So I've had the Weber going for a while and overall still runs significantly better than the worn out Mikuni although not without some faults. I read about mechanical fuel pumps, the pulsing pressure, and how regulators reduce pressure as well as volume.

The issue I'm seeing is how the Spectre regulator I got has dial settings for 1-5.5psi. If I leave it on 3.5, it runs fine at low speed, but seems to have a starvation issue (if in fact this is the problem) at highway speed under load. If I nudge it up to 4, it will often diesel and appears to use more fuel (have not run the numbers yet, however). I have searched for threads like this and those seem to point at either ignition or fuel starvation. I would like to go electric either way, but this situation is a catalyst for the switch.

Question is, how did you guys go about the wiring? Did you get an aftermarket fuse block with a relay and use an existing wire for ignition source? Perhaps lengthened an existing power wire? I'm looking to get the wiring part done before I sift through the almost endless fuel pump options.

Also have a question about filtering, need one before the pump? Do you guys just keep the factory filter as well?

It sounds to me like you have multiple issues.

1) The excessive fuel consumption and dieseling may be due to too much pressure for the carburetor to handle on the #4 setting.

2) The lack of power at higher rpms or under load on the #3.5 setting sounds like the main metering jets aren't large enough for your engine or the choke isn't opening completely. Look at your tailpipe to see if it's sooty or brown. If it's brownish white, your jets are too small..... sooty means your jets are too large, or the choke isn't opening all the way. A tannish brown is just right. Check the choke action with the engine fully warm and make sure it's completely open.

I use a Carter P4010 rotary vane electric pump to feed the Weber 32/36 on my 2.0L Mighty Max. It's a loud pump, so if you use one, mount it to the frame rail and with rubber grommets to isolate it a bit.

I don't use a regulator, although I think the pump is just a little strong for the 32/36 because I get a little dieseling if the rpms aren't all the way down to dead-low idle when I shut it off. I find if I blip the throttle just before shut-down, it doesn't diesel at all. I could also install a regulator, but it doesn't happen often enough to concern me.

I use a standard automotive type relay as a pump relay and trigger it with the coil B+ post - because that is only hot when the ignition switch is in the RUN or START position.... main power to the pump goes from the battery to the relay to the pump.

Someday, I'll wire in the oil pressure cutoff switch that kills the fuel pump when the engine oil pressure drops below 7psi - even though the ignition switch is in the RUN or START position. For starting with such an arrangement, you can rely on the fuel contained within the carburetor bowl - or wire an override momentary switch that you push and hold while cranking until you get oil pressure showing.

Others will likely have some different ideas for you..... there's no one perfect way - you have to find what works for you and your engine.

Frank

Thanks for all the info Frank!

There were a couple people that mentioned using an electric in combination with the mechanical. Is this for redundancy or just for those who don't feel like removing the mechanical? Is there a generic blockoff plate for these motors?

The best blockoff plate would be to swap in an EFI non jet valve head, but absent that, all you need to do is pull the pump and push rod, fabricate a 1/4" steel plate that covers the hole, drill it for the mounting holes, cut a paper gasket and bolt it in place.

I have seen electric pumps used in combination with the mechanical pump, but I wouldn't even think about it. Usually, the mechanical pump is shot and doesn't deliver enough flow and the next thing that could happen is the mechanical pump diaphragm will rupture and the sump will fill with gasoline. Once that happens, you're going to catch fire and have a nice Montero bar-b-que.

Frank

"Someday, I'll wire in the oil pressure cutoff switch that kills the fuel pump when the engine oil pressure drops below 7psi - even though the ignition switch is in the RUN or START position. For starting with such an arrangement, you can rely on the fuel contained within the carburetor bowl - or wire an override momentary switch that you push and hold while cranking until you get oil pressure showing."

Since the carby motor has one coil b+ wire hot at start, and the other one hot at run, a oil pressure switch could be wired to the one hot in run with a diode, and the pump could be wired around the oil pressure switch with another diode and the wire hot in start.

I think I see what you're saying, but it seems to me that the easiest thing to do is to wire the pressure switch into the fuel pump power lead coming off the relay and a bypass (or shorting) switch across the pressure switch leads.

But in all likelhood, the bypass switch wouldn't be needed unless extended cranking was necessary for starting.... because there's enough fuel in the bowl to run the engine until oil pressure closes the pressure switch.

Frank

I had the same fuel regulation issues with a 34/34 I installed on my '87 Raider. After buying new jets and a regulator and having it still run like crap, I sent it back to Weber Direct and they credited me towards a new 38/38. I have never had an issue with the 38s I have on my rigs.

That's good anecdotal information, Shirebourn - thanks for the info.

Frank <img src="/forums/images/graemlins/cheers.gif" alt="" />

I had the 38's as a pair on a fiat 1598cc one time, and it was a pretty nice carb. Not as nice as the 40idf's i put on later, but nice.

I'm just looking for a stable psi/volume before I start trying to tune the carb.

I've been looking at relays and pumps, but the pumps don't have an amperage spec. Is there a typical amperage you need for a fuel pump? Is there a somewhat easy path to route the wire back to the tank? I'm guessing you just run a power wire and the pump itself is grounded to the chassis? Maybe not the case, but at least the ground wire I guess.