UK Car Repair: 1998 Range Rover 4.0 - stumbling, electronic cars, fuel gauge

Question
QUESTION: I have a 98 4.0 that has been stumbling occasionally while driving at all different speeds. At first I suspected water in the gas, dry gas and several tanks, still happening. Changer plugs and wires, no help. Change fuel filter (as dirty as I have ever seen), still happening. No codes on 2 different readers, but still happening. Next stop replace the fuel pump but now we are starting to get expensive. Any thoughts?

ANSWER: So many times blocked fuel filters cause pump failure.  The pump is strong enough to force the fuel through but it overheats badly causing it to stop erratically and eventually fail.  The only way to really tell is to Tee a fuel gauge into the supply hose at the rear and drive with the gauge on it.  With electronic cars there are many things that can cause erratic misfiring, so positive diagnosis is very important.

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QUESTION: Thanks for the quick response. Would the fuel pump acting erratically spit out error codes? Also, what gauge would you recommend?

ANSWER: No, there will be no error codes as it is a momentary problem, Even when it stops pumping it just shuts the engine down as nothing actually failed! get a simple 0-100 PSI gauge, get it long enough so that you can have it up on the windscreen when driving.

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QUESTION: Thanks. I hooked up a pressure gauge and went driving. During the stumble, the pressure didn't not change or drop off at all? At this point, not sure where I should look next. Any thoughts? Thanks again.

Answer
Well at least you are going through the proper process. Now you know it isn't fuel pressure so, it has to be electrical. Whether it is a faulty signal to the injectors or the ign system (or both) is the next phase. You can buy a spark tester, this unit fits into the HT wire between the coil & distributor,  Similiar to the fuel test, get (make up) a long plug cable to extend the connectors on the tester so that you can see it and drive again. These types of faults are tricky to find as they are usually a bad/poor connection somewhere. The problem is the connection may be at any of the hundreds of connectors there are between the various modules and their sensors. keep going!