Carb Help

Hi All.

I have a 1978 campervan that at some stage has had a replacement 1600cc Single Port engine fitted.

The carb that has been fitted to that engine is a EMPI.

From what I have read the EMPI carbs are bad news and I am assuming that is what is causing the engine to misfire/backfire. Judging from the black sooted up plugs the mixture is far too rich causing the plugs to eventually breakdown and misfire.

Anyway, I have decided the way forward is to fit an original but reconditioned carb.

The first question is, what would have been originally fitted to a 1600 single port engine?

The second and probably more important question, what would be the best upgrade.

I can obtain a Solex 31 PICT 3 and a Solex 34 PICT 3 and am hoping that I can use one of those to replace the EMPI.

Thanks for your help.

Phil

 

^ I agree with him - I've had two PICT 34 EMPI copies (one on beetle, one on T2) and a set of twin IDF copies (on a T25). They all required a bit of basic fiddling but were fine in the end.

Have you attempted to 'tune' what you have? A basic check of idle mixture settings and choke operation might get you up and running. This page offers a basic guide to get you started: http://www.vw-resource.com/34pict3.html

 

The EMPI sounds like it is delivering fuel OK but is badly set up or installed. If you do not have a stock air cleaner but an EMPI chromed job then the carb will have been tuned too rich to overcome flat spots.
Before switching to another possibly even more ancient and dilapidated carburettor you should start by getting a stock installation sorted. This will help even the other 34PICT-3 or the other smaller carb you mention.
Then check the float needle valve is good so petrol level in the float chamber is good. Then with nice stock hot air going in the top of the carb you can set the tuning...

 

Thanks Guys

We did discover a problem with the EMPI carb, there was a problem with the petrol tube, rather than producing a uniform spray of petrol it was going in every direction. When fixed, it helped but did not cure the misfire.

Before having the Solex 34 Pict 3 rebuilt I will look into having the EMPI adjusted to see a leaner mixture can be achieved.

Can anyone suggest what jet sizes will provide the best overall performance?

Thanks.

Phil

 

The jets should be fine, although the existing jets probably aren't labelled anyway.

What symptoms do you have, when does it misfire? Is it at idle, when you accelerate or at some other time?

 

The idle is fine, accelerate and it misfires and backfires.

Change the sparkplugs and the problem is cured, engine starts, idles and runs fine. That is until the plugs soot up to the point they fail to spark properly.

The choke is going off so that is not the problem.

It appears to be running very rich and given the EMPI carb does not have many fans I assumed there was not much I could do with it.

All this happened some time ago, I did not have much time so it got left, now I am getting back into it I am trying to find a solution.

Recently, drove it about 10 miles without any problems to have some bodywork done, during that time it was started several times as it was being moved around the workshop. Drove it home and all was well during the warm up phase and then it started backfiring during acceleration.

Phil

 

Hmm, odd that it runs with the choke on, but is mega rich. Normally that would make it run worse.

What is your accelerator pump set at - the middle or t0wards one end?

 

Oh, and what are the various rubber O rings on the idle and volume screws like? Mine perished which caused some surprising running!

 

Oh and what dizzy do you have? Non vacuum 009 style? And are your pre heat pipes all in place?

 

Not sure about the position of the accelerator pump, will need to check. Where should it be set?

‘O’ rings appear to be fine.

Dizzy is currently a 009 but I am going to change that to 123 Ignition with vacuum.

Checked the plug gaps and they are 32”. Now wondering if the increase gap is the source of the problem.

I am going to fit the 123 Ignition, renew the plugs (set to 24/25 thou), plug leads and coil.

If the problem remains at least I have narrowed it down to the carb.

Phil

 

The 009 is prone to give bogging as you accelerate.

A crude 'fix' is to up the accelerator pump volume so it squirts more fuel in. Its possible to over do it though! Most sit roughly in the middle of the adjuster, be wary if its rammed right to one end. Its something you need to set by trial and error. Set it, drive around for a bit and see what the throttle response is, adjust a little to suit and repeat.

Replacing the 009 would eliminate any timing related issues, so you could set the carb up to the proper baseline specs again and take it from there.

 

I ran out of patience with mine and dumped the empi repro and got a nioe refurbed solex and Pertronix svda dizzy and coil and new leads and plugs. Been fine ever since.

 

Where are you going to buy the 123? Just curios.

 

I purchased the 123 from Southern Carburettors.

Just need some advice on the initial curve setting, will probably put up a separate post.

Phil

 

Thanks,
Southern Carburettors didn’t come up as a supplier on Google but a good price, even after adding VAT to their price list.

 

Thanks to the replies about the EMPI carb I decided against replacing it with a rebuilt Solex until I had done some further investigation.

Hopefully I am not speaking too soon but it appears that the misfire/backfire was not due to the carb.

Having cleaned the soot off the plugs and reset the gap to 24/25”, replaced the coil and leads my mate took it out for a test drive.

When he came back he said, ‘not only is there no trace of a misfire it is pulling like a train, however, there is a very bad flat spot when pulling away from rest’.

Out with the 009 Dizzy and in with the 123 cured that problem.

The van now pulls away from traffic lights, roundabouts etc. with only a very slight hesitation.

I am confident that a bit of fine tuning and the job will be a goodun.

I suspect the carb is running a bit rich due to an attempt to cure the flat spot caused by the 009 so a little bit of carb tuning may be required.

Thanks to everyone for their input.

I can now move onto the next problem, the fuel gauge.

Phil

 

Excellent, although a plug gap of 25" is a bit excessive ...