D.I.Y. Rolling Road on-the-real-road ; how would you go about it? serious Dellorto subject creep in this thread

[anthony1956]

13 minutes ago, 7 wonders of the world said:

Item 304958193391

 

is that ebay.co.uk or another?

Ok found some; not cheap given I don't need them at this point, but well noted that they even exist.

Edited September 9 by anthonym

[7 wonders of the world]

Re your dribble...

It would normally be a partial blocked jet since on the DHLA the pum jets are fed via light spring pressure behind the diaphram rather than a postive foot pressure.

To prove swap two pump jets over and retest

[anthony1956]

4 hours ago, OldAndrewE said:

What I am saying is that you can achieve a certain rpm at different throttle positions depending on the load on the engine (what work it is having to do).  To achieve say 3000 rpm on a level road will need a certain throttle position but up a steep hill will require a wider throttle opening.  The carbs will be working differently in the two situations

So this means I can take measurement on actual roads that I drive at actual speeds I drive.. I can think of several already to use as my own standards. 

[anthony1956]

On 09/09/2024 at 23:04, 7 wonders of the world said:

To prove swap two pump jets over and retest

that's a darn good idea; sadly too late unless the problem now persists EDIT: now swopped . Most of my chatter about these things is in my "blogs" and is in real time, would be great if you might keep an eye on those as clearly you can relieve some of the extensive grief I experience since e v e r y t h i n g I do is my first time. I don't prattle on here in techtalk (so much) not wishing to drive everyone to distraction.

I have replaced all the springs in the pump mechanism and the diaphragm spring is now "strong" - I don't know what it was before, but it did not feel strong then again all the springs I have replaced, which is every single one I can find, have all been stretched and brittle (that  brittle one was the central accelerator return spring that broke when I bent it to refit it).

These carbs were refurbed in the car rebuild, but this does not include many of the components.

Edited September 10 by anthonym

[anthony1956]

Update:

ok so I gave in and once more, this time with patience, at idle, sprayed Easy Start on the front carb inlet manifold, several times, each time waiting for the engine to slow down, squirted and it went faster.

Anyone who read my inlet manifold story will know both have new Cometic gaskets and only the rear one has additional sealant round it. This was an experiment which now bears fruit and demonstrates that the extra sealant was a good idea. 

I found this was the case when fixing the coolant system and dealing with metal surfaces that are very old and mottled. In the case of the coolant system I replaced with new parts. It seems with these inlet manifolds the sealant is effective. 

So next task is remove carb 1 (again), remove and refit inlet manifold 1 front this time with sealant.

The clue to all this is the Manometer shows a MASSIVE difference between carb 1 and carb 2, carb 1 showing it has vastly more air getting in somewhere. 

The pump dribble is much improved and it was quite easy to get the emissions compliant with requirements, though not as I would like and have had previously. This leaves the door open to the jet swap; trying to recall if this can be done without removing the carbs from the car. 

Edited September 10 by anthonym

[OldAndrewE]

55 minutes ago, anthonym said:

This leaves the door open to the jet swap; trying to recall if this can be done without removing the carbs from the car. 

They are accessed from the top of the carbs Anthony

[7 wonders of the world]

Worth flatting the mating face of the manifold before refitting.

Sheet of glass with a sheet of 800 wet and dry paper.on it liberally spray with wd40 or similar and using circular motion move the mating face around the paper keeping g it flat to.the paper shiny witness marks with show high spots etc.

Re your dribbling jets take the out and clean with aerosol carb or brake cleaner.

Until this is sort you can't get accurate idle.emissiins or evaluate the idle jet operation.

Pump jets do have a short term effect on idle transition due to there design as irrespective of jet size they displace a fixed amount of fuel albeit over a different duration.

[anthony1956]

53 minutes ago, OldAndrewE said:

They are accessed from the top of the carbs Anthony

thank goodness.. thanks. 🙂.       (I thought so but I get confused!)

[anthony1956]

1 hour ago, 7 wonders of the world said:

Until this is sort you can't get accurate idle.emissiins or evaluate the idle jet operation.

yeah I'll say! The manometer says very loudly "you have a massive problem here!"  Sometimes I have trouble accepting reality.

"Pump jets do have a short term effect on idle transition due to there design as irrespective of jet size they displace a fixed amount of fuel albeit over a different duration.

You mean as we progress across our six progression holes? Can't say I ever thought about that. Yes fixed amount, the jet size determines duration (i i r c) nope. Lost me. What do you mean?

 

Yes will try 800 w&d with WD 40 . Interesting idea. tx

 

"Re your dribbling jets take the out and clean with aerosol carb or brake cleaner."

Yes I did that, all my jets, but happily do it again, I also give them a blast with compressed air. Isn't there a ball bearing in there somewhere?

I find ball bearings always look great and may not be as round as they look.

Edited September 10 by anthonym

[anthony1956]

Check this out, inside surfaces of gasket are sopping wet i.e. air leaks

 

Edited September 10 by anthonym

[anthony1956]

I have swapped the pump jets, as well as giving them a clean and compressed air blast, now both seem to be drivelling, but I think that’s like it was when I last checked them, the problem is the engine is cold and I have to keep pumping the accelerator to keep the engine going consequently we also get dribbling 

Edited September 10 by anthonym

[anthony1956]

Done with 600 w&d and wd40.. standard rubber one no glass. Seems to me they look like a sieve anyway so my interesting this is a bit academic. However, a good idea.

 

Going to clean dry with acetone then apply Motorsil D which is what’s on the other one and refit

Edited September 10 by anthonym

[OldAndrewE]

What is the tapped hole for?

[7 wonders of the world]

The pump jets are supplied from a fixed volume reservoir, a diaphragm is held back with the throttle linkage at idle, this has fuel on one side supplied from.the float chamber, on the other side is a compression spring at rest this is fully compressed.

As the throttle us opened the level holding the diaphragm back moves allowing the spring to.push it forward forcing the volume of fuel via drilling to.and thro.the pump jets

A bit like pulling a crossbow string.. loading it on idle... opening the throttle is like pulling the trigger.

Variation in pump jet size cannot alter the volume discharged but does alter the duration of the discharge, so a larger capacity engine or cars  with larger chokes etc and lower initial air speed need a sudden dose of fuel administered quickly so something like a 60 pump jet , alter this to a 40 and you still.have the same volume of fuel to dischage with the same spring rate thro a smaller orifice so hence the duration of discharge increases, so you need to check your idle jets on progression can sustain light throttle driving for a few seconds without flats or coughs if it runs clear for a couple of seconds but then shows these symptoms then the delayed fuel form the pump jets is compensating for an idle circuit deficit.

Sort the idle jets first and the pump jets last.

 

[7 wonders of the world]

Other manufacturers used a similar principle controlled.using engine vacuum, some, Ford (VV) springs to mind varied the discharge volume.on the same carb across various vehicle models using coloured plastic washers sized to reduce the volume.

[anthony1956]

22 minutes ago, 7 wonders of the world said:

Sort the idle jets first and the pump jets last.

Yes got that - just up from the garage.

Edited September 10 by anthonym

[anthony1956]

33 minutes ago, OldAndrewE said:

What is the tapped hole for?

it's blocked off on the other side - I think it's to do with when there is vacuum advance, both inlet manifolds have one. Not used.

Edited September 10 by anthonym

[anthony1956]

sealant applied and refitted, story is here in pictures https://www.caterhamlotus7.club/blogs/entry/1080-bdr-inlet-manifold-removal-and-now-to-refit/?do=findComment&comment=1652

 

[anthony1956]

2 hours ago, 7 wonders of the world said:

The pump jets are supplied from a fixed volume reservoir, a diaphragm is held back with the throttle linkage at idle, this has fuel on one side supplied from.the float chamber, on the other side is a compression spring at rest this is fully compressed.

As the throttle us opened the level holding the diaphragm back moves allowing the spring to.push it forward forcing the volume of fuel via drilling to.and thro.the pump jets

A bit like pulling a crossbow string.. loading it on idle... opening the throttle is like pulling the trigger.

Variation in pump jet size cannot alter the volume discharged but does alter the duration of the discharge, so a larger capacity engine or cars  with larger chokes etc and lower initial air speed need a sudden dose of fuel administered quickly so something like a 60 pump jet , alter this to a 40 and you still.have the same volume of fuel to dischage with the same spring rate thro a smaller orifice so hence the duration of discharge increases, so you need to check your idle jets on progression can sustain light throttle driving for a few seconds without flats or coughs if it runs clear for a couple of seconds but then shows these symptoms then the delayed fuel form the pump jets is compensating for an idle circuit deficit.

Sort the idle jets first and the pump jets last.

 

I need to disect this, as I grasp it up to now, presssing the accelerator quick does a pump, and all that does is activate the process, it doesn't determine any of the paramters of how the pump operates. And we have three springs that do that... so let's see:

"The pump jets are supplied from a fixed volume reservoir," yes this is the one with an X in the middle and the diaphragm and (now) "strong" spring, 

"a diaphragm is held back with the throttle linkage at idle,"

no it's not,  at idle there is supposed to be a 0.5mm gap between the actuating rod end and the diaphragm brass "pole".. except there isn't, so my actuating rod end is pushing slightly (about 1.5mm) on the diaphragm brass pole, which is held against the actuating rod end by the "strong" spring the other side of the diaphragm. 

and the next bit I find even more difficult:  a slow push of the accelerator will not activate the pump

When the throttle is opened **slowly**, the movement of the lever is much more gradual, and the diaphragm in the pump moves slowly. As a result, it does not build enough pressure to force a significant amount of fuel through the accelerator pump jets.

a good pump will activate the pump - which it does by the actuating lever moving downwards and its end pushing the brass pole inwards into the (quite small) reservoir, which doesn't pump anything and then as the actuating rod lets go, the "strong" spring is released to use all its might to push fuel out of the reservoir to each of the two pump jets. In this last process there is a ball bearing that prevents fuel passing until that fuel is pushed under pressure from the spring.

Given I have a carb off just now I need to look see if I can match your description to it. Does my head in does this... in fact I'll go get it.

Edited September 10 by anthonym

[anthony1956]

Here’s the weight and ball bearing, one per jet - how to check a ball bearing ?

Edited September 10 by anthonym

[anthony1956]

Now then, the weight has indentation at one end, is it supposed to ?

[OldAndrewE]

8 minutes ago, anthonym said:

Now then, the weight has indentation at one end, is it supposed to ?

I will try and have a look at one of mine tomorrow

[anthony1956]

So this is embarrassing, I found the other one has the ball bearing on top of instead of underneath the spacer rod (a.k.a. "the weight"). I don't recall if the other one was like that as I undid the screw and tipped it upside down to remove them without looking. I'll check the other carb tomorrow. I know which way round they go so it's straight forward fumbling ineptitude by me. This has to be a dribble cause. EDIT: It sure was all dribble stopped, also put all 4 weights the other way up because all 4 have wear marks from the ball bearings.

 

Diagram 47,48,49

 

Edited September 11 by anthonym
Dribble solution added

[anthony1956]

I have rolled the ball bearings around a flat surface and it seems always to respond to tip movements correctly, so short of replacing them anyway they (these two at least) seem ok. 

Edited September 10 by anthonym

[anthony1956]

19 minutes ago, OldAndrewE said:

I will try and have a look at one of mine tomorrow

I found an online pic, but frustratingly neither end is shown - never mind if you find you cannot extract it without turning the car upside down.