Intermittent no start condition

Mike Pearson · 09-18-2013, 10:40 PM

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 · 09-19-2013, 07:19 AM

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 · 09-19-2013, 07:55 AM

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 · 09-19-2013, 08:21 AM

Quote:

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

Rich Biebel · 09-19-2013, 09:33 AM

The sensor outputs a very low voltage and it would be millivolts......

A Fluke can read this accurately....

I just had some trouble with the ABS sensors in my GMC....

They do the same thing.......and can easily lose low speed output from rust building up under them. I found the info readily available online as to what they should read just by turning the wheels by hand......and a little work with a file and a wire brush.....and Viola....all better...

That was after I had already replaced both sensors and they were probably good.....

John Nechiporchik · 09-19-2013, 09:44 AM

Mike/Joe/Kirk,
I did the test of the crank trigger as Joe stated. Simple and effective.
Next, I spoke to MSD and the tech rep indicated the ohms reading of the MSD pickup (test leads on purple and green wires) should be between 65 and 85 ohms. This is for the non magnetic pick-up.....magnets are in the wheel, not the sensor.

Will test mine tonight along with using my newly acquired noit light to test injectors.
Also got a few other areas to check (connections, grounds etc) tonight.

buzzinhalfdozen · 09-19-2013, 12:50 PM

Rich , I believe there is a special coverage for the wheel speed sensors you can check with your local GM dealer as it varies year to year. We clean and apply a compound to the knuckle so rust doesn't redevelope. John, good deal testing this stuff is not hard at all, but does require a few items, sounds like you're on top of it. Joe Oh and sorry bout that wrong resistance spec, I was shooting from the hip on that, which is the spec GM uses withtheir sensors must have got stuck in my head.

Steve Williams · 09-19-2013, 05:20 PM

Quote:

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

This is exactly what I was referring to when I spoke of voltages and weak signal.

John Nechiporchik · 09-19-2013, 08:54 PM

FED 387....after testing every circuit I could test....it appears that the only logical conclusion I can come to is the coil is the problem, as you stated a few days ago.
Tonight, I checked the ohms on the crank trigger sender....78.2 (MSD said between 65-85)...OK
Tried to start....fired right up.
Repeated 2 more times and fired up.
4th. try....no start
Grounded coil wire (dist. end) to block in two different locations approx. 1/16 gap......no spark
Tried again about 15 minutes later....spark like 4th of July.
Replaced coil wire.....fired right up.

Gotta be the Friggin coil.....
Going to get one tomorrow.

John Nechiporchik · 09-20-2013, 09:31 AM

Went through test process again this morning.
I believe when I tested the coil last night (metal screw in dist end of not) I did not have a proper connection.When I use a spark tester, it gives me a signal.
Throw out last nights test.
Tried to start car this AM....fires right up
Second try ...no start.
put spark tester on coil AND noid tester on injector simultaneously...Result...no start, spark at coil, NO light at noid tester.
Repeated several times same result.
HELP AGAIN!!

09-18-2013, 10:40 PM	#1
Mike Pearson VIP Member Join Date: Mar 2007 Posts: 2,473 Likes: 632 Liked 1,987 Times in 599 Posts	Re: Intermittent no start condition 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 Pearson 2485 SS

09-19-2013, 07:19 AM	#2
Rich Biebel VIP Member Join Date: Jun 2007 Location: Northern New Jersey suburbs Posts: 2,320 Likes: 25 Liked 557 Times in 217 Posts	Re: Intermittent no start condition 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. __________________ Rich Biebel S/C 1479 Stock 147R

09-19-2013, 07:55 AM	#3
Kirk Morgan Member Join Date: Jan 2009 Posts: 230 Likes: 1 Liked 81 Times in 45 Posts	Re: Intermittent no start condition 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

09-19-2013, 09:33 AM	#5
Rich Biebel VIP Member Join Date: Jun 2007 Location: Northern New Jersey suburbs Posts: 2,320 Likes: 25 Liked 557 Times in 217 Posts	Re: Intermittent no start condition The sensor outputs a very low voltage and it would be millivolts...... A Fluke can read this accurately.... I just had some trouble with the ABS sensors in my GMC.... They do the same thing.......and can easily lose low speed output from rust building up under them. I found the info readily available online as to what they should read just by turning the wheels by hand......and a little work with a file and a wire brush.....and Viola....all better... That was after I had already replaced both sensors and they were probably good..... __________________ Rich Biebel S/C 1479 Stock 147R

09-19-2013, 09:44 AM	#6
John Nechiporchik Member Join Date: Mar 2007 Location: Grosse Ile Mi. Posts: 316 Likes: 85 Liked 13 Times in 7 Posts	Re: Intermittent no start condition Mike/Joe/Kirk, I did the test of the crank trigger as Joe stated. Simple and effective. Next, I spoke to MSD and the tech rep indicated the ohms reading of the MSD pickup (test leads on purple and green wires) should be between 65 and 85 ohms. This is for the non magnetic pick-up.....magnets are in the wheel, not the sensor. Will test mine tonight along with using my newly acquired noit light to test injectors. Also got a few other areas to check (connections, grounds etc) tonight.

09-19-2013, 12:50 PM	#7
buzzinhalfdozen Senior Member Join Date: Sep 2006 Location: Bellevue Ohio Posts: 984 Likes: 0 Liked 11 Times in 8 Posts	Re: Intermittent no start condition Rich , I believe there is a special coverage for the wheel speed sensors you can check with your local GM dealer as it varies year to year. We clean and apply a compound to the knuckle so rust doesn't redevelope. John, good deal testing this stuff is not hard at all, but does require a few items, sounds like you're on top of it. Joe Oh and sorry bout that wrong resistance spec, I was shooting from the hip on that, which is the spec GM uses withtheir sensors must have got stuck in my head. __________________ Joe Buchanan SS/BX 3117 Last edited by buzzinhalfdozen; 09-19-2013 at 01:22 PM.

09-19-2013, 08:54 PM	#9
John Nechiporchik Member Join Date: Mar 2007 Location: Grosse Ile Mi. Posts: 316 Likes: 85 Liked 13 Times in 7 Posts	Re: Intermittent no start condition FED 387....after testing every circuit I could test....it appears that the only logical conclusion I can come to is the coil is the problem, as you stated a few days ago. Tonight, I checked the ohms on the crank trigger sender....78.2 (MSD said between 65-85)...OK Tried to start....fired right up. Repeated 2 more times and fired up. 4th. try....no start Grounded coil wire (dist. end) to block in two different locations approx. 1/16 gap......no spark Tried again about 15 minutes later....spark like 4th of July. Replaced coil wire.....fired right up. Gotta be the Friggin coil..... Going to get one tomorrow.

09-20-2013, 09:31 AM	#10
John Nechiporchik Member Join Date: Mar 2007 Location: Grosse Ile Mi. Posts: 316 Likes: 85 Liked 13 Times in 7 Posts	Re: Intermittent no start condition Went through test process again this morning. I believe when I tested the coil last night (metal screw in dist end of not) I did not have a proper connection.When I use a spark tester, it gives me a signal. Throw out last nights test. Tried to start car this AM....fires right up Second try ...no start. put spark tester on coil AND noid tester on injector simultaneously...Result...no start, spark at coil, NO light at noid tester. Repeated several times same result. HELP AGAIN!!