Replace mechanical fuel pump with electric 79 spider.

[paulw106]

Morning folks,

I have a 79 spider, which I believe has a dud mechanical fuel pump (only a dribble of fuel getting to the carb but the lines from the tank appear clear).

I am thinking after looking at a couple of forums of replacing this with a self regulating (i.e. built in pressure switch) electric pump and fitting this in the boot.

Couple of questions:

1- Is this a good swap, is it worth doing as I can pick up an electric pump relatively cheaply in the UK but the mech pumps are not so easy to get hold of or cheap as most of them are in the US and with the shipping and import duty just about doubles the price.

2- If this is a reasonable idea, how easy is it to wire and does any one have any advice on where I should take a live feed from for the pump.

I am quite prepared to concede this might not be the best option hence why I'm throwing it out for comments.

Regards,

Paul

[seabeelt]

Paul, I think I have seen this topic before, not sure if on this forum or another, but it has been done. Try using the search feature and see what pops up. Best of luck. Have you tried DTR? I think they are in your neck of the woods so to speak.

[baltobernie]

Easy-peasy. A small cube pump like this Facet



goes in the boot near the fuel tank, as low as possible. These pumps like to push, not pull. Make sure you get the version for carburetored cars, with a 3.5 psi maximum. This particular pump has a provision for an inlet filter, which is a good idea. You can use 5/16" regular fuel line, not necessary to use the expensive EFI-rated stuff.

Electrical feed from any switched source. The pump runs continuously when the key is On.

[kmead]

I personally am not a fan of making this sort of change. Unless you do the extra work of putting in some safety additions to reduce the dangers these can pose.

If you hardwire this to run any time the ignition is in the on position, should perchance a line come adrift, you have an accident or other mishap, the pump will continue to dutifully pump more gasoline on to your already bad day.

There are good circuits you can create to tie it to an rpm or oil pressure based signal so if the engine isn't running or loses oil pressure the fuel pump shuts off. There would be a bypass for the starter circuit.

I have seen bad things happen and wouldn't want to see it happen to you.

Karl

http://www.pacificp.com/pdf/Fuel%20Pump ... iagram.pdf

Another way:
http://www.ratwell.com/mirror/sfraser/relay.html

[bobplyler]

Have you checked the fuel filter? I know from experience they will completely clog at about 120000 miles.

[paulw106]

Thanks to all for your replies, most insightful and helpful,

@Kmead, thanks for the pump wiring diagrams most helpful, I have been reading a bit further and will be looking to get a relay to power the fuel pump that works off either the tacho or coil feed.

@Bobplyler, my first though was a blocked filter but on investigation I discovered that a previous owner had very kindly removed all the fuel filters from the system so I didn't have to worry about those getting blocked (I will of course be replacing them).

@baltobernie, thanks for the tip on the pump I have ordered a 3-4psi facet pump for about 1/2 what a mech pump would cost me.

@seabeelt, I'd had a look through the forums previously and there are people who have done similar things but not one that I could find that had done a mech for electric replacement.

[bradartigue]

This used to be a very common swap but seems to have petered out in the last few years. The Facet cube pump is not the most reliable thing in the world; if you use it put a filter in front of it, get a safety switch (like from an Alfa Spider), and wire it up right. By the time you're done you will have spent 10x the amount of time and 3x the amount of money.

The mechanical pumps last a long time, are easy as anything on a Spider to replace, and require no reworking of the wiring. They also stop running when the engine stops, which is a good thing.

If you do decide to go ahead then I'd suggest a better pump than the Facet cube. A Bendix-type pump is far more reliable, but you pay for that reliability.

[kevsem65]

Brad ! I've been reading your posts and your guides I need some help. I recently replaced the ignition switch with a lada switch when I did there was a wire stuck into the original ignition switch. It went to a connection under the dash next to the ignition pigtail the stripped end stuck in the ignition was obviously not original. I thought at first it went to the aftermarket radio but everything still seemed to work without it. After that when I went to drive it it stalled out and was hard to restart and its been happening ever since . I replaced the fuel filter in the engine compartment and tapped out the end , lots of orange sediment came out. I then retuned the carb according to your manual but its still happening. Starts and idles fine in the driveway but when I take it for a ride it stumbles and dies at a stop.and is hard to restart. After about ten minutes it will start with me pumping on the gas pedal. I thought the fuel pump might be bad but when I looked it isn't connected to the fuel lines. The lines from the carb that are supposed to go to the charcoal cannister are connected to it. I looked in the trunk and found a facet cube. Could that wire plugged to the ignition switch have been the pump power? And if it was would the car still start and idle cold? When I bought it it had an older but we'll done restoration. the problem is I don't know everything the po did and I'm trying to reverse engineer his modifications. I know its a simple fix but I'm trying to figure out which simple fix it is!

[DieselSpider]

You need to vet this all out including the required safety components to turn the pump off in the event of a crash or rollover. You have to count the cost of converting over to and electrical fuel system.

Do not forget to remove the old mechanical pump and plugging the opening too as once the old fuel pump diaphragm fails it can allow oil to leak out and if still in the fuel circuit it can allow fuel to be pumped into your engine diluting the engine oil.

[kevsem65]

I checked last night after this idea came to me, the fuel is coming from the facet pump. the po installed a kill switch on it in the dash. if I hit it while the car is running it dies, turn it back on and it fires right up. so I know it working. the car only dies when it get to operating temp then after I drive it and come to a stop.

[kevsem65]

could the stripped wire stuck in the ignition switch tha t I mentioned earlier be power to the idle solenoid? like I said it went to a 2 wire connector under the dash right next to the ignition switch connection. im at work now so I cant check for power but whch wire powers it to the ignition?

[bradartigue]

could the stripped wire stuck in the ignition switch tha t I mentioned earlier be power to the idle solenoid? like I said it went to a 2 wire connector under the dash right next to the ignition switch connection. im at work now so I cant check for power but whch wire powers it to the ignition?

It could go anywhere, it isn't stock, so who knows? You're going to have to trace it. If it goes to the idle solenoid then it should be easy to trace or put a continuity meter on either side.

Download a wiring diagram and test the original wires to the switch, see if they're all okay.

As far as a fuel pump, if its a 79 then get a mechanical pump and remove anything electric that someone added. Big waste of your sanity to mess with an electrical pump on a car never designed for one. imho

[kevsem65]

Thx brad! After doing extensive research on this forum for the last two days, including many replies from yourself. I tested the solenoid (tiny spark but no click) ordered a new one from AR, installed some appropriate vacuum caps and did some thorough spraying and blowing with carb cleaner when I got home tonight. Solenoid shows up tomorrow and some new plugs are going in. If all that didn't do it I'm gonna punch myself in the face! Thx so much guys!

[bradartigue]

When diagnosing a carburetor I block off every port except the fuel port, including ports on the manifold (e.g. brake booster). Then I know the only air that will be coming in is through the carb. Sure I have to retune it slightly once I hook the stuff back up, but I can hook things up one at a time, determine if they are a problem, and repair systemically.

[Shadoobie]

I have a carbureted 79' myself and I would advise going with a mechanical. I replaced all the check valves and the pump and now the main problem with the amount of fuel received is from the crappy ADHA carb. you will definitely want to check and see if that has something to do with it.