Fuel pump won't prime

[Blue Chimp]

Hi All,
I'm new to the Forums but have had my Chimp for 6 years, and apart from a new starter and water pump it has given me great pleasure. I also suffered from the hot start issue but I found that it was only an issue when the fans were running so I fitted a delay switch.....all is now ok. Getting on to the current issue, everything was fine until a couple of weeks ago. I tried to start her and nothing, no fuel pump, no starter. This has happened before and 2 new relays did the trick. Not this time. So, I have 2 new relays and the pump is ok if I put 12v to it. I get 12v to the main ECU on pin 85 but the relay doesn't switch. Pin 86 doesn't ground, should it ? Or is this where the immobiliser kicks in ?? It's the same for the fuel pump relay with pin 86 not grounding. I'm not sure if this is a grounding issue. I've also tried trace pin 86 back to the ECU plug but there is no connection, this once again suggests to me that this is where the immobiliser controls the grounding. Please help !!

[swallet]

No fuel pump no starter - sounds like an immobiliser issue to me. These are the two circuits which are "protected". Get the dash top off and have a look. Immobiliser on top left side usually.
Can be bypassed but obviously not something to be published on line!

[Blue Chimp]

Thanks Swallet,
I believe that it's either the ECU or the immobiliser. It could still be an earthing problem though.
Would you be able to help me bypass the immobiliser so I can either confirm it is this or not ??
I appreciate the need for confidentiality, how could I contact you directly.
I'm not bad with a multi-meter but no expert and wiring or cutting in should be no problem.
Thanks

[Blue Chimp]

Sorry Swallet, forgot to mention.
I've had the dash off and checked all the fuses and relays I can find.......no joy.
Thanks

[blitzracing]

I dont know how the TVR immobiliser is installed- but ECU wise you need to have a listen to the realys in the foot well. The main relay and the fuel pump both click shut as you turn on the ignition- then the fuel pump relay should drop out again about 3 seconds later if the engine is not running (as it wont be). Id suspect no clicks would mean the fault was external to the ECU its self.

[QBee]

It sounds like immobiliser to me too

However, if you haven't already dome these, here are some simple things you could try:
Lock and unlock the car - to reset the immobiliser. That solved it for me when I had a dead car in the middle lane at a roundabout with the A1 and A46.
Detach and reattach the main ECU to reset everything.
Check the 80 amp fuse - it is in a black fuse holder IIRC, in the same spaghetti as the fuel pump and ECU relays. Removing it seems to stop many things working.

[davep]

QBee said:

...
Detach and reattach the main ECU to reset everything.

...

Of the 320 odd values that the 14CUX ECU firmware uses only 20 are held in battery backed RAM. Disconnection of the ECU connector, with ignition off, clears these values. Clearing these values has little or no impact on fuel pump priming.

[V8 GRF]

Just a suggestion, but has the battery been flat in the meantime? If so you may well need to reset the immobiliser.

Pull the +ive terminal off the battery for about 15 seconds then as you reattach the terminal press the remote fob button and there will be several beeps signifying the alarm/immobiliser has reset.

[Blue Chimp]

Thanks guys, but still no joy.
I've tried resetting the immobiliser which I think I do as I get all the right signals.
Also I can feel / hear a click coming from the M99 under the dash ( which is now in the kitchen !!!)
I am now thinking that it could be the ECU.
Any ideas on how I can check the outputs which would not be affected by the immobiliser if it is faulty !!!
Thanks All

[davep]

There's an explanation in this thread:

http://www.pistonheads.com/gassing/topic.asp?h=0&a...

This circuit diagram may also help:

Edited by davep on Tuesday 26th May 20:31

[Blue Chimp]

Thanks DaveP.
I have this diagram from the bible but the connections I wanted to check we're either dashed or dotted. What does that mean ??
I have a question: on the relay for the main ECU which is labelled as 22, I have 12v at pin 15, and at pin 86 at the relay, so no problem there but this is where I get a little confused. On pin 85 on the relay, or pin 12 on the ECU, I don't have a ground, so obviously the relay doesn't switch. My question is this, is it the immobiliser, is it the ECU, or is it a simple grounding issue. If it is a grounding issue, where does the ECU and immobiliser ground.
Thanks

[Blue Chimp]

Thanks DaveP.
I have this diagram from the bible but the connections I wanted to check we're either dashed or dotted. What does that mean ??
I have a question: on the relay for the main ECU which is labelled as 22, I have 12v at pin 15, and at pin 86 at the relay, so no problem there but this is where I get a little confused. On pin 85 on the relay, or pin 12 on the ECU, I don't have a ground, so obviously the relay doesn't switch. My question is this, is it the immobiliser, is it the ECU, or is it a simple grounding issue. If it is a grounding issue, where does the ECU and immobiliser ground.
Thanks

[davep]

Blue Chimp said:

Thanks DaveP.
I have this diagram from the bible but the connections I wanted to check we're either dashed or dotted. What does that mean ??
I have a question: on the relay for the main ECU which is labelled as 22, I have 12v at pin 15, and at pin 86 at the relay, so no problem there but this is where I get a little confused. On pin 85 on the relay, or pin 12 on the ECU, I don't have a ground, so obviously the relay doesn't switch. My question is this, is it the immobiliser, is it the ECU, or is it a simple grounding issue. If it is a grounding issue, where does the ECU and immobiliser ground.
Thanks

I'm not sure what you mean by connections that are shown as dashed. In the reference diagram only the EMI screening to earth circuits are shown as dashed and these shouldn't cause fuel priming issues.

As I said in my explanation: as part of its start up procedure the ECU is responsible for earthing the two relay coils (21) and (22) when ignition is applied. This is done internally within the ECU module, probably with transistor switching. The earth circuits for ECU pin 14 and pin 27 can be traced through to one of the usual TVR earthing points for continuity. Where your immobiliser intersects the Fuel Pump circuit depends on the specific installation for your car. If you know its location try bridging it to eliminate it as the cause of the fault.

[QBee]

I think I have a spare ECU you could try. Just need to check what chip is in it. Where are you geographically?

[phazed]

Again, the problem is probably caused by your car being sensitive to being called a chimp, (a very derogatory term often used by grief owners).

Remove the "p", talk nicely to it and it will probably start.

[Blue Chimp]

Thanks DaveP. I have earth at 14 & 27 but not where the relay should ground. If the ECU is responsible for grounding modules 21 & 22 to make the relays switch this could be the problem.
I have a bit more testing to do now but it increasingly pointing to the ECU.
QBee, I'm in Leicester but travel extensively for work mostly north from there. I have a 450 chim 1998.
Phased, it's a term of endearment, 6 years driving with a smile on my face as big as a chimp at a tea party !!! 😀

[davep]

Blue Chimp said:

Thanks DaveP. I have earth at 14 & 27 but not where the relay should ground. If the ECU is responsible for grounding modules 21 & 22 to make the relays switch this could be the problem.
I have a bit more testing to do now but it increasingly pointing to the ECU.

If you have +12V at ECU pin 19 with ignition On and the Fuel Pump relay (21) is not energising, and the relay has been swapped out with a known good relay, and the ECU connector is correctly located then the ECU is suspect. Note that relay 21 will de-energise after a few seconds with ignition On if the engine is not cranked (no ignition amp signal).

[QBee]

I have opened my spare ECU and it has a 4.0 chip in it. If that suits, then you are welcome to borrow it to try, and we can I am sure come to an inexpensive deal if you find it works and want to keep it.
I am just outside Newark on Trent if you want to collect, or I could post it to you.

[Blue Chimp]

QBee said:

I have opened my spare ECU and it has a 4.0 chip in it. If that suits, then you are welcome to borrow it to try, and we can I am sure come to an inexpensive deal if you find it works and want to keep it.
I am just outside Newark on Trent if you want to collect, or I could post it to you.

Firstly, sorry for the delay, I was called out on short notice for a few days.

DaveP, I will try all your suggestions today but I think that in a roundabout way I've already done this.

Qbee, I would live to borrow your ECU if it's still abailable. I am in Sheffield for 2 days next week and Nottingham for 1. Please let me know what say and time would be suitable for you.

Many thanks guys

[ClassiChimi]

I sometimes try starting my car and nothing, sometimes the pump primes and sometimes it doesn't, I've bump started the car once when this was an issue and car fired instantly, I'd still be looking at the immobiliser on the starter circuit.
I think Chimp on gas does a diagram of how to bypass said circuit so maybe contact him also, Goodluck.

Qbee, have you had your immobiliser replaced/repaired, if so who did it please, I'm sick of mine playing up, I seem to remember you had a longer time out put to yours etc, cheers Alun

Blue Chimp, if it's possible try bump starting the car in second gear, if it starts I'd suggest the starter side of your immobiliser.
Just trying to cut down the odds! Alun