Griffith cutting out briefly when warm

[kabaman]

There are a number of posts I've found similar to my problem but none exactly like this. If anyone has encountered something similar - please share your experiences.

I've just recommissioned car after laying up for a couple of years.

Car starts, runs fine, however once it gets up to running temperature (say after about 10 minutes) it starts to cut-out. The cut-outs last for a fraction of a second and make the car a bit kangarooish. I've not had it happen at idle.

I removed the nest of wiring and ECU and draped it out on the footwell and I can hear what I presume to be a relay operating intermitently at the same time - so here's a big clue. However it doesn't appear to be the ECU or fuel pressure relay. I've tried holding them whilst driving to see if it's them (the things we TVR owners have to do!) - but saying that the problem has never happened whilst holding them. This could be a clue or bad luck.

I've tried wiggling all the wiring around by ECU when the car is idling with no luck.

It only happens when warm - so far is brief enough that it only cuts for fractions of a second before recovering, and never so far on idle. It's defintely cutting firing completely rather than losing say a cylinder or a bank.

I've also looked for a change in LED status of alarm/immobiliser whilst it's happening to see if that gace any clues - but none.

Just a note - there's no problem starting the car when warm - it's just a problem whilst running.

This sounds like a very slow process to de-bug, so if anoyone has seen anything similar please let me know.

Cheers,

Neil

[FlipFlopGriff]

Leads, ignition amp, coil to start.
FFG

[kabaman]

Thanks FFG but none of those would cause the relay in the footwell to operate in sync with the problem. That's the clue...

Neil

[Barreti]

I'd put money on it being one of the metal fuel/ecu relays.
They are the only ones you would hear aren't they.

[FlipFlopGriff]

Disconnect the ECU for 30 seconds and see if it resets itself.
FFG

[kabaman]

Thanks FFG, tried that... Went further last night. Took a Rover 14CUX and swapped over the socket and fuel map chip so that I'm running it into the fresher ECU. No change (I thought it might be the relays inside it. It doesn't appear to be ECU or fuel relays.

I have discovered that the heater valve touched the light delay relay causing the solder joint to crack and for it to click as it's rocked. I've just re-soldered that. When I replace it - it could be that the clicking goes away and was just a function of the movement of everything as the power comes off as it cuts. If so, then that was a red herring and I'll be back to checking HT side (as you suggested) as well as LT side.

I'll know more tomorrow.

It is only when it gets hot though - it's fine until it's properly warm.

?

Cheers,

Neil

[Loubaruch]

Do you have air conditioning?

Apparently there is at least one relay in the birds nest that is associated with ac, its a long shot but could that be the relay you hear clicking.

Obviously if you dont have air/con ignore the above.

[Barreti]

If you have a 100a fuse take it out and check it for cracks.
If that's ok, change the ignition amp. They aren't expensive from a motor factor.

Then as FFG says, it's leads and coil.

[Peter66]

I think your clicking noise is from the heater valve stepper motor. The motor kept running against the microswitch end stop causing the clicking sound. The resoldering cured a short circuit. Possibly the short circuit also caused the cutting out. Otherwise the clicking noise is likely not related.

Peter

[ChimpOnGas]

Does it go rich (strong smell of raw fuel from exhaust) when it starts to falter & stall?

[blitzracing]

I dont know the wiring for the TVR immobiliser, but if it cuts the ECU or Pump supply, then an intermittent relay connection in the immobiliser would make the ECU relays click. There are no relays inside the ECU.

[kabaman]

Thanks guys, I'll see how I get on this week checking various bits as suggested.

N

[kabaman]

@chimp, it misses so briefly it doesn't really get the chance to get noticeably rich (even if fuel were going in with no spark). It's still reasonably driveable - just with this periodic annoying juddering.

N

[Barreti]

Have you taken it out for a good run since it started doing this?

[kabaman]

yes and no - once it warms the thought of going too far with it jerking around isn't too pleasant. I've given a fair few runs.

N

[Rob_the_Sparky]

Mine developed this on the way up to TVR Power on Saturday - most disconcerting when the engine turns off every so often when on the motorway in the middle of a ~100mile drive!

The chaps up there reckoned it was probably one of the fuel relays as the rev counter continued as normal during the cut-outs and if it were loosing spark you would expect to loose the rev counter. FYI: the other possibility mooted was the throttle pot but thought to be less likely as I was on constant throttle when ti was doing it.

Rob

[Hedgehopper]

Could the Ignition Feeds Relay (p.243 of the bible) be loose or faulty? Just a guess, but you never know.

[kabaman]

Today's update - I've run it with the covers off the ECU and fuel pump relays and they never falter during the problem. I'll look at the rev counter more carefully next time.

Cheers,

N

[kabaman]

Something else is puzzling me here. Today I located the fuel pump relay in the relay panel - not the loose one (I have two being an early 400 (or so I thought, and so my handbook tells me)). I believed that this ran in series with the ECU driven fuel pump unit but was connected to the inertai switch.

So I took it out, it looked fine. I cleaned the contacts up gently anyway. Put it back with no cover on it.

When I turn on the ignition, the ECU driven fuel pump relay operates but this relay doesn't. But the pump works anyway! So it can't be in series.

So I'm at a bit of a loss to know what if anything this relay does.

If only I had a decent wiring diagram I might solve this a bit quicker....

N

[Barreti]

Your two fuel pump relays (fuel pump and ECU for the fuel pump) are on the same flylead by the battery - or at least mine are on a 1992 4.3 Griff

Where on the fuseboard is this other relay you're talking about?
Count them from left or right so we can get a fix on it.