Hi. I am not sure if this is the place to be posting this but I have searched all over MT and other forums but can find any advice

I have a 1990 Mazda mx5 1.6L with 100,000 miles

i have just recently switch to megasquirt (ms2 diypnp) and I have plugged it all in. ran vacuum line to ecu, installed IAT sensor. ran the 2 wires to the MAF plug and connected them to slot 1 and 6. I went to turn the ignition on and the fuel pump didn't prime. So I tried starting and no fuel pressure. The fuel pump works if I jump the F/P slot and GD slot together. And the car will start up but run rough as I haven't mapped it yet. There doesn't seem to be any broken wires to and from the fuel pump relay or the main relay also there seems to be power being sent out of the ecu slot second in from the left which if I am right is the fuel pump slot.

Any thoughts or test I could try would be great as I have spoke to the person who built the ecu and they can't think what could be wrong. I have also sent the ecu back to be check on and all is fine as they tried the ecu in there own mx5 and they found no problems with the ecu.

I have had a few people suggest that it could be a faulty main relay? Can the main relay still control the fuel injection fine but not talk to the fuel pump? As the car start if you force the pump on.

Any advice will be greatly appreciated

thanks in advance

 

https://www.miataturbo.net/megasquir...4/#post1094911

Jump those pins

 

Great thanks I'll give that ago in the morning. I had read up about the fuel pump using the MAF for something but I wasn't sure what

 

Gave that a go and doesn't seem to have done much I had a look at that thread you linked and I am not to familiar with the internals of the megasquirt but this is the board I am using if this helps

 

I had another look around and sourced that on the ecu 1C is for the fuel pump 1c is at top right 2nd down
and this goes through to a purple wire then to the fuel pump relay I did some testing with a multimeter and there seems to be only 0.178V coming from 1C and the purple wire? Should this not be a 12V as it is telling the fuel pump relay to turn on and also is the ecu grounding the fuel pump relay? Does this indicate a faulty ecu?

 

if you didn't pull the ST_SIG fuse, then you blew up the driver that runs your fuel pump.


failure to pull the fuse, when using the High Side Driver circuit, means failure to the circuit and no fuel pump.


jump FP directly to 4O and use the jumper in the AFM connector like @aidandj mentioned

 

Thanks for the advice.

I deffenatly did remove the fuse. I have also sent the ecu back to get look over and according to the people that made the ecu. They say it is fine and have used it on there own mx5's to test it.


where abouts will I find the FP and 4O to jump?

Thanks

 

FP is currently going to IN on the high side driver, remove it from IN, and put it on 4O on the connectorboard. that sends the FP ground to an unused wire on the AFM, when you jump it, it connects the ground to the fuel pump relay.

 

Thanks again for the advice that seems to have done the trick fuel pump now turns on with the ignition but is always on? It doesn't prime it just stays on. I take it that this is because I am now just grounding the fuel pump and the ecu doesn't control the fuel pump?

Because of this working. does this indicate a blown driver or faulty ecu?

thanks

 

i dunno is it always on? it shouldn't be in that method (like I said, you connect the FP output from the MS directly to the fuel pump relay, when the MS grounds that output, it activates the relay) -- otherwise i would have told you to simple jump F/P and GND in the diagnostics connector.

 

So unfortunately my dad went ahead without my permission and decided to plug in the stn fuse. I kind of understand when you are saying but can you give me a step by step process because wiring is a whole new thing for me? I will give you a quick run down of what happened; tried to start the car and heard no click or prime. Went and bought a fuel pump relay and still had the same problem. And that's when I figured out my dad had plugged in the fuse.

 

What exact MS are we talking about here?

 

Will the FP run through the test modes in TS?. If not that would point to your FP fuse inside the ECU. I had this exact issue. Try jumping the FP in the Diag box (paperclip in FP and GND), that should manually enable the FP and you should be able to proceed with it as a temporary fix.