Yes,the fluctuation in pressure is a problem! There must be a restriction somewhere.
The Carter fuel pump pressure should be 6-8 lbs.Yes,you should always use a fuel filter.Some of the dual feed fuel lines do have a built in filter. Is this a new pump? Why did the electric pump fail? Was the car running god before the pump change? Floats in carb could be sticking. Faulty guage? Dirt in fuel lines?

good luck, john

 

Hmm, good questions, and thanks for the info. 6 - 8 psi is the advertised pressure, so if you suspect the higher reading is due to an obstruction do you suspect it between the carb and the pressure gauge or between the pump and the pressure gauge? Or somewhere else? How can I tell if the carb floats are sticking?

I believe the fuel lines to be clean as I replaced the section from the old electric pump to the mechanical pump and the section from the mechanical to the pressure gauge which is directly attached to the dual inlet carb feed. The in-dash fuel level gauge hadn't worked since I owned the car and for a bout a week before the electric pump died it seemed to be running poorly. It wasn't particularly well padded in its installation and so it was very audible when the flow would change - it had a "normal" whine that would periodically start to taper off then rev back up. At idle you could watch the pressure gauge drop down below 2 psi then jump up to just under 5 psi. When it finally quit it would emit no noise. Multimeter revealed steady power to the electric pump during these issues, even when it didn't pump at all anymore.

Anyway, I removed the pump which was mounted on the outside of passenger frame rail. I replaced the sending unit to fix the in-dash fuel level problem (float was full of gas) and inspected the tank - looked cleaner than I was expecting (shiny interior) with no sediment or other crap I've seen in other tanks. I blew out the line from where it attached to the sending unit to where the old pump was attached, re-routed it to the inside of the frame rail and attached a new section of line and ran it up to the mechanical pump, which is brand new and purchased to replace the failed electric.

I don't really know why the electric pump failed - I took it apart and found nothing that would cause the vane to stick and the filter screen was clean - the vane turned easily by hand, I just assumed the electronics crapped out.

The car ran pretty well before the electric pump started crapping out - then started to experience surges at cruising speeds, preiodic small backfires, rough idle... in short, pretty bad then not at all when the pump finally gave up the ghost.

Thanks for the reply!

 

install a filter after the pump
12-15 psi is way too high
most carbs are designed for somewhere in between 4-8. you'll need a regulator, if not the pressure can force the floats open and the carb. could flood

 

If that red pump only put out 5 psi it was bad from the beginning
or your gauge is bad. Much over 10 psi starts to over power the float needle make the engine run rough

 

Thanks everyone.

How would I go about testing the pressure gauge for accuracy?

I'm going to investigate the possibility of obstruction as well as get a filter installed.

I'll re-post with the results.

 

The very FIRST thing I would suspect is a gauge problem, possibly caused by the fact that now the pump is much closer to the gauge and causes a surging problem with the gauge. I would definately check it's accuracy, and determine if there is an orifice in the line/ gauge. If not, I'd figure a way to PUT one there. The pump pulsations may be causing false readings or may have even damaged the gauge.

One thing you must realize about all mechanical pumps is, that the PUMP ARM does NOT pump gas. All the cam / pump arm does is "****" the pump. The pump stroke then occurs because of the SPRING. This means that the spring is regulating pressure. Unless there is some sort of quality control issue with the spring, or it somehow got "cocked" when installed in the pump, I'm really skeptical that pressure is actually that high.

If you have a hydraulics/ pneumatics supply outfit near you, they might be able to test it, otherwise, just buy another general purpose gauge in the same general pressure range. T them both together, and use something like a tire so that you can "bleed" pressure into the test. If you have a spray gun/ regulator that would be the cat's meow.

 

OK, so how's this?

I removed the fuel line from the pump to the dual feed inlet - it turns out the inlet also housed a filter that I was previously unaware of. Removed it, cleaned it, cleaned the line, reinstalled and presto! fuel pressure dropped to 7 1/2 psi. Then... test drive left me stranded a few miles from the house - wouldn't run - turned over but it wouldn't catch. After towing it back to the house it would fire with some starting fluid in the carb but wouldn't pump fuel, so it wouldn't run. Long story short, I pulled the pump and found the arm was no longer attached. It had broken off - attached picture.

Now that I've replaced the fuel pump again everything is right where I expect: fires right up, 7 psi, no problems.

So what do y'all think? Defective pump? Restriction/Obstruction? Bonehead Installation??

 

Never seen that happen, May have overworked the pump with the high pressure

 

Because this pump put out way too much pressure, I say it had a problem from the getgo

It is IMPORTANT to realize that the ARM does NOT pump gas

The cam "*****" the arm, and the SPRING in the pump is what actually pumps gas. This means that if the pump puts out too much pressure, there must be something wrong with the spring, or how it was installed, as in cocked out of it's seat. This would explain the broken arm, which must have been pushing against abnormal force.

 

Thanks everyone. Running normal now with new pump installed.

Thanks for the education 440 - I didn't know that about the pump ARM / Spring.