Electric fuel pump conversion

[70spider]

Hey, I will be pulling out the motor in a few weeks and have a bucket list of to-do's. One of the items is to convert it over to an electric fuel pump. I have done a ton of online research and it seems the best way is to install a relay and Ford inertia switch before the the pump plus a filter before the pump and a filter with a return line in the engine compartment. My question to those whom have done this is what wire did you use for the power wire? I have a 1970.

[RRoller123]

and a low pressure regulator as well?

[AriK]

I'm converting from a mechanical to electric fuel pump on my 79 stock Spider and am amazed at the bazillion ways people recommend wiring these things. I have a question for the experts in this process and want to bounce my logic off of others with extensive mechanical and electrical experience. My goal is to eliminate the hard starting problem caused when the car sits for long periods of time....a common problem with the ADHA carbs

Spidernut did you ever follow through with this procedure? I was under the impression that you had mastered the carb setup with the upkeep of the accelerator pump, auxiliary pump and power valve diaphragms. What were your final developments with the ADHA morning sickness?

[spidernut]

I haven't converted to an electric pump yet. I first had to whip a problem I was having with oil and trans leaks. Now that they're fixed, I'll go back to the carb issue.

I did have it whipped at one point, but it seems that fixing the diaphragms only works for a short time (a few months), then I'm back to square-one with the same problem. It absolutely must be related to these diaphragms, but I cannot find any leaks.

What I've found interesting is that I have put an ADHA on my workbench, filled the float bowl with fuel and let it sit. The float bowl does not drain down after days of sitting. I can then put the same carb on the car, hook everything up and run the motor, shut it off and it drains down overnight. Put the carb back on the bench and it doesn't drain down.

You'd think that this would indicate that there would be a crack in the float bowl or leak in one of the diaphragms that only open when the carb is bolted down. However, I have three ADHA carbs (and one parts carb) on my shelf. I've tried it with one other carb with the same result. I can't see or find any leaks or cracks on any of the carbs.

I now have an intake manifold in my parts stash, so will bench test the carbs bolted down to see what I find. There must be a leak somewhere that I'm missing. I may nickname the ADHA "Houdini" since the fuel has a habit of vanishing into thin air.

[AriK]

The trouble most likely lies with vacuum left in the plumbing after shutdown and not a crack or leak from the float bowl. I'm not quite so sure in which direction the pull may be. For the longest time i was under the impression that the vacuum sucks toward the tank. However, a reliable source came on here at one time and specified that the vacuum sucks toward the cylinders and eventually ends up in the crankcase. I'm not so convinced about that, in that case there should be a fresh smell of fuel plus a cloud of black exhaust upon start-up. This is not the typical pattern of morning sickness prone to the 79s.
These various diaphragms that correspond to the 79-only are pricey items if they have such a quick turn-over rate. There's also a one-way fuel valve in the feed line between the firewall and the carb. Although i cannot blow through it with my lips, sometimes i question its performance.
My see-thru fuel filter depletes only halfway in a day, even two. I see the occasional bubble forming after shut-down but cannot tell in which direction the vacuum acts. After several days of inactivity the carb is empty. I renewed my ageing mechanical fuel pump at the end of last season hoping for a quicker draw in the mornings. I have no results yet but at least i'll feel more confident on roadtrips in the future.
I will not opt for an electric pump, i'll endure the 79 hiccup. It's a minor issue. I may try a new power valve one day as my fuel mileage has room for improvement.
In any case i'm interested to know how you progress with your old or new setup. Keep us posted.

[spidernut]

If you disconnect the fuel line to the carb and plug it off, you can tell if the fuel is bleeding back into your tank by watching the level in your fuel filter. Mine bleeds back by about 1/4 after one day of sitting and that's with a new check valve. The check valve is apparently not the greatest. However, the real issue is the empty float bowl. The fuel can't travel upwards from the carb into the fuel supply line so it wouldn't be the check valve. The only points lower than the float bowl are the power valve, auxiliary pump and the vacuum accelerator pump so it must be one of these (or like you said a crack).

The vacuum comes from the intake manifold and stops when the motor is turned off. The thermal valves are all open (excluding one) when the engine is warm, so the vacuum would immediately stop when the motor is turned off. The thermal valve that is closed also would have no vacuum because it is closed. I could be wrong, but I don't see that there would be any residual vacuum.

If you wanted to test the theory, you could disconnect the vacuum lines when shutting the motor then check the float bowl the next day. If it only drained with the vacuum lines attached, you would have found the cause.

I'll let you know what I find when I bench test the carbs on the manifold. It might be a while since I'm doing body work on my project car and rebuilding the motor, but I will figure this out if someone doesn't figure it out before me.

BTW, my son's 77 Spider does the same thing and it isn't and ADHA.