Midas Cars Forum - www.midascarsforum.com

Hello,
I have a problem with my fuel pump. I want to lower the voltage bij adding a ballast resistor. I had one for an ignition, it measures between 1 and 2 ohms so I suppose it's around 1.5 ohms. When I put it in series with the pump (which is 3 ohms) I should lower the voltage of the pump to around 8.1 V. Total current would be 2.7 amps (U = I x R, 12V = I x (1.5 + 3), so I = 12/4.5 = 2.7 amps. I did this mod and within 1 second the inline fuse blows. It's a 10A, so should be fine, but also a 15A blows. I've hooked the ground up to a running ground wire in the boot, but I don't see this adding any amps. Does anyone with a better understanding of electrics have an idea how this can happen?

oops, had made a wrong connection on the relais. sorted and no more blowing fuses. Carb keeps dumping fuel though, so next step is he pressure regulator.

Hans,have you ran it with the pump before? just asking because most electric pump systems have a return to the tank,which takes the pressure off the carb.I had to plumb a return to the tank on my spyder when I tried an electric pump conversion,but then I found that the pump would only work on a bottom feed from the tank and mine was a top feed!. hope you fix it,Stan.

stan1396 wrote:Hans,have you ran it with the pump before? just asking because most electric pump systems have a return to the tank,which takes the pressure off the carb.I had to plumb a return to the tank on my spyder when I tried an electric pump conversion,but then I found that the pump would only work on a bottom feed from the tank and mine was a top feed!. hope you fix it,Stan.

Yes I bought it this way. Pump sucks it via the standard Midas hose from the tank. It's a turbo tank with a return. Return is from the pressure regulator. I found the return line kinked. Also used a hose on the turbo inlet of the pressure regulator and sucked/blowed in it to make the valve move. It worked and no more fuel dumping. Then I started the engine and the lamda gauge worked great but ik kept on saying lean. After giving it max co I noted the sucking sound of the anti run valve. It hadn't closed. I found no earth so pulled a new earth. I think I have damaged the wiring because the brake fluid warning doesn't work either. After a new earth the anti run valve closed and it turned out the engine was running rich:

Just a matter now of adjusting the carb and hopefully not to many problems anymore. If all is well next week for the MOT

Hans, the gauge on the right, the "multigauge" - what does that read, and how many functions can you use it for?

David L wrote:Hans, the gauge on the right, the "multigauge" - what does that read, and how many functions can you use it for?

It can be used for many things, but in this case it's the wideband lambda read out. It can also record a run that can be displayed as a graph (it has 3 touchplaces on the screen). 14.7 is the perfect stochiometric mixture. Below that is rich, above it is lean. So it's quite easy to adjust the carburettor and see how it performs on the run. I am preparing fuel injection with an Emerald ECU and the PLX signal will go directly into the ECU so it can adjust the injectors itself via a feedback loop. I just program the mapping telling the computer what mixture I want under what load and at which RPM. But for now it is used to find the correct needle without the need to do a rolling road test.

I do like the idea of an instant readout of mixture strength, but a quick Google told me the price of these gauges, which has rather put me off the idea...

David L wrote:I do like the idea of an instant readout of mixture strength, but a quick Google told me the price of these gauges, which has rather put me off the idea...

A complete kit is 185 euro's including lambda probe and free shipment. It's this kit. Not a bad price for a complete kit:
http://www.ebay.co.uk/itm/PLX-DM-6-AFR- ... 45ff38c11d

Hans Efde wrote:

David L wrote:I do like the idea of an instant readout of mixture strength, but a quick Google told me the price of these gauges, which has rather put me off the idea...

A complete kit is 185 euro's including lambda probe and free shipment. It's this kit. Not a bad price for a complete kit:
http://www.ebay.co.uk/itm/PLX-DM-6-AFR- ... 45ff38c11d

It would tempt me more if I didn't have a list of things my Midas needs, already a mile long! Also, I've just fitted a new LCB without a lambda probe mounting point. However, my experience of mild steel LCBs is that they don't last very long, so maybe next time...

David L wrote:

Hans Efde wrote:

David L wrote:I do like the idea of an instant readout of mixture strength, but a quick Google told me the price of these gauges, which has rather put me off the idea...

A complete kit is 185 euro's including lambda probe and free shipment. It's this kit. Not a bad price for a complete kit:
http://www.ebay.co.uk/itm/PLX-DM-6-AFR- ... 45ff38c11d

It would tempt me more if I didn't have a list of things my Midas needs, already a mile long! Also, I've just fitted a new LCB without a lambda probe mounting point. However, my experience of mild steel LCBs is that they don't last very long, so maybe next time...

It's only necessary when you upgrade your engine regularly and want to save money on a rolling road test or CO adjustment. For me it's necessary because I need it for the conversion to injection. But I pulled this mod forward because I will be using a SU carb this summer and want to make sure I am not running the engine too lean. Also I am not sure which needle I need.