How many volts at EGI Main Relay?
02-23-2006, 12:50 PM
#1
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Join Date: Feb 2006
Posts: 3
Hi All,
First post here so first up, hello.
I'm in the middle of trying to diagnose a problem with my '94 FD. To put it short it won't start, turns over fine but won't fire. I've traced the problem back to getting no switched power at the PCME (Terminal 1B) so I guess it's probably the EGI Main Relay (or possibly a bad ground). With the ignition on and testing for voltage I get just over 9v coming from the + power terminal that the relay plugs into, is this correct or should I be getting a full 12v there?
First post here so first up, hello.
I'm in the middle of trying to diagnose a problem with my '94 FD. To put it short it won't start, turns over fine but won't fire. I've traced the problem back to getting no switched power at the PCME (Terminal 1B) so I guess it's probably the EGI Main Relay (or possibly a bad ground). With the ignition on and testing for voltage I get just over 9v coming from the + power terminal that the relay plugs into, is this correct or should I be getting a full 12v there?
02-24-2006, 05:46 AM
#4
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Join Date: Feb 2006
Posts: 3
Fuel pump relay gets 12v as expected, then the fuel pump resistor drops it down to ~9v for the low speed mode. EGI main has 9v going to it for some reason, I would have thought it would be the full 12v. Will have to check the wiring going to that as it would seem it might be dodgy, would an ignition switch on it's way out cause this kind of problem?
02-24-2006, 10:37 AM
#5
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Join Date: Feb 2006
Posts: 3
You'll have to forgive me, am still learning this stuff and took the reading from the wrong terminal in the relay's box, had the orientation of the relay wrong .
Basically my problem is that my FD won't start up, it turns over just fine but doesn't fire. Previously to this the problem was intermittent, sometimes it wouldn't work at all and other times you'd hear lots of clicks from the relays (I guess both fuel pump and main) and then they'd settle down and you could turn the engine over and it would fire perfectly and then run with no problems. I was pretty sure that it was the main relay on it's way out as I have a gauge wired into the PCME on the switched feed (terminal 1B) that comes from the main relay, if the gauge lights up then I know power from the relay is ok. But right now nothing, so I'm definately not getting the switched power supply through.
The main relay + feed from the ignition is reading 12v as it should be, so is the + for the fuel pump relay. I've had both relays out of the car and tested them with a spare battery, both click as expected and both seem to have continuity, so I think they're ok. Could the relays still be bad, even if they seem to check out like that?
I've checked the fuel pump works by bridging F/P and GND on the data link connector and listened for it operating with the ignition switch on, I can hear it so I guess the pump is ok...haven't tested the actual unit but I figure I don't need to yet as I'm not getting the relays clicking when I turn the ignition on and until that happens it's not an issue.
I've checked voltages and lots of grounds at various points and all check out ok. Other than one or both of the relays being shot I'm running out of ideas as to what the problem is. I would just buy new relays and try them out if they weren't so expensive. 50 quid and 70 quid ($210).
Any thoughts or suggestions would be welcome.
Basically my problem is that my FD won't start up, it turns over just fine but doesn't fire. Previously to this the problem was intermittent, sometimes it wouldn't work at all and other times you'd hear lots of clicks from the relays (I guess both fuel pump and main) and then they'd settle down and you could turn the engine over and it would fire perfectly and then run with no problems. I was pretty sure that it was the main relay on it's way out as I have a gauge wired into the PCME on the switched feed (terminal 1B) that comes from the main relay, if the gauge lights up then I know power from the relay is ok. But right now nothing, so I'm definately not getting the switched power supply through.
The main relay + feed from the ignition is reading 12v as it should be, so is the + for the fuel pump relay. I've had both relays out of the car and tested them with a spare battery, both click as expected and both seem to have continuity, so I think they're ok. Could the relays still be bad, even if they seem to check out like that?
I've checked the fuel pump works by bridging F/P and GND on the data link connector and listened for it operating with the ignition switch on, I can hear it so I guess the pump is ok...haven't tested the actual unit but I figure I don't need to yet as I'm not getting the relays clicking when I turn the ignition on and until that happens it's not an issue.
I've checked voltages and lots of grounds at various points and all check out ok. Other than one or both of the relays being shot I'm running out of ideas as to what the problem is. I would just buy new relays and try them out if they weren't so expensive. 50 quid and 70 quid ($210).
Any thoughts or suggestions would be welcome.
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