Yet another car won't start thread (it is running!)

Post by **jtbo** » 24 Jul 2006 04:11 pm

Ok, so now I have been testing a bit and what I found out is that engine starts kind of, when I pull choke and push throttle couple of times it will run for 2-4 seconds, after that engine shuts down even if I push throttle, sometimes pushing throttle seem to help a bit, but eventually it shuts down. If I don't push throttle few times before starting it is really hard to start.

I have now swapped carb thermal resistor and idle cutoff solenoid wires but this seem not to cause of problem. Solenoid does work and seem to operate as it should.

When engine shuts down and I open carb top plate there seem to be around 10mm of fuel at float bowl (float not in bowl then) no matter if I set float to original or my measured setting, is this normal?

Rpm gauge works normally, so I think that at least renix does not loose power.

I have tested with electric pump and with mechanical pump, electric pump seem to be working better as it is easier starting with it.

I'm getting only one idea that is that only acceleration enrichment circuit feeds fuel to carb, however often when engine is shut down I can see one throttle plate being wet from fuel.
So carb is getting fuel ok I think at least, it is getting spark too, it won't start without it. Really weird, imo.

Idle mixture is set to default setting, from Haynes it was 1 1/2 to 2 turns from bottom, I did turn it one more turn, but that seemed not to help and if we think logically can that even be problem?

What different reasons can cause engine to run only so little time?

It was much easier one year ago

Oh yes, managed to broke that nozzle from renix where you put vacuum hose

Now where that glue was again?

Post by **jtbo** » 25 Jul 2006 11:25 pm

Okay, it looks like that there is no fuel coming out from main jets or idle circuit, only from acceleration enrichment circuit, I try to get another carb so I can check if there is possible problem with carb or some other thing so I can focus my efforts to right things.

I got also suggestion that it would be air leak, which I have not yet managed to close out from equation, but this waits other carb too, makes diagnostics much easier.

I'm bit puzzled by the fact that there is very little fuel in float chamber after it runs 2-4 seconds, but when I pump with electric pump without turning engine there is fuel more than half way, has this fact any meaning to equation?

Learning carbs is not as easy as learning injection systems I see, much harder to get engine even started

Post by **redline** » 26 Jul 2006 07:34 am

could be perished pipes allowing air in , a blocked fuel filter ( not allowing enough fuel through for the car to run underload ) a weak fuel pump , or a warped carb base .

Its harder to check for the presence of air leaks without the engine running as the usual test is to spray something like wd40 around the carb base while its running.

good luck

Post by **mac** » 26 Jul 2006 08:33 am

Hi jtbo,

Don't worry about "no fuel coming out from main jets or idle circuit" - I doubt you would see it anyway. The engine has to be running for fuel to be drawn through these circuits. (as air is drawn through the carb venturi a low pressure zone (less than ambient) is created which 'sucks' the fuel out as a fine mist. However, operating the throttle activates the accelerator pump which 'squirts' a metered quantity of liquid fuel from the acc.pump jet into the venturi throat (this of course you can see).

One possibility for your problem that I've come across is a collapse of the small filter on the base of the fuel pick-up in the petrol tank. This would allow the car to start, but as the pump replaced the fuel used from the float chamber the base of the pick-up filter would be drawn up to seal the pick-up pipe, cutting off the fuel supply. Float chamber level would fall and the engine would stop!. The filter would 'relax' after a time and the car could be restarted.

The filter in question is a small gauze tubular unit push-fitted to the bottom of the fuel pick-up pipe in the tank (part of the tank sender unit).

this may well not be your problem - but it's something else to check!

Good luck - Mac.

Post by **jtbo** » 26 Jul 2006 11:30 am

Thanks from tips

Indeed I do have not standard fuel pickup from tank, it is t-piece installed to hose that connects two halfs of tank and then copper pipe frome there to engine room, every hose is rather new parts and it did run well with Efi, still using same secondary pump too.

Only filter is before fuel pump, that is new part and I can see fuel there, however electric pump seem to work differently as there is only little fuel there when it is pumping, while with mechanical pump there is half filter full, however electric pump is pumping clearly more fuel forward.

It actually did run almost 10 seconds, I could adjust rpm quite well with throttle pedal too, but then it died all of sudden and and did not respond to throttle while rpm did go down. But when it did run so long it sounded normal as it does when it runs for few seconds.
But it is running just as long as there is fuel coming from accleration pump.

Carb base then could be very possible problem as I don't trust those gaskets at all, maybe I try to find that gasket sealant and test what that does

How does fuel end up to carb with standard setup?
As that cylinder shaped separator (thing with 3 hoses) is letting fuel to return line immediately when it is full, so there is no pressure that pump could create, then carb should suck fuel upwards and I find that bit difficult.

There clearly is no any spring in valve that is in separator, when I turn it I can hear it moving when I turn upside down, sounds like small loose stone inside of thing.
I did test now without that thing and results are still same so sealing gaskets is up next.
Also I try to test with mechanical pump and without separator, some of my test should provide some difference I hope at least

Post by **jtbo** » 27 Jul 2006 06:42 pm

I made deal from carb so maybe next week I can get to test bit more

Website · Post by **antiekeradio** » 27 Jul 2006 08:27 pm

you say that when you take off the carb top, with the float included, the fuel level is only 10 mm from the top edge????

if so; this simply means your carb is totally flooded with fuel!!! thats far far far too much!!!

check:

- float valve (whether it moves and seals properly)
- float condition (lots of info's already)
- fuel pressure.

Greetings Wouter

PS it should be just over halfway full when you take off the top.

Post by **jtbo** » 27 Jul 2006 08:59 pm

Oh no, not 10mm from top, but 10mm from bottom, so there barely is enough fuel to cover those holes at bottom, must be that I have been writing something odd again, sorry

As it is adjusted now, fuel level is precisely as you describe, it is just over half way when I take out the top.

But when it starts and runs for 2-4 seconds or sometimes bit longer, then there is only that 10mm fuel at bottom, no matter how I do adjust float, but if I wait and pump fuel into carb with electric pump it seem to be getting to adjusted level.

So this leads to conclusion that there is either not coming enough fuel from pump or then fuel is not getting to float chamber enough fast.

Because fuel pump was enough for Efi, then I believe there must be something bloked in carb, or am I totally wrong?

Website · Post by **antiekeradio** » 27 Jul 2006 09:09 pm

could be that the air jets are blocked and way to much fuel is sucked into the inlet manifold? could be an explanation for the wet butterfly (throttle valve)

normally when the fuel bowl is up to its normal level, the engine should be able to idle for a considerable time before stopping!

it will keep idling as long as the primary fuel jet is under fuel level, and the fuel usage at idle is supposed to be quite low.

you could compare it with a moped when you close the fuel valve. it will run for about half a minute, start revving up a little, then dying.

Post by **jtbo** » 27 Jul 2006 09:37 pm

Yes, that is what I was thinking too, but it really is not idling at all, it runs only when I pump throttle so acceleration pump squirts fuel.

Also I can pour some fuel to intake manifold and it runs so long how much I pour fuel in, of course I have had no possibility to pour fuel in when car is running as it is such short time.

I believe that acceleration pump uses lot of fuel so that is why float camber is empty so quickly (it would not be perhaps empty if I would not touch gas pedal, but then it would not start), of course there should be enough fuel coming to float camber that it won't get empty but it seems not to be case.

Website · Post by **antiekeradio** » 27 Jul 2006 10:05 pm

when I shut the engine off and want to empty the fuel bowl by using the accelerator pump, I usually need to press a fair number of times before the fuel runs out (I reckon 6-10 times) you should be able to keep the engine running with that.

I think you have some serious blockage issues in that carb.

either the tip of the richness adjuster has broken off and is stuck in its hole, or some jets/ducts/calibrated drillings are blocked.

time for complete dismantling and inspection with carb cleaner and compressed air.

Post by **jtbo** » 27 Jul 2006 10:33 pm

That sounds very much like it, well next week I get another carb to play with, then we see if it is carb or something else.

I'm so beginner with carbs that I like to make absolutely sure that it is carb before I start to disassmble and of course when I have two I can look how everything was on place in case I forget something

It is great help that I get from you all, big thank you from this.
It is first time I ever am having issue with carb technology so I feel like lost puppy. Anyway I feel it is good exerice, I will learn lot from this

Website · Post by **antiekeradio** » 27 Jul 2006 10:39 pm

past weekend I had a friend visiting that had something wrong with his carb so it wouldn't idle (the fuel leak/squirt movie)

The carb i had in mind to put on there had some error too, the primary throttle valve did not close properly when the accelerator was released. luckily I had another spare carb close by so i could check. turned out the return spring was fitted correctly, but not tight enough (had to bee hooked behind other side of lever) and the metal bushing and some other plastic bit that guides the coil spring for another lever were mounted backside to front. It was very useful to have the correct example in hand

the non-idling finally showed up to be caused by a huge big vacuum leak in the brake servo (totally shot).

so thats something to check do, does it build up a vacuum?

Website · Post by **antiekeradio** » 27 Jul 2006 10:48 pm

its a weber (1.4) but its not thát different from the solex.

PS Clubwise, I sport a small collection of those:

Mac, perhaps you remember experiments with pieces of glass fitted to the fuel bowl, glued in place with a fuel-resistant resin?
I have one of these in the collection too. Also a number of carbs with temperature sensors glued to several locations.

Was a leftover from the test/development department of volvo NL in Helmond. There are some weird carbs there, even the first year's special version for Sweden, already with a decelleration mechanism, and still the mechanical switch instead of the tacho relay.

Website · Post by **antiekeradio** » 27 Jul 2006 10:49 pm

oh now i see on the pic that I have 1 B200 carb as well. will have to look into that if it may provide more info for you.