2001 GT40 Repower - Check engine light

On the temp sender, have you tried disconnecting the wire at the sender, and grounding the wire directly to the block? If the gauge pegs, then the guage is working and it's a sender issue.

Bri892001 wrote: On the temp sender, have you tried disconnecting the wire at the sender, and grounding the wire directly to the block? If the gauge pegs, then the guage is working and it's a sender issue

No, I just swapped the guage as the guage was reading well above zero when switched off and I had a spare but will try this to confirm.

Fl Inboards wrote: Disconnect the oil pressure switch (not the the oil pressure sender for the gauge) see if the problem goes away. If not reconnect and then do the same with the water temp Switch (not the sender for the gauge). The check engine light circuit runs through the oil pressure and water temp switches, it is a green wire in the harness. Chase that circuit down you will find your issue. Also did the mechanic replace any sending units in the rebuild?

Sorry, it was the oil pressure switch I disconnected. The sender and guage are fine so I'm thinking that the issue lies in the temp sender and switch. No switches were replaced in the rebuild to my knowledge.

Where abouts are temp sender and switch on the GT40?

Thanks again folks, these little issues are taking the shine off my new engine a little!

D.

"it is a green wire in the harness. Chase that circuit down you will find your issue."

Darren there are 3 water temp sensors on the GT40 engine.

1. The ECT sensor near the front on inlet manifold it is a two wire device as it has a signal return to the EEC. This is the main one for controlling fuel and ignition via computer.

2. Engine temperature gauge sender

3. Engine temp switch that puts the EEC computer into limp(SLOW) mode


The engine EEC Slow temperature switch is located here:-


It is more obvious on my engine as there is a tee piece for the heater.
The temperature gauge sender is on the engine water pump.
The switch is either open circuit or short circuit while the temperature sender varies its resistance with the temperature of coolant.

I bet they have the wiring to the SLOW temp switch and temperature gauge crossed over. The SLOW temp switch should have one green wire and one brown wire with black tracer on the single terminal(i.e. 2 wires). The green wire goes back to dash engine check light. The brown/black wire goes to pin 24 on ECU to put computer in SLOW mode. The wire on gauge temperature sender is more of a tan wire with no tracer. I think they have this wire on temperature switch and the brown/black wire on gauge sender. There is also the possibility of the sender and switch being mixed up and now in the wrong location.

lewy2001 wrote: Darren there are 3 water temp sensors on the GT40 engine. 1. The ECT sensor near the front on inlet manifold it is a two wire device as it has a signal return to the EEC. This is the main one for controlling fuel and ignition via computer. 2. Engine temperature gauge sender 3. Engine temp switch that puts the EEC computer into limp(SLOW) mode The engine EEC Slow temperature switch is located here:- It is more obvious on my engine as there is a tee piece for the heater. The temperature gauge sender is on the engine water pump. The switch is either open circuit or short circuit while the temperature sender varies its resistance with the temperature of coolant. I bet they have the wiring to the SLOW temp switch and temperature gauge crossed over. The SLOW temp switch should have one green wire and one brown wire with black tracer on the single terminal(i.e. 2 wires). The green wire goes back to dash engine check light. The brown/black wire goes to pin 24 on ECU to put computer in SLOW mode. The wire on gauge temperature sender is more of a tan wire with no tracer. I think they have this wire on temperature switch and the brown/black wire on gauge sender. There is also the possibility of the sender and switch being mixed up and now in the wrong location.

Good theory - could that might explain why the light comes on faint at first and then get brighter?

I'll have to have a look when I get down at the weekend.

Thanks all - I love this forum. I 'll let you know my findings.

D

Problem solved. A big thanks to all, esp lewy2001 for the photo.

It was the temp sender/switch wiring after all. For some unknown reason the tech had 2 wires (one from the temp sender and the switch) going to the tan wire for the temp guage (the original tan wire has been cut - not sure why). This was causing the guage voltage to travel to the light as well as the switch signal to travel to the guage and hence kill it. I've remedied this and now all seems well.

The only thing i'm confused about is the black/brown wire from the switch. I've found two coming from the harness and neither were connected to anything! I've connected one to the temp switch and the other is not connected to anything.

Any ideas what the second wire is for? Both seem identical in colour.

D.

That makes sense. Cheers!