1989 740 cranks but won't fire

Chenko · Post by **Chenko** » 24 Mar 2025, 11:39

Hi,

My trusty 740 is having a bit of a problem right now and I'm completely at my wits end.

The car sat for a while and received a new engine block. Every ground contact got cleaned.

Engine:
B230F, 2.4 LH Bosch

Problem:
The engine cranks but won't fire up.

My diagnosis so far:
Made sure the timing is correct. Took off the timing belt, aligned the marks on the cam and crankshaft and put it back on.
Made sure I got spark. I will install a new set of plugs just in case, but they do have spark.
The distributor cap is dry and clean.
I got plenty of fuel coming to the cylinders. The spark plugs are soaking wet after trying to start which makes me think the plugs went bad.

There are no fault codes in the computer.

Is there something I'm missing? Some sensor that could have gone bad that stops the engine from firing up?
Thankful for any advice.

Post by **volvolugnut** » 24 Mar 2025, 11:51

To run an engine must have fuel, air, compression and a spark at the proper time. SInce this engine had been apart, you need to confirm everything.
You have spark, but do you know if the spark is at the proper time to fire the fuel? Use a timing light to confirm ignition timing and check that the piston is actually up when the plug fires.
Do you know if you have compression? Test with a compression tester for each cylinder.
Is the air flow getting measured properly? Is the duct from the air flow meter in place and has no leaks? Is the air flow meter working?
volvolugnut

Chenko · Post by **Chenko** » 24 Mar 2025, 11:54

Will check tomorrow.

I thought the ignition timing was set electronically, so I didn't check if my ignition timing was "correct".

Vova585 · Post by **Vova585** » 25 Mar 2025, 20:35

I would verify correct instalation of the distributor inside the engine first. Verify correct instalation of distributor rotor in relationship to distributor shaft. Make sure totor is pointing on #1 cylinder spark plug wire with timing marks alighned. If that all checks and you have plenty of fuel and spark- you likely washed oil coating in the cylinders. Turn off the fuel supply and disconnect connectro at distributor. Remove spark plugs. Turn the engine over with starter for 10 sec or so. Take 20cc of engine oil put it into each cylinder. Turn engine over manually several times and let it sit for half and hour. Turn it again manually. Then put cloth over spark plugs wells to catch oil drops and turn the engine over with starter for 10-15 sec. All extra oil will be pushed out. Carefully clean spark plug wells from oil with attention to threads. If you are worried about spark plugs(take butane torch and warm them up. Slowly warm all over and when equal temp can concentrate on electrode end for a short period of time and it will be good. But this is overkill likely. As long as gasoline evaporated and there are no oil deposits on the spark plug it should be perfect. (Can use simple butane cigarette lighter with quick warm up of the electrode). Verify correct gap on the spark plugs. Reinstall all back and hopefully it will start to you.

Chenko · Post by **Chenko** » 26 Mar 2025, 11:41

I’ve checked the following things on my car:

Put in new plugs
Checked distributor position
Used timing light.

When I checked the timing I noticed my ignition to be too early.

Could it be that I installed my flywheel the wrong way? I know that I didn’t check for anything when installing it, as I thought it only goes in one way. And I have been wrong before.

So if my flywheel is off, does that affect my ignition timing in such a way?

Thank you.

Post by **volvolugnut** » 27 Mar 2025, 15:37

I have to get out my shop manual to check details. If 740 is different, my 240 manuals will not help.
volvolugnut

Vova585 · Post by **Vova585** » 27 Mar 2025, 15:59

Have you tried to put engine oil in cylinders as I was offering above? I am still concerned that oil coating on the cylinders was "washed down". Another crazy possibility is malfunctioning temp sensor or incorrect placement of spark plug wires. Doubt you installed flywheel incorrectly. Any other new aftermarket parts?

Post by **volvolugnut** » 27 Mar 2025, 18:59

It appears there is a correct way to install the flywheel to get the position sensor correct. I will supply 240 model info soon. I think this will be correct for 740. I expect you have the electronic ignition that does not have timing adjustment other than correct flywheel position.
volvolugnut

Post by **volvolugnut** » 30 Mar 2025, 14:07

Instructions form Bentley Publishers Volvo 240 Manual:
Flywheel and driveplate (for automatics) removal and replacement requires a tool to lock the flywheel so it does not turn while tightening the mounting bolts. Volvo has a special tool that mounts on a bell housing bolthole and locks the flywheel teeth. Fabricate something to work for you.
Position #1 cylinder at top dead center.
Install the flywheel so the bottom crankshaft position signal pin is 15 degrees below horizontal on the right side of the flywheel. This is approximately 4 o'clock position.
Install and tighten the bolts evenly.
The locking tool will also help to install the clutch if manual transmission.
volvolugnut