124 Special gets a new fuel pump

JimD

Waiting for Godot...
Moderator
So the oil in the 124 was saturated with fuel again. :(

The first time I noticed this I thought the problem was the worn out DHSA carb dribbling excess fuel down the intake. I replaced the carb with a new DFEV and thought that would be the end of that. Well no.

I spent the last 2 days removing the mechanical pump (the only other place the gas could come from), installing an electric pump and changing the really gassy oil. I wired it up thru a relay and put in an inertial cut off switch as well. I used my HF rivnut tool to put a couple 1/4" rivnuts on the DS side inner wheel well to mount the pump.

fuel_pump_rivnuts.jpg


I had fun figuring out the wiring. Fortunately, nothing went BOOM and there were no leaks on start up. I will check again tomorrow to see if anything decides to drip.

electric_fuel_pump.jpg


I took a short drive and it seems to run OK, hopefully there won't be a lot of gas in the oil tomorrow.
 
I hope this solves your problem.

Electric pumps tend to like to push not pull. Hopefully you won't need to move it to the back of the car.

I am glad to read that you included some great safety features in your build. I have also had a real liking for the VW style power relay which gets a signal from the coil to keep running.

The following site uses a standard VW 409 Relay which uses a signal from the coil to keep the pump running when the engine is running.

http://www.ratwell.com/mirror/www.dolphinsci.com/relay.html

Turning off the pump when inverted or after a high energy event is important but you don't want the pump running for long when the engine is no longer running.
 
Engine bay vs trunk

Hi Karl,

I tried to figure out where I could mount the pump in the trunk, but really wasn't a good location. Every place that looked promising would have needed to be protected with some type of shield in case something in the trunk decided to go rogue and start sliding around.

After a few days of test fittings locations in the trunk or in the engine bay, I decided to put it in with the engine. I wasn't looking ford to trying to wire the trunk for the pump anyway, so I wasn't too sad. I got the more expensive Facet rotary pump with 50" of dry lift, since I was going to have the long pull to the front.

When I switched to the DFEV carb I removed a fast idle switch. That switch's wiring is a key-on 12v source. I was able to reuse to power the carb's electric choke and now as the trigger for the fuel pump relay. So when the key is on the pump is running, which meant I needed some type of cut off. I found an inertia cut off cheap on Ebay. i plsced it in the corner in front of the driver. The instructions said engine bay is fine, but interior is preferred. It is not a small switch and needs to be mounted to the body where two panels meet. Given those guidelines, I am not sure where they think anyone would find space for it inside the car where the driver can reach it. You can see the big red button in this picture.
fuel_pump_switch.jpg


The inertia switch is interesting. It sounds like there is a ball bearing in there that is under tension to complete the circuit. If the ball gets jolted out of the holder, the circuit is broken. I can make it cut off if I hold it in one hand and slap it with the other to make the ball dislodge. However, once I mounted it to the fire wall I can't make it cut off by tapping it fairly hard. I think that's the way it should be. It is made to cut off in a big hit, you don't want it shutting off every time the hood or a door is closed. :)

fuel_pump_engine_bay.jpg


That coil triggered relay sounds like a good idea. I will look into it. I was pretty well out of my depth wiring the regular relay, so I might actually get a BOOM if I try to redo the wiring with a fancier relay. Something to look forward to. ;)
 
Thanks for the data on the coil relay. I've had straight wired electric fuel pumps in Fiats for 20+ years and for the same 20+ years I've had a back-burnered project to install a relay, inertia switch or something! Something about the oil light signal relay setup (which, I believe is how the '74 124 factory electric fuel pump is wired) I always found distasteful. Anyway, oil light/coil/inertia, I need to do it about 2 or 3 places.

On the way to FFO last month I was reminded about (at least the box type) electronic fuel pumps wanting to push not pull. About 300 miles in, my engine bay (approx where yours is) pump started failing. I had installed it there in a hurry when the mechanical pump failed (amazingly, externally only) and had decided to see if it would actually work ok there. It did for a long time. There were other compounding factors such as new fuel lines which could have kinked (maybe??) in the rear. Anyway, halfway there, there was a pit crew style team effort to install the pump in the trunk (and that DID create line kinking issues at first, but it was fine once we realized it). It had been ingrained in my head many years ago to mount the pump as low in the trunk as possible. I don't recall the tank setup in full on a Sedan (left side, rather vertical?), so it's a different recipe than on 124 Spiders and Coupes. Anyway, what "got" me was that I had driven on countless short around-town, off & on all day drives and never had a problem, but 300 basically continuous miles (with a number rather spirited on back roads) took it to failure.

Also, in thinking about inertia switches, it looks like Ford uses one that is rather popular for this type (I don't mean Fiat specific) application,so it might be a good one for the pull-a-part shopping list.


Chris G

Sent from my iPhone using Tapatalk
 
Tank is vertical on the right

The tank is vertical on the right. I am not even sure if this is really a 124 Special tank, since it doesn't seem to fill out the strap that holds it (or attempts to) in place. The tank looks fairly new and clean compared to other trunk areas, so who knows. It came to me this way.

I thought about placing the pump on the little "shelf", but it didn't quite fit and the plumbing would have probably led to kinks or really long hoses.
elec_pump_test_fit1.jpg


Then I thought about putting it on the frame rail in a spot that would allow for less strained hosing, but the pump would be in the cargo area. It would really need some type of cover to protect it from trunk junk.
elec_pump_test_fit2.jpg


There is a big "shelf" behind the rear seat, but that would require really long hoses.
elec_pump_test_fit4.jpg


Ideally, I would have placed it above the tank somewhere. Here is the rats nest of fuel line, return line and vents hoses on top of the tank. With the trunk hinge rotating close to them I couldn't see a good way to squeeze the pump up there.
elec_pump_test_fit3.jpg


The fuel and return hoses are the two short, newer looking hoses. Those were reversed when I got the car and I just recently set them straight and replaced the old hoses. This hose mix-up is another reason I think that is a replacement tank.
 
You should stop by some time Karl

All around a good piece of work.

Other alternatives are to have an oil pressure switch act as the means of signaling if the engine is running or not.

http://www.how-to-build-hotrods.com/electric-fuel-pump.html

Before I got started I Googled "fuel pump wiring" and saw many variations on the oil pressure sensor option. My wiring skills are weak and are more likely to lead to a harness fire than a working solution. I decided to go for a more straight forward approach to get it working. In the future I may try something different, for now this will have to do.

And I like the idea that I can prime the carb with the key on before firing the engine. This car sits for really long periods and that "feature" will be useful.
 
don't forget that 90 degree elbows can give you more options for a pump also. Yours may simply be a more versatile design than the one I was using, so I wouldn't sweat it anyway unless you plan on entering a coast-to-coast road race in the car! The best layout will become apparent in time.

My '74 (stock) 124 Special TC sedan had a very small tank mounted as yours (I just couldn't remember which side), but I don't recall it being loose. I would imagine for the 124 Sedan there are decades' worth of Lada spare tanks, and commensurate decades' worth of almost-correct spares!
 
I thought about 90 degree fittings

don't forget that 90 degree elbows can give you more options for a pump also.

I thought about 90 degree fittings, but I was worried they would hurt the flow of the pump. I bought 8' of hose because I couldn't decide where to put the pump. I was picturing big smooth loops to avoid kinks in the trunk. I only used about 3' in the engine bay. It's nice to have some extra hose around for the next emergency. :)

The tank is definitely loose. Finding a long bolt of the proper size for the strap's tension bracket is on the list of fixes that need to be completed. I bet between 72 and 74 some govt official somewhere in the world decide that all fuel tanks might be better off bolted into the car.
 
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