Car issues already - FIXED

[leegav]

well after the first relay going and a fix i thought great... we are all good. Took the car out for a spirited trip last week into wales along the A44. A very cold morning so took my flask. My right hand catches a small bit of wind deflected under the mirror onto the wheel..and by god it was ice cold.
Anyway...stopped for coffee.... Already to set off..car wouldnt start. Same issue...no fuel pump on prime and no injector firing.... School boy error i never took any proper tools or electrical wire to by pass. So...ended up home on a trailer!!

After many many hours trying to figure out what was causing the relays to go.. i figured out the ECU is not firing to ground. So it was never a relay issue....its an intermittent ECU grounding causing the relay not to fire. Bloody typical! Its one of only 2 parts on the car that are second hand and i bought myself! No problem im by passing the relay now and putting pumps and injectors on a switch...

No trust in the car as yet so need to keep chugging the miles away! Just need some dry weather.

[greenwoo]

well atleast you seem to have caught the issue Lee.....so as you say, time to put some miles on it when it drys up a tad!!

[DJ.]

I am keeping my fingers crossed that you are sorting these issues now, so that you can really enjoy the car when the season starts.As you say, the more miles you do in a new kit, hopefully the more reliable it becomes.

[ChrisL]

Are you saying that the ECU isn't providing the ground signal for the relay? If so does the ECU think that it should be, i.e. does it try to send the signal but nothing comes out of the correct wire?

[leegav]

Are you saying that the ECU isn't providing the ground signal for the relay? If so does the ECU think that it should be, i.e. does it try to send the signal but nothing comes out of the correct wire?

hi Chris.

As far as i can work out the ignition live (Blue) 86 into the relay should run through the relay and the ECU triggers the ground connection (grey) 85 to work the relay and connect pins 30 to 87 and 87b firing fuel pump and injectors.

I have tested the fuel pump relay off the harness and it works fine.
When i wire it back into the harness and ground pin 85 manually the fuel pumps prime.
So i guessed it was a ECU ground out.

I by passed the relay last night and fitted a switch. basically putting a live into the switch and 2 outputs (one to pumps and 1 to injectors). Fuel pumps primed but car wouldnt fire up.

So i decided out of curiosity to change the power relay too. So essentially i have changed both relays. The car fired up first time. So now i am thinking that the fuel pump grey 85 is actually linked to the Power relay coil live 86 and the power relay was knackered not firing to ground. The other high possibility is that the intermittant ground has just decided to work again.. in which case i wont know unless the car stops again. Im not convinced this is correct though as FP relay grey would not change colour into black power relay 86 on a SBD built harness surely

I need to start the car and run the engine and check all the pins. Every single pin should have power when its running.

[leegav]

This is where I’m at at present.

[ChrisL]

My FP relay is basically wired the same with 85 connected to the ECU. I think you need to understand the following to work out what's wrong:

1. What pin output on the ECU is supposed to be connected to the FP relay (from the manual not by looking at the ECU)?
2. Can you trace it, using a continuity tester (or a bulb & battery) when it is disconnected to both the relay and the ECU?
3. If it does the connect the ECU and measure resistance to ground, switch the ignition on, does it change?

Let us know what you find....

[ChrisL]

Just reading back I didn't realise you have an mobiliser fitted so it may not be the same between the ECU and FP Relay 85, but I'd find the ECU manual and understand what's is supposed to be happening. Also If you can connect a computer to the ECU then at least you know what it thinks it should be doing.

As an aside when I wired mine up I had a few issues mainly caused by me getting the connections wrong but the best one was thinking there was something wrong when the FP stoped after a couples of seconds of not cranking, which it's supposed to do!

[ChrisL]

Which MBE ECU have you got. If it's a 9A4 then the loom has colour coded outputs that connect to the rely as shown here, might be worth double checking:

https://www.sbdmotorsport.co.uk/application/views//web/viewer.html?file=https://www.sbdmotorsport.co.uk/upload/pdf/LM9A4_FWD-RWD_Basic_Wiring_and_Relay_info.pdf

And some useful info worth reading, esp the battery charge. Might be teaching you to suck eggs but you never know...

https://www.sbdmotorsport.co.uk/application/views//web/viewer.html?file=https://www.sbdmotorsport.co.uk/upload/pdf/Helpful_hints_when_starting_your_engine.pdf

[leegav]

Hi Chris, thanks for replying.

I have been trawling through the SBD stuff before and the relay diagram is great and did help originally. but it does not tell you what color wires go where from the relay. The SBD relays are built into the harness too so no way immobiliser is linked into it.

Problem is Chris i dont have a laptop which is why im trying to cadge one off Rob

Yep its the ECU that grounds the relay for a few seconds to prime the system then shuts off. it grounds again when the crank sensor registers movement (when you turn the engine), and stops grounding if crank sensor cant sense movement. This is a built in safety device which ensures fuel is stopped in the event of a crash. If it was a sensor failure my car would prime but not start.

im putting off having to remove wiring harness to check pin outs as the car is built whereby everything is hidden and difficult to get to without taking the scuttle off. Which is an absolute nightmare to do too. . If i can understand what wires from the relay go where it will make solving this much easier.