fuel pump relay check

Why not just connect it directly to the battery to see if it runs? (A trickle charger may not be able to supply enough current.) Use whatever bits of wire you have laying around; if you're careless, nervous, or both, make up a lead with an inline fuse. Chance are you could carefully use jump leads if that's all you have.

Don't run the pump dry for too long.

You can't just power up the relay to test its function; there are essentially two parts to it. Firstly, the magnet coil. If you can identify which terminals of the relay are the coil, connecting 12v to those should make it click, and show that part is probably working.

However, the likeliest failure mode is that the contacts that the magnetic part operate are worn. You won't be able to check that, at least without a multi-meter.

Best bet is to try another relay. A generic one is not going to be expensive. There may be another suitable one on the car that you could temporarily use, but be sure it is suitable first.

Alternatively, identify which two pins of the relay socket connect to the switching part. Bridge those with a short bit of wire poked in the holes. With the ignition on, the pump should then run. If so, the relay or the supply to the relay coil is the fault.

TBH, if you really are not confident about this sort of stuff, and you run an older car, AA/RAC cover would at least give you a chance of some fault diagnosis.

Chris

Do you mean starvation - ie not enough fuel - or none at all?

The driver's handbook usually gives details of where the fuses are and what they do. If there's not a list on the actual fusebox.

Pumps usually take more current than a trickle charger could provide. But many battery chargers won't give any output unless connected to a battery anyway. And aren't suitable as a power supply substitute. So why not just use the car battery?

Is the internal battery flat? If you switch it to resistance and short the leads, does it read zero, or near zero? Ebay is full of cheap DVMs and they're usually ok for simple things. Or Maplin.

You can test relays, but it sounds like it may be beyond you. If it is a standard type, take it to a decent accessory shop and see if they can supply a spare - should cost about a fiver, so better to eliminate it by substitution of a new one if possible. If it is a unique type and a maker's spare is expensive, ask again.

Hear's a mail order source of the common relays:-

All the fuel injected cars I've seen will switch the pump on for a couple of seconds as you turn the ignition on, to pressurise the injectors.

This being the case, couldn't you do a simple test of the wiring, relay & fuse by substituting the fuel pump for a headlight bulb? Flick the ignition on and if it lights up nice and bright, you have a healthy power supply to your pump. The other advantage to using a bulb, besides providing a quick indication, is that it will draw a few amps of current and prove your connections are good.

Stu

My early Rover with EFI doesn't. Operating the starter does, though.

If it does run the pump when you switch the ignition on you should be able to hear it - perhaps from outside the car.

Stand corrected. I have experience of Nissan, Toyota, Bosch and Ford systems, which all behaved as described so I just thought it was the usual case.

This I know - it's how I came to understand the above. ;-) You're quite right to point it out, though.

I had assumed, perhaps wrongly, that the OP had already tried listening for the pump and was now beginning fault diagnosis by confirming the power supply and/or testing the pump on a seperate source.

The Lucas/Bosch system was the first EFI in the UK - and they reckoned it would hold pressure for a long time. As it will when perfect. But even if it doesn't, not much cranking is needed.

There are many options for testing it. And just as many possible faults. ;-)

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Thanks to all. It turned out to be be: 1. i didnt test *properly* to see if current was going to pump.(either meter was playing up or probes didnt go in properly to make contact). So after advice i thought it was the relay or something. But checking more carefully the current was getting through to the pump. Taking the pump out, it turns out the contact on the top of the pump had been shorting out, in the process; destroying the contacts and inside the plastic housing.

this makes me think if contacts were sparking inside the petrol tank, am i lucky to still be here?

thanks for all the help.

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petrol is quite fussy about the concentrations that it will explode in and the conditions inside a tank are far too rich to go bang. Now if it had been acetylene..........