Starting issues
 

Coming to my wits end with a starting issue!

So as per my thread, 1988 B230 K-Jet fed engine.

My current issue is that on a cold start the car needs a very long crank before it will pick up and run. Once it picks up, it runs fine.

Hot starts, it will pick up first turn and run for a second or two before stalling. Then it will start and run absolutely fine.

Here is what I've eliminated / changed:

- In-tank fuel pump, replaced with an airtec one. It works, I can jump fuses 4-6 and you can hear it buzzing away.

- Main HP fuel pump. The old one was getting very noisy when hot and causing the car to kangaroo. Replaced with a Lucas pump. Noise and kangarooing has disappeared.

- All fuel hoses replaced - the one in the tank sender, and the out and return lines. New clamps.

- KJet fuel pressures are bang on, set with a pressure gauge. Car runs exceptionally well when running.

- Bridging fuses 4-6 to run the pumps before starting does not improve anything.

The problem seemed to start when I swapped the main pump. Before I did this, car would start first time, every time, but the pump would get very very hot and pull amps way above spec. After 15 minutes or so the car would kangaroo and occasionally die.

I can't see how a new HP pump that's working better than the old one, would cause a poor cold start?

Have you checked the Air Admittance Valve:~
On a cold engine pull the curved hose away to view the fibre valve- it should be open.
As the car warms up the valve should move into a closed position.
You can lubricate the above with GT85 or whatever you prefer- the valve can be moved from open/closed positions with a small tool to test the spring.
Regards Bob.

Come to think of it.. I may well have messed with this! Thanks for reminding me..

Managed to sort this.

The problem was the o-ring under the metering head. I recently replaced this as it had perished, but I used one from a box I had lying around instead of measuring it. It was about 3.6mm thick.

I replaced this with a 2mm one and it appears to have fixed a few things. Thinking about it, the thicker o-ring would have changed the relationship between the airflow plate and the plunger position.

I had to dial the co screw down quite dramatically after that as it was set in relation to the wrong o-ring.

Continuing with this (sort of), I have an intermittent problem where despite starting first time, the engine is utterly gutless for a few minutes. It's clear the mixture is off (lean) when this happens.

I know exactly what the issue is, but I don't know why, or how to stop it.

I have narrowed it down to the warmup regulator (control pressure regulator). I have set this exactly right so that it's around 0.5-1 bar when cold, and 3.5 bar when hot. This is the spec both in the K-Jet manual and the 240 Haynes.

However, at the times when it's misbehaving I can see from fitting a gauge that the cold control pressure rockets to 5 bar (super lean) and doesn't move. It's almost as if the WUR is blocked. It isn't though, as I can get flow through the return quite easily.

I can fix it easily by giving the WUR a smack on the body with a hammer. This seems to reset it back to the 0.5 / 3.5 bar setting, and then it runs fine again for a couple of weeks.

So, somehow my WUR is drifting out of alignment and sticking in the fully closed position. I have no idea what could cause this, or why a shock from a hammer would fix it?

Everything inside the WUR has been cleaned up and looks great.

Does the metal diaphragm stick in one position when it's worn? Is there something else that sticks?

the bi metallic strip and the spring that holds it in position once warm

http://b2resource.com/PDFs/wurfix.pdf

have a look at that PDF