electric fuel pump (For carburator cars) wiring

[manoa matt]

Trying to diagnose a problem with a friends 79 automatic. The car is in pristine shape for being in Hawaii and all original parts. The problem with the car is that it won't idle and runs a little rough. The car originally had a mechanical pump, but a previous mechanic installed an electric fuel pump. It was mounted in the engine compartment and received power from the idle solenoid.

I moved the pump to the trunk but I temporarily kept it wired to the solenoid. I want to properly hook up the pump with the inline fuse and relay, does anyone have a diagram from a 74-76 that shows this, or even a detailed description.

They also filled it up with a mixture of 2-3 different grades of gas, one of which was premium, could this make it run rough and not want to idle? Will be bringing it back to my "fiat shop" for a more complete inspection.

What else to look for? dirt in idle circuit.

[So Cal Mark]

different fuel grades-no problem
what powers the idle solenoid now if the wire has been switched to the fuel pump?

[manoa matt]

I drained the tank and refilled it with 87, seems to run better but something is still not right. The idle solenoid and fuel pump share the power supply, could the pump cause the solenoid to work intermittently but still allow the car to run?

The fuel tank builds up a lot of pressure, when unscrewing the cap off the last turn of the threads the tank actually has enough pressure force the cap to fly up in the air about an inch or so. Would a clogged or non functioning vent line cause the car to stall out at idle and run a little rough.

Also hear a sucking sound from the gulp valve system on the drivers side fender, there is so much emissions crap on this car it is ridiculous. I got an extra 32 ADFA but no extra manifold, I'd love to just swap it out and cap the emissions stuff to eliminate that from the equation. Also thought about reverting to the mechanical fuel pump still on the car to eliminate the electric fuel pump and associated wiring.

Kind of grabbing at straws here, want to get this fixed quick so I can have my Saturday back.

[rlux4]

Lucky friend you have there Matt, it sounds like he got a California '79. Do you have to pass smog tests in Paradise?
Ron

[manoa matt]

"Lucky friend you have there Matt, it sounds like he got a California '79. Do you have to pass smog tests in Paradise?"
Ron

Lucky for her, you should say. No smog tests here, I guess they figured the trade winds would blow all the smog out to sea. It sure isn't hovering over the islands.

After verifying the ignition system was good and draining and refilling the tank with known good gas, I figured it must be something to do with the carb. Took the top off, checked the float, needle, air corrector jets, main and secondary jets, idle solenoid, all seamed good.

I took the 28/32 ADHA carb off and started to look at it, just then I noticed a piece of white/cream colored plastic sitting on the intake manifold. It broke off from somewhere, after looking at the carb for a minute I saw were it broke off from. On the 28/32 ADHA just below the automatic water choke is this cream/white colored plastic thing that has something to do with the stepped choke unloader. It is not on any diagram, even if it was, the shaft that it rotates on is riveted/pressed in and can not be removed.

I dropped on a spare 32 ADFA and the car started right up and idled perfectly. I'm not sure if it was the little plastic thing that broke or something else in the carb that was at fault.

Unless I convince her to go back to the mechanical pump. I still need the wiring diagram for the fuel pump, relay, and inline fuse for a 74-76 model year car so I can get the electric fuel pump hooked up correctly.

Anybody got the diagram, trade you or the Fiat vs MGB article.

Matt

[racydave]

Matt, I helped a friend hook one up. We tapped an ignition source from the ign switch, ran it to the trunk, and used a Bosch relay. You can use fused power from the battery. I can tell you Mon what terminals to use as the info is at work...

[manoa matt]

I finally found a 76 wiring diagram, with the inline fuse and relay, however the circuit also contains the ignition mode relay.

Should the pump be on all the time the key is in the on position? Or is it like the FI version where you turn the key on, the pump to primes the system then it cuts out before starting the car? If so could it be wired to the seat belt relay that cuts out after a few seconds?

After the car is started the pump runs constantly.

[So Cal Mark]

if you want to set it up so the pump doesn't run without the engine running, use an oil pressure switch for a relay ground. The only problem is that the pump won't run until you start cranking the engine and pressure builds

[tglancy]

The wiring to the the oil pressure switch is to ensure that in a car crash and the motor not running the fuel pump will stop. The solution to the starup is an ignition switch which has contact 16. It along with contact 50 are on during starting and forces the fuel pump to run ie. bypasses the oil pressure switch.

[mbouse]

have the return lines and vapor lines for the tank been tampered with? I did not hear that your shooting gas cap situation was resolved.

or, was the cap replaced with a F.I. cap? the carb'd two litres should have a vented tank, and a properly plumbed electric or mechanical pump should have no affect on pressurizing the tank.

[manoa matt]

The last time I fiddled with her car was on Aug 2nd of 2008. She hasn't called me or asked me to help her out. I think she only drives the car once a week or once every two weeks just to keep it going. She has been trying to sell the car for over a year now. 1979 automatic all stock except for the 32 ADFA which replaced the "boat anchor" The car is in great shape, a few steps down from mint, but still one of the nicest non-restored cars I've seen in a while. She was asking $4500 on craigslist Honolulu, but thats right next to 2-3 other spiders with 5 speeds going for $750-$1500.

[mbouse]

does that mean the intake manifold was replaced, or just the punky carb?

i am not familiar with the 32 Weber, does it have a carb to tank return line?

[baltobernie]

FWIW, most Webers don't like any more than 3 psi fuel pressure. Maybe check and see what type of electric pump was installed, and what fuel pressure it generates. Was an aftermarket fuel regulator installed in the engine compartment?

[manoa matt]

No manifold change, I did not have a spare one at the time....so its not taking full advantage of the carb. The single plane manifold would help, but remember its an automatic and driven by a lady that does not care about going fast or performance and wanted to keep all the emissions stuff for originality.

Yes the 32adfa has a fuel return line back to the tank.

The pump was the standard "cube" electric pump for carburated applications, I cant' remember the manufacturer, it was 7 months ago.

There was a broken plastic cam on the "boat anchor" carb that has something to do with the stepped choke unloader and was also the stop point for one of the linkages. Once I replaced the carb with the 32 ADFA all of her stalling and idleing problems stopped.

Since she hasn't called me in 7 months, so either she sold the car or does not have any problems with it. She was very happy with my services as I did not charge her anything and found and fixed a few problems previous mechanics missed. I told her it would be a good idea to remove all the emissions stuff to clean up the engine compartment, simplify future problem diagnosis, and give the car more pep, but she was trying to sell it and didn't want to fiddle with it too much.

I told her to give the new owner my number as I would be more than happy to provide assistance and make a new friend.

She originally contacted me because two prospective buyers backed out because "the steering was too hard to turn" The first thing I checked was the tire pressure. 15psi will make even a car with power steering hard to turn. Pumped them up to 28 and you could turn it with one hand.