M2 Valver won't start

[Dirk Diggler]

1988 MK2 valver, everything stock engine wise.

It has had an intermittent problem with starting whereby if it does not start first try or if it catches but then doesn't run first go, it tends to flood when you try re-starting.

In the past I have got around this by pulling the fuel pump fuse and it will then start and die once it has burnt off the fuel in the cylinders.

This morning it just never caught at all. Pulled the fuse and it still just turned over. You can smell fuel pretty strongly when doing this.

So tonight I have tried turning it over again and nothing.

Pulled the plugs and it has a good spark. There was a puddle of fuel you could see sitting on top of the pistons, so I turned it over and it was puffing vapours of fuel out. Dried off plugs and have tried again and again and still nothing.

Evidently there is a problem somewhere.

The injectors are only about 2 years old and were brand new. Plugs are new, all leads in good order as is dizzy cap & arm.

Anyone got experience of this problem or any hints/ tips?

Cheers in advance

Lee

[rubjonny]

pull the plug off the 5th injector, maybe its stuck open and flooding the engine. another possible cause could be leaky injectors though they are new so unlikely

take the plugs out and give em a clean and allow to dry off, pull fuel pump fuse and the black wires from the coil, then crank it to blow the fuel out the bores, or  just leave it to evaporate away

[Dirk Diggler]

Thanks dude, I've done all of the above already and still the turd won't have it.

I will look at leaving the plugs out for longer as I had them out for about 30 mins last night and turned it over a few times to blow the fuel out the bores. I even replaced the plugs last night to give it the best chance and it still didn't want to know, had the 5th injector disconnected also.

Are 5th injectors available new as I replaced ours with a second hand one around Autumn last year, but I guess there is no way of knowing if that was any better than what I removed.

[rubjonny]

take the thing off the inlet then crank it over, if fuel comes out even when its disconnected then its duff. basically it should only spray for a short burst when the engine is completly stone cold, this is controlled by the big brown thermoswitch on the side of the head. its unlikely to have gone wrong they are pretty reliable as dont get much use.

i wonder if it needs setting up, perhaps the metering head flap needs a tweak? there is a sdping under the flap, you set the adjustment of it so the flap is flush with the narrowest part of the cone on the front edge nearest the fuel metering block.

if that looks ok take the fuel metering block off the flap part (3 bolts) then check the fuel metering pin moves in and out smoothly. be carefull as sometimes the pin can drop out either from gravity or by pressure inside the metering head. after that possibly look at the WUR on the side of the head

ideally you need to get the fuel pressures checked, this will tell you straight away if wur is faulty or if there is some other problem with the fuel system

[Dirk Diggler]

Thanks Jon, I appreciate your help & replies.

Will do some investigating of these areas.

I have a later metering head from a 1990 valver, are these a direct replacement to the earlier ones? - Just curious if this will work in the event my metering head is fubar (or I lose  components from it when pulling it to bits  )

I have a Bentley manual somewhere, maybe I should dig that out lol

To be honest the fuel system probably needs setting up properly as the car has never had the performance a 16V should have IMO

[rubjonny]

yeah you can use early/late, the only difference is the airbox plastics attqached to it. the later one is much larger, you can swap to the later setup but only if you also have all the later rubber inlet pipework to go with it, the earlier elbow on late airbox hits the bonnet!

can always just swap the flap/fuel bit over to the current one though, only a few bolts hold it on

[Dirk Diggler]

Right I have been doing some checks and need some input if possible.

The cold start injector sprays a good even cone of fuel when cranking over, but it just keeps doing it for as long as you crank it over. I'm sure if should stop after about 5-7 seconds on a very cold engine. So I have measured resistance at the pressure regulator on the side of the block. This reads the correct 22ohms. So I measured for voltage at the power supply to the pressure regulator and it is supposed to read 8v according to my Bentley manual. I am getting nothing. So what gives the connector the power? Where can I check elsewhere down the line?

Secondly - even with the fuel pump fuse disconnected, when cranking over, the cold start valve is still spraying fuel. Is that right? I was testing for the voltage to the feed for the regulator at the time, so that was not getting any power, but the 5th injector was still spurting fuel.

What are the tips here then folks?

Any help appreciated, cheers Lee

[Dirk Diggler]

Sorry, i have some corrections to make to that last statement.

I forgot i did not have the fuel pump fuse in. So with the fuel pump fuse in place, if I crank it over, the cold start injector does it's stuff and I have about 11v at the power supply for the regulator. If i disconnect the cold start valve socket, then it does not spray when cranking. So all appears to be working as it should, except that the cold start injector does just keep spraying for as long as you crank the engine, which I believe is only supposed to happen for about3-5 seconds.

The resistance at the regulator on the car (and a spare one I have) both read 22ohms, which is within spec, so why does the 5th injector want to keep dumping fuel in?

[rubjonny]

sounds liek wur is ok, that gets 12v whenever the fuel pump is active and the resistance reading is correct, but it wont tell you if the thing is actually working right internally though you need fuel pressure test kit for that.

with the 5th injector it should get 12v from the starter when cranking, which it has. it then earths via the brown 2 pin plug on the side of the head, which is the thermoswitch. if it never shuts off id say the swqitch may be faulty, but check the red/black wire gets 12v when cranking this powers an internal heater on the sensor, if its not getting 12v then it will only switch off when engine heat eventually heats the sensor enough.  it may be the sensor is duff or the heater inside too, or perhaps a wire short. disconnect the plug from it and see if the 5th injector fires, if not the earth wire at kleast is ok, then move on to checkign the sensor.

you need to check the earth path between the green/white wire pin and ground, both when stone cold and engine hot. if it never breaks the path to ground you need a new thermoswitch