Weird problem - ideas?

The Oily Bits S1 Specific Topics
1

Engine keeps stopping.

For a while now the engine (standard VHPD 190) has beeen even more undriveable than normal below 3000 and cold.

Then last week, after standing in heavy rain for 4 hours, I drove home along the A14 and suddenly the engine cut out - at 70, in the rain, passing a line of lorries. Just about managed to weave in to the side and rolled to a slip road.

I checked the fuel pump fuse which I thought was blown (it was dark and using streetlights) so I replaced, but the battery was dead by then and ended up getting a tow home.

This morning after a couple of days drying out in the garage, I went out the car and it started first time. So I switch off and wash the car, whereupon the thing refuses to start again.

After 4 hours of drying, blowing with compressed air, spraying with WD40, heating the plugs, replacing the ignition leads, using a jump start battery in parallel etc., I finally got the car to start and run for a few seconds … then it cuts out. Dead.

Leave it a few minutes with battery isolated, recharge the jump battery, start, it runs. Leave it for 5 minutes, suddenly it starts to falter. Catching the revs I can keep it going, but it sounds very lean, and eventually stops again. I can start it first time, but eventually it always cuts out again (like ignition cut). When it cuts it sounds as though it’s blowing back as well (through the chokes).

So what is it? The leads are old but good and there is plenty of spark to the distributor and no sign of arcing in the cap or from the leads. The fuel pump is priming and AFAIK the fuel is good. All the chokes are opening and “sucking”, the idle valve is opening and closing as you’d expect.

My thoughts:

  • alternator wiring shorting somewhere
  • battery cut out faulty (I have an Armtech isolator)
  • ECU dead/dieing
  • water in the fuel?
  • random alarm/immobiliser problem
    …

Any other thoughts?

2

Could be the coil breaking down.

3

Throttle pot ?

4

Could be many things actually.
Check/replace TPS, Crank Positon Sensor, MAP, MFRU, Immobiliser, wiring/connectors, ECU, Oxygen Sensor.
In my opinion it is either the TPS or MAP sensor.
By the way, if you visit a dealer, can�t they just connect it to that diagnostics computer and say directly what it is?

5

Had it running perfectly today - drove to Ely, turned round to come home, and … came back on the end of a tow rope.

Yes, I’m thinking TPS or the coil.

I;ll probably drop it off at Pat Thomas this week.

6

Nope.

Changed TPS, CPS, rotor arm and distributor cap. Loads of spark to distributor, no sign of breakdown to the plugs. I haven’t taken the plugs out again since the weekend but then they were dry, a nice colour, properly gapped and thoroughly dried out in the oven. Given the huge spark at the distributor cap I don’t think the coil is breaking down at all. I’ll put new Magnacor reds on but I don’t think that will change anything.

Fuel is good, no water, smells normal, the pump works and no gunge. I plugged in a Lumenition ECU (set up for a high spec single choke 170) to see if it would start - it didn’t but that ECU is set up to pump almost continuously and the pump is certainly working fine.

So I am utterly flumoxed. No ideas. Zip. Nada. All I get is the occasional cough. I’m giving up and taking it to have the full diagnostics done.

7

Can you try taking a separate fuel supply? Not sure if it was a Lotus problem but reminds me of a fault I read about that had similar symptoms and was due to a partially collapsing fuel filter.

8

Do a last check to the wiring/pins of the MFRU connectors, as sometimes the pin for the fuel pump gets burned. If you are close to Huddersfield, you are welcome to borrow my MFRU so you can check it.

9

It was the coil.

Car now fully functional and set up by Dennis Vessey, producing around 200bhp, pulling in top from 2000. Wow!