Hi all

I thought I would dip into the font of knowledge and see if anyone can come up with a locost answer to my problem...

The problem is this. I have a Rover V8 running on webber carbs. Once the car has been stood for a bit the fuel evaporates from the carbs. Now, I have the oil pressure switch installed that will not allow any power to go to the fuel pump until the oil pressure is up or whilst the car is cranking (on the 3rd terminal).

The problem is that with the high output starter the voltage of the system drops that low there is not enough voltage to run the pump so I end up having to keep cranking the car until the starter motor has built up the oil pressure so the pressure switch turns the pump on. Not good.

My theory to fix this is to either fit a fuel pump "primer" button to the dash to manually prime the system or use a relay with a timed period (i.e. 10 seconds) to run the fuel pump to prime the carbs when the ignition is first turned on. The relay option seems the neatest but the only relay I can find that will do this costs about £40 and is therefore a bit expensive...

Anyone have any ideas of any other relays I could use for this? Any cars out there with one in that would do the job and cost somewhat less than a custom relay?

Many thanks

Mark

can you not just fit a push and hold switch that will give power direct to the fuel pump so that it bypasses the relay?

I could, although I would prefer it to be automatic. The dash mounted button is the backup plan.

Mark

some cars, pugeout i believe have relays that supply fuel only when it recieves an ignition pulse.
On inital turn on there is an initial delay.
Darren

looking at it from another angle Webers are known to to back syphon from the carbs if the carb is higher than tank. On the Elite/Eclat Lotus fitted a solenoid operated valve to get round the problem.
These valves are also used in LPG conversions and most LPG suppliers sell them.
see
http://www.tinleytech.co.uk/acatalog/Filter_shut-off_valves_and_filter_elements.html
also see Ebay
item 190356177492
item 300322245297
item 110467338300

If you want to use a relay a diesel glow plug relay from the scrappies should do the job.

Hi

I will check to see if I can find the Peugeot pulse solenoid, thanks!

I did initially think it was the fuel siphoning back to the tank so I fitted a non-return valve in the fuel line. This hasn't made any difference unfortunately. Not sure if those electronic ones would make any difference...

Regards

Mark

why not just bypass the pressure switch thats stopping it from starting.
adam

Do away with the pressure operated switch and replace it with an inertia switch That way in the event of an accident the pump will stop and it shouldn't flood the carbs anyway if the pressure is correct and the needle valves working if the ignition is left switched on for any reason.

Is the oil pressure/fuel supply going to do anything quick enough in the event of an engine problem.
If your running carbs, presumably the engine could carry on for quite some time enough to go bang anyway?

If your after a cheep timer relay, we got one from somewhere like SVC that was an interior light relay.

It comes on for about 10 secs when triggered and then goes off, you could use that to trigger a 2nd feed to the fuel pump when the ignition is sqitched on and then when things are running the original fuel pump feed would take over.

I think early Ford fuel injection motors used a timed relay. XR3 & 4's I think used a purple relay which had a yellow spot on it to show it was a timer type. If I remember correctly it ran for 3-5 seconds to prime things up..

Pickup the starter solenoid feed so as soon as you start cranking you feed 12v to the fuel pump - you'll need to put a high current diode in the new feed to stop the fuel pump feeding the starter solenoid, but unless anyone can see a reason why this won't work seems like a true locost solution? A high current diode can't cost much surely??

quote:

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Originally posted by russbost
Pickup the starter solenoid feed so as soon as you start cranking you feed 12v to the fuel pump - you'll need to put a high current diode in the new feed to stop the fuel pump feeding the starter solenoid, but unless anyone can see a reason why this won't work seems like a true locost solution? A high current diode can't cost much surely??

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^^^ wot they say - wire up the pump so that it will be on when starter is running.

that may not be enough to prime the pump so my suggestion isto have a little circuit with push botton that you press, it runs the pumps for about 10 seconds in addition to the above.


e.g. maybe something like this

a bitpriucey though - you can make something simular for a couple of quid with 555 timer.

Drive it more often. Then the fuel won't get chance to evaporate although knowing how much fuel it burns when running, thats not the locost solution.

How about this for a crazy (possibly clever) idea.
Wire the fuel pump to the brake light switch. Then when you get in the car, ignition on, foot on brake, fuel pump is on. Then no need for relay, no need for changing the switch wires.
basically the same as having a dash mount switch, but its not mounted in the dash

[Edited on 20/12/09 by balidey]

SD1 rovers and pre EFI range rovers had a wire when cranking that powered the fuel pump and bypassed the coils ballast resistor when cranking.

Regards Mark

Thanks guys, a few options there.

I prefer the idea of having a timed priming time but it is looking like bypassing the pressure switch might be the cheapest/easiest option..

Thanks

Mark