Cold Start Problem (again)

On the Cab this time.

Will only cold start after cranking for about 10 secs with foot on the floor.  Once started sounds like it's running rough/missing for about another 10 seconds then all of a sudden that clears and it runs fine.

Cold start injector is working and thermo time switch ok - i.e. getting 8 secs of additional fuel from the CSI when cold starting.

Could be an air leak but I don't really think so.

Done a full fuel system pressure test and all within spec - injector spray test is OK also.  Timing is on the button.

Anyone got any ideas on this?  

One thought is that the CSI is firing too much petrol (worn injector) making a very rich cold start mix????

Problem is the same with the CSI disconnected.

Will start with a compression test and a good look round for air leaks.  Then maybe swap the CSI and TTL for known good ones.

Also used some injector cleaner - wynns i think - improved performance on both the black Campaign and the cab.

Rich

Do a leak down test with the injectors out. sound like they r leaking

Cheers Wellsy

Done that me old mate and no loss of pressure over 20-30 mins  

Would it not suggest that there's not enough fuel/too much air instead of the other way round for the first 10-20 seconds of running?  :dontknow:

just thought that if there's more fuel getting in, it would still start without throttle… and probably wouldn't with full throttle

dunno, maybe the sensor plate is sticking open a little or has too big a gap round it?

as you know i'm still trying to understand the forever seemingly annoying fuel system and setup but thought I'd add my 0.5p worth  :wink:

New plugs/leads often help with poor starting - are yours old or fairly new?

I would agree with AL_MK1 you have an ignition fault devolping , missing coughing etc classic ignition . Better once slightly warm .
Rich have you ? Leads , cap , rotor arm , coil etc etc ….

Nigel C….

The Astra i ran this winter was a pig to start from cold when warm no problems . I looked [that is just looked] at the ignition system and decided it was that crappy auto choke system that Vauxhall love playing up , so i bobbed down to the local scrappy and spent a tenner on a replacement carb with all the bits on . You guessed it same next morning so i checked the ignition , the ends of leads feel apart in my hands , the dizzy cap was burnt to a crisp inside the rotor arm black , replaced cheaply never had another problem .
Had the last laugh with the Astra though - Scrapped it last week -       

Leads, cap and plugs are of unknown age  8O

Gonna check everything out before i splash the cash so will look at fuelling first methinks and make sure that is on the money.  Worth doing anyway i rekon  

I'll keep this post updated - thanks for the ideas  :y:

Definetly ignition, quite possibly HTs. Had a similar problem with the Golf C which got to the point where it failed to fire at all from cold, but would burst into life with a push/tow start then would run fine for rest of the day - new leads solved the problem.

Cheers

Rich - my fuelling / starting woes turned out to be a combination of factors - the warm up reg (although yours sounds OK if pressure tests are OK), but also the coil on my car was duff.

For the money a new coil, decent HT leads and a dizzy cap and rotor arm are probably money well spent for piece of mind.

I take it you have had a chance to try out that fuel pressure test gauge from JC Whitney then? Was it any good? Mine is still in its box at the mo since the fuel probs were been fixed using Wellsy's gauge….

Chris

Chris,

Yeah used it a few times - does the job nicely

OK done an injector leak test like Wellsy said - he's good, very good  

fitted a pressure guage to injector line 1
Ran engine up to temp
40psi on injector at idle
switch off engine
Pull all injectors and place in bottles
Walk away……………

Came back 24hs later
Pressure guage reads zero  8O
Can't see fuel in jars one to 3 but jar 4 has about 1/4 a teaspoon in it

I think conclusive proof that I've got leaky injectors  

Might just have to buy new - anyone got new recently and where from?

That place in the states looked quite cheap imo.

Cheers

Rich

24hrs?!

Think the Acumalator only supposed to maintain pressure for a couple of hours. Would have thought any system will lose pressure after 24 hours.

Peter.

Good point pete - but the pressure loss in the injector pipes is different to the system pressure drop - I've known pressures to be maintained - system and injector - for much longer than 24 hrs

tallpete said

24hrs?!

Think the Acumalator only supposed to maintain pressure for a couple of hours. Would have thought any system will lose pressure after 24 hours.

Peter.

A properly-working accumulator keeps the pressure for weeks - I've started my Golf after about a month, and it still started within about 2 seconds. However, when the pressure is fully lost (eg: fuel filter just changed), it takes up to about 10 seconds to build up enough pressure to start.

Hmm, all very interesting. I can't see how you would have two lots of closed systems. Surely the closed pressure system coming out of the accumalator is the same as that at the injectors?

even the control pressure from the warm up reg is on the same feed, they all come off the distributer.

Theres no one way valve in the distributer, it's always open to some extent dependant on control pressure.

Type 17, I have always read the accumalator was only connected with poor warm starting.
i.e when the cars cold the warm up reg, cold start valve and aux air valve all do their bit and the lack of pressure doesn't matter so much.

Peter.

pete,

The fuel ditributor acts like four valves closing off the pipes to each injector.  

The accumulator is only there to deal with transient pressure losses from the pump - air in fuel etc and provides a short pressure backup.

Here you are - all Mk1 owners who are interested in their fuel system need to digest this webpage thoroughly.

http://www.auto-solve.com/mech_inj.htm

(If you don't own one/aren't interested, it's a good cure for insomnia    )

If you want more details on individual FAQ's, this might be good.

Reading this with great interest   , if the pressure is dropping where is it going ?
How does the system keep its pressure from the accumulator forward and at what pressure? Eg its not working pressure so what should it be ?

I no an injector requires 3.3 bar to open and as soon as its open will close due to lack of pressure until it builds up again but if i go to my car and it hasn't been run for say a week there is fuel in the lines but its not under pressure just sat in the lines . Yet mine starts okay all ways first turn of the key .

Can injectors be chemically cleaned to give them new life ? Has any one had this done and if so how much was it ?

Cheers ……..

chudd said

if the pressure is dropping where is it going ?
How does the system keep its pressure from the accumulator forward and at what pressure? Eg its not working pressure so what should it be ?

Can injectors be chemically cleaned to give them new life ? Has any one had this done and if so how much was it ?

Cheers ……..

The pressure can only drop after the engine is stopped if the accumulator, injectors, or system pressure regulator in the metering head are leaking (or some other joint somewhere is leaking)

When not at working pressure, the system should not have dropped below 23psi after 20 mins (Haynes)

Injectors can be cleaned, to improve spray pattern/get rid of leakage, but the spray pattern/leakage is more likely to be due to wear, in which case cleaning is no good, and replacement is necessary.

Cleaning (by ultrasound, incidentally) is most beneficial on diesel injectors, which get clogged more easily, and where the spray pattern is more crucial to good running. Smokey diesels are often due to clogged injectors, giving a poor spray pattern, and fuel not mixed properly with air is only partly burnt, leading to soot (black smoke).