Engine stops when it rains!

[hally]

Hi everyone,
yet another question. To those who wondered about my headlights... Yep it was the ignition switch

Finally down here we have had some decent rain (although we still only have 34% in our water catchments). The strangest thing occurred to me. I did have this happen about 12 months ago replace the fuel filter as I thought it was a case of bad fuel....

The problem is this. When the van has been left outside in the rain and I go of to drive it everything seems normal. I get down the road a mile or two and I lose power eventually with the engine stopping. It is as if the engine is starved for fuel....If I am quick enough and rolling along I can just turn the ignition off and then on and everything is ok for another mile or so.

Lucky for me it does not rain that much here.

Engine is a 1989 2.1 MV,,,,,

Any clues to point me in the right direction? I am thinking that I might have a crack in the wiring somewhere that is getting wet and shorting. I just can't understand why turning the ignition off then on again would make everything appear correct again.

Can anyone tell me what the little black box behind the RH tail light is?. I think water might be getting down the air vent and making things not work correctly

Cheers
Hally

[dugcati]

I had an old motorbike that did this - for me it turned out to be bad electrics in that when the bike was in the rain water sat between the coils and stopped them from earthing. If the engine was revving high (motorway use etc) then it was able to overcome the water; at tickover it died...

Have a look at your engine earth and be sure any electrics that are in the line of fire are OK and not scabby

[Ian Hulley]

Water in fuel due to a porous petrol tank ? Is it gassed ? If so does it do the same on lpg ? Try running the engine with the lid off in the dark ... if there's a short you'll soon see it

Ian.

[HarryMann]

Yes, box is probably the Idle Control Unit that connects to the infamous idle control valve

This is close to being Vanagon syndrome.. read up on that in the Wiki, lots there!

Check the wiring on MVs to the O2 sensor (nothing to do with the Dome, its the lambda sensor )

Even change the sensor in the exh pipe if you can get one to swap-test, at least it will eliminate it

Best to know about Vanagon Syndrome if own an MV

PS

Finally down here we have had some decent rain (although we still only have 34% in our water catchments).

But we wouldn't know where 'down there' is until you put your location in your profile

[hally]

Thanks for the replies everyone. Some further information. Driving into work this morning to pickup the Chrissy ham and it was raining again. Only lightly this time. Everything appeared to be ok. Until the rain got heavier and the road was wet. So I am guessing something underneath is giving me grief.

Leads to. Fuel tank, fuel pump. Lambda sensor. earth strap on gearbox

The other thing I did was fill up before the trip so gauge was on full for most of the trip.. I'll take a look tonight and see if I can see any unusual wiring issues.

One other thing I did forget to mention was the fact that filling the tank right up makes a mess on the forecourt. I suspect a breather pipe might be off so that could also be contributing to water in the fuel....I typically keep the tank at half on gauge also.

On another point to note. I know it is timebn to cycle the ignition when I notice a drop in power. Switch off then on and everything is back the way that it should be. So the question here is, is there something that happens to the ECU or some other part when you cycle the power. Does it initiate a secondary circuit to the fuel pump, reset injectors of something else?

Oh yeah, what is that box behind the RH tail light?

Cheers Hally

HarryMann that's Australia by the way. When I was in the UK I had the red Devon diesel that got set on fire when we were at Dub Freeze.

[HarryMann]

On another point to note. I know it is timebn to cycle the ignition when I notice a drop in power. Switch off then on and everything is back the way that it should be. So the question here is, is there something that happens to the ECU or some other part when you cycle the power. Does it initiate a secondary circuit to the fuel pump, reset injectors of something else?

Did you read the link I gave Vanagon syndrome, classic symptons..ign key resets the ECU. Does it backfire at all when you do that

I'd check the lambda sensor and wiring to it... but also take other advice above to look at night when its raining, see if you might see some arcing, sparking.

I also mentioned what that box was in reply above too...

=======================

Assuming a 2WD not a syncro, the fuel on forecourt is probably the top of your fuel tank rusted away, loads of posts here about that... but like you say, could be some of the pipework.

Cheers

[hally]

Well there you go. I am obviously going blind..... Thanks

I'll take a closer look tonight. and get my hands on a lambda sensor....If I recall correctly this was replaced by the previous owner cutting wires.....Although I thought I had sorted this when I went over the whole loom repairing dodgy connections. Maybe moisture is getting into the sensor at the wire entry point.

That profile is updated now by the way

Cheers
Hally

[Fritz]

Eh up Hally,,,,,,,,we met on that fateful day when your van was 'torched' during your trip to Dubfreeze.........

You suggest your problem is regular when it rains ? are we to assume it is fine at any other time......


Regards



Fritz,,,,,,,,,,,,,,,,

[HarryMann]

That profile is updated now by the way

Ah ta! Seem to rememeber the party on here when you left, if I got that right?

The other thing is it a std exhaust system witht he lambda set in pipe where it should be?

There are two types of lambda sensors I believe, single and twin wire. There are also VW ones and many replacement ones, some good and some not.

But the rain water wet synndrome is not one frequently associated with this MV cutting out problem.

Read everything in the that link (inclusing the inks in the link) and then see what makes sense with your symptons.. wet maybe almost coincidental e.g. it brings it on earlier, but would otherwsie occur at a further disance out of town from cold start-up.. US cases are most heavily documented, ranging from a few miles to 50 or 100! You'll see there are a few big areas to check..

AFM - Air Flow Meter, connector at back/side and potentiometer track condition
Earthing - everywhere, inc star earth on engine... a substitute heavy (50 amp) earth from alternator body to firewall body area can help diagnosis
That ISCU behind tail-light - get it all out, dried out and inspected!Check quality of connectors/corrosion etc.
(drill 1/4" hole in centre of that snorkel box to help drain (right where the pressed 'fingers' cross) Checkout HacksawBob's inlet louvre drip trick (a cable tie) in Wiki... https://club8090.co.uk/wiki/T2 ... g_air_vent

That should keep you busy for a few late nights, now you've got the sun down there