Cutting out

[redshift]

wierd one this.
start the car and the motor cuts out after 6 seconds. Restarts perfectly normally every time but only for 6 seconds when it cuts out again.

It did this before in summer and during the B Service the ECU was swapped with another and that didn't cure it. However after the original ECU was re-installed the problem dissappeared and the car has been perfect for 6 months/1000 miles.

No CEL, no error codes.

[swindon_alan]

Hello Pete. That sounds like a horrible one. Have you hooked up an OBDII reader/laptop and had a look at the ECM data before starting/when briefly running/after cut out? If you do comparisons you might be able to spot an anomaly.

[mike_sekinger]

Hi Pete,

Did you check (continuity) the ECU GNDs:

- pins 7 and 67 (engine GND)

- pins 27/28 (power GND)

[redshift]

Thanks for the suggestions Mike. I'll try further over the week end.

[Barrykearley]

I'd be inclined to clean every single contact on the ecu harness and ecu head.  sounds like something's a bit suspect there. Plugging in and unplugging a couple of times could scratch any tarnish or oxidisation off the pins and sockets so that maybe why. 

Definately scan the ecu - just cos the light isn't on doesn't mean it hasn't logged any errors.

[Steve V8]

Sounds more like an immobiliser fault to me, cutting out the fuel pump, the car will run for a few seconds until pressure drops will then cut out.

Rover cars from the mid nineties had the same problem that you are experiencing and describing, the cause of Rover problem was a small electronic relay box  associated with key recognition. 

If Lotus had installed coded keys on the late model V8's,  it maybe worth a look.

Steve

[Barrykearley]

Really easy to wire out the immob - pm me if you need to know how @redshift

[Steve V8]

Might not be that simple  @Barrykearley the later models had a lot more high tech electronic gizmo's than our old bangers have. If it's got coded keys it will have the box, and software that only Lotus can sort out. 

The car would need to be trailered to a dealer to sort this one. (that's if it has coded keys?) 

[Barrykearley]

It's a lotus mate - lucky it's got central locking !!

[Steve V8]

Central locking?....lucky b..tard....mine is in the top left hand corner just under the window.

Just a thought @redshift have you changed the battery in the keyfob?? 

Sometimes problems like this can be that simple.

[redshift]

Confirm that the keyfobs work fine. I had wondered about fuel as it would hold pressure for a few seconds before cutting out

[redshift]

Quick question.
Should you hear the fuel pumps running when switching the ignition to ON before start up?
I fairly sure I used to.

 

 

[swindon_alan]

Hello Pete. On my V8 the secondary fuel pump cycles for about 5 seconds on the ignition switch and then stops (as per the manual). I have never heard the primary though.

[redshift]

Right well that narrows it down a bit then.

See if I can bridge out that connection and have another go.

[redshift]

Further comment.

Only does this when cold. So I am assuming the ECU runs the secondary fuel pump for enrichment at start up and then switches it off a few seconds later?

Would explain everything.

[swindon_alan]

To quote from the Service Manual:

The two fuel pumps are mounted in a plastic housing and are fixed via the fuel return pipe to a mounting
plate secured by cam ring to the top face of the RH tank. Both pumps operate as the engine is started, but
thereafter, the secondary pump runs only when the ECM demands the additional fuel supply. Both pumps run
at constant speed, with fuel delivery being always greater than the engine’s requirement, with the excess fuel
returned from the fuel pressure regulator valve to the RH tank. This constant circulation of fuel through the
in-line fuel filter, fuel rails, and fuel pressure regulator valve, helps avoid high fuel line temperatures with the
consequent risk of vapour locks.

When the ignition is switched on, the ECM energises the primary fuel pump which will run continuously if
an ignition pulse is present (engine cranking or running), or for 3 seconds only in the absence of an ignition
pulse. The pump will switch off 3 seconds after a stall. The secondary pump runs during engine cranking for
pump exercising purposes, and subsequently only during conditions of maximum demand, typified by 130 mph
road speed.

So I don't think so...

 

[redshift]

More notes.

It runs for a about 6 seconds then the idle stumbles and cuts out a second later.

The primary pump does not run when the ignition is switched on.It's not the immobiliser which only cuts the starter motor and the coil packs on the V8 (does cut the fuel pump of the 4 cyl though)Its not the inertia switch which would cut both pumps.The ECU provides the Supply for the primary pump relay which is also the injector supply so I doubt its the ECU.
Next check will be to see if the primary fuel pump has failed?

Thanks for all the comments so far

[swindon_alan]

16 minutes ago, redshift said:

It runs for a about 6 seconds then the idle stumbles and cuts out a second later.

Pete - your six second problem seems to correspond to these numbers in some way?

When the ignition is switched on, the ECM energises the primary fuel pump which will run continuously if
an ignition pulse is present (engine cranking or running), or for 3 seconds only in the absence of an ignition
pulse. The pump will switch off 3 seconds after a stall.

It might be a cold condition problem with the ignition/camshaft/crankshaft sensors perhaps? If it helps I have spare camshaft and crank sensors that are available for testing if you would like me to loan them to you? That's after you test the primary pump and it turns out to be ok of course!

[redshift]

Alan,

That is exactly how I remember it. Switch on and the pump would run a few seconds and then off again. That is what it is not doing now.
Don't think it can be cam or crank sensors as that would inhibit starting.

I got as far as taping the primary pump relay closed and still no pump by then it was too cold and dark in the garage to continue.

[redshift]

More this afternoon:

Primary pump relay taped closed and no pump runs.

Pin 30 on the relay has 12v. ECU sends 12v to the coil.

Put an ammeter across Pins 30 and 87 and no pump, no current drawn, would expect about 8A for an injection fuel pump? Same with 30 and 87b and I can hear a solenoid clicking.

Seems conclusive no?

[swindon_alan]

Hello Pete. It sounds like it, doesn't it? Does the secondary run for a few seconds when you turn the ignition on? If so then presumably that provides enough fuel pressure to allow the engine to start and run briefly.

[sailorbob]

Are you getting +12v on pins 87 and 87b on the primary pump relay?

[redshift]

Just to confirm:

Primary pump should run 3 seconds on switch on or if ignition pulses are present. (The ECU emulates the classic Fuel Pump Relay pulse detector circuit so it is often said that if the pump doesn't operate that the ECU is suspect.)
Secondary runs during cranking and under high demand.
There is supply to both relays.
Bridge pins 30 and 87 on the secondary pump relay and it runs.

Bridge pins 30 and 87 on the primary and nothing!

Battery died at that point so will resume later when I've got a new one.

Edited January 24, 2017 by redshift

[sailorbob]

On the primary pump relay you'll not see any activity from the fuel pump when you bridge pins 30 & 87 as pin 87 goes to the injectors. You need to bridge pins 30 & 87a (it's 87a on the wiring diagrams but I think a lot of cars have relays that have 87b).

[redshift]

Good point Derek,

Bridging was done by latching the relay shut with an elastic band so all connections were made.