Intermittent no start condition

[buzzinhalfdozen]

Originally Posted by John Nechiporchik

Rich, I did test the coil immediately after experiencing the no-start condition. I placed the spark tester between the coil and the coil wire. Spark was there. I did not, however, test it on the other side of the coil wire (your process). I will do that tomorrow. That would eliminate or validate a bad coil wire. I will go through all the wiring this weekend....after I do the noid test.
I will find a noid between now and the weekend.
Thanks.

Having spark coming out of the coil indicates you indeed do have the necc. trigger to initiate spark. Where you tested it isn't an issue, you've proven that the MSD portion is operational. I really doubt you would have a bad coil wire causing this as you would have other symptoms. Though it is a good idea to regularly change the coil wire as all the spark energy is directed thru it as opposed to single events thru the plug wires. Seems as though you are down to correct signaling to EFI controller or the controoler itself, BTW how are your injectors powered? The ECU merely provides the ground, if your power to the injectors is erratic you'll see the same issue. Joe

[John Nechiporchik]

Joe, I need to find out how the injectors are powered. There are enough wires under the dash that it will take some time to figure all this out. Also, crawling under the dash is an event in itself!
I talked to MSD again today...and I will do a resistance check on the crank trigger pick-up tomorrow. He said the reading should be between 65-85 Ohms. With this and a noid test, I should have enough info to determine the source of the problem....then finding the root cause may be another journey.

[buzzinhalfdozen]

John, having a spare crank sensor is a good idea regardless, however it seems apparent that it is not the cause of your problem, unless of course your no start "fixed" itself during your test. Do you know what switch you turn on to power the injectors? This would narrow the search a bit. As I've stated I'm not familiar with your system however can you "real time " communicate with it via a laptop and if so does it display any active parameters? Such as engine RPM? If so then you could monitor for RPM while attempting to start which I would expect to see, then during a no start event see if it is in fact displaying RPM. Hope this isn't too confusing. Joe

[John Nechiporchik]

Joe, Don't know which switch fires the injectors. I will assume it's either the ignition or fuel pump switch. Will be part of my "trace the wires" event tomorrow night and this weekend.
Relative to your other comments, I'm not familiar enough with the laptop interaction with the ECU to understand what you mean. This stuff is all new to me.

[buzzinhalfdozen]

Ok, can we assume that you have had the laptop connected at all? If so then you'll just have to look around and see what info is displayed, but I'd bet you'll be able to see engine rpm. That would help in determining whether the ECU "thinks" the engine is running. I would like for you to have comm. via laptop as soon as you can as it may help find the issue.Quickest way to find the power source I would think is to use a test light at the injector connector and start trying switches, the 1 that makes the lite come on is it, then it's a matter of tracing that 1 circuit. Once you get a bit more info you'll be fine, knowing how things are wired up is a huge step in the right direction.Please keep us updated on your progress and good luck. Joe

[Mike Pearson]

Just freshened my engine. Now it won't start. No spark at the plugs. How do you check the pick up on the crank trigger with an ohm meter. Using a 7AL box and crank trigger. Carburetor set up. Just looking for some ideas. The coil is nearly new. The MSD parts are older but have been real reliable.

[Rich Biebel]

There are 2 types of pickups. Magnetic and non magnetic.
Both have a coil of wire inside them and if you use an ohmmeter acorss that coil you should get a reading. I don't know what that reading is or should be for various pickups.....but an open reading would clearly be N/G
The wire is super fine and many turns.

MSD uses the flying magnet style and the magnets are in the wheel. The pickup is non magnetic.

With the ignition on.....you usually can get a spark out of the coil by connecting and than disconnecting the trigger wires that go to the MSD.

1 spark every time you break the connection.....

If you had an MSD tester you could test the box and the coil.

Pickups get blamed for a lot of ignition issues and routinely replaced but I really don't think they are usually the cause of most problems....

In the generator world that I work in .....similar pickups are used to generate a signal from the engine to a controller. We change them a lot when something is not working right but like I said I don't think they are ususally the problem unless they clearly have physical damage. If anything rubs the pickup face then it is likely to be damaged inside.

[Kirk Morgan]

I have been working on this stuff since it all started, Certified mech for 30 years. I went to a A/C Delco class many years ago and learned that the magnet type makes A/C voltage when cranking. I believe the spec is 3 volts. I can dig out my old books to confirm if needed. That will confirm signal strength which can cause intermittent problems.

Kirk

[buzzinhalfdozen]

Originally Posted by Mike Pearson

Just freshened my engine. Now it won't start. No spark at the plugs. How do you check the pick up on the crank trigger with an ohm meter. Using a 7AL box and crank trigger. Carburetor set up. Just looking for some ideas. The coil is nearly new. The MSD parts are older but have been real reliable.

Mike, make a small jumper wire, disconnect your crank trigger, with power on to MSD and a spark tester or an old spark plug on the coil wire (grounded of course) momentarily touch the jumper across the 2 terminals of the crank sensor harness. You should get a spark from the coil each time you remove the jumper.Other than that I believe you should see 800-900 ohms from the sensor, I agree with Rich crank sensors are very robust and do rarely fail though they're often blamed. I think MSD has a trouble shooting section on their web site but don't remember for sure.I'd bet someone you know has a MSD ignition tester, invaluable piece of equipment well worth the investment. BTW stay clear if the coils terminals as the have very high voltage potential DO NOT lay your arm against them (ask me how I know). Good luck. Joe

[buzzinhalfdozen]

Originally Posted by Kirk Morgan

I have been working on this stuff since it all started, Certified mech for 30 years. I went to a A/C Delco class many years ago and learned that the magnet type makes A/C voltage when cranking. I believe the spec is 3 volts. I can dig out my old books to confirm if needed. That will confirm signal strength which can cause intermittent problems.

Kirk

KIrk yes they do produce an AC sine wave however the actual voltage can vary dependent on many factors, frequency and amplitude increase with engine speed.I've found that most (not all) have a hard time with the AC voltage test so a quick resistance test of the sensor or the jumper wire test usually indicates which way to procede. Thanks for sharing the info. Joe