Starting problems

[spludge]

Well I've spent a fair while trying to trace the cause of my starting problems and really don't seem to have made much progress. If it doesn't catch on the first or second turn of the key I have to leave it for 5 minutes or more before trying again to stand any chance of it starting, whether the engine is hot or cold doesn't seem to make any difference.

When cranking the spark appears weak and after a few unsuccessful tries disappears altogether, when it does run the spark appears healthy. This evening after another fruitless day I noticed that I can hear the fuel pump prime again as the key returns to on from start when the engine doesn't catch, I don't think it was doing that before.

I've checked and cleaned up all the connections I can find and fixed a few problems that were probably waiting to bite me when I'm done with this one.

I'm wondering whether there may be a problem with the immobiliser. Some of the connectors weren't very tight, there is evidence of overheating around a couple of them and their solder joints on the board didn't look too bright. I've resoldered and tightened the connectors, which didn't make a difference. I can't hear any buzzing from the relays but I still wonder whether they are ok.

If anyone has any idea what the problem might be please tell. I'm starting to despair a little, the sun is shining and I have to use the Passat .

K

[clarenceboddiger]

spludge said:

I noticed that I can hear the fuel pump prime again as the key returns to on from start when the engine doesn't catch, I don't think it was doing that before.
.K

Mine does do that, however can you access a pressure gauge to test the fuel regulator? I would assume it has some form of Diaphram which may have perished, and as it is Vaccum sensitive depending on wether it fires or not may have some relevance on wether it works or not.
Clutching Straws here but worth a go

[spludge]

Interesting thought, I'll need some outside help for that one but it's now on the to-do list.

I'm still clutching at the electrical straw at the moment, maybe the voltage gets dragged so low during cranking that the fuel pump relay trips and the coil does't produce a spark. At the coil it drops to less than 6V.

K

[ketvrin]

Hey Ken, your problem might be the amplifier unit on the side of the dissy... add that to your list too.

"other" K

[spludge]

The ignition amp is about the only thing electrical I hadn't checked, plan to take a look at that in the morning. Does anyone know what it actually does, would a faulty amp cause weak or no spark during cranking and good one with normal running?

K

[clarenceboddiger]

The only test I can find for the amp module is that it should be getting full battery voltage from pin 3 to earth when cranking and 4 to earth with ignition on, this is with the plug disconnected and the securing clip on top when viewed looking at the pins, i know this doesnt help you check the module but it will eliminate any probs with supply to it.

[spludge]

I checked the supply out and it all seems ok. I also found a thread on the wedge forum that described how to check the amp for function and again it all seems ok. Without a great deal of certainty I've come to the conclusion, for now, that the amp is good.

Today I turned my attention to the fuel pump relay, this is what I found:




Odd thing is that it still works, the contacts are clean, the pump primes ok and when I can get it started the engine seems to run fine. I think I'll get a replacement.

K

[hvdweerden]

spludge said:

Odd thing is that it still works,
K

quality cars our S ;-)

Br, Han

[spludge]

Fitted the new relay and................it works. Well here's hoping it does. It started first turn of the key and, more importantly, started again a few seconds after switch off. Tried it a few more times and it still worked. I'm thinking, fingers crossed, its done with. Halleluja!

Its been a bit of a frustrating exercise but I have at least learned a bit more about how these things are put together. Thanks to all for the helpful suggestions and guidance.

Now for the MOT

K