LM964

Have the C4 which had a completely dead battery while having some minor paintwork done over 5-6 week period. Tried jumping but realised first hand that unless the 'donor' battery on the other car is up to it or (almost) the same spec as well it still ain't gonna fire up. It turns over (just) but that was all. However, strangely enough after recalling a couple of previous posts I'd thought I'd give switching DME's a go even though the one I had was fine. Did this and presto - we're in business and she fired up immediately!

After a day or two of driving around I swapped back to the earlier DME relay out of interest and that works fine too - although a tiny tiny longer on turn over before firing up but fine otherwise. But, for some reason the fuel pump whine up front is permanently on regardless how long any journey is. It never used to do this for some reason. Swapped over the DME again this morning and that has made no difference - loud whine still there. So, a couple of questions...

- What is that loud whine? Maybe getting a new DME might cure this? Or is my pump knackered?

- How or what makes a DME 'degrade' or differ from the next when using my dead battery or slower firing up as examples and can DME performance be measured (test bench or otherwise)?

Thanks in advance chaps...

Indycam

Are you sure the noise is the fuel pump and not the hydraulic pump ?

LM964

The motor whine originates from and around the fuel filler hose into the tank. It's a bit weird as any pump noise would/should be originating from right down there at the bottom of the tank. Maybe it's the sound transmission up through the tank and liquid contents - he says trying to make a tenuous link!?

I hear low voltage can play all sort sof games with the relay so will get a new DME to be sure... and try again.

Indycam

If you do a jumper to turn on the fuel pump , you can see if the noise changes .

LM964

Believe my battery to be in less than ideal condition with that as a possible problem too. Ordered a new battery... will see what happens. Whine is only there when the engine is running and not with ignition on only...

sml

bosch hammer system adaptation is required everytime you change battery or have a dead battery.

my car was terrible prior to an adaptation .. slightly harder to start and often an idle glitch .. after adaptation all is perfect.

dorisjyb

The motor whine originates from and around the fuel filler hose into the tank.

robt964

>bosch hammer system adaptation is required everytime you change battery or have a dead battery.

Really?? I don't know but that doesn't sound right. Would certainly cause lots of issues for cars fitted with kill switches.

sml

Yes.

If you think it doesn't sound right, then you are wrong.

There are plenty of posts here with people reporting big improvements after an adaptation .. about 10% that say it makes no difference.

And yes, I wasted 1 year of my life researching forums & replacing parts only to discover it was a simple 5 minute adaptation. Instant resolution. Completely obvious on the first start after the adaptation.

If you believe the people that started the myth about a 'spirited drive' then you too can waste a year of your life.

robt964

Hi, No I certainly don't doubt the benefits of an adaptation. My query was more aimed at the need to have one each time the battery is disconnected. Seems darn inconvienient as I generally remove batteries from vehicles that are laid-up over the winter months. Something to be aware of then.

boxsey911

Rob, this only seems to affect C4s. I often disconnect the battery on my C2 without any issues. It idles and runs the same (well) before and after disconnecting it. But I do (now) agree with sml that if someone has idle and running problems that the 'adaption by spirited drive' doesn't do anything to rectify it.

robt964

Thanks for the clarification :-)

LM964

That's a pain in the a**e for C4 owners then...

What does this do then - reset the ECU to factory settings?

Indycam

I've disconnected and switched out the battery in my 89 C4 many many times without a "bosch hammer system adaptation".

alexjc4

can an adaptation help idling and running problems? yes

is it mandatory every time you have a dead battery or change the battery on a C4? no

As per Indycam, I've had more dead batteries and battery ins and outs than you can imagine and mine runs fine.

I've also tried and failed to use jumper cables on a dead C4 battery - the RAC guy said my weak **** jump wires were to blame.

The DME is mechanical, you can open it up and have a look to judge it's condition, not sure I'd bother - if it works it works in my book.

Just to be sure I'd unplug the AWD pump under the front slam panel (both plugs) with the car running to see if the sound goes away. Obviously you can only do this stationary - as you'll soon have no brakes on the road when the servo assistance runs out.

How much petrol have you got in the car?