Full Size Jeep Network

My ‘87 wagoneer has an inline electric fuel pump pushing fuel to the mechanical pump. Is this normal or did someone put the electric pump in and just didn’t want to remove the mechanical pump?

Some electric pumps can operate inline like this. Depends on the fuel pump.

There are reed valves in the mechanical pump that prevent backwards flow from the pump stroke. I expect they would allow flow through if there were pressure.

These carburetors often suffer from "dry bowl syndrome" when they sit for a few days. Varies a lot between vehicles. Sometimes an electric like this is added to prime the bowl for quicker starting. Not real safe to let the pump run constantly with the key on. There are safety devices including electronic and oil-pressure-dependent switches. Your ideal electric setup has these.

So would the best option be to bypass the mechanical pump and use a block off plate?

Dunno. Does it work now? What kind of electric pump is it? Does it have the capacity to fuel the engine on its own? You could disconnect it and see if the Jeep runs, ie can the mechanical pump draw through the electric pump? If so, you could put a momentary switch on the dash and prime the mechanical pump when needed, or add the electric pump if or when you have vapor lock.

Certainly the mechanical pump is capable of fueling the engine. Mechanical pumps are reliable and durable generally. I'd remove the electric pump and see what happens.

My thoughts, for what they are worth.

I have a carb and run an electric fuel pump bypassing the mechanical. There are a couple of advantages of an electrical pump. Like Tim mentioned, you can prime the carb bowls. You can set up a 'anti theft' switch to make it more difficult to steal. I carry a spare electric pump and when the working one dies, I swap it out. Takes about 15 minutes. A mechanical pump is a pain in the butt to swap out road or trail side.

Some will argue an electric pump pushing from the rear of the wagon will help reduce vapor lock.

I don't recommend to folks to run both. If the mechanical pump diaphragm ruptures fuel can get into the crank case. If this happens and it is not being fed by a secondary electric pump the amount of gas that gets into the crank case won't be too bad. An electric pump will continue to push gas into the crank case while the engine is running until the carb finally dries out. This will ruin the oil very quickly and might cause engine damage. It's a lot of 'ifs' but I just don't see a benefit of running both kinds for the damage that could happen.

The plus side to a mechanical pump is, well, it's mechanical. No wires to break, no fuses to blow. If your charging system isn't working the draw on the battery from just the ignition is pretty nominal so you will have more drivable miles if you are not running an electric pump.

Go electric, excellent way to prime the carb after 2 weeks to 6 months of non use. I have electric fuel pump in all the oldies... I used a carter P4070, a bit big and annoying to change $80ish . Currently testing (not driving off-road too much between the heat wave and the fires) the cheapo $50 edelbrock installed in the engine bay... bought a spare for easy swap.

PIct in my sig

On some carbs you can also just put some fuel down the vent tube with a small funnel and have enough gas in the bowl to prime mechanically.

I like tgreese's advice - unplug, see if it still runs with mechanical only, and put it on a switch so it's there when needed.

My Jeep finally let me down over the weekend. Got about 20 mins from the house and it sputtered and slowly died. Mechanical fuel pump not pushing fuel to the carb. I'm making a blanking plate and plan to try the Edelbrock electric pump letank is currently testing. They're available locally and I plan to buy 2.
When I bought the truck, it wasn't running. PO said it was the fuel pump. I got a pump from Kanter (I think) and it fired right up, no other engine work aside from basic tune up stuff. That was 4 years ago, but I don't put many miles on it per year. Little disappointed in the longevity. I understand electric pumps can be short lived also, but I'll have a spare in the truck and it will be a lot easier to change on the side of the road.

that is the edelbrock I installed on the latest project






the chevy blanking plate works, this style



or bjs

https://www.bjsoffroad.com/search.asp?k ... te&search=

Yup, that's the one. Advance Auto has them in stock.
I measured my fuel pump mounting flange and had a blanking plate laser cut at work. 3/8" stainless steel sheet.
Just need time to get it put together. Planning to run the hard line up the fire wall and then over to the carb. Right now it runs across the front bottom of the engine to the mechanical pump.

letank, are you running a regulator or a return line to the tank? I have neither and not sure if I need one with the edelbrock pump.

Brly wrote: ↑Thu Jul 29, 2021 6:48 am letank, are you running a regulator or a return line to the tank? I have neither and not sure if I need one with the edelbrock pump.

No regulator on any of the FSJs:
the 74 has no return line per stock, it is fine, Ouray and Moab trips.
The 85 is running a return line, Ouray and Moab trips.
The 86 project is running the edelbrock epump with return line , I did 2x 400miles round trip with this set up.

If you are running a carb you can use a low volume electric pump like letank shows without a return line.

Got it, thanks guys.

Just wanted to update. I got everything on and wired a few weeks ago. Relay and oil pressure safety switch. Wired a momentary push button on the dash to prime the carb after sitting for a while. Everything works great, pump is a little noisy but I'll live with that. Hope it lasts!