Carb motor-EFI fuel pump - Ford Forums - Mustang Forum, Ford Trucks, Ford Focus and Ford Cars

uteman · 10-16-2002, 17:15

Once again I call on the help of the people at FF.

Can someone who knows stuff about running carby fed motors with EFI fuel pumps and not the old mechanical pump help me?

At the moment my setup consists of the standard XB fuel tank, EFI fuel pump, feeding upto a XF Weber carb, motor is an EFI 4ltr out of an EB but running the carb NOT efi.

Is there anything missing in this setup? I dont really want the hassle of a surge tank, but do I need a return line for fuel from the carby back to the tank? Is this possible to rig up on an XF Weber? Do I need to run a fuel pressure regualtor?

I find that Im having trouble starting the car in the mornings and even when it has warmed up. The symptoms are that the car turns over but wont start. Then after a while of frigging about with the accelerator it kind of "choofs" shit back up the carby. Sometimes I see smoke waft out from the air filter! I have also found the air filter holder base (sports filter, that chrome bit) has sometimes had fuel sitting in it, like seriously pooling in it. I have found one way to start the ute is to switch off the fuel pump (by flicking the kill switch) and then once it starts switching it back on.

WHATS GOING ON???

Another thing I have noticed the ute doing is when I back off while driving (irrespective of the revs) I get a lot of small backfiring. Its not a bang just more of a pop/rumble.

I have a theory (could be way off track) that the EFI pump is pushing too much fuel into the carb and is flooding it at start up. Then as Im driving it is still doing it when I back off and dont need as much fuel as when Im accelerating. But I thought that when the float is full the inlet for the fuel would get cut off.

Any ideas guys? Anyone with a carby/electronic fuel pump setup that can explain their system to me?

Thanks,
Simon

XR8DAZ1 · 10-16-2002, 17:44

Mate , ditch the EFI pump (waayyy too much pressure) as it will be pumping fuel past the needle and seat and flooding your engine.
Get a small (carter?) electric pump and use it with a regulator.
hope this helps
Daz

uteman · 10-16-2002, 20:46

Cheers Daz

I was just looking at it now before I started the engine. The fuel pump was on and pumping fuel. As you said it was pumping too much fuel and it was just pouring inot the carb, hence the flooding.

Any idea on the price of the regulator? Small pump shouldn't be too expensive I wouldnt think. I might check what brand/type of pump I have at the moment.

With the setup you mentioned Daz, I dont need any return lines or anything do I? It should pump enough for my needs?

Jase_ELXR8 · 10-16-2002, 21:31

You dont really need a regulator if it's just a basic setup. You can by electric pumps for carby cars from repco and burson that just bolt straight up, no other bits needed....

uteman · 10-17-2002, 00:41

I assumed that my mechanic got one of those pumps for caby cars but he must not have. I can remember seeing the box it came out of and I dont think it was any brand name or anything it just said EFI Fuel Pump. I spose I could always check the flow rate of this pump and get something that is a lot less.

Cheers for your help guys.

WBT56 · 10-17-2002, 03:08

Quote:

Originally posted by uteman
I spose I could always check the flow rate of this pump and get something that is a lot less.

It's not the flow rate you worry about, it's the pressure. If you put a low pressure regulator in the line after the pump and bridge the return line back to before the pump you won't have to run a full length return line. Check specs on carb input pressure for regulator set pressure.

gregaust · 10-17-2002, 04:02

The XF weber should have a return line connected to it at the same fitting as the inlet line.As for using the EFI pump from what i've seen it is almost impossible to cut the pressure down enough to run a carb..
I did see someone try out a holley reg with an f100 efi pump and it didn't work on a carb,the reg made all sorts of strange noises.. Just go with a basic electric pump...

Kieron · 10-17-2002, 04:38

Just a suggestion, but would a carby XF fuel pump fit into the older tank? must be heaps of em around and cheap as chips - grab the return lines too.

What sort of dizzy is it using? I would have thought you would have had to go back and use an XF carby computer/dizzy arrangement, could be that the back off popping is related to some sort of timing issue?

Kieron

uteman · 10-17-2002, 15:16

WBT56: I get it now, its got to much pressure so it pushes fuel past the needle and seat as DAZ said. Wouldnt it be better to plumb the return line to the tank and not the line before the pump? Would the fuel heat up if it wasnt plumbed back to the cool fuel in the tank?

Kieron: So did the carby XF's have electronic fuel pumps? I thought they would have had a mechanical one? As far as I know it runs (I think) and XF dizzy. Its an electronic one with an orange dizzy cap. Can you tell what its from?

gregaust: I have no idea where the return line is at the carb! There is an outlet on the front right which is identical to the inlet on the front left. Is this it? At the moment there is no "barb" to connect a hose to.

Cheers
Simon

Extreme_2020 · 10-17-2002, 15:54

Uteman...the Carby XF's run a Carter mechanical pump, which orignally was located on the passenger side of the engine, operated of one of the rockers.

According to the gregorys XF manual...the fuel delivery pressure of the carter pump at idle is 48-56kpa.

The EFI XF's ran electronic in tank pumps...with the station wagon having a both a high pressure and low pressure pump as well. They are rated at 250kpa idle fuel pressure.

The unleaded XF's run a eletronic dizzy off an EST system...but mine has a black dizzy cap...dunno if the color means anything though...your cap might be a different brand to the original bosch part?

Hope this helps

Extreme