Electronic interference with ECU - is this possibly?

[roseytvr]

Hi Guys

I have just had a new ECU and associated gubbins fitted and now have a real weird problem.

For some reason the car is running fine in the garage with no issues but as soon as I drive it it cuts out when slowing down at junctions or stopping in traffic. A quick on off with the key and it fires up fine and off I go until slowing down at the next junction! I have noticed that it will bump start immediately if I just switch ignition on and off whilst rolling but unless I switch the ignition off and on again it will not start. Its almost as if I am having to reset the ECU via the ignition to start it again.

However I have noticed that if I pull the ECU, relays etc away from the foot well by the battery (its a grif) and spread all the electronics out on the passenger side floor I do not have any problems. It seems the electronic shutdown only occurs when everything is squeezed into place above the battery.

Is it possible or feasible that electronic interference could be occurring with everything crammed together tightly in a real small space? If so how would I go about identifying the culprit and resolving the problem?

I can take it back to installer but he has already had the car 6 weeks and not identified the issue. I would prefer to identify/solve the culprit/problem before I take it back.

Any help appreciated.

Thanks
Ian

[roseytvr]

Thanks guys, I am running DTA Fast ECU with a new bespoke loom, twin lambdas etc. the ECU is earthed, albeit light gauge.

I have put the ECU back in the footwell protected with rubber roofing material but the problem has now reappeared. I appreciate your opinions and the difficulty of a forum diagnosis but I don't think it is a fracture as the symptoms are predictable and consistent.

I can drive like a looney braking and pushing on without problems but as soon as the revs drop down below c2000 rpm and the gearbox is engaged the engine just dies and the car will come to a stop unless I turn ignition on and off and it bump starts immediately. Obviously I can't bump it when stationary but it will start immediately on the key.. As mention previously it's like an electronic shut down that clears when I turn off and on ignition.

Will my ECU software give me any clues, I am not that good at understanding what it tells me!!

Will keep you updated as I try moving stuff around. Any material recommended to reduce possible interference?

[roseytvr]

Thanks for the responses guys, I will get back to you on progress with this but its "worse than that, shes dead Jim" - I cant start her at all now to check anything. The fuel pump is not priming and whilst its cranking like a good un clearly it isn't going to start.

All fuses checked, relays checked, immobiliser by passed and still no life. I will try +ve to the fuel pump tonight and work back from there. The car is not stock - aftermarket ECU, bespoke loom etc so no stepper motor and associated gubbins.

Cheers
Ian

[roseytvr]

It goes from bad to worse unfortunately. DTA ceased trading last month so I cant go to them and I cant even pick up a connection with the ECU via my PC. It as if the ECU is dead. All pin connections appear OK will see if I can check if the ECU is getting power tomorrow.

[roseytvr]

It gets even worse unfortunately - the loom configuration to the ECU bears no resemblance to the wiring diagram issued by the now departed DTA Fast. I cant even make sense of the wiring to the two relays that I assume are for the ECU and fuel pump. For example Ignition on :

Relay 1:
Pin 87 12v
Pin 85 12v
Pin 86 12v
Pin 30 0v

Relay 2:
Pin 87 12v
Pin 85 0v
Pin 86 GND
Pin 30 0v

Completely baffled so its back to the installer on a trailer when he can fit me and no doubt hang on to it for another 6 weeks. Grrrr.
Well it.At least its Friday night

[roseytvr]

v8s4me said:

rev-erend... said:

My first step would be to check the ECU gets power at the correct pins.

There are likely to be 2 pins that get power. 1 constant from the battery and the other from the ignition.

Also test the earth(s)....

Based on personal experience I'd agree this as a first step. My problem turned out to be a broken joint in the loom where TVR spliced the ECU connections into the main loom. So check your permanent live feed and also the connectors around the tune resistor. They might look OK at first glance but the wire could be broken inside the little plastic connector giving an intermittent connection. if you have this issue, combined with a faulty permanent/switched live feed you'll have all sorts of fun and games. Good luck.

Thanks both but both power supplies are going to different pins than DTA say on the wiring diagram so I am well out of my depth here. All I can say is the ground is good with 0 resistance!! I can do no more so its going to have to go back..........I will post up when sorted

[roseytvr]

Okay update time.

Car has been back to installer - power loss to ecu was a wire fracture on the ignition side and this has now been fixed but cut out problem still there.

I have narrowed the cut out down to overrun only, if I dip the clutch when I slow down it wont cut out, so at least the car is useable. Its almost as if its a decell fuel cut out. I am trying to work out if there is a setting for decell fuel cut out so I can disable it.

I can now access the ECU through the pc so I am also learning how to follow the log to see if that tells me anything. I will share my learning's and findings as I go along!

Meanwhile any recommendations on an ECU/electrics guru I could take it too, get the problem sorted and car mapped whilst they are at it?

Ian

[roseytvr]

Thanks Guys, Jools it is as I am well out of my depth here and don't want to take it back to the installer again!

Is Jools/Kits and Classics and V8s4me all one and the same?

Cheers
Ian