TVR Tuscan Start Issue

[Rhyno]

Hi all I'm new to the forums so here is a little teaser for the more experienced.
This is an intermittent fault so really tricky to isolate.
Car sometimes fails to start properly. Fuel pump will prime and stop. Car starts but runs lacking power then conks out 100yds down the road. Then will not start no matter what. Leave it to dry out for a good few hours and you might get lucky.
On start up fuel pump primes but does not stop. At the same time as this the injectors hang open and the engine fills with fuel.

2001 TVR Tuscan with the T2 immobiliser(this has been checked and verify by META) and E6549 Wedge shape Ecu.
New fuel pump relay fitted and new fuel pump. New coil pack leads and spark plugs.

Still the problem persists. Unless anyone has any other suggestions I'm now thinking the ECU is randomly failing.

[nawarne]

OK, bit of a bi**h to diagnose just from symptoms described in a few lines of text.

I'd recommend getting the car to one of the respected TVR service guys...loads of recommendations on here/Tuscan/Speed six forums.

They will be able to plug into a laptop and drive the car to experience the symptoms described.

Could be ecu...OR...engine loom related.

Nick

[Rhyno]

Hi nawarne thanks for suggestion. My problem is more the irratic nature of the fault.
I'm sure i could take it and have it plugged in but sods law says all would be well.
80% of the time its fine and behaves normally.Its the 20% when your along way from home and it
goes tits up.If anyone has experience of similar and a possible fix.

[Phil Tudhope]

Sounds like it may be related to the ECU. Could be something simple like a bad contact or maybe something burnt out on the board.

Agree that it will probably be best to have it plugged in at a TVR dealer. maybe there is a fault code that can be read by some garages. There's a zillion codes stored in the ECU but I don't know if they are all readable and interpretable. If you go into the 'SERVICE' screens in the dash display you'll see what I mean. These are in addition to the displayed fault codes.

Phil.

[Rhyno]

Hi Phil,

thanks for getting back. SERVICE screens? How do you find them? Not seen that as an option. As a bit more background on the car its has had the Phos bronze valve guides replaced in the head with the cast iron ones Valves reseated and new head gasket. The most recent was a bottom end rebuild with reground crankshaft new main bearings and big end shells.Also the oil feed to the head modified in line with RND Engineering .Only 33K on the clock.
On the diagnostic software all parameters are spot on.

[m4tti]

You need the software and a diagnostic cable. Alternatively you could use an oscilloscope to determine the crank position sensor is generating the correct sign/wave.

[Rhyno]

Thanks for post mt4ii. The cranks sensor is also new .Forgot to mention that ooops. TVR (total vehicle rebuild).££££££
i know the crank sensor pulses to the ECU which drives the ignition in wasted spark mode and the injectors are fired in two banks and flip flop back and forward between bank A and B
Only sometimes on start up, no cranking yet key in 2nd postion, the fuel pump stays on and injectors hang open filling the engine with fuel. So perhaps the crank sensor wiring may be intermittent giving rogue pulses fooling the ECU that the engine is running. Does that sound plausible ?

[m4tti]

Rhyno said:

Thanks for post mt4ii. The cranks sensor is also new .Forgot to mention that ooops. TVR (total vehicle rebuild).££££££
i know the crank sensor pulses to the ECU which drives the ignition in wasted spark mode and the injectors are fired in two banks and flip flop back and forward between bank A and B
Only sometimes on start up, no cranking yet key in 2nd postion, the fuel pump stays on and injectors hang open filling the engine with fuel. So perhaps the crank sensor wiring may be intermittent giving rogue pulses fooling the ECU that the engine is running. Does that sound plausible ?

Possibly an intermittent crank sensor problem, but don't discount the starter wire pin from the immobiliser unit. The only way to resolve that would be to bridge the relevant pins and the main harness.

Sounds odd that all other start up operations happen but the engine doesn't crank.

Just thought... Make sure all earth points are spotless.

[Rhyno]

0h no no .key turned to postion 2. not yet to 3 which starter motor which works fine every time.
normal operation at position 2 is fuel pump primes and stops .you can here the relay click. However sometimes
it doesn't and fills the engine with fuel as the fuel injectors are being opened.

[m4tti]

Ah sorry I work in binary. So off is position zero

The ecu controls the priming activity so like suggested earlier your best bet is to try another ecu.

[Rhyno]

Hi yes i have been pursuing that route as well. They are rarer than rocking horse Pooo
£1000 quid for a new one, don't think i had all six numbers at the weekend.

[m4tti]

There's a couple on fleabay right now I think. 300 ish.

[Rhyno]

hi wrong type i'm afraid its the later style

[m4tti]

What's actually different? I's the connector on the ecu side still the same.

[Rhyno]

Yes. The earlier ones have one big connector. Then for the later models 2001 onwards they introduced the wedge style
one as per photo. This has 3 connectors in the rear of It.Subtle differences like 4 wire lambdas. i'm sure there are more i'm unaware of.

[Rhyno]

Well back again for the conclusion to my Post on TVR Starting Issue.So after much investigation and process of elimination. The other night i plugged the laptop in and tried to start ..(fault not random any more, now permanent).
Nothing doing would turn over try to start then run badly and immediately die. So reset the adaptive maps.Tried again and bingo it starts. Stopped.Tried to start again and it again and as before dies. Then i noticed that i had -56 on one of the adaptives and 0.2 on the other. Now i'm thinking RAM chip. So bought a new one and fitted. Car now starts on the button first time.So either the RAM chip had dead cells or more likely the in built battery had died.

Hope this helps anyone experiencing the real erratic problems i had for ages,

Mark

[Sagi Badger]

Yep could have told you this if I'd spotted the post... sorry.

Had the same issue on my Tuscan, bought as a non runner after being laid up for three years. Symptoms as you describe. These RAM chips are becoming hard to find, I keep meaning to cut the old one open as they have a, I think, lithium battery in there that frazzles out. Think Farnell sell an equivalent but watch the speed as there are variants.

Glad you got sorted and sorry I didn't see your post first time round

J

[PetrolHeadPete]

Hi John
On your advice I changed mine. On my 2002 car its right on its limit for data retention.

Get them here

MBE ECU non-volatile RAM digikey DS1230AB-200 IND (or faster eg -70 from digikey) Dallas/Maxim £19 No Thread

I got the -70. Works fine.

[nawarne]

PetrolHeadPete said:

Hi John
On your advice I changed mine. On my 2002 car its right on its limit for data retention.

Get them here

MBE ECU non-volatile RAM digikey DS1230AB-200 IND (or faster eg -70 from digikey) Dallas/Maxim £19 No Thread

I got the -70. Works fine.

Pete, to a complete computer numpty - where is this RAM 'chip', and how do you go about changing it?
Does it need soldering in?

In anticipation - thanks. Nick

[Englishman]

It's in the ECU box and held in a socket, just like the fuel map Eprom as per the picture above. All you need is a small screwdriver to replace.

I bought mine from Mouser Electronics, just search for DS1230AB. Similar price though and half the price of parts suppliers

Edited by Englishman on Tuesday 4th October 12:49