Cold start issue

[mikesp]

Engine starts first turn of the key when cold, revs go up and then, instead of settling to a fast idle, they drop so low that the engine cuts out unless you catch it on the throttle. If it stops it then won't start without full throttle, similar to flooding but with no petrol smell. I know there are probably three items which could let this problem happen, two temp sensors on the manifold and a bi-metal strip controlling a disc valve on the air side of things, but where do I start. Once the engine is warm it runs very well and ticks over reliably. So gotta be something on the cold-start side of things. Any technical help appreciated. Thanks

[Number 7]

You could try disconnecting the cold start injector and see what effect that has. Then I would try replacing the coolant temp sensor - less than a tenner, and easy enough to do.

7.

[mikesp]

Number 7 said:

You could try disconnecting the cold start injector and see what effect that has. Then I would try replacing the coolant temp sensor - less than a tenner, and easy enough to do.

7.

Thanks for that. What effect should I be looking at by diconnecting the cold start injector if it's faulty or not?

[B-Reight]

Check your idle air gallery is free of gunk. You might also want to test your Extra air valve, mine was seized and needed freeing off and a good squit of lube.

Guide here: http://www.vintagemodelairplane.com/pages/Download...

Edit: Ignore me, thought yours was a flapper

Edited by B-Reight on Tuesday 8th December 22:26

[pwd95]

Yours is a hotwire Mike so it won't have a cold start injector. (Rob sent me some pics before I bought the 450, I was going to go & see it)
My money is on the stepper motor sticking a bit. Unscrew it I give it a good clean, inside the thread too.
Make sure it's air tight when it goes back.

[mikesp]

pwd95 said:

Yours is a hotwire Mike so it won't have a cold start injector. (Rob sent me some pics before I bought the 450, I was going to go & see it)
My money is on the stepper motor sticking a bit. Unscrew it I give it a good clean, inside the thread too.
Make sure it's air tight when it goes back.

Had the stepper motor out recently and it looked brand new, but was only finger-tight so put some PTFE around threads and screwed it back tight. It was new a year ago according to a receipt I have. Think it still might be a problem?

[mikesp]

B-Reight said:

Check your idle air gallery is free of gunk. You might also want to test your Extra air valve, mine was seized and needed freeing off and a good squit of lube.

Guide here: http://www.vintagemodelairplane.com/pages/Download...

Thanks a lot. Good info

[pwd95]

...Hmm, just re read the first post. As you say, if it's fine when warm & it's new then it's unlikely to be at fault.

[mikesp]

Having read the replies it would probably have been a better idea to say what model I have, oops. It's a 1990 400se.

Thanks for all your comments. Spose the easiest start will be temp sensor for the massive layout of £7, then start testing the air valve?

Edited by mikesp on Tuesday 8th December 22:39

[pwd95]

With the Hotwire system I'm sure the stepper is the only thing that controlls the idle. The Chimp used to do something similar but when warm, fire up then virtually die (run on 3-4 cylinders @ 4-500 rpm), but it would recover if I stayed off the throttle for about 20-30 secs. It's as if the stepper was stuck then suddenly decide to work.

Edited by pwd95 on Tuesday 8th December 22:46

[BadRed]

Just plucked this from the interweb, well worth a read

http://www.britishv8.org/Articles/Rover-14CUX-EFI....

[mikesp]

BadRed said:

Just plucked this from the interweb, well worth a read

http://www.britishv8.org/Articles/Rover-14CUX-EFI....

Good stuff, thanks

[adam quantrill]

I've always had this problem but on mine the feed for the EAV comes from the throttle body which is in front of the blower. I think I need to replumb the air feed to the EAV so it's after the blower, then the blower will be pushing air in, rather than sucking it out. There's also a one-way valve between the EAV and the plenum, I suspect because of this very problem.

On mine it won't idle at all without lots of throttle, until (I suspect) the EAV closes, after about 2 minutes of running.

[mikesp]

adam quantrill said:

I've always had this problem but on mine the feed for the EAV comes from the throttle body which is in front of the blower. I think I need to replumb the air feed to the EAV so it's after the blower, then the blower will be pushing air in, rather than sucking it out. There's also a one-way valve between the EAV and the plenum, I suspect because of this very problem.

On mine it won't idle at all without lots of throttle, until (I suspect) the EAV closes, after about 2 minutes of running.

Can't leave it running that long early morning where it's garaged. Have to get going. Gets to be a pain in the bum knocking it out of gear, left foot braking, see if it's clear at the junction, stick it back in gear and drive on. Just so it doesn't stall and not re-start. Can't be doing with that. Gotta get it fixed this week. Bought temp sensor. Will put it on before I start it again, see if it works, if not, start looking from there...EAV next methinks.

Edited by mikesp on Wednesday 9th December 13:04

[pwd95]

So it won't idle the whole time it's cold? That could well be temp sensor. It think's it's warm all the time.

[mikesp]

pwd95 said:

So it won't idle the whole time it's cold? That could well be temp sensor. It think's it's warm all the time.

Yeah, that's right. Let's hope it's the easy fix.

[jmorgan]

Won't harm checking the throttle pot voltage setting. That gave me no end of issues including cutting out. Eventually got to the point of flooding whilst 70 on the M way. Must have been working lose, it was way out.

[honestjohntoo]

Runs crap when cold, OK when hot.

Right - bearing in mind my only knowledge of Hot Wire is to do with stealing cars please bear with me:

o An Extra Air Valve ONLY provides air when cold, to raise the RPM to overcome the cold engine friction losses. PRECISELY the same as feathering the throttle pedal.

o At the same time a Coolant Temp sensor tells the ECU that the engine is cold and "please enrichen the mixture for cold conditions" to increase the available torque. It does nothing significant to raise the RPM.

o A throttle pot ONLY fires the acceleration and full load enrichment circuits and even if it is faulty would not really inhibit starting when cold.

o Indeed the TP can be disconnected and the Efi system will work normally EXCEPT the enrichment cicuits are dead.

o The AFM just measures Air Flow and reports its finding to the ECU so the CORRECT amount of fuel is dispensed.

o The air temp sensor simply reports air density to the ECU.

o The thermotime switch ONLY controls the length of time the Cold Start Injector is active.

o The Coil Negative Signal "tells" the ECU the engine is running and please fire the injectors.

o The AFM fuel pump contacts "tell" the pump to keep running as long as there is air flow.

o Based entirely on the symptoms described your problem might be due to the EAV Stuck closed - unusual because it is a very robust component and should rarely fail mechanically unless jammed by debris, human interference or corrosion.

To read all about about the EAV - Click here

On the other hand, there are mysteries of Hot Wire beyond my understanding.

Edited by honestjohntoo on Wednesday 9th December 18:17

[pwd95]

I don't think there is an EAV, thermotime switch or a cold start injector on the hotwire system is there?
Deffinately no cold start injector on my old hotwire system.

Flapper system complete with EAV & cold start injector.....




Hotwire system without either....



ignore the blue arrow pointing to the clutch resevoir.

[

Edited by pwd95 on Wednesday 9th December 18:29

[combine]

BadRed said:

Just plucked this from the interweb, well worth a read

http://www.britishv8.org/Articles/Rover-14CUX-EFI....

Interesting stuff !