1.7 Warm Start Issues

Post by **Chris_C** » 14 Apr 2006 05:07 pm

Right, have now finished completing tests. These are how it starts, and what is needed, and times are from turning off the engine warmed up, (to just past the LED, which on the initial cold run takes about 5miles). Each start was followed by a run, then turned off and timed for the next start.

20 minutes (repeated a few times, as it was doing something different to normal) - Starts dies, but will idle if you give it a little choke

45 minutes - same as for 25 minures

1:30 - No choke needed, starts and idles perfectly straight away.

Post by **jtbo** » 14 Apr 2006 05:14 pm

How is your fuel filter, is there fuel when engine running?
Fuel is coming from tank easily?

When engine is running and you open fuel tank cap, does it make sound like air getting sucked in?

My father has boat once and it had tank that had this replace air valve such type that you could close it, once he forgot to open it and engine run little while and then could not take fuel, he was really out of ideas why engine kept shutting down, we found that fuel tank was twisted and collapsed because of vacuum fuel pump did create...

Lesson of story, if fuel tank ventilation is blocked, it may cause your engine not to run. You can test starting engine without that fuel tank cap to see if that makes difference at all.
However as it does this only when has been not running some time this sounds not very possible either, it should be always....

Because you have replaced renix unit, then it can't be ignition related, so it must be fuel related.

Is there solenoid on your carb? If there is that could cause some trouble, but I'm not sure if webers had those.

When you say plugs were black, were they wet too?

Post by **jtbo** » 14 Apr 2006 05:18 pm

Also got yet more idea, do you have starter spray or something to spray to carb base and to connection of intake manifold/head?

That would test those vacuum leaks if rpm rises, however I don't think those alone could cause all this...

Post by **pettaw** » 14 Apr 2006 05:28 pm

Chris and I have talked further on this prob and we reckon there were two issues. The float was set about 1mm too high and was causing the float chamber to flood slightly after shut off because of heat soak and causing fuel percolation and therefore over rich mixture for start.

So now it seems to be excessively lean on a hot start. I reckon this is another heat soak issue, this time causing fuel to vapourise in the hoses. The reason it runs badly for a while and then recovers is because the pump is getting weak and therefore can't pump fuel properly when there's not a supply of good liquid fuel around.

Its a weird thing trying to take someone through a partial carb stripdown when firstly you don't know what you're looking at (never seen a Weber conversion carb before) and secondly its suprisingly difficult to explain exactly what you mean...."yes, that one over there, yeah that one"

I think we worked it out though

Post by **jtbo** » 14 Apr 2006 06:25 pm

Indeed, that could cause this kind of behaviour. Specially if fuel hoses/lines are near hot side of engine. In B200K it was easy as there was exhaust side and fuel side of engine, so no problems, but 1,7 intake and exhaust are same side?

Does this fuelpump in 1,7l engine has that one way valve that should keep fuel up? Injection pumps have this, but these carbs, grrr, I have never studied them.

Post by **pettaw** » 14 Apr 2006 07:50 pm

Don't have a clue I'm afraid.

Post by **Chris_C** » 14 Apr 2006 11:32 pm

I fitted a fuel filter to the inward pipe a little while ago Jani, and thats always half full of fuel, the system doesn't have a one way valve (that I've found

) but used to hold that level for the months at a time that I have left Fake before starting before bringing it into daily service, and now that filter still stays full.

I have a spare 1.7 fuel pump here, I'm going to swap the inlet fuel line (the 30cm long bit, not the tank to engine bay section!) as even though it was only replaced about 6 months ago, the edges are cracking, and a leak on that pipe was the reason I had non starting problems a summer or two ago with her. As for opening the tank.. if it's vented, surely opening it would be ok, and thats what I do when I fill up with petrol!

And I think we did ok Andy, definately got somewhere!

Thanks again guys!

Post by **SteveP** » 15 Apr 2006 10:24 am

Chris, I have a new 1.7 fuel pump if it's needed.

Post by **Chris_C** » 15 Apr 2006 03:53 pm

New new? I have a s/h one laying round, but not sure of it's condition, if yours is all shiney I'd be greatful

Thanks for the offer mate.

As for todays new developements, I went to get a new earth strap custom made, and watched something pretty strange.

As I was taking the strap off to be measured (I'm on Kars strap atm) the fuel filter was visibly emptying, then, as we were fitting the new one (about 50 mins after turning the engine off) it could be seen filling again. Weird thing!

Post by **SteveP** » 15 Apr 2006 05:07 pm

Chris_C wrote:New new? I have a s/h one laying round, but not sure of it's condition, if yours is all shiney I'd be greatful Thanks for the offer mate.

New new... I think it's only a Unipart unit, but still... it's new, and its yours for a price of a pint.

Post by **Chris_C** » 15 Apr 2006 06:48 pm

A pint? Extravagent... although I should be seeing you up norf next weekend, so I might be able to manage a nothern priced pint

Cheers mate, sold

Post by **jtbo** » 16 Apr 2006 01:46 am

Hmm, so for some reason fuel is not staying where it should. My father told me that even mechanic pumps have often some sort of valves that prevent fuel from going back to tank.

Also as I don't know much of carbs, but shouldn't there be some kind of mechanism to prevent that fuel chamber going empty? Maybe some ventilation valve is stuck open or something?

Post by **foggyjames** » 16 Apr 2006 05:51 pm

If the choke is hyper-sensitive, try reducing the throttle-offset it applies (should be a screw attached to the throttle arm which is pushed by a cam on the choke arm). The Stromberg on my 240 couldn't be set to a nice cold idle no matter how precise you were with the choke, as it was adding too much throttle, and I had the same problem with the CISAC on my 360.

I was about to suggest a fuel level problem...but luckily I read the final page

Good work Andy and Chris

cheers

James

Post by **Chris_C** » 02 May 2006 12:12 pm

Right, had more issues with it this weekend, I thought I'd solved them, but then got 100 miles to me £20 last night

Went to Swindon from Southampton, and all was fine, picked Kate up, and drove her back to Devon. Didn't get about of Swindon before the thing was stalling, so pulled off to side of the road, stripped the carb (I replaced dodgy fuel lines and pump last thursday). Found one of the long jets (each choke seems to have one long and one short jet, if that makes sense) had a lump of perished rubber blocking the hole in the side of the tube (not the central hole, that makes the rod into a tube).

Put it back together, it was a tad better, but not right. Carried on, and before I made it to the 303, it was stalling whenever I lifted, so I was bump starting it from intertia after every roundabout, and on starter motor if I had to stop. Got further towards devon, and then started to have even more fun, nothing until full throttle (when the second butterfly opens I later found...)

Basically, driving Devon lanes on either full or no throttle isn't fun, but managed it, got into Kates drive (2 tight 90's...) by bump starting in both second and then first (it goes on a full throttle bump start in first, nearly ended up in a wall...). Stripped carb down at Kates, and found another lump of perished rubber in the shorted or the jets. Now, as the thing only went on the last 5mm of accell pedal (when the second choke butterfly opens) I'm guessing air goes down that short jet? and it was only getting enough air with the second butterfly open? Running fine now, no bumpyness, no starting issues, although the day I cleaned it I did have teh wouldn't start after 30minutes thing again, that has now gone away.

So, basically, I'm going to clean the carb (again) and make sure there is no crap in it (again). What I don't understand in the fuel inlet on the carb has a wire mesh filter, that these rubber bits seem to be able to get past, but I cleaned all bits I took off in petrol, so should all be ok. Can smell fuel from exhaust again though, so I'm guessing one of those rubber bits was screwing up the mixture setting Andy and Dai were doing last weekend.

What I'm confused about, is how I got such cr*p economy last night, ok, it was a lot of roundabouts and hills, but even with a few other runs, it was 110miles, and minimum of 17 quid of fuel. Although I did wonder if the float sender in the tank was sticking low, as when I stuck another 20 quid in this morning it shot further than normal, going to 3/4 (Fake only seems to get to the right side of the warning LED on £20, Kar would make the F line on the same amount).

So, see what I get out of this tank, looked fine on my run from Swindon to Soton this morning, but basically, with the rough running patch (which I;m expecting to be thirsty) I got 450 miles from 80quid of juice. Still finishing the last bit of it, but not looking to be more than 500 from £80, I should have bought the bloody 960 after all

Last weekend, even with rough running, I got 600 from £60. I don't mind putting the first £40 down to rough running, but the 100 miles last night taking £20, when it felt to be running sweet?!?! And then this mornings £20, I'll have to report later on

Post by **foggyjames** » 02 May 2006 08:19 pm

Short jet is usually the idle jet, while the long thing has an air corrector at the top, the main jet at the bottom, and the emulsion tube in between. My ADDHEs also have a secondary air corrector, but they're a bit wierd like that (only having single skinned emulsion tubes).

I suspect your jetting isn't right, but that isn't the cause of your main problems. It can only really be blockages, float height, or air leaks. The stalling smacks of the first two. Try radically lowering the float height - the worst that will happen is that you'll have a bad misfire after 10+ seconds of full throttle...and you should rule that one out once and for all.

cheers

James