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Zolder

S4s hot starting problem.

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I have a slight problem where as in if I've been on a run, turned the engine off and then start it again while the engine is still warm (up to 60mins later), the engine will fire up and tick over, but if I try to pull away it will falter and stall. (bit like fuel starvation).

After it has stalled it will start straight away and if I leave it ticking over for a minute or so it will behave as it should..

Any ideas?

 

Cheers!  :cheers:

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Hi,

 

It does sound as if the fuel in the header rail - ie the fuel in the engine bay area has vapourised.

 

If this only happens after a "spirited drive" then there may not be anything mechanically wrong.  I do find that keeping the fuel tanks >1/2 full can slow down the heating up of the fuel.

 

If it happens a lot it suggests a problem, perhaps with the return line to the fuel tank or the fuel pressure regulator (fuel is circulated through the header rail back to the tank to keep it cool).  Not sure of the best way of testing that though.

 

Another possible cause might be the action of the fuel pump when you key the ignition - you should be able to hear the pump running for a few seconds (often drowned out by the noise of the vaccuum pump).  If for some reason this is not happening when hot it could cause a problem.  Try keying the ignition on/off (ie dont turn over the engine) a few times before starting to see if that improves things.

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Could also be too much fuel from the charcoal canister.  Try venting the fuel tanks before starting the car and see if the problem goes away.  I've been having this lately on my 89SE.  I noticed my A:F gauge going rich then lean as I put some load on the engine after a hot start.  Once it clears the pressure from the canister, then the car runs fine.

 

Check the one way valve to the charcoal canister as well.

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I have the same headline problem (hot starting) but mine is the opposite. If the engine has warmed up to temp. and is switched off, it will not start again at all until it has been stood for literally only 5 or 6 minutes?

This problem occurred a while ago and after much deliberating, i tracked it down to the IAC valve being loose in its fitting. This is not the case this time so am at a bit of a loss again.

It may sound like a minor issue, but its a worry every time i stop for fuel for example, or even in the event of just stalling in traffic.

 

Any thoughts guys?

Ps. Mine is an S4

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Nick,

The ECU is particular as far as what range the IAC isoperating in.  If you can Log data with Freescan or espritmon.  Start the car cold while logging data, let it idle to 80C on the water temp gauge in freescan.  Do Not touch the throttle at all until after it is warm.  You can drive it while logging data as well.

 

Send me that data.  Then record data again with your hot start issue from starting the car while warm.

 

Also while you are having this hot start issue, try removing the fuel caps to vent the tanks and see if that helps the engine start.  That would point to the charcoal canister.

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Travis, i'm not sure i am able to log data-have never been able to get it to work with Freescan. Have only recently got hold of espritmon and used it once for an ABS sensor fault, so not tried with that.

When i had this fault the first time, if i let the engine warm to 80 on idle ie. without actually driving, then switch it off, it would start again straight away. However, now it makes no difference-it just doesn't start.

I have tried resetting the IACV with Freescan just before switching the engine off but it makes no difference.

Would it be possible that its just broken and needs replacing? I'm convinced that this is where the problem lies.

With regards to the charcoal can. i'm pretty sure its been made redundant anyway.

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Hello, hot starting problem can be many things. I have an old 1984 S3 N/A car without wenting on top of the engine so problems get more worse on this car. I have looked at other things then the classic fuel evaporating issue, which is ofcourse one of the reasons!.

 

1. I changed the pluggs and leads rotor and cap = little better but not solving the problem.

2. New better fuel lines on top of the engine = not solving the problems but improvement

3. Battery, i changed the battery and battery cables and all the shoes and cleaned everything=big improvement. Probably the ground cable and shoes because of dirt.

4. Another thing that is important is the coolant. Change it and clean the radiator and evaporator carefully on the outside.

 

!!! Problem is not gone on the S3 but the car starts faster. This should be better on the S4.

 

/Fred

 

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Nick,

Don't replace the IAC until you can log some data, otherwise you'll just be throwing money at the problem . What do you mean the charcoal canister has been made redundant? Did yours get removed in the past?

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Ok. The canister is still there and plumbed in, but i believe the solenoid has been disconnected. Not 100% certain, i will have to check this.

Having just read the service notes on this, it would seem this could well be an area to investigate? As im understanding it, it only allows purging when the engine is warm, thus aiding hot starting?

Have to say, when trying to start it when it is warm, its literally as if its run out of fuel.

Does this sound like a possible cause?

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If your solenoid is disconnected, then you have no method of purging excess pressure from the tanks... a dangerous problem...

 

Could explain your hot start issue.

 

Try a hot start with and without the fuel caps removed.  See if that changes the problem... then you'll know.

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Will look into it over the weekend and get back to you.Cheers,

 

Nick.

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Had a check of things over the weekend and fromm what i can see, the carbon can. is all connected although wouldn't know how to check if its actually doing its job. Obviously with its positioning, its really difficult to get to with everything else in situ.

Tried hot starting with fuel caps removed but it makes no difference.

Any more ideas anyone?

 

Nick.

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Leaking where, around the seals?

If so then i can confidently say that's a no, presuming it would give off a strong fuel smell.

As i said earlier, when trying to start from hot its as if its run out of fuel?

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No, I meant leaking inside the injector around the pintle and into the cylinders.  So when the car sits over night, the fuel evaporates, but on a hot start, the fuel hasn't had enough time to evaporate, and the clearances are larger due to the heat, so extra fuel is sitting in there.  Too much fuel chokes off the engine, similar to how if the charcoal canister purges too much fuel vapor it can stall the engine.

 

The other thing to watch would be see if your fuel rail is holding pressure, if not then that can point to a bad pump or bad seal at the pulsation damper.  Can you connect a pressure gauge and see if the pressure goes down after the engine is stopped?

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If your car is like my SE, it could still be an IAC problem. The vacuum hoses run over some pretty hot parts of the car and eventually degrade/go soft. When vacuum is applied, the hose simply collapses and little vacuum goes to the IAC.

 

Before spending big bucks, replace the hose section (Having said that, the original hoses can be pretty expensive :huh:  )

 

Cheers

Ian.

Edited by Qavion

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hallo Nick

are italian

i have the same problem

have you solved?

you can help?

thanks

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The Esprit has a "clear flood mode" if you try to start the car with the throttle pedal pressed all the way, it will clear the flooded fuel, and turn the injectors off.  let it crank a bit.

 

Then you can retry starting the car.

 

If it starts, then your engine was flooded, and you'll need to check for leaky fuel injectors.

 

If it doesn't then you need to check fuel pressure to see if you have enough. 

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I cured my hot starting problem by fixing the chargecooler (fitting an electric pump). 

I think the air was just too hot (lacking in oxygen).

Edited by Zolder

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hi

cold engine starts immediately

from hot side after 3 minutes

 

charged:

pump electric chargecooler

fuel pump walbro 255 + fuel filter

oxygen sensor

spark plugs denso iridium iw20

vacuum tubes + valvw no-return

oil engine castrol edge 10-60 + filter

sport exhaust

battery bosch 74ah

 

eliminated:

catalyst

valve EBPV

valve throttle jacking

 

no error with Freescan

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When did you replace the fuel pump? Did you re use the pulsation damper above the pump? Or did you use a fuel hose instead?

Are you sure you have the one way valve in the right direction between the charcoal canister and the manifold?

When you remove the fuel filler caps, is there a lot of pressure that escapes?

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eliminated pulsator

no-return valve position ok

 

put anso:

air filter K&N

modification air intake direct

 

i removed the cap tanks without result

 

tomorrow i measure the fuel pressure on the rail

 

thanks for your help

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