![]() When you shut off the ignition, it powers down the fuel pump. When you turn on the ignition, the fuel pump relay is activated and will supply electricity to turn on the fuel pump. It is usually controlled by the ignition or the power control module. The combustion engine needs fuel to run, and the fuel pump relay ensures that that engine gets what it needs. The fuel pump relay is a necessary component for the combustion engine model to function. (Photo Source: arrow) What is a Fuel Pump Relay? The relay is vital for the function of combustion engines. Learn how the fuel pump relay works, the telltale signs of a failing fuel pump relay and how to diagnose, replacement costs plus regular maintenance tips. Therefore, problems with the fuel pump relay will result in the fuel pump malfunction, which in turn will cause start up issues.Ī bad or failing fuel pump relay will often show symptoms to tell the driver something is wrong. Whenever the ignition is turned on, the fuel pump relay will supply or “pass on” a consistent voltage to the fuel pump. To “relay” means “to receive and pass on”. The fuel pump relay is the electronic component found on all vehicles with an internal combustion engine. The fuel pump can malfunction due to several reasons, one of which is the lesser known issues with the fuel pump relay. Hence the fuse protection.You might be familiar with the fuel pump, the component inside the fuel tank that creates pressure in the fuel lines to push gasoline to the combustion engine for it to run. Perhaps it’s failure mode(s) - eg stalled motor, are such that in those circumstances it consumes more current, and Jaguar were concerned that it would heat up - probably not a good thing when immersed in fuel. The Lucas pump is a centrifugal pump which is immersed in the fuel tank, and (I think) runs continuously when the ignition is on. It would seem to me that this is unlikely to be a coincidence. If this is correct, this change coincides with the replacement of the in-tank Lucas fuel pump used in the 3.8s, by the SU pump fitted in the rear wing. Later cars simply used a switched unfused power source - White wire. As I had always been led to believe, the fuel pump is only fused in the S1 3.8s. So, it seems that the Jaguar wiring diagrams are correct, and others (including XKs) are not. ![]() It’s clearly wrong showing a fused fuel pump for the 4.2 models. ) I end up using the factory wiring diagram for most things, though the layout of the XKs booklet comes in handy sometimes. On my car, the #4 fuse legend is blank, and no wires are connected to the #4 fuse block.īTW I have found a number of inaccuracies in the XKs Unlimited wiring booklet for the 4.2 (I have the early one which is black and white, I believe the later editions were in color. The #4 fuse position was converted to support the hazard switch circuit on the S2 4.2 models and appears accordingly on the fuse panel legend. Of course I couldn’t say that a fuel pump fuse is lacking on some very early S1 4.2s, perhaps someone has documented this (or not.) I’m confident that the vast majority of 4.2 Series 1 E-types lack a fused fuel pump, and all of the 1.5 and Series 2s. A few months ago I was doing some troubleshooting where I wanted to engage the ignition but not pump up the fuel system, and learned this. I have a 1967 S1 4.2 E-type OTS, and it doesn’t have a fuse for the fuel pump. ![]()
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