1800: 1800E on carbs won't start!

[sleek lemur]

Hi All

A bit embarrassed to write this. It really is basic stuff!

After the winter break the car won't start. Unfortunately, the last thing I did before the break was to pull out the old fuel injection wiring, but the car was running ok after. So...

There is no spark at the plugs and none from the centre contact in the dizzy cap. Car cranks over fine. Battery is good and on charge as I write.

With the ignition on, should I get 12v at the terminal that receives power from the ignition? I get nothing. I assumed that would be the issue, yet when I tried connecting the input terminal of the coil directly to the battery, still no spark.

Any suggestions gratefully received (as always).

Is there anything obvious I'm not checking?

[c1800]

Hi, check the coil, could be non-op. there’s a load of methods on line.

[sleek lemur]

Thanks, C. Will do. I think apparent lack of power reaching coil has confused me. will check the coil today.

[Derek UK]

With the ignition on, if you flick open the points you should get a tiny spark across them. A rather bigger one can indicate that the condenser is u/s. You can also flash the coil king lead to earth with the ignition on. If there is sparks from the coil but not at the points the low tension wire connection at the dizzy is suspect or the through bolt is shorting to the case. Have you replaced the points recently? What dizzy are you using now you are on carbs.

[sleek lemur]

I have a 123 electronic distributor. I should have mentioned that, shouldn't I?

[142 Guy]

With the ignition switch in the run position (with or without the engine running) , you should have +12V present on + terminal of the ignition coil. That +12v is supplied from the #6 fuse position. It is connected to a common electrical supply bus at the #6 position and is not actually fused. This supply bus plus should get 12v when the ignition switch is in the run and start position.

On the D jet equipped cars there is also a wire that runs from the + terminal of the ignition coil to the main fuel injection relay which powers up the the D jet system when you turn on the ignition system. My initial reaction was that in removing the D jet harness you removed the wrong wire connected to the coil + terminal. But, since you said the engine was running after the removal of the harness that does not seem to be the problem.

Since you report no voltage at the ignition coil + terminal (which should be marked 15) I would go to your fuse panel and check the supply side of the #6 fuse to confirm that you have +12v on the common supply bus. I have attached a screen grab from an 1800ES wiring diagram which shows the connection from the coil + terminal to the fuse panel marked in red. If you have +12v at the panel and don't have 12 v at the coil you have an interesting problem since there are no connections to break in that circuit. You will have to engage in a physical examination to figure out what is going on. If you don't have 12 v at the fuse panel when the key is in the run position then you have an ignition switch problem or a wiring problem between the fuse panel and the ignition switch. One thing to check is that you have +12v at the supply side of the #6 fuse position with the key in both in the run and start position. A relatively uncommon switch failure is for the contact that supplies +12v to the cars ignition system in the start position to fail. The more common failure is that the engine will start and then die when you release the key from start to run. You need 12v supply to the coil in both the run and start positions so check both.

If you manage to get +12v to the ignition coil + (15) terminal and it still will not start, then check the following:

1) The Volvo 1800 tach is series connected in the coil negative connection to the distributor. There is a connector in that circuit (marked 24 in the diagram). Make sure that connector has not separated. Make sure that the tach has not failed in an open circuit. The best way to check both of these is to use a continuity tester to confirm that you have a circuit from the coil negative terminal to the 'coil' connection at your 123 distributor (whatever that is). If it is an open circuit you have a wiring problem or a failed tach.

2) I expect that the 123 distributor requires a switched +12v supply for its internal electronics. Make sure that the distributor is getting +12v supply when the key is in the run or start position.

3) Something has happened to the 123 distributor. This is a low probability event that should only be investigated after you have ruled out other possibilities.

[sleek lemur]

Thanks 142! Since the connection to the bottom of the fuse box is also involved in the FI wiring, I started with that and sure enough, one of the two wires leading to the coil had cracked; presumably after me fooling around pulling out the FI loom. Car started immediately.

Except I have no charging, or at least I should say the IGN light in the speedo stays on when the car runs. Could I have damaged the alternator by repeated attempts at starting the car with a booster charger connected I wonder?

Oh well, gives me something to do tomorrow. Await sheepish post requesting help with that !

[c1800]

“ Car started immediately”

Good to hear that! I did completely miss the fact you had no power to the coil. Glad you got it sorted.

[sleek lemur]

Not at all, C. The no power to the coil was a red herring, as I had assumed that the power came from the back of the tacho, rather than the lead from the bottom of the fuse box. The fact that that lead also ran to the main FI relay added a further variable. In the end it was disturbing that wire that caused the problem.

Really appreciate you taking the time to help. I'm really running up quite a debt on this forum!

[Laird Scooby]

Originally Posted by sleek lemur

Except I have no charging, or at least I should say the IGN light in the speedo stays on when the car runs. Could I have damaged the alternator by repeated attempts at starting the car with a booster charger connected I wonder?

It's possible but does the IGN aka charge warning light come on with position 2 of the key as it should?

I'm wondering if you've disturbed another wire that feeds the charge warning light which in turn feeds the alternator field terminal.

If it doesn't have a feed then it could be a back feed from the alternator so check the warning light lights as it should to start with.

After that, check the silly things like have you refitted the fan belt (i know! ), check the pulley is free to turn on the alternator, that the main battery connection hasn't come off the alternator and if it happens to be a battery-sensed alternator, check the wire for that hasn't come adrift as well.

Most Bosch alternators are machine-sensed so that's unlikely to be the problem but double-checking your connections for anything silly that might have been loosened by removing the EFi might just bring the fault to light.