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Old October 9th, 2020, 21:59
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8Mud 8Mud is offline
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Join Date: Sep 2003
Location: Central Germany
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Re: 1991 XJ SE - Crank no start problems

I may be wrong, I'm old three relays control the fuel pump. ASD relay supplies power to the whole sytem, the ballast relay is power to the pump while cranking and bypasses the ballast resistor, the fuel pump relay supplies power while running through the ballast resistor.

The black green (?) wire at the ballast resistor should be hot both during cranking and running. I may be wrong on the color, one end of the resistor should be near battery voltage the other end noticeably less than battery voltage, but hot none the less. A quick check for both the fuel crank and fuel run relay.

Unclewolverine may be onto something, seen it before, the fuel pump wire/harness goes through multiple connectors (5-6?) which increases the chance for one to cause issues. The fuel pump ground can also cause issues.

If you have power at the ballast resistor, at the pump in the rear, a good ground and still no fuel try wacking the outside of the fuel tank near the pump hard a few times with a rubber mallet. When the pump sits idle for a long time, the varnish in gasoline can cause them to seize. It is sometimees possible to free the pump with a sharp blow to the side of the tank.

Another quick test, when the key is first turned to/or through the run position the fuel pump should run for a few seconds to prime the fuel rail. Turn it to run a few times, then push in the shrader valve on the fuel rail, you should get a squirt of fuel. On mine I can hear the pump run for 2-3 second when I turn the key to run, it's subtle but noticeable.

Lastly when they have been sitting for a long time the fuel filter gets gunked up. Have some extra fuel line handy and take the filter off, wash it in some solvent or gasoline, blow through it backwards. Make sure to keep track of in and out on the filter. Have something handy to plug the line from the fuel tank, it may start to siphon drain the tank with the filter removed. A new filter isn't really very expensive, I usually put one in after I've had it running for awhile, I reuse the old filter until things have cleaned themselves out some with fuel flow.
I don't have a 91 schematic, but the basics transend multiple years.
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