[Alx]

Ciao!

Maybe some of you 🧙‍♀️ can help me think a bit, because I'm out of ideas atm 🙎‍♂️

Cold engine (0C/32F)
Engine fires up almost the instant I turn the key, but as soon as I release it will die. No matter how many tries, it will bog down and die.
To get around this I need to keep cranking the starter along with the engine running for 10 seconds or so, before I can let go of the key. It will then drop down but catch up just in time to keep running.
It seems like playing with throttle meanwhile has no effect, but keeping a steady slightly higher rev may do.

With warm engine, turning the key and a light foot on the throttle and its up and running.


It had the Mikuni carb when we bought it, but I never even tried understanding it so it got replaced with a weber 23/36 w electrical choke almost day one ;-)
Timing is correct (like 8 degrees with disconnected vacuum), fresh plugs and leads/cap.
New (mechnical) fuel pump.

Things not yet replaced are the ignition coil and ballast resistor (and timing chain, tensioner and such)

Have not played around with choke settings too much -could it be too fat mixture? ( I don't have the specs on the jets..)
Or could it be ignition coil?

Once started it runs fine (a bit thirsty but it comes with the age, like me )
I do have the workshop manual but it is for 1992 B22 and B26i so it is not fully useful to me...

Appreciate all ideas

 

[Axel Breaker Earl]

Welcome to the forum!

Now........are you sure that your truck is an 1989 model truck? If you are sure, what country are you in? In the USA & Canada, the B2600 trucks that had a Mitsu engine in them, typically were 1987-1988 only. The 1989 model year was a FI Mazda engine, and therefore labeled as a B2600i (for "injection"). Now, stranger things have happened, but it is possible if your truck is indeed a 1989 B2600, it would be a very early edition......I would think.

A known issue with all of these trucks (1986 through 1993 in North America) is the electrical portion of the Ignition Switch. As they wear, they will sometimes lose the ability to energize the ignition coil, once the key is released after cranking......sometimes, the truck can even die when your running down the road, if the ignition switch is worn enough.

Before I dive into the ignition switch theory though, I would make sure that the choke is adjusted on your new Weber for your climate. It could be that the electric choke coil tension on the choke plates, is simply not sufficient enough to allow the choke to stay "ON" after the engine cranks.......in other words, the rush of air being pulled into the carb top, is pulling the choke flaps open, and effectively killing the engine due to a too lean fuel mixture.

 

[Axel Breaker Earl]

Also, if you haven't followed the installation instructions that came with the new Weber carb, about the "Lean Best Idle" adjustment.......you really need to do this!

Here is a link to the instructions......

CARBURETOR SET UP AND LEAN BEST IDLE ADJUSTMENT

 

[Alx]

Hi,
thanks for the welcome and advice

It could be older than -89 I guess.. It was recently exported to Sweden from Finland so I don't have the history ( and what was noted in export/import)
VIN is JMZUF8U4200102958

Anyhow, I thought about the ignition switch earlier and had the steering wheel covers removed just to have a look. Apart from a ton of filth... the cables and soldering were loooking good and the little screw that keeps the back end in place was tight.
If it is worn on the inside as you mentioned, is there any easy way to test it? (Without dimantle it I mean, been there -done that, didn't work too well ;-) )
I guess I could have someone turning the key as I probe those soldered pins and see what happens.

Choke...not my main suspect...the fumes ...and the consumption are pointing more towards the "not energizing the coil" or coil itself, but I will have a look at it. And report back of course!

Thx!

 

[Axel Breaker Earl]

You could have a helper try and crank the truck while you watch the choke plates at the top of the carb, and see if they are opening too wide during startup. There is also an adjustment procedure for adjusting the "Choke Pull Off" amount once the engine starts running, and the choke flaps open a small amount. Most data that I have seen for the size of the opening on the Weber carb, once the engine starts, is approx. 7mm. The adjustment for this is a bit harder to do, than just turning an adjustment screw, so hopefully this is not an issue on your carb......it would be the first one that I have heard of, if it needs to be adjusted.

 

[Alx]

Been watching "MazdaMitch" videos more than once
I need another weekend between the weekends to sort things out...