Southern GT40 - Fuel Pump Problem

[Jay Gadsby]

Hello everyone. My first post asking for some help and advice.

The car's a Southern GT40, 347, Eight Stack, Accel DFI.
2x Mitsuba's and 1x high pressure fuel pump.

The car was running great. It took me to the Le Mans Classic, did 3 track sessions and brought me home. A circa 400 mile round trip. It used no oil and no water.

The problem,
I took it out for a 20 mile jaunt and then it wouldn't start. I traced the fault to "no voltage" at the high pressure fuel pump. I traced the voltage back through the relay, and to the Accel DFI. The relay is working. The wiring to (from) the Accel DFi has continuity. The connector for the DFI wiring loom/DFI Unit appears good. The earthing is good. The pump functions with a temporary 12volt supply from the DFI Wiring Loom end (if that makes sense). The problem to my mind's eye is the Accel DFI is no longer providing the voltage.

1) Does this sound credible?
2) Can I provide a temporary 12volt feed to the high pressure pump without causing damage to the Accel DFI?
3) I'm in the UK. Does anyone here know of anyone who can work on Accel DFI's, given they are now dated and no longer manufactured?
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A possible Red Herring - The L/H Fuel Tank/Pump has been "clattering"for a while (pre Le Mans Classic) and I have been using the R/H Tank/Fuel Pump.
A filter/bowl check showed no significant blockage (looking for Explosafe). Just very tiny amounts of equal quantities in L/H and R/H Bowls. The filters are clear.
I can't see a connection but clearly do not have the knowledge base of this community at large.
The noisy Mitsuba is going to be replaced.

Any thoughts or pointers would be greatly appreciated.

Thanks.

 

[Davidmgbv8]

Have you spoken with Mick, he had this problem on a l other access unit 2 years ago. Simple enough to wire around though with switch and or a relay

 

[Jay Gadsby]

Have you spoken with Mick, he had this problem on a l other access unit 2 years ago. Simple enough to wire around though with switch and or a relay

Hi,
With Adam, but about the Mitsuba, Tank and Explosive thing. I'm mostly concerned about what's happening to the Accel System and what might lay ahead. Best case, it's a bug as opposed to the start of something bigger. I'd like to find someone who is familiar with the DFI and can investigate it.
Thanks for replying.

 

[Ian Anderson]

When you turn on the ignition does the relay activate and provide output 12v which would in turn power the pump?

if the relay does activate and provide output voltage then I would check the wire from the relay to the pump as you could have a break in it!

Now a possible warning as I am not sure on your ECU but normally when turned on the ECU will power up the fuel pump for approx 3 seconds to prime the system. They normally then turn the power feed off until you crank the engine and then the relay stays powered unail a) the ignition is turned off or B) the engine stops turning like in a stall. So the crank sensor would will be telling the ECU that the engine is turning and hence keep power to the fuel pump.built in safety to ensure in case of accident the pump stops running.

Ian

 

[Jay Gadsby]

When you turn on the ignition does the relay activate and provide output 12v which would in turn power the pump?

if the relay does activate and provide output voltage then I would check the wire from the relay to the pump as you could have a break in it!

Now a possible warning as I am not sure on your ECU but normally when turned on the ECU will power up the fuel pump for approx 3 seconds to prime the system. They normally then turn the power feed off until you crank the engine and then the relay stays powered unail a) the ignition is turned off or B) the engine stops turning like in a stall. So the crank sensor would will be telling the ECU that the engine is turning and hence keep power to the fuel pump.built in safety to ensure in case of accident the pump stops running.

Ian

Hello Ian,
We might meet at some point, somewhere!

Your first question, Nothing happens because the DFI is not providing any voltage to the relay.
When I disconnect the circuit at the DFI and provide a temporary voltage the circuit works, the relay then the pump. So, I am certain the circuit is all good - it's the supply (DFI) that's not doing it's job.

Your second point, if I am grasping it, nothing is happening at all - the circuit as intended is failing at the DFI exit point - if that makes sense.

 

[Ian Anderson]

I presume the ECU also generates the spark signal, are you getting a spark?

If not i would look at the crank position sensor,it would not be the first time I have heard of these failing or coming loose so not picking up the tooth count

Ian

 

[Jay Gadsby]

Hi Ian,
Yes, there's a spark. When I connect a temporary 12volt supply to the high pressure pump the pump runs. And when I then start the car everything runs as normal. The primary symptom I believe is specific and that is the Accel DFI is not providing 12volts to run the high pressure pump.
Cheers.

 

[Ian Anderson]

Hi

that certainly sounds like the ECU is not sending an output so will need traces by an EVU specialist

 

[Jay Gadsby]

Hi

that certainly sounds like the ECU is not sending an output so will need traces by an EVU specialist

I'll try and find someone who can work with this Accel System and see what they come up with.
Thanks Ian

 

[Ian Anderson]

There is not something simple like an in line fuse that has popped?

 

[Jay Gadsby]

Hi Don,
The circuit from the Accel DFI is all good and is working fine. There is a fuse before the relay on the power side that is tested and intact.
I have stumbled on some manuals/wiring diagrams for Accel stuff so i might find some clues there.

 

[Dr. Bob Woods]

Most ECUs ground a wire to turn something on instead of providing 12 v. Probably your relay has 12 volts already to the solenoid and the ECU grounds the other solenoid wire. One might think it makes more sense to supply voltage than to ground it, but it generally is better to sink the current to the relay than to source it.

Bob Woods
Tornado GT40 in Texas

 

[Paul Hendrickx]

my small experience with those electronics, as Bob Woods says, the ecu puts to ground for commanding things (fans, pumps ear etc) In my Renault days , some car refused to start...

inside the ecu their is what you could call an floating earth -12v connected to chassis ground by a transistor , this is done too do before start up a diag of all the electric lines (takes roughly 3 milliseconds to do) and then the transistor puts that floating earth to chassis earth and ecu execute his commands.
when the transistor burns ... no contact is made.
Now by putting an eart between the body of the ecu and chassis ground , the ecu start functioning , but the mal function light on the dash stays on because the ecu can not check the isolation of every outgoing wire, in this case .
this is my experience...
so try to put earth wire from ecu case-housing to chassis..
Hope this could help
Paul

 

[Jay Gadsby]

Most ECUs ground a wire to turn something on instead of providing 12 v. Probably your relay has 12 volts already to the solenoid and the ECU grounds the other solenoid wire. One might think it makes more sense to supply voltage than to ground it, but it generally is better to sink the current to the relay than to source it.

Bob Woods
Tornado GT40 in Texas

Thanks very much for this. I'll have a closer look with that in mind.

 

[Jay Gadsby]

my small experience with those electronics, as Bob Woods says, the ecu puts to ground for commanding things (fans, pumps ear etc) In my Renault days , some car refused to start...

inside the ecu their is what you could call an floating earth -12v connected to chassis ground by a transistor , this is done too do before start up a diag of all the electric lines (takes roughly 3 milliseconds to do) and then the transistor puts that floating earth to chassis earth and ecu execute his commands.
when the transistor burns ... no contact is made.
Now by putting an eart between the body of the ecu and chassis ground , the ecu start functioning , but the mal function light on the dash stays on because the ecu can not check the isolation of every outgoing wire, in this case .
this is my experience...
so try to put earth wire from ecu case-housing to chassis..
Hope this could help
Paul

And thank you for going into this in a bit more detail. Both suggestions are very enlightening.

 

[Davidmgbv8]

Did you find the cause and fix it?

 

[David Garton]

Some smart modules stop sending voltage when they see a circuit fault or short to ground. The other pump you mention making all the noise might be drawing high amperage if failing and causing the DFI to stop sending voltage.??

 

[Jay Gadsby]

Sorry for the delayed reply.

The high pressure pump with no voltage supply problem.

After tracing the lack voltage back to the Accel DFI, I decided to recheck and reconnect / check the wiring, relay and the high pressure pump; with a view to wire in the high pressure pump with a separate circuit as a temporary solution to get me back rolling.
I was expecting there to be no voltage being supplied to the high pressure pump.
I switched on the ignition/fuel pump and low and behold, there was the three second whine of the high pressure pump!
So, I'm happy it's running again, but not clear about the problem causation.
The DFI is doing it's thing. The relay is working and the high pressure pump is working, so I'm guessing it was a circuit continuity fault.

Thanks very much for everyone who gave me their ideas and views.
It was all very much appreciated.