Fuel pump help
Discussion
Hi all
Went to take the wedge ('87 S2 350i) for a spin this morning in the sunshine. Wonderful for first 5 miles, then started missing, before stopping completely.
Got 'im back home and went to try and start. Will just about catch when starting up but running really really rough.
Checked plugs, cap and arm etc, nice strong spark at each plug.
Went back to fuel pump and no whirring / clattering. Checked electrical connectors, and put multimeter across cables (pump disconnected) and no voltage. Checked FP fuse ok, but no voltage either side of fuse carrier. Substituted FP relay with known good spare and still no joy. Checked power to relay base, there is power to supply side but nothing to coil of relay.
Am I on the right lines here? If so, where next?
Grateful for any clues
Chris
Went to take the wedge ('87 S2 350i) for a spin this morning in the sunshine. Wonderful for first 5 miles, then started missing, before stopping completely.
Got 'im back home and went to try and start. Will just about catch when starting up but running really really rough.
Checked plugs, cap and arm etc, nice strong spark at each plug.
Went back to fuel pump and no whirring / clattering. Checked electrical connectors, and put multimeter across cables (pump disconnected) and no voltage. Checked FP fuse ok, but no voltage either side of fuse carrier. Substituted FP relay with known good spare and still no joy. Checked power to relay base, there is power to supply side but nothing to coil of relay.
Am I on the right lines here? If so, where next?
Grateful for any clues
Chris
The fuel pump only gets power when the air-meter flap (flapper engines) is open (i.e. when the engine is running or when the starter is cranking.
I don't know how this works with hot-wire engines.
So turn on the ignition and open the flap before testing power to the pump.
This sounds as though the fuel filter could be blocked a bit.
Russ
I don't know how this works with hot-wire engines.
So turn on the ignition and open the flap before testing power to the pump.
This sounds as though the fuel filter could be blocked a bit.
Russ
OK, latest update:
Ignition ON, flapper OPEN, DMM shows voltage at the pump:
Connected existing +ve supply to pump but substituted temporary cable directly from -ve side of pump to battery -ve.
Still not working.
Removed temporary -ve cable, connected exisitng -ve supply to pump and put in temporary new cable between pump +ve and the O/P of FP relay.
Still not working.
Put in temporary cables between battery -ve to pump -ve AND pump +ve to O/P of FP relay and Bingo!
Assume then it must be dodgy cabling on both +ve supply from FP relay and earth, so my question to fellow Wedgers : - Does anyone know the cable route(s) or if there is a point where both cables run together and are susceptible to damage?
Ignition ON, flapper OPEN, DMM shows voltage at the pump:
Connected existing +ve supply to pump but substituted temporary cable directly from -ve side of pump to battery -ve.
Still not working.
Removed temporary -ve cable, connected exisitng -ve supply to pump and put in temporary new cable between pump +ve and the O/P of FP relay.
Still not working.
Put in temporary cables between battery -ve to pump -ve AND pump +ve to O/P of FP relay and Bingo!
Assume then it must be dodgy cabling on both +ve supply from FP relay and earth, so my question to fellow Wedgers : - Does anyone know the cable route(s) or if there is a point where both cables run together and are susceptible to damage?
Sorry, not much help. The lamp bit proved my supply was OK when it should have been and discounted the pump (well, more than likely elsewhere) and it was a hot wire not flapper. But my wire appear out the body behind the drivers seat belt enclosure trim bit. I did trace them just in case and they were OK. Just means taking some trim off, well, on mine anyway.
Thanks Jeff, your pointer was helpful - proved that a DMM can lead you (me) astray. In fact had my 13yr old busy for an hour or so knocking up the test-lamp, until the soldering iron broke too. Not a good day for electrics.
Wondered if there was a known failure point somewhere with these two cables, but will just trace the cables back bit by bit and replace them.
Wondered if there was a known failure point somewhere with these two cables, but will just trace the cables back bit by bit and replace them.
Only on the flapper I'm afraid but the main Efi relay, the fuel pump relay and the steering module all act in harmony to make sure the pump runs as required, check out the full process here:
http://www.vintagemodelairplane.com/pages/Rover_Te...
it may point to your problem.
http://www.vintagemodelairplane.com/pages/Rover_Te...
it may point to your problem.
Edited by honestjohntoo on Sunday 15th June 20:45
flattyland said:
proved that a DMM can lead you (me) astray.
Used to work where a bulb was sometimes more help than a meter. But changed disciplines and forgot all that until I asked about a problem here. V8S (??) I think put me back on the straight narrow. Cannot take credit for it.Sounds like a break in one of the wires, probably the live feed to the pump.
When you disconnect the wire there's probably a little bit of corroded wire bridging the gap.
The voltmeter takes very little current so will see a healthy +12V.
To find the gap what you'll have to do is trace the wire as it goes back to the fusebox, but still connected to the pump and live. You can stick a pin or needle into the wire at various points and check with the voltmeter to home in on the break.
Then cut out the duff bit and re-join the wire - don't forget to slip on some sleeving before you join the two halves - then you can slip it over this join.
I had exactly this problem on my starter wire and used the same method to find the breakage.
When you disconnect the wire there's probably a little bit of corroded wire bridging the gap.
The voltmeter takes very little current so will see a healthy +12V.
To find the gap what you'll have to do is trace the wire as it goes back to the fusebox, but still connected to the pump and live. You can stick a pin or needle into the wire at various points and check with the voltmeter to home in on the break.
Then cut out the duff bit and re-join the wire - don't forget to slip on some sleeving before you join the two halves - then you can slip it over this join.
I had exactly this problem on my starter wire and used the same method to find the breakage.
SOunds like it could be the dreaded wire rot. Used to see it sometimes on the negative battery lead on my Radio controlled aeroplane receiver batteries.
Some kind of galvanic effect between the metal of the battery tab and the wire I guess...Used to make the copper rot and turn to black dust.
Ed.
Some kind of galvanic effect between the metal of the battery tab and the wire I guess...Used to make the copper rot and turn to black dust.
Ed.
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