[Hybrid]

I'm running a VL efi pump off of a megasquirt ECU. Basically the ecu sends a trigger to a relay which then runs the power to the pump. I turn it on once and nothing. Turn it on the second time the pump turns on. It's more of an annoyance than anything. I thought the ecu wasn't triggering until each second time but I checked the ECU log and its working every time. The other day I noticed that the when I have my head lights on it wont trigger the relay at all. Could this be voltage drop and just could be as easily fixed as an increase in the wire guage? Or is it possible to get a relay that triggers on half the current for example? I've got a digital multimeter and can measure voltage and resistance but don't know how to set it for current.....

[Damo]

Hybrid wrote:

I'm running a VL efi pump off of a megasquirt ECU. Basically the ecu sends a trigger to a relay which then runs the power to the pump. I turn it on once and nothing. Turn it on the second time the pump turns on. It's more of an annoyance than anything. I thought the ecu wasn't triggering until each second time but I checked the ECU log and its working every time.

I think the datalog goes on what's happening in the ECU, eg, is that output on or off, not actually monitoring what is happening past the ECU itself. So i'm thinking it may be something to do with the output stage. Did you assemble your MS? It's not hard to get the ouput transistor the wrong way around, especially if you are substituting components. Ask me how I know If you put a meter on the actual output and hit the ignition and see if there is any signal there, that should give you an idea of what's going on.

Hybrid wrote:

The other day I noticed that the when I have my head lights on it wont trigger the relay at all. Could this be voltage drop and just could be as easily fixed as an increase in the wire guage? Or is it possible to get a relay that triggers on half the current for example? I've got a digital multimeter and can measure voltage and resistance but don't know how to set it for current.....

How do you have your relay hooked up? Does the 12v feed go direct to the battery? Cable size could be an issue.

Current can be calculated if you have the resistance and voltage, it's ohms law, I = V/R or current = voltage/resistance.

[Hybrid]

Damo wrote:

Hybrid wrote:

The other day I noticed that the when I have my head lights on it wont trigger the relay at all. Could this be voltage drop and just could be as easily fixed as an increase in the wire guage? Or is it possible to get a relay that triggers on half the current for example? I've got a digital multimeter and can measure voltage and resistance but don't know how to set it for current.....

How do you have your relay hooked up? Does the 12v feed go direct to the battery? Cable size could be an issue.

Current can be calculated if you have the resistance and voltage, it's ohms law, I = V/R or current = voltage/resistance.

If I had the transistor back to front wouldn't it just never turn the fuel pump on. Not on the second go. It definately seems to trigger as a current build up as it wont work the first but will work 2nd 3rd and so on. Also if I get out of the car at say the shops it will sometimes work first go when I get back in provided it hasn't been too long. Def seems to be a voltage drop or something.

Ahhh yes I remember V=IR from physics. It was taught around the same time as the right hand grip rule . It would be hard to get the probes on the ecu output and the relay at the same time though. I want to just run the multimeter to measure the current at the relay to see if its provided the 300ma trigger (I think thats what they require) as soon as it is turned on.

[royce]

hook your test light (multimeters are shit for this stuff) across the power and earth at the pump, then turn it on and if the light lights up but the pump dont run the pump is faulty, if it doesnt light up then youll need to get it back to where it will fault and check power across terminals 85 and 86 on the relay, if they light up but power out of it then start working that way and so on, eventually you will find whats not working