Need some help out there if anyone has run into this. I recently bought a 79 xj12 seriesIII that had been sitting up for about 2 years. A friend and I replaced a bad starter, freshened the battery, flushed the gas tanks and got good fuel flow. We also verified spark. This where we are running into issues. We cleaned the relays and they appear to be working, but when turning the car over, the relays are only working intermittenly and therefore the fuel pump is only coming on intermittenly. When it does, the car seems to want to start but doesn't. We put a noid light on the injectors and there doesn't appear to be a signal to fire the injector. We found, in a Haynes Manual, a test procedure for the trigger that send the signal to the ECU, which in turn signals ththrough the relay to fire the injectors and fuel pump. Anyway, the test procedure involved using an analog ohmmeter to measure the variance between the plugs on the lead. Problem is, we had a digital meter. we tried to get a before and after reading and use this, but that didn't seen to be the best way to go. And the way the book had us doing didn't seem to be the best route either. Has anyone out there run into a similar problem? Does anyone know of a good way to test the various components in the system to narrow down my issues. I'd much rather replace a faulty part knowing its bad vs replacing everything from the ECU back! This stuff isn't cheap or easy to come by! Thanks in advance for any assistance anyone might could throw my way!

Will

 

OK, you are new, so welcome to the real world of motoring.

I know NOT where you are, and this is going to make diagnosis a tad easier, as the mighty PreHE was very different for different markets.

I will assume USA, as that seems to be where most "no locations" generally are????????.

The trigger board inside the distributor comes in 2 versions. One is a 3 wire, and the other is a 4 wire. Until I know what YOU got, the rest is guessing (my pet hate).

The rotor arm SHOULD have a magnet in the heel. Make sure it is still a magnet, after all this time, who knows.

Once I know the board you got, we can start.

Oh, some fresh J D will help also.

 

My apologies! In my desire to be as accurate as possible with my issue I did neglect to say where I was. I am indeed in the USA. I will, as soon as possible, determine the wire configuration you mentioned. I appreciate your help on this

 

Ok, the trigger board is a 3 wire set up. I plan on getting under the distributer cap and give it a good cleaning as well.

Thanks, Will

 

OK, the 3 wire is the original, and quite problematic, hence the later/update 4 wire board.

The 3 wire has reed switches imbedded in teh mastic stuff, and they are fickle at best. The easiest way of testing them is to get one of those "magnets on a stick" (look like a ball pen), and in TOTAL silence, wave that magnet over one end of the board, and you "should" hear that switch click. Then go to the other end of the board and do the same. If you hear the clicking, the swiitches are fine.

Now the magnet in the heel of the rotor is another suspect. The magnetism gets weak, and that is not good.

There are 2 different rotor magnets, one is square, and the other is round. One is for the 3 wire board, and the other is for the 4 wire board, and I truly have forgotten which goes with which, BUT, I have no idea why there are 2 styles, as I always understood that a magnet was a magnet, and I see no reason to change that knowledge.

If reliabillity is strived for, I strongly suggest sourcing a 4 wire trigger board kit. It includes the newer board with hall effect sensors (very reliable), and a new rotor. The 4th wire is connected to 12v ignition power.