740 (B230A) undrivable without choke

[Tim740]

Hi all,

Together with some other students from Delft (The Netherlands) I am the proud owner of a Volvo 740 GL from 1985 with B230A engine.

Before we bought it, we went for a test driven. After the engine had warmed up using the choke, it ran without problems, also when pushing back the choke. Starting the engine when warm also wasn’t any problem.

At the sale, we agreed that the seller would get it through general inspection before we bought it. During this inspection, they found that the CO was higher than legally permitted, for which they adjusted the carburetor.

When we pickup up the car after this inspection, we noticed that the car ran less smooth. Even with a warm engine, we needed the coke and also during driving the engine sputtered when we turned off the choke. When shifting down, the engine drops out for a second, and when pulling away, the engine barely responds to the gas. On our way back, we had to use the choke for the entire journey.

On the way home, the pre-heater hose came loose on the side of the air filter, but as far as I can find, this shouldn’t have any impact when the engine is warm – apart from that it looked quite catastrophic when we saw a hose dropping down under our new-bought car.

Because the car is somewhat drivable with the choke, combined with the fact that the carburetor (a Zenith 175 CD) was just adjusted, I suspect the problem lies in the fuel fixture.

Before we start adjusting the carburetor ourselves, I’m curious if you have any advice. Do these symptoms ring a bell for someone? Is adjusting the carburetor indeed the right approach, and if so, do you have any tips on what to look at?

Huge thanks in advance!

Kind regards,
Tim

[Laird Scooby]

Originally Posted by Tim740

Hi all,

Together with some other students from Delft (The Netherlands) I am the proud owner of a Volvo 740 GL from 1985 with B230A engine.

Before we bought it, we went for a test driven. After the engine had warmed up using the choke, it ran without problems, also when pushing back the choke. Starting the engine when warm also wasn’t any problem.

At the sale, we agreed that the seller would get it through general inspection before we bought it. During this inspection, they found that the CO was higher than legally permitted, for which they adjusted the carburetor.

When we pickup up the car after this inspection, we noticed that the car ran less smooth. Even with a warm engine, we needed the coke and also during driving the engine sputtered when we turned off the choke. When shifting down, the engine drops out for a second, and when pulling away, the engine barely responds to the gas. On our way back, we had to use the choke for the entire journey.

On the way home, the pre-heater hose came loose on the side of the air filter, but as far as I can find, this shouldn’t have any impact when the engine is warm – apart from that it looked quite catastrophic when we saw a hose dropping down under our new-bought car.

Because the car is somewhat drivable with the choke, combined with the fact that the carburetor (a Zenith 175 CD) was just adjusted, I suspect the problem lies in the fuel fixture.

Before we start adjusting the carburetor ourselves, I’m curious if you have any advice. Do these symptoms ring a bell for someone? Is adjusting the carburetor indeed the right approach, and if so, do you have any tips on what to look at?

Huge thanks in advance!

Kind regards,
Tim

Refit that preheater hose! It makes a huge difference and if it's been adjusted with it on then it won't run right without it!

I have the opposite problem on mine, if i refit it then it runs too rich (LH2.2 injection) so i leave it off. The problem is the thermostatic air valve in the air intake, it's meant to provide a constant temperature to the engine but it goes weal and just supplies hot air.

[loki_the_glt]

Check the dashpot oil level; depending on whose advice you take, any of Duckhams Q-Matic ATF or 3-in-1 oil or sewing-machine oil or a light-weight engine oil should be used as the damping medium on these carbs.

You may find that the carb diaphragm is split; replacement is straightforward and spares are readily available in the U.K. though export to the E.U. might be problematic. Likewise the needle and jet do not last indefinitely and should be replaced after about 25000 miles or 40000 kilometres. A full service kit is, again readily available in the U.K.

[Laird Scooby]

I also wondered about the diaphragm but usually they won't be driveable, even with choke, if the diaphragm is split. Volvo recommend ATF for the dashpot and i've found that works better on all other constant depression carb equipped cars i've owned.

[Clan]

Originally Posted by Tim740

Hi all,

Together with some other students from Delft (The Netherlands) I am the proud owner of a Volvo 740 GL from 1985 with B230A engine.

Before we bought it, we went for a test driven. After the engine had warmed up using the choke, it ran without problems, also when pushing back the choke. Starting the engine when warm also wasn’t any problem.

At the sale, we agreed that the seller would get it through general inspection before we bought it. During this inspection, they found that the CO was higher than legally permitted, for which they adjusted the carburetor.

When we pickup up the car after this inspection, we noticed that the car ran less smooth. Even with a warm engine, we needed the coke and also during driving the engine sputtered when we turned off the choke. When shifting down, the engine drops out for a second, and when pulling away, the engine barely responds to the gas. On our way back, we had to use the choke for the entire journey.

On the way home, the pre-heater hose came loose on the side of the air filter, but as far as I can find, this shouldn’t have any impact when the engine is warm – apart from that it looked quite catastrophic when we saw a hose dropping down under our new-bought car.

Because the car is somewhat drivable with the choke, combined with the fact that the carburetor (a Zenith 175 CD) was just adjusted, I suspect the problem lies in the fuel fixture.

Before we start adjusting the carburetor ourselves, I’m curious if you have any advice. Do these symptoms ring a bell for someone? Is adjusting the carburetor indeed the right approach, and if so, do you have any tips on what to look at?

Huge thanks in advance!

Kind regards,
Tim

This is actually a Pierburg copy of a stromberg .. A very poor quality Carburettor by the usual Volvo standards ..

It is way overdue for an overhaul , I will list the very likely faults below ..

The float level is likely to be way too high due to the plastic float fulcrum shaft securing bridge piece having collapsed ...

The Needle and jet Will be worn requiring a new needle ( PN from memory) and a new Jet ...

The choke kick off valve will be dysfunctional and leaking air through it's internal diaphragm,. What it does is that as soon as the engine has fired and produces vacuum , it introduces an air bleed to weaken off the mixture a touch .

The float camber gasket will be rock hard and not sealing properly anymore ..

The diaphragm is changed on the 24000 mile service so this shouldn't be an issue !!

You will find this transforms the Cold start , drivability and fuel economy when set to 2.5% CO on the exhaust gas monitor ( MOT emission test machine these days )

Due to the mixture getting richer and richer over time people weaken it off on the adjuster resulting in a very weak mixture out on the road under load so not that pleasant to drive .

The Hot air pipe is vital as the carburettor is calibrated to use inlet air at 35 degrees C

I have overhauled dozens and dozens of these from around 1990 to 2005 with much satisfaction !

[Tim740]

Good news, we found the problem! after struggling with the carburetor adjustment tool for one and a half hour, we decided to open the carburetor. When we did this, we found that the needle, which is normally attached to the part that screws up and down, was just laying at the bottom of the carburetor, which explains why it was running so lean.

We screwed back the needle in the intended location, reassembled the carburetor and indeed, the engine runs as smoothly as we knew it from the test drive

Thanks a lot for all the advice!