Mildly warm start problem

[KKson]

Hi all, just wondering if anyone has had a similar issue. Had the 350i for a few years now. Always on the button, whether cold, hot or somewhere in the middle. I've used it several times this last week and if the engine has cooled down from a run, maybe for 2 hours, then it churns over, picks up on a few cylinders after say 10 seconds churning and then after another 10 or 15 seconds runs clean again. There is also a very strong smell of petrol under the bonnet accompanying this start up period but no obvious leaks. After a few minutes the petrol smell clears and all is good. The car pulls like a train with no issues.

The car has never suffered from vapour lock, and given the fact that the issue is after the car has sat for say 2 hours I don't think it is this. The fuel pressure regulator holds pressure when the engine is turned off so again there doesn't appear any signs of fuel leakage and emptying of the fuel rail.

HT electrics appear fine and as it starts from cold and from hot without a moments hesitation I don't think this is the issue. I've pulled the plugs and mixture looks spot on.

Could the infamous CTS be the fault, maybe thinking the engine is colder than it is and over fueling it? One thing I have noticed of late is a lot of air gurgling around the engine and header tank/ bottle when I switch the engine off. It doesn't use any water but I can hear a load of trapped air moving back into the header tank. Could it be trapped air around the CTS confusing it? If the CTS is sat in an air pocket rather than warm water could this make the difference?

Thoughts would be appreciated. Cheers.

[mrzigazaga]

KKson said:

One thing I have noticed of late is a lot of air gurgling around the engine and header tank/ bottle when I switch the engine off. It doesn't use any water but I can hear a load of trapped air moving back into the header tank. Could it be trapped air around the CTS confusing it? If the CTS is sat in an air pocket rather than warm water could this make the difference?

Thoughts would be appreciated. Cheers.

Its a possibility Keith.

It could also be the Thermotime switch...Signalling the CSI to over fuel...Test the ohms on the CSI & Thermotime cold and hot, you can obviously unplug the CSI to test, this is a controversial part that gets labelled redundant, however I'm not convinced that it is as it is linked to the thermotime and relates signals to the ECU which adjusts fuel accordingly, albeit primitive.

Another check is to let the car completely cool down and open the blanking cap on the swan neck..Top it up and try that....


Good luck

[KKson]

I have just checked the swan neck. Header tank is brimmed but swan neck was empty. I got almost a litre of water into it. I'll check tomorrow if that makes a difference but all seems a bit strange. I do have a spare CTS and thermotime switch so easy enough to swap out.

[Convert]

Keith, if swan neck was empty, then CTS will probably be reading temp of fresh air rather than coolant, and as such might overfuel.

Are you losing coolant anywhere?

I do hope it's not blowing it out of the expansion tank, that's how my HGF started.

[KKson]

Convert said:

Keith, if swan neck was empty, then CTS will probably be reading temp of fresh air rather than coolant, and as such might overfuel.

Are you losing coolant anywhere?

I do hope it's not blowing it out of the expansion tank, that's how my HGF started.

That's what I was thinking re the CTS. If it's sat in fresh air it may well cock up the fueling. No obvious coolant loss, it just seems to have relocated itself. The header tank level is usually down about 60mm but today despite a cold engine the header was brimmed up to the radiator cap yet the swan neck was totally empty. The engine temperature is also rock solid mid way up the gauge.

Now thinking about it about a month ago I did lose a load of water from the header tank. I checked the radiator cap and the rubber seal was very worn so fitted a new cap and had no loss since. I'm wondering if the swan neck emptied at that point and could all be down to an air lock? Fingers crossed tomorrow when I run it up and see what happens after a couple of hours. Cheers.

[KKson]

Hi gents, well after much investigation I have found the reason for air getting sucked into the swan neck and it was a perished small hose for the plenum heater. I did fit a new radiator cap and blanking cap which made no difference and also checked all other hoses. The plenum one is tucked out of sight. Although it didn't appear to leak water it was certainly so perished that air was getting drawn into it. That's the good news.

The bad news is that despite now having water submerging the CTS and thermotime sensors the car is still a pig to start unless it is stone cold. Starts first crank in the morning, every morning. If the car has stood for a couple of hours and even up to 8 hours, as it did today in the sunshine, when I try and start it is stinks of fuel out of the exhaust and appears to be flooding. I drove to work this morning at 8.00 but when I came to start it at 5.00 it just churned and churns and spluttered. Eventually I disconnected the cold start injector, floored the throttle to try and get some air in it and it did catch and immediately ran clean. I then had a very spirited run home chasing a 500 Abarth and the car didn't miss a beat.

This evening I've pulled half of the plugs out and colour is spot on. There's now no water loss, no bubbling into the overflow bottle, nice clean oil, big fat spark, obviously a shed load of fuel. Something is telling the ECU to pour fuel in. Would this be the CTS, thermotime or could it be related to the auxillary air valve?? The car had a new CTS last year but we know they all fail eventually. I've spares of all three items so wondering where I should look first? Any help would be appreciated. Thanks.

Edit - just had a look at the Vintagemodelairplane website and it does state the following:

"A faulty thermotime switch can cause uncontrolled over-fuelling during cranking if the internal contacts are permanently closed. Also the cold start injector can cause over-fuelling if its injection orifice is corroded or contaminated causing it to leak fuel continuously".

I'll try the thermotime first then unless anyone has any other suggestions?

Edited by KKson on Wednesday 15th March 22:01

Edited by KKson on Wednesday 15th March 22:02

Edited by KKson on Wednesday 15th March 22:08

[mrzigazaga]

Hi Keith


The EAV valve should of opened when the engine has cooled...So that would lean off any enrichment..Unless its stuck open.

Personally I would test the cold & Hot values on the thermotime & CTS.

I believe the values are on the said site, and it tells you which component works with each other..Very enlightening...

[ElvisWedgeman]

I had a similar hot start problem when I first bought the car which developed over several weeks. It was the ignition module on the side of the distributor. Replaced it with a good quality item, not a cheap one from the fleaby. It starts first time hot or cold and never had a problem since. That was two years ago.

Tony. TCB.

[KKson]

ElvisWedgeman said:

I had a similar hot start problem when I first bought the car which developed over several weeks. It was the ignition module on the side of the distributor. Replaced it with a good quality item, not a cheap one from the fleaby. It starts first time hot or cold and never had a problem since. That was two years ago.

Tony. TCB.

Thanks for the reply. I've a known good spare àmp also so thermotime first and then I'll try swapping the amp. Cheers.

[gmw9666]

Check the ground / wires from the afm etc to the back of the block

I had this on the 420 ages ago and it was a bad ground telling the cts to go open circuit

[adam quantrill]

Also take a reading of the CTS with an ohmmeter when it's

a) Difficult to start - in the warm phase
b) after starting in this difficult phase, but the engine has cleared and has just started running sweet.
c) Dead cold just before an easy start.
c) fully hot after running

and let us know the results.

[KKson]

Right had a further play with it tonight.

Even from cold it wouldn't start, which is a first, so something is breaking down further.

1. Tried disconnecting the cold start injector - no good.
2. Swapped the thermotime switch for my spare - no good.
3. Replaced the CTS and the car started but was misfiring badly.
4. Swapped the ignition amp with a known okay one - engine ran a little sweeter but fluffed every time I tried blipping the throttle.

I took some resistance readings - installed thermotime had a resistance of 48.8 ohms and spare that I then fitted 50.8 ohms.

For the CTS I have the installed plus three spares. At around ambient 15C the installed unit fitted in the engine had a resistance of 3490 ohms and the three on the bench were at 3310, 3280 and 3290 ohms.

I fitted one of the spares and ran the engine up a little to I'm guessing 45C and resistance of installed one dropped to 980 ohms. All resistances generally look about right compared with the info on vintagemodelairplane website.

For peace of mind I'll buy a new ignition amp and CTS so at least I can rule them out. Any other ideas??

[ElvisWedgeman]

Your symptoms sound very similar to mine. At first it was harder to start when hot, then it got even harder when hot, then eventually wouldn't start even when cold. Spread over a couple of weeks. Notice there was an improvement when you replaced the ignition module. It's possible you may have a secondary fault as well as the ignition module. If you replace the ignition module make sure you get a good quality one. My one was made in Italy and cost over £30 from local motor factors. That was two years ago.

Tony. TCB.

[KKson]

ElvisWedgeman said:

Your symptoms sound very similar to mine. At first it was harder to start when hot, then it got even harder when hot, then eventually wouldn't start even when cold. Spread over a couple of weeks. Notice there was an improvement when you replaced the ignition module. It's possible you may have a secondary fault as well as the ignition module. If you replace the ignition module make sure you get a good quality one. My one was made in Italy and cost over £30 from local motor factors. That was two years ago.

Tony. TCB.

Thanks Tony - certainly the ignition amp made a difference. I've just found an original old stock but new Lucas amp which I've bought. Cost a few quid but it is an original so we'll see how that goes. The temporary amp I've fitted was a Powerspark three pin unit with two wire adapter which was running okayish last year but not ideal. I've also got a couple of spare coils so may well try one of them on, BUT I will only replace one item at a time so I know which is the culprit. Thanks for your advice. You looking for another Wedge or moving on to something different this time?

[mrzigazaga]

Sounds more like something has/Is working itself loose??.....Check the plug connector on the resistor pack on the wing, If its loose then a couple of cable ties help to hold it in....Also check the ECU plug is firmly home....You could use some contact cleaner on them both and clean up the pins on the ECU...Especially pin 13.

[ElvisWedgeman]

Hi Keith. If the Wedge sells I won't be buying another. I would like a Tuscan or possibly a Cerb but what ever happens I won't be without a TVR for too long. Good luck with your fettling. Let us know how you get along. Cheers.

Tony.TCB

[KKson]

mrzigazaga said:

Sounds more like something has/Is working itself loose??.....Check the plug connector on the resistor pack on the wing, If its loose then a couple of cable ties help to hold it in....Also check the ECU plug is firmly home....You could use some contact cleaner on them both and clean up the pins on the ECU...Especially pin 13.

Hi Mark, I checked both of them thanks and did blast them with contact cleaner, and the AFM multiplug. Earths appear good. There obviously was an air leak in the cooling system so the top of the engine wasn't getting enough water around the top pipes, even though the temperature sender was submerged as that never showed an elevated temperature, so wondering if it's cooked anything?

I'll plod through one thing at a time, the same as I did 2 years ago............ At least I have a full garage loft of spares!

[adam quantrill]

Re-check the CTS resistance from the ECU end - take the big plug off the ECU and use the ohmmeter there. You will have to look up which two terminals it is.

It's not unknown for the loom to have a fault and if the CTS can't be read by the ECU it will go all wrong (cue Zig's piccy....)

[mrzigazaga]

adam quantrill said:

Re-check the CTS resistance from the ECU end - take the big plug off the ECU and use the ohmmeter there. You will have to look up which two terminals it is.

It's not unknown for the loom to have a fault and if the CTS can't be read by the ECU it will go all wrong (cue Zig's piccy....)

I put that pic away now mate......Besides mine wasn't working from day one.....

Have a good look at the vintage site as it gives a good description of how to test everything...Apparently you have to also be careful with testers as holding the meter on the CTS and Thermotime for too long can cause it to fail...

It could be a million and one things really...ECU...Injectors...CTS...ATS....What I found was since I broke my maintenance regime of cleaning every accessible connector...Wiping out the dizzy cap etc every month I have had problems arise...Test & Eliminate...

Hope you sort it soon.....

[KKson]

Well still not found the root issue with the 350i but a new CTS and ignition amp are due tomorrow so fingers crossed they might be part of the problem. I did have a good look at wiring etc. I did a full earth check of all components - AFM, power amplifier thingy, coil, block, ancillaries and all had a good earth with virtually no resistance between the components or back to the battery earth so not that.

Going on Marks advice to check wiring condition I did peel back the CTS connector and did find three cuts in the wiring insulation, two next to each other just as the wires exit the rubber shroud. I've cut the connector off and soldered in a good replacement. I was hoping this might be the cause but sadly not. Checking the wiring back to the ECU again with the new connector there's virtually no resistance so I know the wires are good.

The engine now just churns but doesn't wire, even though there is a spark and loads of fuel. The spark however does not appear to be as strong as it has been, despite a fully charged battery.