GT6 Fuel issues - hard to keep running

[dklawson]

It sounds like you want to put the pump "up front". Our GT6 has the Facet pump mounted on a plate attached to the frame at the rear of the car. I chose the location for two reasons. First, I wanted the pump working more as a "pusher" than a "puller". Second, I wanted the pump away from engine heat. I also placed one of those glass bodied, serviceable fuel filters between the tank and pump so I could see when rust and scale were starting to plug the filter.

The old AC pumps do look cool but I chose to put a cover plate on our engine's mechanical pump boss. You can buy the covers (I believe they are the same as those used on small block Chevys) or make your own. Our cover plate is nothing more than a 1/4" thick piece of aluminum with two holes in it and a profile traced from a pump gasket then cut and filed to shape.

 

[Richter12x2]

It sounds like you want to put the pump "up front". Our GT6 has the Facet pump mounted on a plate attached to the frame at the rear of the car. I chose the location for two reasons. First, I wanted the pump working more as a "pusher" than a "puller". Second, I wanted the pump away from engine heat. I also placed one of those glass bodied, serviceable fuel filters between the tank and pump so I could see when rust and scale were starting to plug the filter.

The old AC pumps do look cool but I chose to put a cover plate on our engine's mechanical pump boss. You can buy the covers (I believe they are the same as those used on small block Chevys) or make your own. Our cover plate is nothing more than a 1/4" thick piece of aluminum with two holes in it and a profile traced from a pump gasket then cut and filed to shape.

I'll just put the pump back where it was, attached to the frame on the inside of the rear wheel, like you said, there's physics involved in pushing fluid rather than pulling, not that it probably makes much difference at 1 psi - the regulator I've got to figure out though. When it was that plastic feeling Spectre pancake filter, I just hung it where the mechanical pump would attach, using the lines that would feed into the mechanical pump.

I'm thinking though, the way the check valves are and the way fluid flows through the pump, I'll just leave the AC pump plumbed, and you'll be able to see the fuel go through the glass bubble. As long as it doesn't leak or anything, it should LOOK stock, even though the mechanical part isn't really functional (although actually, the primer part would still work, if needed.)

 

[dklawson]

...it probably makes much difference at 1 psi - the regulator I've got to figure out though.

I'll just leave the AC pump plumbed, and you'll be able to see the fuel go through the glass bubble.

Go a little higher in fuel pressure. SUs and Strombergs seem happiest between 2-3 PSI.

Since you are on a short schedule to sort this, bypass the AC pump for now. Once you get the car through inspection you can sort out the final plumbing.

 

[Richter12x2]

Go a little higher in fuel pressure. SUs and Strombergs seem happiest between 2-3 PSI.

Since you are on a short schedule to sort this, bypass the AC pump for now. Once you get the car through inspection you can sort out the final plumbing.

Running through the pump works great, can see the fuel flow and looks normal. Spending a little more time on mounting isolated the noise from the electric fuel pump better.

I was intending to drive it down to get the inspection taken care of Friday at lunch, but lacked power pulling out of the neighborhood - so I turned around and went back. After a couple hours of off and on troubleshooting, discovered that the engine instantly died whenever I touched the piston on my front carb, no matter what the adjustment of the screw on the bottom. Finally discovered that it looks like the fuel valve was sticking on the rear carb, so no fuel was getting through. (Confirmed float height for about the third time in as many weeks probably!) Toggled it by hand several times and it doesn't seem to stick anymore, I also dialed the fuel pressure up on the regulator a bit to see if the pressure will help it pop open easier. Idling it works a ton better, and both of the valves work as they're supposed to (slight increase in power for about 1cm and higher it starts to stumble. After getting it fixed, there wasn't enough time to get it done before my daughter had to go to her Easter Egg Hunt.

So, fingers crossed, I'll be taking it for inspection here in about an hour!

 

[Richter12x2]

Passed inspection, and drove the 6 miles there and back without any real incident. Still a bit dramatic though, and I feel like there's more power to be had. 98 hp in a 2600 pound car should feel a little stronger than that, I'd think.

Started, drove, stopped, idled, hot-started, all with no complaint. Now that it runs and comes up to temperature, I've got the colortune that I can use on it when I get some time. Also ordered a fuel pressure gauge so I can get the fuel pressure regulator dialed in, which may make a difference as well.

It was still a good feeling to just walk out, turn the key, start the car and drive away like it was a real motor vehicle.

 

[trrdster2000]

Rich, glad all is well.
A side note, got a GT6 (72) last week to make a Spit6, rebuilt a couple of carbs I had on the shelf, put them on and hung a bottle up. This car was parked in 1986, changed oil and filter, ran a hot wire to coil, plugs and oil in cylinders. Runs and idles like a dream, the wires are cut all over the place, so had to jump the starter direct to battery. Hood was real good and that was why we got the car, engine running is one bonus, let you know about the rest. The tranny shifter is all over the place, sure it's the rubber and plastic bushings, but it may be garbage, no big deal, already ahead of the game.

Wayne

 

[dklawson]

Excellent news! Congratulations!

With the inspection out of the way you've got time to dial the tuning in at your leisure. I'm glad you met your deadline!

I have had problems on and off over the years with one or both of our GT6 carbs sticking after sitting for a prolonged time. In addition to float valves sticking open or closed, we have had fuel in the bowls gum up and basically glue the needle to the jet. It has happened enough times over the past 20+ years that I recognize the symptoms immediately. Thankfully the issue is easily fixed with a bit of minor disassembly and spray carb cleaner.