Replaced bad XR-700 with Petronix - Still wont start!

[Nigel]

I need some help diagnosing a no-start condition on a friends Z. Last week, his car wouldn’t start after running fine for years, and it turned out there was no spark. He was running a 240Z distributor, MSD 6AL, and an old (early 90’s) Allison XR-700 optical ignition. I narrowed it down to the XR-700, and last night I replaced that with a Pertronix ignitor. We have spark again, but it still refuses to start. It came close a few times, but no go.

 

The Pertronix is fixed in place in the distributor, but the XR-700 optical pickup was adjustable, which could have an impact on timing. I was wondering if perhaps at some point the distributor timing may have been adjusted to compensate for the optical pickup location some how not being correct? Now with it back to a stock like condition, could the distributor timing be too far off? How far off would the timing have to be to prevent the car from starting? There are timing marks on the distributor itself. Is there an initial position that the distributor can be set to where it is most likely to start? BTW, the distributor has NOT been removed.

 

The only other possibility that I can think of is that the engine is flooded (triple Webbers). We were cranking it a lot the week before trying to diagnose the problem. But it sat for a week before we tried again, and we didn’t crank it much last night. However, it did come closest to firing after we took all the plugs out and let the engine sit for about 15 minutes.

 

My friend is getting understandably frustrated and wants to get the car towed to a garage, but it seems like it should be a simple issue and easy to fix. Unfortunately, all of my experience is with my SDS EFI distributor-less system. I went with that so I wouldn’t have to deal with issues like this! Any help would be greatly appreciated!!!

 

Nigel

'73 240ZT

[MAG58]

Do you get any popping? I have the XR700 on my car and it runs well. Bring it up to tdc and look through the shutter plate. The eye should be uncovered to shoot through the shutter, and at 5-10btdc (depending on what your initial timing is), the eye should just start to be viewable through the shutter. Also make sure that the cap and rotor are engaging at the ignition events as this was a problem I ran into as well.

 

Hope this helps

[ezzzzzzz]

Follow MAG58's visual instructions. Pull the dipstick and smell it for raw gas from flooding. Do an oil change if it reeks of fuel. Pull a plug and look for a wet sticky mess possibly requiring a blast of brake cleaner or replacement of plugs. Do a rough static timing of the engine (assuming the distributor was removed or turned in the petronix install). If there is any question about the battery charge then add another vehicle using jumper cables. Pull the coil secondary lead off. Push AND hold the gas pedal to the floor. DO NOT LET IT UP. Turn the engine over to clear the flooding condition (assuming you didn't change the plugs). Turn the ignition key to 'OFF' BUT do not lift off the throttle pedal. Reconnect the coil secondary lead. Shoot a blast of ether into the filter housings. Turn the engine over again. Be ready to come off that go-fast pedal when the engine fires up and races for 10,000 rpms.

Edited March 4, 2011 by ezzzzzzz

[Nigel]

I did figure it out. I initially wasn't aware that there are two timing adjustments possible on the distributor. As I suspected, whomever had installed the XR-700 had positioned it without any consideration for the stock timing marks on the distributor, so that both the timing adjustments on the distributor had to be pretty much maxed out to get 10 degrees of advance. The Petronix positioning is fixed to match the stock points. After I learned about how to do a static timing check, I discovered that with the Petronix installed, the timing was now ahead by something like 20 deg. AFTER TDC! So, no wonder it wouldn't run. I got it part way back with the adjustment directly under the distributor, but it wasn't until I discovered that the distributor could be rotated even further at the other adjustment point closer to the timing cover that I got the timing back to where it should be. She fired right up after that.

 

Learning how to do a static timing check turned out to be instrumental in diagnosing this problem. I was even able to set the timing almost dead on to 10 deg. before TDC without a timing light.

 

Nigel