SKCC - Southern Kit Car Club. A Club for kit car owners across Southern England. Kent, Sussex, East Hants, Surrey, Berks, Middlesex, London

You need to proper ECU cable, cheap compared with what you have paid for the car.

Hi guys..

Well the starting problem is solved and hopefully by explaining what has happened it might help some one else..
Symptoms were fuel pumps not priming first of all.
Fuses checked, fuel pumps checked, relays checked for switched live. All ok. We by passed relay to see if pumps worked and they did. We tried to start car via the by pass but the car wouldn’t start, we checked spark and all was ok. We checked injectors and this is when we realised injectors weren’t firing either. I then swapped the 2 sbd harness relays (fuel pump and power over with standard 5 pin relays) the fuel pumps worked on ignition but still no injectors.
Here is the issue and why I couldn’t figure it out. Mostly my own fault but an easy mistake to make if you are not electrically savvy.
The sbd relay / ecu for the fuel pump uses switched ground to fire the relay, this is done through pins 85 & 86. With a constant live to pin 30. When the relay fires it joins 30 to 87 which is linked to another pin 87 in turn lighting up the 2 external items wired to both 87s. In the case of the sbd relay the numbers say 87,87,30,85,86. On the relay I bought the numbers were 87,87a,30,85,86 which means that the relay only lights up one 87 external item when fired. which in this case was the fuel pumps not the injectors. The sbd fuel pump relay fires injectors and pumps from the 2 87s that are linked.
So I had put the wrong relay on...but in my diffence they looked the same and I assumed 87a on my new relay was just another companies way of saying there is 2 x 87s.
I also mentioned that my throttle position sensor was reading 50% even when foot off the peddle. This also made me think that was knackered and causing ecu to assume I was in flood mode and not fire injectors. This wasn’t the case.. the accelerator cable cover at the throttle end had slipped back and caught on the edge of the cable attachment causing the throttles to be slightly open...not 50% other wise I would have noticed but when I released it I noticed the throttle moving back around 2cm. The reason I never saw this before is because I hadn’t seen the throttles in their proper position and they were stuck slightly open the first time I looked down the pots and the cable is underneath the air box and cannot be seen withought taking full air box off which requires the throttles to come off the head.

So issues were wrong relay and stuck open throttle. Car has gone back for a couple of other tweaks anyway... new fuel tank with AIM sender unit so I can see fuel levels via evo4 logger into the steering wheel screen.
Good news is it wasn’t an ecu issue and the wiring is fine..

Thanks for everyone’s input... @chris - always something easy...but finding easy is hard.

Good news

Interesting info about the relay, I'll try and remember that for future reference.

Nice one Lee, as Duncan, I’ll take note on the relay issue.

Well done I’m glad you got there in the end

Nice one, glad it was a simple fix - but also frustrating that it was such a simple fix! At least you're getting the fuel tank sender sorted too.

I've seen/used 5-pin relays before where the extra 5th pin (87a) is normally closed (whereas 87 is normally open), but I never knew such a relay existed with a 87b pin that is the same as 87.
Learn something new everyday! I had to google it to educate myself and found quite a useful graphic - enjoy! (I guess Lee had to use one of the two bottom varieties)

Yes steve. Relay with double output is what should have gone in. I put in a changeover

Well done, Lee

Brilliant Lee, sounds like it is all done

thats good news Lee....as you say, often easy things that are a bugger to trace...