Problems with twin Solex carbies, keeps stalling

[BAD-SIG]

Hi guys. Here is my current build (I still got my original blue GE Sigma SE that I bought as my first car over 12 years ago, but that's getting way too rusty to fix up). The car is a 1978 Chrysler Sigma SE. I'm currently working on the finishing touches of fitting twin Solex carbies complete with extremely rare Japanese-market stock airbox, so it should be much easier to register the car if it looks stock. I've also fitted an electric fuel pump and glass/chrome fuel filter.



Now to the bad stuff. The car was running perfect with the stock carbie. Not even a bit of engine smoke, started first time every time and didn't miss a beat. Now with the dual Solex carbies, the car is a bit harder to start on cold weather due to the mechanical chokes not being connected (in the process of fixing that though). Once the car warms up a bit, I can get it to idle and rev without misfire for about 10 to 15 seconds then it seems to start strugling more and more until it stalls, and if I try to rev it it seems to make things worse and cause it to stall even quicker. It's almost as if it starts and runs fine then it gets flooded with too much fuel and stalls.



Can anyone help? Am I right to think its just getting too much fuel? Could it be the secondaries vaccuum solenoid being stuck on open? The carbies seem to be getting correct amount of fuel and I don't think the fuel pressure is too high as the electric pump I'm running runs at 4 to 7 psi. Do I really need a pressure regulator?

I've done a few searches here in the forum but the only people I found with similar issues didn't really post what was wrong in the end and how they fixed it.

Any help, suggestions and comments would be greatly appreciated.

*edit* the engine photo above was taken just as a mockup of what it was going to look like with the twin carb airfilter. Note the factory-stock air/fuel separator (little crappy surge tank near the battery) was still connected. I've had many issues in the past when fiting aftermarket carbies to Sigmas due to these little surge tanks so the first thing I did was remove it! The fuel line from the fuel pump is split into two and then goes to each carbie at equal length, so both carbies should be getting equal amounts of fuel and fuel pressure. The electric Facet fuel pump is rated at 4 to 7 psi. I got this model because the stock mechanical pump was rated at 3.9 to 5.6 psi according to two different workshop manuals (one of them being a proper Chrysler/Mitsubishi original dealership one).

[Leeroy]

I don't know much about carbies but theres a little bubble window on the front of the carbies (facing the front of the car) that shows the amount of fuel being pumped in. According to my mechanic it should be at least half or a little over half way. Don't know if that helps with the possible fuel issue.

[BlueThunder]

Hi Bad-Sig

I think you have to check if your carbs are synchronized/adjusted properly.

I have a Mitsubishi Carburetor - Fundamentals & facts Manual that discribes everything about the carb's but the pdf-file is about 25 Meg. If you want it just pm me to see how I could send it to you...

Cheerz
Sven

[BAD-SIG]

Thanks guys, BlueThunder you have a PM. And about the carbie clear level indicators, the carbies do have them and they show that the fuel level is just a tiny bit higher then the halfway mark, as it should be. Not sure if the carbies need syncing as the car does start and runs perfect for 15 seconds or so then chokes and stalls.

[75wagon]

Have you got a pic of the carbs themselves (not just the aircleaner)? There's nothing to see in those pics really?

Do you have the fuel cut solenoid connected (44)? How many solenids do the carbs have 1, 2 or 4?

To tune the carbs to each other you need to remove the rod assembly (48) for each carb, and tune as per a normal carb, but taking into account that there is 2 and they need to be tuned to each other.
The only adjustments you should need to touch are mixture screw (32), idle setting screw (26) and the balance screw (51).

- lower the idle on both carbs as much as possible
- adjust the mixture screws on each carb until smoothest idle is achieved and the carbs are the same
- re fit and adjust the rod assembly.

All else things working well, this should solve your problems.
Check everything else first though, make sure the fuel cut solenoid is hooked up and working (44), without it they don't idle well at all.

Reference the numbers to the pics in these diagrams 4G32 solex/ mukini twin carbs close up shots and info......

I hope this helps?
Dave...

[BAD-SIG]

Thanks for the suggestions guys. I'll have a better look at the car this coming weekend. I had planned to work on the Sigma this past weekend but me my wife and kids all had gastro. I'll post a better photo of the carbies and engine too so you guys can have a better look. Thanks again.

[BAD-SIG]

Well it's been a while, I haven't really had much time for the Sigma lately, with family commitments, kids birthday parties and all. I did find out though that the head gasket needs changing due to corrosion, so that will certainly help it work a bit smoother once changed. I've ordered the new head gasket and it should arrive this week. I'll report back once it's changed and tested to see if the stalling issue is still there or not.

[BAD-SIG]

Head gasket changed and while I was at it, also fitted Crow Cams mild street cam! Tryed starting it for the first time last sunday after I finished putting it all back together but not sure if I put the distribuitor in the right gear! Can someone help? I checked the workshop manual but found no reference, strange. If the crank pulley is showing that the first piston is at 0 degrees TDC, does that mean the dizzy should be linned up so the no. one cylinder is ready to fire? (meaning dizzy rotor pointing to no 1 cylinder on dizzy cap?).

[astronturbo77]

Change the needle and seats!

[BAD-SIG]

Where can i buy the valve needles and seats for these rare twin solexes in Australia? Is that going to fix the issue of it being a pig when cold? The manual chokes arent connected either so i guess thats not helping either

[75wagon]

Where can i buy the valve needles and seats for these rare twin solexes in Australia?

The only thing rare about them is the manifold and linkage set up (and a few other small differences to the ports in the carb bodies themselves).
They use the same carb kit as a standard carb.

Dave...

[astronturbo77]

What dave said, chuck a couple of kits through them and get back.to us..

[BAD-SIG]

Wow so much has happened since my last post here. So far the car has been going good, although I only drive it around the block about 3 times a month. The carbies are synced properly and tuned, I checked the ignition timing with a proper timing gun and the car is still hard to start and won't idle at all until engine is warmed up to normal operating temperature. Once warmed up, it idles perfectly and only hesitates when I want to make the car accelerate and press the accelerator (doesn't matter if I press a little or a lot), sometimes it hesitates so bad that it stalls. But I can keep it from stalling after the hesitation if I quickly pump the accelerator a bit and get the revs up. It feels like it gets too much fuel too quickly or something.

I still haven't gotten around to re-kitting the twin Solexes, I moved house, setup my new garage, got a new daily driver, had another project car (VW Type3 Fastback) which I then sold a couple of months later due to having too much rust, lost my job, etc, etc. Now until I get another job, I can only do work on my Sigma myself and fit parts that I already own, so the carbies will have to wait. Being only a 2 litre, it's a bit gutless on low revs, but it really gets up and pulls hard above 3500rpm with the twin carbies and mild cam! Can't wait to fit the sports exhaust to it too.