Fuel solenoid nightmare!

Can anyone explain this? The white wire from the ignition reads 12volts BUT as soon as you put it on the solenoid spade NOTHING! Also when the wire reads 12 v and you dab the bare end on metal...nothing! WHY? whats happening to the power? What is causing this drop to zero volts? HELP!

check the spade at the end of the wire or do a contanuity test on the cable, the chances are the spade is connecting to the cable properly or there is a break in the cable

correction not connecting to the wire, and when you do the test move the wire at the same time

or a knackered switch

Thanks but have done that. You can twist it every whichway and still get 12v reading BUt as soon as it meets other metal ( ie solenoid spade) output drops to zero

You have VOLTAGE but no CURRENT.

Your test meter reads VOLTS (reads electric pressure) without drawing any current in the process.

This means that wherever the supply to the white cable is coming from is a HIGH RESISTANCE. As soon as you apply a load on the while tag (solenoid coil), that tries to take CURRENT, so the voltage collapses at the Resistance in the line because the CURRENT can not pass the resistance, and that kills the voltage, possibly down to a fraction of a volt, like nearly nothing

Take off the battery leads - BOTH of them. KEEP THEM BOTH OFF DURING TESTS or you may burn out your meter.

Now, using the resistance scale on your meter OHMS x 1 to start, turn the IGN KEY ON, then measure the resistance from the tag on the white solenoid wire to the PLUS battery CABLE terminal. It should read in single figures, possibly at worst up to about 10 ohms.

If it shows nothing - too many Ohms to show on that scale (= high resistance) - change scales to ohms x 200 and try again. Then try Ohms x 2000 .... at which stage you KNOW you have a problem.

Let us know what you find, BUT, you definitely CAN get 12 volts at a loose cable end that drops to zero the moment a load is applied IF THE SUPPLY COMES THROUGH A HIGH RESISTANCE of any kind.

Dodgy switch contacts, bad connector, broken wire, whatever, but you've got one of them somewhere. Your mission (should you care to accept it) is to find and eliminate that resistance ....

CharlesY

Thanks Charlsey .... Will try it ........ I may be gone some time!

edorc said:

Thanks Charlsey .... Will try it ........ I may be gone some time!

Click to expand...

I have amended my post to try to make it clearer. Leccy can be a pain!

Disconnect BOTH battery terminals.

IGN ON all the time.

Measure between white wire tag and RED + Battery LEAD terminal, not the battery + post.

That could have been misleading earlier.

It may help if I say that on a RESISTANCE scale, your meter acts like a tiny BATTERY, and sends a very small voltage out of one of its test leads
- usually the red one goes positive. Let's say you clamp this red lead to the detached RED battery-cable terminal. There OUGHT to be a clear LOW RESISTANCE connection all the way to the white lead tag IF the IGN is ON. This path goes through the IGN switch or a relay.

IF, BUT ONLY IF, a continous circuit exists, some of that voltage will reach the other end of the test which means the tag on the white wire to the solenoid will have some voltage on it. You now connect your black test lead to that tag, and the meter can work out the RESISTANCE because it now knows what the voltage drop is in the "circuit". It's OHMS LAW at its best.

V = I times R .............. or to put it another way ...... Volts = Amps times Resistance.

R = V divided by Amps ............. or to put it another way ...... Resistance = Volts divided by Amps.

If you were careful, and if you have a good meter (!!!) you could try to measure the CURRENT the white tag can pass when the battery is connected again and the IGN key is ON. It ought to be HEAPS of amps, and it SHOULD send your 10-amp meter off the scale. You will probably have a separate terminal for the RED lead of the meter to read the 10 amp scale, AND set the knob. Test this only for an INSTANT! Else you may fry your meter and blow a fuse. But, as we expect now, if there is no apparent reading, set your meter to current 200m (move the red lead back to normal place first) that's 200 milli-amps, one fifth of an amp max. Test again. You will probably get a low reading. Let me know what it is.

CharlesY

Will do Thanks

that or the solenoid has failed and gone short circuit, pulling the white wire to ground on contact. If it had though you would get some sparks.

boydy1989 said:

that or the solenoid has failed and gone short circuit, pulling the white wire to ground on contact. If it had though you would get some sparks.

Click to expand...

......... and some smoke and flames from burning cables, or a blown fuse.

The solenoid would be more prone to fail OPEN circuit I think - coil burns out.

But all things are possible ... it's a LandRover!

CharlesY

I'm with CharlesY. At a complete guess pick out of the sky I would say a dodgy wire behind the ignition switch or dodgy switch itself. But it needs to be fault found as stated to get the exact fault and not change everything we think it could be. Once the fault is found its easy. Jai

Not wanting to hijack this thread but is my problem related?

Changed the fuel solenoid as it was leaking, started fine but refused to stop when ignition turned off. When I removed the wire the engine stopped. I put a multimeter on to the solenoid and when the engine was running +12v but when the ignition off, and engine still running, a few volts (1.7 - 2.4) were still present.

I've fixed it by putting a switch in the white wire to the solenoid so replecating taking the wire off. Any ideas?

Okay guys back from under the bonnet. Tested as Charlesy suggested and the resitance was infinite! Obviously the lead is knackered. Now about to re wire with a working lead. Many thanks to all who contributed their ten pennuth And Charlesy you are the main man! RESPECT!