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Electric Fuel Pump for Jeep Stroker into an AMC Eagle

Posted: August 16th, 2021, 6:12 pm
by OverKnight
Hello - we are installing a 4.0 L engine from a 1993 Jeep Wrangler Sahara into my son's 1986 AMC Eagle, and we're using the crankshaft from his 4.2 L engine in the 4.0 L. We need to install an electric fuel pump, and I'm a little stuck on what kind of pump to get. The test specifications for the in-tank Jeep pump are 53 psi and 15.75 gallons per hour.
  • Are the test specifications the right way to go to select an external fuel pump?
  • Does anyone make an electric pump that fits into a stock Eagle tank? I haven't found any.
  • Does anyone make a fuel tank for a 1986 Eagle designed for an internal fuel pump? I haven't found any of these, either.
  • If we have to go with an external pump (likely), can anyone advise us on a decent one that with work with this engine?
Thank you.

Re: Electric Fuel Pump for Jeep Stroker into an AMC Eagle

Posted: August 16th, 2021, 8:09 pm
by Randy Bobandi
86' Eagles had mechanical fuel pumps right? You could get an aftermarket tank with an in-tank fuel pump or use the OE tank with an inline fuel pump/regulator & filter. The fuel pressure is set by the regulator not the pump. Walbro universal inline fuel pumps can run from 43Psi-87Psi. Your power goal/fuel octane#, of course, needs to match the fuel pump's flow rating.

I'm assuming this is a fuel injected engine correct? You'll want to make sure the injectors can support the target power level as well. It's always smart to go with a fuel system that can more than support the engine's demand. The last thing you want is fuel to be your bottleneck and feel like the engine build was a big waste of time, when all you needed was a stronger fuel system. Even if you tune the engine for max output, pumps & injectors with low flow ratings like 155LPH pumps and 24#/HR injectors can run at a high duty cycle % and burn out in short order.

255LPH pumps are excellent choices for the Jeep stroker engines with a set of 30 #/HR injectors. That will support 300 crank HP all day. The GSL392 would be a great pump for 300 HP. The GSL 394 would likely support 300 crank HP as well, it would just run a little hotter. Holley has a great selection of filters and regulators for EFI systems.

Re: Electric Fuel Pump for Jeep Stroker into an AMC Eagle

Posted: August 17th, 2021, 9:52 pm
by OverKnight
Thank you, Randy. Yes, the 1986 Eagle 4.2 L engines were carbureted with a mechanical fuel pump, and the 1993 Jeep 4.0 L is fuel injected. I’d prefer in in-tank pump because they run cooler, but I haven’t been able to come up with a tank designed for fuel injection that fits into an Eagle, nor have I found an electric fuel pump that fits into the stock Eagle tank. Are the Walbro pumps reliable? Whatever pump I decide upon, I’m thinking of getting some aluminum heat sink material and bending it to fit around the pump; this should help to keep things cooler. Why would I need an external fuel pump with a regulator? There is a regulator on the fuel rail. Would a regulator be needed at the pump to reduce the pressure down to whatever the fuel rail regulator needs?

You raise a good point about the stock injectors possibly being insufficient for a stroker. I think we’ll assemble the engine with the stock injectors (because we already have them and we’ve spent far more money on this project than we should have) and once we have it running we’ll look into larger injectors.

Thank you for the advice on the desired flow rates of the fuel pumps and the 30 lb/hr fuel injectors. Note that this engine will NOT be raced or run hard; my son is quite responsible in this regard, so we don’t need to tune this for mega horsepower. I still have a lot to learn about fuel injection systems.