to "ported" vacuum, not manifold vacuum. It is connected to the port just above the drivers side idle mixture screw.

As a test, I installed a (one) heavier mechanical advance spring. That seemed to help with idling down from rpm's. But it still seems to be taking to long to get down to idle.

I also removes and pluged the vacuum ports for the power brakes and headlights. I wanted to remove that variable.

I had the engine idling and at different rpm's for about 30 minutes, no stalling. This engine has less than 1 mile on it and fewer than 2 hours running. I installed all new componants, including a new stock fuel pump from Zip.

Ok, I just got back from taking it for a road test. The hood is off, and mounted the pressure gauge in such a way that I can monitor it from the drivers seat. The vette started right up, 5 lbs of pressure. I backed out of the driveway, still 5 lbs. I put it in first and started forward, maybe 20 feet, the pressure went to zero. I let it sit for 5 minutes, started it, and got 1-2 lbs.
I poured a shot into the bowl vent to get the vette running. Drove it into the car port, still zero psi.

I removed the gas tank cap to eliminate any vacuum, still no pressure.

I checked the fuel lines, they didn't feel colapsed. May be it's a heat related pump failure. The first time I road tested the vette, it was idling for maybe 5-10 minutes and it took about a mile to die. Today I had it running for about 30 minutes and it took 20 feet.


Here's what happened after an hour of cooling down:

The vette fired right up and had 5-7 lbs of fuel pressure. Road tesed, pressure dropped again after 5 minutes and vette died.


This is wierd. I'm pissed, I want to drive it for more that 20 feet, lol. Do you have any suggestions? Did I get a defective pump?

Thanks, Steve.


[Modified by snb73, 8:23 PM 8/12/2003]


[Modified by snb73, 8:25 PM 8/12/2003]


[Modified by snb73, 8:44 PM 8/12/2003]


[Modified by snb73, 10:30 PM 8/12/2003]

snb73

ttt

Fevre

Might be crude clogging the sock, if it is still in the tank.

lyonsh

How is your gas tank vented? I can't remember which years had the vented gas cap and which didn't, but it sounds to me like you have a missing vent - which is creating a vacuum inside your gas tank and reducing fuel pressure. Make sure there's a way fresh air can get into your tank.

Just a thought. :cheers:

Matt Gruber

yes, look in the tank.might try changing the hose from sender to frame line. and the S hose up front, you do have an S hose?

15% of c3 ers dont run at all so 20 feet is not all that bad :jester

snb73

Thanks Guys,

I had the same problem with the cap removed. I too thought it might be vacuum lock. All the rubber lines were replaced.

I found the problem, a clogged fuel sock. I used a two foot long rod and tapped the sock, in an attempt to loosen any debris. Road tested the vette and it ran for about 5 minutes before clogging/loss of pressure. I removed the sending unit and could barely see through the sock.

I removed it , temporarily, and road tested. No more problems, fuel pressure is 7-8 lbs on start and 5-6 lbs after warm up. A new sock is on order.

Thanks Steve.

Fevre

:thumbs:

My69

I had a simular problem. My car died and I thought I had vapor lock. What I had was a dirty tank,and no pick up sock. I ended up dropping the tank and cleaning it out, replacing the sock and the fuel pump. I should have the project completed by Saturday. Hopefully this eliminates the problem. :smash: