Hard cold starting

[John Tancredi]

Hi, re the Aux Air Valve, I had a new one fitted earlier this year and made a world of difference. Was supposedly for a VW Passat but fitted and went well... NOT CHEAP though.

Also just fitted a set of new injectors (from Braydons @ 21quid each, thanks!!). Performance has improved but idle is as rough as ever, esp when warm. Any relevance to the current discussion?? starts ok from cold (although starter motor sounding tired!).

Kind regards, John.

[Clan]

The auxilary air valve is only to raise the idle speed for the first few minutes from cold as soon as your foot presses the accellerator pedal it is redundant so wont cause bad starting , it just helps when starting off from cold with power steering loads etc .. so if you are starting with your foot on the throttle it wont have any effect ..

The cold start injector , all that does is get the engine fired up , as soon as the engine starts running ie the starter motor stops , the cold start injector shuts off so again wont have any effect on the engine once fired up ..Unless it is dribbling of course which is unlikely .. If the engine wont fire up from cold then the cold start injector is a likely candidate OR More likely the thermal time switch which controls it .

A very likely cause of bad running after starting from cold is air leaking between the injector housing seals and the head . They last about 60000 miles before they go hard and start leaking causing weak mixture , people not realising sometimes richen up the mixture on the CO adjustment which increases fuel consumption ..

a quick test .. with the engine idling pour some water over the injectors , if the engine stalls or starts running rough thats the problem . Often you will hear sucking noises as the water gets sucked in ..

[John Tancredi]

I understand that this vacuum relay/switch whatever on the bulkhead also affects the idle... (+/- other aspects)...? Does it also need changing periodically? Thanks..

[vanapeer]

CI FUEL INJECTION SYSTEM FAULT TRACING 240,260

[vanapeer]

For B2XX solex owners:
Isn't it raise-the-idle-in-case-you-switch-on air cond? Do you have air cond?

In case your tubes route the same way then this valve should either raise the idle +-100 rpm or alow them to drop if air cond switched on.

Originally Posted by John Tancredi

I understand that this vacuum relay/switch whatever on the bulkhead also affects the idle... (+/- other aspects)...? Does it also need changing periodically? Thanks..

[PTJS]

Hi All

Slight change of tack with my auxiliary air valve problem - still trying to find one. Have read most of the forum threads regarding the notorious fuel pump relay and am beginning to wonder whether I should direct my attention to this given a collection of 'minor' problems the car suffers from. These are,

1. Rough idle and hard cold starting previously mentioned.
2. For approx 4 years the engine has run on for 1-2 seconds when turned off.
3. Buzz at lowish fuel level for last 6 months, believed from in tank fuel pump.
4. In last 2 weeks intermittent slowing at speed as if brakes being touched but no overheating of brakes noticed.

As all of these items could be caused by irregular fuel feed I am wondering whether the fuel pump relay is at fault. I have owned the car for nearly 20 years and to my knowledge it has never been replaced. Does the relay 'meter' the flow of fuel? Can anyone advise if there is an easy way of checking whether the relay is working without removing it. I've tried turning the ignition on to listen for any sound of the fuel pump priming but can't hear anything - although from one thread I understand that with the Bosch CIS injection system this test does not apply. However, there was a spell a few months back that when the car had stood for a few days and the ignition was turned on there was a brief clicking noise like an electric fuel pump priming but this no longer happens.

Any pointers would be much appreciated.

Phil

[MazakMan]

Originally Posted by PTJS

Hi All
1. Rough idle and hard cold starting previously mentioned.
2. For approx 4 years the engine has run on for 1-2 seconds when turned off.
3. Buzz at lowish fuel level for last 6 months, believed from in tank fuel pump.
4. In last 2 weeks intermittent slowing at speed as if brakes being touched but no overheating of brakes noticed.

As all of these items could be caused by irregular fuel feed I am wondering whether the fuel pump relay is at fault. I have owned the car for nearly 20 years and to my knowledge it has never been replaced. Does the relay 'meter' the flow of fuel? Can anyone advise if there is an easy way of checking whether the relay is working without removing it. I've tried turning the ignition on to listen for any sound of the fuel pump priming but can't hear anything - although from one thread I understand that with the Bosch CIS injection system this test does not apply. However, there was a spell a few months back that when the car had stood for a few days and the ignition was turned on there was a brief clicking noise like an electric fuel pump priming but this no longer happens.

Any pointers would be much appreciated.

Phil

The relay doesn't meter the fuel flow, it's either on or it isn't.
As far as i know the fuel pump relay is triggered by the ignition control unit so it only powers the fuel pump when the engine is turning over.
If you remove the relay and bridge terminal 30 to 87 and 87b, then drive the car a bit and all the problems are gone then you'll know it's the relay.

To me it sounds like you might have a problem with the control pressure regulator, this would cause the cold starting problems and possibly the running problems too. You need a fuel pressure gauge and various fittings to test the control pressure so i would leave it to a (good) garage.

The running on after switch-off is probably carbon deposits in the cylinder head, try feeding it some injector cleaner, this makes the combustion hotter and can burn off deposits without the trouble of removing the head.

When did you last change the fuel filter, spark plugs, HT leads, dizzy cap and rotor arm? Any of these could be at fault and could be all or part of the trouble you've been having.

Isaac

[PTJS]

Thanks gain Isaac for your advice. I replaced the plugs, dizzy cap, rotor arm and fuel filter just over a year ago but deferred renewing the HT leads and king lead. Following your reminder I have done this and it has sharpened things up a bit. However the air idle control valve is not fully functioning and I am still having problems finding a replacement one. I notice that the base of the unit appears to be held on with a small nut - is it easy to take the unit apart to check for any obvious defects like a wire off or obstruction, effect a repair and to then reassemble it?

All the best

Phil

[MazakMan]

Originally Posted by PTJS

Thanks gain Isaac for your advice. I replaced the plugs, dizzy cap, rotor arm and fuel filter just over a year ago but deferred renewing the HT leads and king lead. Following your reminder I have done this and it has sharpened things up a bit. However the air idle control valve is not fully functioning and I am still having problems finding a replacement one. I notice that the base of the unit appears to be held on with a small nut - is it easy to take the unit apart to check for any obvious defects like a wire off or obstruction, effect a repair and to then reassemble it?

All the best

Phil

If you're talking about the auxiliary air valve, (bolted to the cam cover just in front of the inlet manifold) this cannot be taken apart, all the nut does is allow you to shift the cut-off gate around to vary the amount of air passed. Trust me, don't do it, it won't make it any better! If you PM me your address i'll pop one in a jiffy bag to you, i've got at least 4 or 5 kicking about.

Isaac

[PTJS]

Still at it! First, many thanks to Isaac for the tested replacement auxiliary air valve - with this fitted tickover improved but from cold start the car still wouldn't initially hold its revs. Had the cold start injector out and gave it a blow down the nozzle with carb cleaner, no difference. After much gazing into the engine bay I idly checked the tension of the throttle cable and found loads of slack, must have stretched over the years. With this adjusted up so that the throttle opened as soon as the pedal was touched things started to look a bit more optimistic. The car pulled much better when warm and tickover better too but cold start problem persisted.

I then read somewhere that the fuel pump relay not only triggers the fuel pumps but also the AAV, and thermo time switch (a pig to get at with my mits) which in turn co ordinates the cold start injector. I decided to get a new relay and with this connected the cold start was a bit better, warmed up the tickover was now superb and performance smoother. I use V power so I am now waiting until a tankful has been through the system to see if it is just that the cold start injector has gummed up with non/poor operation. If not I will try a can of injector cleaner in the next tankful and see if this helps. If it doesn't, I thinks its a case of getting the cold start injector and thermo time switch tested. Are these latter items usually prone to failure - bearing in mind the car is now 20 years old?

Never a dull moment!

Phil