It appears I'm getting intermittent Spark... started car yesterday ran about 15 min sounded good and put it in the trailer.. unloaded at the track today would not start. Checked for spark, plug would spark once and not again. Tried a different coil had the same the result. Checked cap and rotor seem ok.. verified voltage was good while cranking.. tested distributor mag pick up with ohm meter.. tested mag pick up out of box was working and it fired coil as it should.. any ideas? Thanks

Is this a complete MSD 7720 / 7730 install?

Or is this 7730 with a Legacy ignition ( 6al, 7al2, ect)?

Here’s some easy things to try. While cranking the Green LED next to the USB port should be blinking ON / OFF/ ON /OFF. This indicates that it is seeing the firing pulses from the CT or Distributor trigger.

Attach to Grid and see if there are any alerts. The alerts are located under the “VIEW” tab on top.

Complete 7720/7730 install.. it also has spark if I put a spark plug in the coil wire and crank it over..

If you have continuous spark at the coil wire when cranking with a spark plug installed the ignition is working. Where did you ground the spark plug for this test?

Firewall..

Light blinks while cranking..

Only alerts are for the sd card.

If Grid is seeing the CT pulses, try unplugging the small 4 pin connector (red, black, orange, white) from 7730 (mail pins) to 7720 (female pins) and verify visually that the pins (especially the female ones on the 7720) are fully out and seated. I’ve seen female pins pushed back into the plug housing and not making proper connections. The female pins need to be tight against the back of the plastic face plate.

If you now have continuous spark at the end of the coil wire and no start your problem lies at the distributor. Pull a plug wire off a cylinder and put a plug in it and ground plug to the head or intake manifold. Does it spark?

quote:

Originally posted by markemark:
If you now have continuous spark at the end of the coil wire and no start your problem lies at the distributor. Pull a plug wire off a cylinder and put a plug in it and ground plug to the head or intake manifold. Does it spark?

Earlier today it was intermittent now I have nothing...

I'm ordering new pick up cap and rotor..

If Grid indicator light is blinking ON/OFF/ON while cranking you do not have a CT problem.

7730 commands 7720 to fire through the white wire in the small 4 pin connected between them.

Unplug the Large 4 pin connector that goes to the battery and the coil from 7720. Meter the black /orange wires that go to the coil. They should read the primary coil circuit that should read less than 1 ohm on your meter.

So you dont feel the pick up is bad?

Turn ON ignition with laptop attached to Grid, go to the Gauge Tab in the upper right and select the Engine RPM. Crank engine and watch display. What does it indicate? If showing cranking speed, CT is not problem.

Shows 150 rpm while cranking.. 2 alerts pop up.. crank sensor voltage low and missing sd card.

Unplug crank sensor and meter. It should read between 70 – 90 ohms. If good plug back in and unplug the large 4 pin connector at 7720 and meter the black / orange wire pins going to the sensor. You should have the same reading as at the sensor. This verifies the cable is good. Look at the pins to verify they are seated properly in the connectors.

I don't have a crank sensor. It's hooked up to a distributor

quote:

Originally posted by vega3410:
I don't have a crank sensor. It's hooked up to a distributor

It should read 500 – 700 ohms at distributor and same value at Grid cable plug in as described. Check the plug in at the distributor. I’ve seen the distributor have pins push out the back of the plug. To keep the plugs together use a small zip ty installed between the wires pulling the plugs together.

If all meters correctly and you are seeing rpm when cranking in Grid your problem could be 7720 or 7730 or wiring between both (small 4 pin plug). Plugging a different 7730 or 7720 can help narrow down what the actual problem is. I understand most do not have spares.

To troubleshoot 7720 follow my detailed advice HERE found at the end of the first posting. Exercise care when doing this as you can damage 7720 if not done correctly.

Problem Solved

markemark
which usually has the highest failure rate? the 7720 or the 7730?

quote:

Originally posted by jenavet:
markemark
which usually has the highest failure rate? the 7720 or the 7730?

I believe 7730 will be the higher of two, but also think both are very reliable imho.

Looks like his issue was resolved.
Here's a new one to discuss.

I went to the IHRA race at Baton Rouge, went up for 2nd time trial and started my burn out. Car would not rev over 2000 even at wide open throttle.
Backed out of water and tried to rev and nothing. Shut engine off and tried again, all was good.
Checked MSD View nothing wrong showed up.
We are thinking I somehow hit trans brake button and ignition timed out and went into safety mode.

Any one heard of this happening without hitting safety mode?

Dave