A update on my vapor/??? problem. I've done some more testing and here's what I'm finding:
I had a bit of a chat with Chris Ames (the water pump spacer guy) about vapor lock problems and he told me a couple of things that helped him. One was insulating the line from the
fuel tank to the frame rail and the other was to wrap the left side exhaust pipe. So I took his advice and insulated the line from the tank to the frame rail with some DEI stuff. I also a installed fuel pressure gauge. On a mid 90 deg day I drove for 1hr and 40 minutes stop and go mixed with 50 mph portions. First thing I noticed was the fuel pressure started out at 6 psi at idle and then as I drove it would drop to about 4 psi at idle. After it got good and warm the fuel would drop to 2 3/4 to 3 psi under hard accel. After about 1 hour of driving I drove home and pulled the car right up to the garage door and left the car in gear and after about 20 minutes the the temp gauge was to the far right. The car still ran fine. So at this point I think I no longer can blame anything in the ignition system. I did make two changes after the two trips when I had my problems. I added the fuel line insulation and I did remove the
carb bowl and the jet plate on the
carb and blew out all the passages. I'm sure nothing was wrong because the fuel circuit, jets to the venturi are large passages, and if the much smaller air bleeds were plugged that would only make the car run rich.
With no other changes I drove the car for 45 minutes and then back with the same results. Fuel pressure didn't drop below 2 3/4. If I run the electric pump the pressure will stay at around 4 1/2.
Then I added the exhaust wrap on the left pipe from the start of the hump over the rear end to almost the end of the tail pipe. I then repeated this same trip and this time the fuel didn't drop below 3 psi. The air temp was still in the mid 90's. I'm thinking that Chris's suggestions did the trick but I still don't understand why when I first had the problem and then added the electric pump, why turning the pump on made no difference on how the car ran.
I'm wondering if the drop in idle fuel pressure from when I first start the engine from 6 psi down to around 4 said anything about the fuel pump. It will go down to 4 psi within a few blocks, too short of a run to heat the fuel I would think. I tried to buy a new pump from our t-bird suppliers but they don't seem to have any in stock. Wanting to put the problem to bed I ordered a new pump from a O'Reilly auto
parts store. The brand name was Precision Fuel Pumps which looks to be a store brand. When I opened the box the first thing I noticed was it was a pump with Philips screws which I heard are the problem pumps. I moved the pump lever back and forth and figured it was defective right out of the box. I went ahead and mounted it anyway and the car would run on the electric pump but not on the mechanical pump. Not wanting to order another of the same fuel pump I had them order a Delphi pump ( to the tune of about $50. extra) hoping that this will be a pump from a different manufacture. I should get the new pump next week.
Does anyone have any idea what the fuel pressure would be during a hard accel? The only spec I see is 4-5 psi at 500 rpms.
