Chimaera 4.0 ‘96 Fuel pump wont prime.

[ChimpOnGas]

Belle427 said:

Could i have them too please, even though i have a foxguard system it will help somewhat.
Thanks

You'll need to PM me.

[Classic Chim]

ChimpOnGas said:

This was done a few moments ago mate

Top man.

[cheltgar]

Hi Chimpongas

Thanks for the Immobiliser bypass instructions.

Took top off dash, to gain access to alarm, and test the output of the two power leads from the black socket, and wasn't getting 12v. So checked all fuses. All fine. Then before re-testing tried disarming the immobiliser with the fob.... and the fuel pump kicked into life, for the first time in few weeks of trying! Clearly an intermittent problem, as hadn't got around to making the modification (which I will probably still do).
However, now when turn the key to start... nothing.

Could this also be an immobiliser issue, or is there something else I could look at before making the modification. Really not keen to make the mod if there is another issue and worried about changing too many things at once now the fuel pump is priming.

Thanks

Gareth

[Penelope Stopit]

I will answer your question just in case Chimp is not here and you are in a hurry for a fix

You now need to carry out a similar test at the immobiliser for the starter circuit in the same way as you tested the pump circuit at the immobiliser

Chimp will go crazy if you don't by-pass the immobiliser as you have disturbed the immobiliser and it started working for the pump circuit, you also proved the immobiliser wasn't switching the pump circuit

Chimp will be pulling his hair out

[cheltgar]

Not sure I proved the immobiliser wasn't switching, as I didn't actually do the bypass, couldn't see 12v at the appropriate wires, so went to check fuses etc before making the modification - and it came to life. (I did spray contact cleaner onto the black connector in the footwell, not sure if that took time to take effect or not - could be unrelated).

I had sort of got my head around the fuel pump circuit - linked relays etc. but don't really know which connectors to test for the starter circuit out of the back of the alarm to the immobiliser.

Chimps explanation was super helpful anyway!

[Penelope Stopit]

Ok, my apologies, I thought you had found the fuel pump power in at the immobiliser and had nothing coming out of it, if you definitely had no fuel pump power in at the immobiliser there is something wrong elsewhere, now please bear in mind that I am assuming that the immobiliser is wired into the fuel pump relays output.

I am also assuming that your vehicle is wired similar to the below diagram and that in your opening post where you mention that you were struggling to find how the White/Purple cable connected to the Yellow/black cable, that was because some cables change to colour Black between those plugs shown.
the cables change to colour Black for a reason, the reason being that it is very difficult to trace through circuits that use several black cables and this is done for security
Moving on - Going by my above assumptions I am led to believe that your vehicles immobiliser will be wired into some of those Black cables

You may have cured the fuel pump fault by disturbing some plugs, you really do need to know which cables are fuel pump power in and out at the immobiliser. If the fuel pump circuit is behaving itself at present....Re-test the cables at the immobiliser so as to find the fuel pump in and out cables and mark them in some way (tape that can be removed would be a good method)
Now when the fuel pump circuit fails you will know which cables to test and will be able to prove that there is no power from the fuel pump relay to the immobiliser or that the immobiliser has the power to it but not out of it or that the power is to it and coming out of it and the fault is further down the line before the inertia switch

Moving on - I appreciate this is not so easy to do but it can be done.....Disconnect the crank wire at the starter motor....Now having someone to help you, instruct them to turn the key into and out of the crank position as you go through testing for that crank supply at the immobiliser cables, if the crank supply is arriving at the immobiliser you will then need to test for it coming out so as to be able to prove if the immobiliser is failing or the fault is further down the line

Be sure to split and connect those plugs 3 or 4 times and slightly tighten the female terminals before making the final connection

The faults could be caused by bad connections at the plugs, unless you spend time carrying out the above tests you will never know for sure what is failing. Depending upon what you find during the above tests you may need to delve deeper and prove that the permanent +, ignition + and the earths to the immobiliser are not breaking down

Good luck in finding the fault

Penelope Stopit said:

Thank the owner of this website http://www.bertram-hill.com/fuel-pump-schematic.ht...
I think this will help

[ChimpOnGas]

cheltgar said:

Not sure I proved the immobiliser wasn't switching, as I didn't actually do the bypass, couldn't see 12v at the appropriate wires, so went to check fuses etc before making the modification - and it came to life. (I did spray contact cleaner onto the black connector in the footwell, not sure if that took time to take effect or not - could be unrelated).

I had sort of got my head around the fuel pump circuit - linked relays etc. but don't really know which connectors to test for the starter circuit out of the back of the alarm to the immobiliser.

Chimps explanation was super helpful anyway!

While it's working go back and check for +12v on the black anonymous wires as per my instructions, now execute my completely reversible bypass on both the ECU and starter solenoid wires you've identified with your meter.

I bet you'll never have another days trouble with it

[cheltgar]

Hi ChimpOnGas

Do you mean just the two thick wires - do they control both the ECU and starter solenoids to the immobiliser, or will I need to do the total bypass?
I am getting the fuel pump now priming, but nothing when I turn the ignition to the starting position.

Sorry for double checking, but want to be sure doing the correct thing before splicing into the wiring loom

thanks in advance

Gareth

[Belle427]

Do the total bypass and then a good test for a few days, if one circuit is worn out the other will soon follow.

[N7GTX]

cheltgar said:

Hi ChimpOnGas
I am getting the fuel pump now priming, but nothing when I turn the ignition to the starting position.
Gareth

When you turn the key to start position, are you getting 12v on the small wire to the starter solenoid?

[cheltgar]

Thanks everyone for your help (especially ChimpOnGas). Just done the partial immobiliser bypass - and the TVR has sprung back into life!!! Perfect for this boiling weather we are having.

I know, being a TVR, doesn't mean it will start in the morning, but at least wont be the immobiliser thats killing it.

Probably due for a speeding ticket now after it not running for so long

Gareth

[ChimpOnGas]

cheltgar said:

Thanks everyone for your help (especially ChimpOnGas). Just done the partial immobiliser bypass - and the TVR has sprung back into life!!! Perfect for this boiling weather we are having.

I know, being a TVR, doesn't mean it will start in the morning, but at least wont be the immobiliser thats killing it.

Probably due for a speeding ticket now after it not running for so long

Gareth

Give it a few weeks

[cheltgar]

Am guessing fuse between battery and supply to fuel relay, but don’t know.. could be between fuel relay and inertia switch. Anyone know ?

[Belle427]

Fusebox diagrams suggest the fuel pump fuse is no 13 from left, also labelled as central door locking.
Try removing it and see if the pump fails to prime.

[ChimpOnGas]

ChimpOnGas said:

cheltgar said:

Thanks everyone for your help (especially ChimpOnGas). Just done the partial immobiliser bypass - and the TVR has sprung back into life!!! Perfect for this boiling weather we are having.

I know, being a TVR, doesn't mean it will start in the morning, but at least wont be the immobiliser thats killing it.

Probably due for a speeding ticket now after it not running for so long

Gareth

Give it a few weeks

Can you give us an update Gareth?

Thanks, Dave.