Carb issue....maybe.....

[69importkilla]

Just some background, the car has a 650 DP mechanical secondary carb. It was installed when I changed over to an LS motor years ago. I also installed an electric pump at the time as well. The car was filled with NON-ethanol gas.

Lately I've noticed when the car is hot ( normal operating temp 185 degrees or so ) after changing gears it would hit a flat spot ( kind of like the accelerator pump wasn't working ) and then take right off without issue. I don't have any issues when I first pull the car out of the garage.

Fast forward to last Friday, took the car to the store ( it was 90 degrees out ). When I left and pulled out of the parking lot, the car completely died. I needed to hold the pedal to the floor to get it to restart. Almost seemed like it was flooded. The whole way home it stumbled a lot but if I put it to the floor off I went.

When I got home, I shut it down and took the air cleaner off. I heard a little hissing type sound and could see fuel kind of stumbling out of the carb down into the intake. Not a lot of fuel but enough for me to notice.

Tonight, I pulled the carb took of the fuel bowls and gave everything a once over. Nothing worth mentioning. I installed a fuel pressure gauge and turned on the pump and had 6-7 PSI.

A couple of guys at work are thinking the fuel is percolating. I have never had a problem getting the car to restart after its been shut down for a few minutes or 10 -15 minutes. The fact that it was "boiling" over it the only caveat to this. Otherwise the car exhibits no other symptoms to support percolating.

Tomorrow I'll take it out again and let it get nice and hot but stay close to home. I'm gonna bring my temp gun to check the carb temp, fuel pump temp and check again to see if anything is overflowing the carb.



I know more often than not this doesn't mean anything, but nothing has been changed on this set-up for years. I can’t really tell if the car had symptoms before I filled up with the non-ethanol gas or not. I guess it could possibly be bad gas, but why wouldn’t it happen when the car runs for the first time that day?

Just hoping maybe you guys could toss some ideas on things to keep an eye out for.......

Thank for taking the time to read thru this.....

[ilikeike]

Is the fuel dribbling out of the accelerator pump nozzle or the boosters ? could be a sticky needle and seat,maybe time to replace them?

[TheJDMan]

That's what my first thought was as well. Needle seat assy are easy to replace.

[69importkilla]

Thanks for the thoughts.

Cant really say where the fuel was dribbling out of, but trust me I'll pay better attention and make notes.

The needle and seat looked good, but then again who knows. Cheap thing to replace though.

I didn't have a chance to run the car today as it was pouring rain. Hopefully I can run it tomorrow and pick up and new needle and seat.

[btmatt]

Your buddies sound like they may be right. If you have clearance, try installing a non-metallic spacer between carb and intake to isolate it from manifold heat. Chevrolet used to have a heat shield they used on 1st gen Z cars that works good. Also, a fuel return will help to keep cooler fuel flowing to the carb. Good Luck

[69importkilla]

Well I took the car out today for a bit. I let it idle in the driveway for 15 minutes building temp. I did notice the fuel pressure gauge needle bouncing between 4 PSI and 7 PSI. After running the car around it was steady at 6 PSI. Weird..was wondering maybe something with the pump caused the pressure to drop down and this is my problem.

Oh yeah, didn't have a single issue. Didn't see any fuel dripping either.

It was a bit cooler today than last Friday though.