240 relay prob
 

Hi. I have an 1989 240, 2litre estate. No start. Fuel pump works, relay seems to, that is, if u hold it an turn key you can feel it click, an click again when turn off. If, as says in Haynes, i jump fuse 4 and 6, engine starts straight up. I bought a new fuel pump relay, no change. Can't see any wiring faults, an as car runs with fuse jump, main wires to pump, ignition switch, etc, must be ok. Any pointers, people?

There are two kinds of fuel pump relay - white and green. I'm not sure what the difference is, nor whether they are even interchangeable in fitting. You do presumably have the correct one?

The fuel pump relays are not interchangeable - green for a k-jet car, white for a 2.4lh car.

Cheers

Well, it had green one when i got it. In glove box was another green one, date stamped july '87. The one fitted was stamped 2007, so i assumed green correct. certainly it ran fine with it, until recently. Car had stood for ten yrs, so i renewed underneath completely, brakes, suspension, exhaust, wheels.

Jumping fuses 4 and 6 bypasses the rely and lets the pumps run continuously.
If the engine then starts and runs properly then it surely can only be the relay faulty, or perhaps the socket it plugs into, or the connections at the fuse board?

Ummm, that's what i thought, but couldn't find anything. But. . . i noticed that fuse 6 had got hot, to the extent of melting the foreward end of fuse enough to sink in the actual metal strip. Does that imply resistance? What could cause that?

"Received Wisdom" in the forum is that heating and melting of individual fuses is caused or exacerbated mainly by most fuses available now for that fuse box do not meet the original specification.

1. The end caps tend to be aluminum or similar. That reacts with the copper/brass terminal in the fuse box. Resistance results and heat follows

2. The fuse body tends to be plastic. That often melts when hot. The body should be ceramic.

True ceramic and cuprous fuses can be found. If you search the forum you might find the information.

Thorough cleaning of the fuse box has been tried and in at least one instance, the problem still re-occurred.

There is a body of opinion in the forum to by-pass those two fuses using inline flat bladed fuses. The name for those fuses escapes my memory.

I hope this helps.




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Izatso? Interesting. Merci.

P.S. ... I believe the name for flat bladed fuses is ...

Blade Fuses ... :)




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You could confirm this diagnosis first simply by bypassing each fuse and holder separately, rather than together.

I think what often happens is that having once run hot, the plastic base holding the terminal strips is then irretrievably weakened and does not hold the terminals properly. Also the metal terminals themselves have possibly been softened by over-heating.