20-60 minutes after driving I canāt start as easy as I used to.
What happens is that the engine turns over quite fast, obviously faster than cold. It occasionally fires on one or two cylinders but rather weakly so. I smell fuel after a few attempts and it will start well after either waiting or a few attempts.
There is fuel pressure. By now it idles nicely. (It does!). Idle mixture smells a little rich but only so it starts nice when cold; or just turned off and restarted, and I suspect the cold start injector thatās waiting will fix this. The cold start circuit works well.
Spark is there, the coil must be good. 0-60 in under 11 seconds. Can my timing be off by much? I get some part throttle pinging on lower octane fuel as itās no longer freezing outside and run on lower octane fuel. The advance is on the manifold, which may or may not be as it shouldā¦ Can this have anything to do with it?
The strange thing is that the idle is as it should be in any situation, and yet there is that small window where something does not match up. And this used to be better.
David,
no idea how you measured it, but anything below 12 should not be repeated too often on a BW66 ā¦
Anyway, several attempts should never be necessary on an XK engine in good fettle. My car is a vroom starter once halfway warm. If a fuel injected car starts poorly, i.e. not on first turn second round something is amiss. Guess thatās why you asked in the first place. As the carbed cars donāt seem to have this problem (on a friendās XK 140 it was the float chamber) Iā d suspect the control unit of your PI - but then, I canā t say much about fuel injection ā¦ My Spitfire has a similar problem that I have yet to resolve.
Consensus seems to be that the injection cars need two or three cylinders to start - I tend to have worse than that. When I take a week to drive it I need four or five revolutions.
The carbed cars always start on the first or second try, even cold.
Iāll try to apply some further logic but feel that I have gone through most things so far. Hence the timing question.
The thing wrong is that it almost spins like with plugs out, but compression is good, naturally.
Sub-12 was accomplished without brakes, so no ālaunch controlā, and I now know that as far as power goes, the engine is wellā¦ and of course the full- throttle shift points, shifts and so on are good. I do have a spare BW65 but no interest in doing the work, at all.
Good luck with your Spitfire, Iām at a point where I no longer know whether I prefer injection.
**
I trust you are cranking āfeet offā, David - engine will baulk if pedal is usedā¦
ā¦itās the job of the AAV to provide the correct amount of air required. As the engine cools down the CTS resistance increases - gradually fattening the mixture. The AAV slide likewise gradually opens - to give the required increased idleā¦
Ideally; the two work in sync - providing just the right combination at any time during cool-down. However, they may be out of step for a variety of reasons - causing starting problems as described.
You may check CTS to ensure that itās temp/resistance relation is to spec. And, with the engine hot, disconnect the air hose on the AAV and watch the gradual and smooth opening on the slide during cool-downā¦?
Neither is necessarily conclusive - but using an infrared thermometer; you can easily compare the temps. But also; you should inspect and clean throttle body - and verify throttle gap. Itās an essential element in start and idleā¦
The best way of eliminating any CSI interference is clamping the fuel hose to it. And if that works - examine it more closelyā¦?
**
This is the āEuropeanā set-up for vacuum advance - and initial advance setting should be to āEuropeanā specs. In any case; check ign advanceā¦
Feet off: naturally.
AAV is long replaced with a verified, smooth working one that happened to look better.
Throttle gap is 0.002ā and reasonably clean
CTS should have to be checked. I know that the engine runs fine during all warmup phases, so it couldnāt be too far off but I will make sure.
The CSI circuit works as intended and a new verified clean injector is waiting to eliminate all doubt. I hope itās not a stray wire. Have to look at the timing as well and will report back.
David
**
You are up to date on everything, David - and donāt deserve starting problemsā¦
But the sync of the two items may still be imperfect, caused by the difference in temps at their sites - even if both items work? What happens if you restart āimmediatelyā after hot shutdown. Or at what stage/temp of cooling down does the problem occurā¦
Essentially; the idle after a start-up is an indicator. Idle rpms should relate to engine temps. Ie, at a given temp the idle should be the same whether the temp is a result of cool-down/start or continuous warm-up. If the engine cannot idle at a given temp, it wonāt start eitherā¦
Imperfect sync must definitely be the (main) issue at hand, immediate restarts are immediate starts. After a few minutes starting gets harder. 20-60 minutes after shutdown is my time; by then the coolant is at 50ā¦80Ā°C. Idle is 600 in gear w/o the compressor and goes up as it cools down. It wants to idle as soon as it catches.
I could imagine that it is āunder-chokedā but fine as soon as it runs, and with some more cooling the CSI takes overā¦? And because it canāt ignite the lean mix sufficiently I smell fuel after some timeā¦ It will get enough fuel as soon as the rpms are up. Iāll check the sensor.
I now have a CTS that measures out perfectly.
The CSI will go in at the same time. If none of that helps I will try this, not permanently, just a grounding wire.
Timing will be experimented with but I believe itās fine and nothing changed there.
There are in fact a few topics on this particular problem and nothing conclusive yet. This comes close. My previous assumption (under-choked) would fit this very, very nicely indeed. Very, very, very nicely. I shouldnāt get my hopes up too much and something is not well either way, but if that fixed it it fixes it.
If this is not helpful I will remove the whole operation and put a complete, like new intake manifold with all the injectors and sensors and wiring and throttling andā¦ you get the idea, in, and if itās not that I will try the AFM and eventually a good price for that particular XJ.
Emissions testing next week will finally let me know the proper settings in terms of richness. 1.75% CO as a baseline and a bit richer after I have the certificateā¦ I am optimistic on all counts.
David
**
The mixture is ācontrolledā by the CTS, David - given the CSI should be off above 35C. The AAV only adds air, but have no influence in the mixture - which is decided by the ECU based on CTS and AFM inputsā¦
As mentioned earlier; the xk is sensitive to pedal use during cranking - pedal just adds air, and the engine baulks at starting with too much of itā¦
In principle, the engine should not be very sensitive to minor AAV variations. However; I still think is important that when the engine starts, it should idle (in neutral) at rpms relevant to engine temps - and should never be below hot set idle (which in your case is?)ā¦
A common experience is that after a brief shopping stop (say 15 - 20 min or more), if restart is recalcitrant; idle will initially show well below hot idle set when the engine starts - too little air from the AAVā¦
The bypass screw on the AFM is a mixture setting control - it may play a partā¦?
Yes. To all. The bypass screw is set a little rich but that can change now as the CSI is now new and should spray significantly better; more on that tomorrow.
The AAV is happy and we both rule that out.
The CTS is replaced with no benefit so far.
I regrounded my water rail with no significant findings.
Hot set idle is between 900rpm at 88Ā° and 750 when off the freeway. This matches my sticker!
I should try to add more idle air and remove some fuel. Maybe I can get the 750 with less fat.
Pedal adds mixture, no clue why it confuses the system but it doesā¦ same as the AAV of course or a stuck overrun valve mightā¦
I should later try starting with CSI on a hot engine. And I will relocate the vacuum of the distributor and if necessary reset timing. If it hurts performance I have certainty.
All restarts of today resulted in specād idle, cold, warm or hot always were where I want them to be. 1200, 900, 750ā¦
Emissions testing is on Tuesday, I have to pass on Wednesday and I will.
**
Engine idle should be the same with the engine hot, David - it should not vary on or off highwayā¦?
Basically, the pedal only varies the amount of air going into the engine. There is no input to the ECU from the pedal to vary mixture - the AFM flap deflection, caused by air flow, is the information the ECU receives. The ECU āmappingā, which is rather intricate, does the restā¦
But the hot start problem should not be there - so you are absolutely justified in pursuing itā¦
I did move the vac advance to the throttle body port and it ran just as nicely (cold, of course, warmed up it wouldnāt run). It didnāt feel noticeably better, so I left it at manifold vacuum.
Startup was about okay, but still underwhelming so Iāll hardwire the CSI next. And more air, less fuel, even though right now it idles surprisingly well for an XK.
Idle variations, I wanted to say that the AAV obviously needs some time to close, and the coolant indicating 88Ā° does not necessarily coincide with the āhottestā idle rpm, but instead itāll take a few miles until the idle speed has levelled off at 750. When off the freeway, the engine is really hot is what I meant to say. So, Iād say, good.
The pedal position varies throttling, which in turn changes the deflection of the flap as the pistons can suck more air in. So very unscientifically, the mixture should not change, but the amount must. Not important to us - but the hot- and cold start problems are, and they need to be fixed yesterday; itās been long enough. The ECU has no mapping - itās all analogue magic, as you knowā¦ some additional screwing around should eventually yield results under your guidanceā¦ right?
David
Oh, and after slight leaning out it starts to surge hot, in gear, so I will try the other way; but it seems a little richā¦
[quote=ādavidsxj6, post:12, topic:374207ā]
some additional screwing around should eventually yield results under your guidanceā¦ right?
**
Such a persistent hot start problem after all you have done has not been reported in my memory, Davidā¦
Something unconventional seems indeed called for - but āwhatā is obscure. Same symptoms could equally be too much/too little fuel, or too much/too little air, or a combination of both - there is not tellingā¦
Shortly after shut-down; the rail temp rise as the pump stops - the āinsideā is considerably hotter than coolant. (The hotter the CTS the leaner the mixture). So with no difficulties at restart after a brief stop; āsomethingā changes as the engine cools down - which basically relates to CTS and the AAVā¦
The AAV is also electrically heated for a rapid closing of the slide - active in cranking/running, otherwise heated by engine. But as the engine is supposed to catch in a couple of seconds - to short for the AAV heating to do anything. But prolonged cranking without a start would.
Itās difficult to arbitrarily vary mixture and air while cranking. Cooling the CTS would fatten the mixture, of course - and slight(!) pedal would increase air ingress. Overdoing either would be very counterproductiveā¦howeverā¦?
As an aside; ported vacuum should read low/0 vacuum in idle - varying with pedal input out of idle. Which is why ign timing is set at some 17 deg ported - while the usual manifold vacuum setting is about 4 - 6 deg. Set for the latter; the engine will not run, or run badly, with ported vacuumā¦
I donāt really suspect an ignition problem causing your symptom - but have you checked spark quality with a spare spark plug during the hot start problemā¦?
Frank,
Good luck with that - be back soon.
I wish you all the best, and a quick recovery. Maybe I have my problems sorted out when you come back. Iāll post my emissions results if not too unfavorable; they might show what was amiss.
Mick took like one week off ā¦ hopefully, youāll be ready to āstart us upā soon again as well! All my best wishes for a successful OP and a quick and complete recovery!
A decade or so ago, the guy that subbed at my barber shop had them both done!! f Two (?)
He had a choice. metal or pig!!! He chose the latter. did not want to āclankā. His term. He seemed fine and claimed he felt great. He owner of a big mid 70ās red Ford convrertible.
So emissions are fine, was slightly rich and slightly too fast and is obviously missing a bit on one cylinder which has nothing to do with our problem except that it must be the ignition.
