Hot / restart starting problem

[philthechip]

2.1 petrol DJ 1990 auto

Starts fine when cold ie overnight / few hours cold but even if you only run it for a minute, then switch off - it will not restart.

Tried all the usual cleaning earths, checking fuel pump etc. I pulled 2 of the fuel injectors out and no fuel is sprayed when cranking? Engine cranks fast and fine but plugs remain dry and no fuel seems to be getting into pistons.

I am thinking it may be fuel pressure regulator on return but don't have a pressure gauge to test. Something is stopping / telling ECU to activate injectors.

Any suggestions as this seems quite a wierd one.

Can anyone recommend a brand of fuel injection pressure tester that is good for testing these older ie non schrader valve pressure test points.

[itchyfeet]

no direct experience of a DJ but I seem to remember the thermoswitch can cause problems

[philthechip]

Ok so I changed the ECU and this has fixed the fault.

Further symptoms were that the fuel pump did not run when you turned the ignition on. Normally the fuel pump runs for a couple of seconds.

The really wierd thing is that from stone cold the pump did its pre run and engine started ok and would run for as long as you wanted until engine switched off

So has anyone got an ECU I can buy and is there a difference between manual and auto ECUs

[skippymoss]

Try this redirection to an ad on the Brick-yard for an ECU
http://www.brick-yard.co.uk/forum/t3-21 ... 8.html?KW=" onclick="window.open(this.href);return false;

(there is a member called Bayvelle on this forum too, probably the same person but haven't seen the same advert over here)

This is interesting to me as I have the exact same set up and the exact same problem so please give us an update of how you get on.

Possibly a couple of dumb questions coming;

Are you certain that it is the ECU that was at fault and it wasn't just the act of changing it over that temporarily solved the problem? (This has happened to me in the past)

Have you been able to test the ECU and the connections to and from it?

Sorry, can't answer the other questions.

Ta

[philthechip]

I took it for MoT this morning with the borrowed ECU (part No ends in F so this is manual ECU) and on return with engine hot put my cold auto ECU (part No ends E) back in. Started fine, ran for 1 minute, switched off and would not restart. My logic tells me this is ECU fault. Also after searching on the web, found German forum which seemed to be indicating same fault with an auto ECU - is yours auto or manual?

[skippymoss]

Hi philthechip,

Mine is 2.1 petrol/LPG DJ 1989 auto so pretty much the same as yours I reckon.

I've just checked my ECU but can't see a part number without removal, so lets assume that it is the original auto one with the 'E' suffix.

I follow your logic totally but don't yet understand why an auto ECU would be more prone to failure than a manual one.

Questions in my mind are;

What is the difference between an Auto ECU and a manual one?

Is it the programming or does it have different inputs?

Does the german forum suggest changing to a manual ECU is the solution?

I would love to see a link to the german forum if you can post it.

Ta

[philthechip]

This is link to German forum

Basically he is saying that he tested an auto ECU in his manual van but when he stopped to close sunroof, it would not restart afterwards

http://www.vwbus-online.org/forum/board ... id=1587209" onclick="window.open(this.href);return false;

I think the inputs are the same and having taken my broken one apart, there is some kind of EPROM (a programmable chip) which would hold specific mapping data depending on the vehicle.

Other tests I did:

Get the ECU into failure mode, disconnect it and earth all input pins to remove all residual voltages - this did not resolve problem, so I sprayed the components on the circuit board with freezer spray but this did not fix fault either.

You know that the unit is in failure mode as soon as you turn the ignition on and the fuel pump does not briefly run.

Pin 20 should go to earth to activate fuel pump
Pin 21 is input from ignition switch telling ECU that starter motor is engaged - this input also goes to the idle switch unit behind offside rear light cluster. The wire is black and red not white as shown in some manuals. I presume that this input tells the ECU to start the fuel pump and injectors. This input is good ie goes to +12V on starter motor activation but unit is already in failure mode.

If this is a common failure mode of these units, someone must have fixed it and know what the fault is.

[skippymoss]

So if I'm reading this right, then Boltze replaced his Auto ECU with a manual one and everything's fine.

Whereas Meikel did things the other way round and ended up with a problem.

You have the same experience as Boltze.

Incidentally I contacted another member who has an autobox and he has a slightly different problem but which also seems to be ECU related;

"It happens on a cold winter's day only, and not every day.
I start the van to drive to work and set off. After about 3 or 4 minutes of driving, usually as I am slowing down each time for the same set of traffic lights where I make a right turn (so I have to slow down whatever the lights are on), the engine stalls. It won't start again for about 10 minutes after which time it continues happily for the rest of my journey. My problem is that because I have a first class mechanic who looks after my van but works a half hour drive away from me, I cannot reproduce the stalling problem for him to fix. He has told me in the past that it sounds like the ECU could possibly have an intermittent fault but says that they are pretty much bombproof and it is more likely to be something else"

Not all that bombproof it seems...

Just been for a quick test and as usual starts beautifully from cold. Then after a 1 minute run, I turn it off and back on again - then the starting is really hard - but it gets there after annoying the neighbours turning it over and over. However, I still get the double buzz of the fuel pump priming so that suggest that my ECU isn't going into failure mode like yours does...

Anyway it seems clear that your next move is to ditch that auto ECU - please let us know if that fixes the problem.

Ta

[philthechip]

So the manual ECU did 300 miles to Busfest and back and delivered 2 mpg better than old auto one. Shame I've got to give it back, lets hope the replacement one I bought works just as well