Volvo Owners Club Forum - Ignition Problem with P1800s

Dear All,

I've recently been wrestling with an ignition problem, which with some help from Ron I have now finally resolved. A more experienced person would probably have got to the solution quicker but as is often the case hindsight makes the solution more obvious. I'm sharing this so that if someone else has the same problem in the future they might get to a solution quicker.

The car

1963 (November build) P1800S
electronic ignition (Pertronix)
original coil
Bosch distributor JFR4 0231 153 003 with centrifugal advance

The Problem Symptoms

The engine is running fine whilst stationary (albeit I can't get it to idle below about 1500 rpm) and it revs fine. As soon as I try to drive it after a short period 10-20 mins) it displays fuel starvation like symptoms, loses power and stalls and can't be restarted until for 30 mins or so.

When trying to restart it, immediately after it stalls, there is a spark from high tension lead from the coil but no spark at the individual plug leads.

Investigation

The fuel pump was working, There was fuel in the fuel bowls when I checked as soon as it stalls. I've in any case fitted new fuel floats since one of the original ones was operating too low and was not adjustable.

I checked the primary and secondary ignition coil resistances and they are OK, from memory 4.5 Ohms on the primary and 10,000 Ohms on the secondary. I have access to the coil positive as someone thought it was a good idea to cut the armored cable to fit the electronic ignition. Of course it could be that the coil stops working due to over heating or some other reason for the dielectric to breakdown. The coil was replaced and did not solve the problem.

The distributor cap, leads and spark plugs are new. Replacing the rotor arm did not solve the problem.

I checked the operation of the centrifugal advance on the distributor and there was no spring resistance. Whilst this would not be the reason for the problem it needed to be fixed anyway. Dismantling the distributor showed that the centrifugal weight springs were missing. A second-hand distributor was sourced and the springs used. On reassemble I noticed that the self-tapping screw holding down the electronic ignition plate was long enough to foul the springs. This explains why they were missing. Whoever fitted the electronic ignition module did not check this (perhaps it was done whilst the distributor was in situ) and the first time it was operated it would have ripped the springs off.

All the electrical connections in the starter circuit were checked and now faults found. A starter key fault was eliminated by hot wiring the coil.

The only item left was the electronic ignition module. When I check this after the car stopped it was not working. A replacement module fixed the problem.

So it seem that the root cause of the problem was an electronic ignition sensor that works when the car is cold but after a period of time stops working (gets hot?) and wont work again until it is cold.

Hope this helps someone else in the future.