urquattro20Vt

Hey guys-
Essentially cross posting from Pelican....

So here's my issue: Car has been running great - as recently as a week ago I drove if for a few days... But three days ago I went to drive it after sitting for several days - mild morning - 50F or so - and the car didn't catch on the first crank (a few seconds) like it usually would. In the past this would happen on occasion and I think it would flood. Give it 30 minutes and it would be fine. So this time I try to force it and crank it quite a bit. A lot in fact. Nothing. Strong gas smell tho. In fact even some coming from exhaust at the junction with header.

So I left it for a day. With battery tender. Figured it would clear after a day sitting.

Next morning (two days ago). Again didn't catch. So again I cranked it. A lot. After maybe 10 minutes or so she caught. Ran fine all day. It wasn't as eager to jump to life as usual after sitting for a few hours but she did start and run fine.

Yesterday morning - slow to start but she did. Drove her just a little. Done by noon ish.

OK so half hour ago - car had been sitting more than 24 hrs - I went to start her and she just cranked. No catch. I thought I removed the FP relay (to let the crank without more gas/ avoid flood?) after the first try but later realized I pulled the wrong one - but after cranking for a few minutes she caught - was rough for a minute than ran normal. Did not drive her - just idled for a few minutes.

Why the sudden change in starting behavior? I have not adjusted the WUR in a few years - have not had a need. Didn't see any disconnected vacuum/boost lines. Will double check tho.

My first thought is bad cold start valve. ??

UPDATE this morning:

I went to start her up - same thing - turn the key - crank - no catching. So after one try (long crank) I pull the FP relay.

Go back to start and she fires up after about 5 seconds of cranking then runs for a few seconds and dies, of course.

Re-installed FP relay and went to start - would not catch - did one or two long cranks.

Pulled FP relay again and had my 10 yr old daughter stand there with it while I cranked it - it caught - started to run so had her push the FP relay in place. Bingo. Car ran normal. Ran around town this morning taking my daughter to school, dropping by a client's office - turned the car off several times - re-starts just fine warm/hot.

My only thought is still CSV? trying to recall if failure mode is to spray too much gas? Or is there something else that tells CSV to stop spraying at startup?

Any thoughts appreciated-

Metal Guru

First thing to do is check the cold control pressure. I say that because you won't see the effects of a bad accumulator until it's hot out, so I don't think it's that. If you are checking cold cp, it's easy to check residual cp too while you've got everything hooked up.
If you want to tackle it, I'll send you the factory procedure. You will have to jump out the heating element power to read and set it (if you have a Leask wur).
I'd do this first because getting to the cold start injector is a real pain.
Mine went bad and caused a stumble on start-up. Had a fuel smell to go with it.
I was able to go right to the injector as the source of the trouble because I had reset/corrected all of my control pressures two weeks earlier.

urquattro20Vt

OK....good info. I did not mention that my AFRs seem to be in line during warmup - and certainly are good while running.

Once it starts, it runs perfectly normal - I'm thinking that is a sign fuel pressures are good, no?
While serfing the interzwebz I saw one your old posts mentioning having a CSV fail and flood the combustion chamber. Me thinks I have that...... well it's what makes sense to me at this point anyway.

I was thinking I'd find a way to disconnect the electrical connector on the CSV - see what effect that had....

Metal Guru

If that is accurate, afr should be as low as 11 - 13 to 1 at start-up on a cold engine, depending on ambient temperature.

It's a guess until you check


That connector is buried under the fuel injection head and is at the back of the throttle body. You won't be able to disconnect it without disassembling a lot of stuff first.
Checking control pressures is cheap and a good way to eliminate wur issues from the diagnosis. If that checks out then you could proceed to the injector replacement while you have the intercooler off.

heliolps2

Hey guys, I think when your unplugging the FP relay the fuel pressure drops and make the system go rich, As we know at cold start they need more fuel, You may be running lean on cold start causing the issue, Why did this happen out of the blue, A lot of variables ....CIS is very simple but also very complicated...

urquattro20Vt

I pulled the FP relay after cranking bc I though it was flooding- didn't want more gas.
By pulling the FP relay car was able to start...

BUT..that said. After sitting for 4 days last week the car started right up Friday morning and I drove it all day Friday.

Then this morning (Monday) - after sitting since Friday night - she started right up no issue.

So at this point I'm not going to do anything until the issue comes back. Knock on wood.

TT Surgeon

You might have a bad relay or pump, when you pull the relay you take the bad one out of line so to speak, remaining good one works. Metal guru would know for sure.

John McM

I don't come in here often. When I had my Turbo 3.6 I started this thread https://rennlist.com/forums/964-turb...trol-unit.html it may be irrelevant but you never know.

Metal Guru

I'm pretty sure there's only one relay on the 965 series, unlike the 930's. I know this because to set control pressures, I have to remove it and jump the system with a switch to trigger the fuel pumps (don't have my electrical diagrams on my work computer).
Brandon, are you sure you pulled the correct relay?

urquattro20Vt

Just some closure on this. What would happen is if it didn't start first time, it would get too much gas and not start. By pulling the FP relay in the fusebox it would start using the gas already in the cylinders for a few seconds - so you'd have to jump out and plug the FP in before it died (easy with your kid helping, much harder when solo) and then it would catch and all would be good for the day.

During the engine rebuild we had the injectors sent out for testing/cleaning. One was leaking, spraying too much, etc and cleaning could not fix it - and was thus replaced.

I had suspected a bad CSV but the CSV was perfect - it was one of the normal injectors causing the issue.
The cold start issue is now gone.

Brandon
'91 911 Turbo
'00 Audi S4 highly mod'd DD