Hi guys,
I recently finished building a MS2 DIY unit and for the most part everything is working but I don't yet have a successful fire. I verified spark today and started to look at fuel.
As I understand the M20 (on motronic) does not ask anything of the fuel pump until it has begun cranking and does not fire a prime. In trying to keep my cranking to a minimum as I have neighbors directly above my garage (the garage directly under my unit becomes available at the end of this month thankfully) I've been trying to get the pump to fire via the priming pulse from MS in an effort to rule out fuel as an issue and then assuming MS can successfully fire the pump if it can prime it. Side note - for some reason my starter sounds like one for a loud truck.. anyway..
I've verified with my multimeter that MS outputs a priming ground closing the circuit to ~12v on the MS fuel pump relay wire vs switched 12v for a couple of seconds upon turn of the key which rules out issues with the build of the megasquirt unit itself (my soldering isn't the best). I've verified that this signal makes it through the stock motronic harness out to the relay by testing 12v+ right off the battery vs the corresponding fuel pump relay pin out of the motronic harness (pin 85 I think? hard to say back at the desk but I know I had it right out in the garage).
I'm able to get the pump to fire by jumpering 30 and 87.
I've verified that the main relay does talk to the fuel pump relay with voltage timing corresponding with the prime timing (by testing between 85 and 86 upon key turn) - however my multimeter shows around .25 volts for this established priming period of time. Being admittedly short on knowledge with relays and google not providing much help as far as switching voltage this has me at a loss.
Is that enough to switch the fuel pump relay? If not does this point towards the main relay not letting enough voltage through? Or to the aging fuel pump relay requiring more voltage than normal to switch? I suppose I can just pony up and buy both new as I've only had the car for around 4 months and god knows what laundry list of problems it came with considering rats have eaten much of my plastic and destroyed my comfort seat... but I figured I'd consult the collective knowledge held here as maybe the issue lies somewhere I hadn't yet considered.
The signal makes it through, but at a fraction of the voltage that it did when testing 85 and 86 vs 85 and 12v+ ... Is it fair to assume that even though the M20 did not originally prime it's pump that the pump should fire when presented with a ground on the fuel pump relay no matter what the condition is?
The car ran perfectly fine with the harness plugged into the motronic ECU before I unplugged it and started stuffing bare wires into the connectors so I'm at a loss as to how a relay could suddenly stop working..
Once I have everything verified I'll be buying an old ecu to make a connector from but for now I don't see any problems with stuffing copper in sockets
Any ideas?
I recently finished building a MS2 DIY unit and for the most part everything is working but I don't yet have a successful fire. I verified spark today and started to look at fuel.
As I understand the M20 (on motronic) does not ask anything of the fuel pump until it has begun cranking and does not fire a prime. In trying to keep my cranking to a minimum as I have neighbors directly above my garage (the garage directly under my unit becomes available at the end of this month thankfully) I've been trying to get the pump to fire via the priming pulse from MS in an effort to rule out fuel as an issue and then assuming MS can successfully fire the pump if it can prime it. Side note - for some reason my starter sounds like one for a loud truck.. anyway..
I've verified with my multimeter that MS outputs a priming ground closing the circuit to ~12v on the MS fuel pump relay wire vs switched 12v for a couple of seconds upon turn of the key which rules out issues with the build of the megasquirt unit itself (my soldering isn't the best). I've verified that this signal makes it through the stock motronic harness out to the relay by testing 12v+ right off the battery vs the corresponding fuel pump relay pin out of the motronic harness (pin 85 I think? hard to say back at the desk but I know I had it right out in the garage).
I'm able to get the pump to fire by jumpering 30 and 87.
I've verified that the main relay does talk to the fuel pump relay with voltage timing corresponding with the prime timing (by testing between 85 and 86 upon key turn) - however my multimeter shows around .25 volts for this established priming period of time. Being admittedly short on knowledge with relays and google not providing much help as far as switching voltage this has me at a loss.
Is that enough to switch the fuel pump relay? If not does this point towards the main relay not letting enough voltage through? Or to the aging fuel pump relay requiring more voltage than normal to switch? I suppose I can just pony up and buy both new as I've only had the car for around 4 months and god knows what laundry list of problems it came with considering rats have eaten much of my plastic and destroyed my comfort seat... but I figured I'd consult the collective knowledge held here as maybe the issue lies somewhere I hadn't yet considered.
The signal makes it through, but at a fraction of the voltage that it did when testing 85 and 86 vs 85 and 12v+ ... Is it fair to assume that even though the M20 did not originally prime it's pump that the pump should fire when presented with a ground on the fuel pump relay no matter what the condition is?
The car ran perfectly fine with the harness plugged into the motronic ECU before I unplugged it and started stuffing bare wires into the connectors so I'm at a loss as to how a relay could suddenly stop working..
Once I have everything verified I'll be buying an old ecu to make a connector from but for now I don't see any problems with stuffing copper in sockets
Any ideas?
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