roxj
NAXJA Forum User
- Location
- the woodlands, texas
is there any difference in the fuel pumps used for a carbed xj and a fuel injected one? i have an 85 with a carbed 4cyl that i am replacing with a 93 model low mileage fuel injected 4 cyl.
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fuel pump differences in carbed and fi xjs?
- Thread starter roxj
- Start date
5-90
NAXJA Forum User
- Location
- Hammerspace
Yes.
Carbed fuel pumps are typically mechanical, and driven by an eccentric on the camshaft.
FI fuel pumps are electric, and develop higher pressures (WP for a carbed pump is 3-5psig, usually - FI WP is up around 45-50, and a regulator is involved.)
Also, the FI fuel pump is usually rated to deliver a higher volume. Since the volume of fuel delivered to the engine is controlled by injector pulse width, that's not a problem - but it should still be considered.
You can probably switch out the "stinger" assembly in the fuel tank and install an FI pump that way, then just run the wiring back. The fuel level sender should work the same, so it's just a matter of running power and ground back to drive the fuel pump. And, switch out the soft parts of the fuel line for higher-pressure fuel hose (due to the higher pressures involved.) You'll probably also need to reterminate the engine end of the thing, and provide a return line, since you don't have return lines for carburettors.
And, you'd have to bring the electronics across to make the fuel injection happen.
However, you should be able to either install the intake and carburettor on the later block (probable) or just swap the carburetted top end onto the FI short block (very likely) and swap it that way. You can replace the OEM carburetted fuel pump with an electric carburetted pump (spec'd for 3-6 psi) without too much trouble. Why for are you swapping the engine?
Carbed fuel pumps are typically mechanical, and driven by an eccentric on the camshaft.
FI fuel pumps are electric, and develop higher pressures (WP for a carbed pump is 3-5psig, usually - FI WP is up around 45-50, and a regulator is involved.)
Also, the FI fuel pump is usually rated to deliver a higher volume. Since the volume of fuel delivered to the engine is controlled by injector pulse width, that's not a problem - but it should still be considered.
You can probably switch out the "stinger" assembly in the fuel tank and install an FI pump that way, then just run the wiring back. The fuel level sender should work the same, so it's just a matter of running power and ground back to drive the fuel pump. And, switch out the soft parts of the fuel line for higher-pressure fuel hose (due to the higher pressures involved.) You'll probably also need to reterminate the engine end of the thing, and provide a return line, since you don't have return lines for carburettors.
And, you'd have to bring the electronics across to make the fuel injection happen.
However, you should be able to either install the intake and carburettor on the later block (probable) or just swap the carburetted top end onto the FI short block (very likely) and swap it that way. You can replace the OEM carburetted fuel pump with an electric carburetted pump (spec'd for 3-6 psi) without too much trouble. Why for are you swapping the engine?
roxj
NAXJA Forum User
- Location
- the woodlands, texas
thanks for the info 5-90. when i bought it it came with a 93 model fi engine, complete harness and computer. the original engine had been removed all ready. ive got the new one in and it turns over and sounds good i just need to get the fuel delivery figured out. at this point i will probably pull a complete tank from the yard. i need to go yard huntin anyway since i want to replace the seats and get a later model electronic gauge cluster and the electric speedo connection for the tcase. this whole thing has been a pia but on the bright side im only in to it for about $200. including what ive spent on new fluids, plugs, wires etc.
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