GMCforum
For enthusiast of the Classic GMC Motorhome built from 1973 to 1978. A web-based mirror of the GMCnet mailing list.

Home » Public Forums » GMCnet » No Spark, No Start (Where do you look?)
No Spark, No Start [message #271155] Wed, 04 February 2015 01:07 Go to next message
Gary Carlton is currently offline  Gary Carlton   United States
Messages: 59
Registered: February 2014
Karma: 0
Member
I started the 403 in the coach a week ago and it ran fine for a few minutes. It died while I was messing with the manual choke and now it will not refire. There is fuel to the carb and being squirted out of the accel jet, 12V to the coil, new cap/coil/condensor/module but no spark.

Where would you look first for the problem?

Thanks in advance for any insights you care to share.

gary


'78 Royale, "Road Grub" Bellingham, WA
Re: No Spark, No Start [message #271159 is a reply to message #271155] Wed, 04 February 2015 02:03 Go to previous messageGo to next message
George Beckman is currently offline  George Beckman   United States
Messages: 1085
Registered: October 2008
Location: Colfax, CA
Karma: 11
Senior Member
Gary Carlton wrote on Tue, 03 February 2015 23:07
I started the 403 in the coach a week ago and it ran fine for a few minutes. It died while I was messing with the manual choke and now it will not refire. There is fuel to the carb and being squirted out of the accel jet, 12V to the coil, new cap/coil/condensor/module but no spark.

Where would you look first for the problem?

Thanks in advance for any insights you care to share.

gary


THe distributor module would be my first guess. Sometimes they break down when they warm up. Not too expensive. If it doesn't fix it you have a spare.

One oddity with an HEI distributor. In the middle of the desert a Blazer quit running. (One of those dirt roads that goes in each direction to the horizon) A crack in the rotor was letting the spark short through to the advance weights. For a while if you could get it revved up it ran fine because the weights moved out of the way. It finally would not run at all. Slit a piece of hose and slipped it over the rib in the underside of the cap to get to civilization. That rig had an extra rotor in the glovebox from then on.




'74 Eleganza, SE, Howell + EBL
Best Wishes,
George
Re: No Spark, No Start [message #271161 is a reply to message #271155] Wed, 04 February 2015 02:31 Go to previous messageGo to next message
Gadabout is currently offline  Gadabout   United States
Messages: 124
Registered: March 2013
Location: Edmonton
Karma: 2
Senior Member
Gary , this can be one of many things . You have already confirmed there is 12v to the coil and you indicated several new components.

Check the following ....

- remove the distributor cap and verify the rotor is installed correctly.
- with the distributor cap removed , crank the engine and verify the rotor is turning.
- make sure the new coil and HEI brush is installed correctly
- confirm all electrical connections to the distributor

If all the above check out, it's now time to swap components for "known good" parts. If you still have the old Coil,cap, module , etc. put them back on. If you get spark, you know that one of the new components are faulty.

Even with a fault cap you will still get a spark , no spark is typically caused by Lack of 12v , faulty module, pickup , coil or broken rotor.

My bet is the rotor or wiring.

This may help to confirm installation
http://chevythunder.com/hei_troubleshooting_page_2_coil_.htm

Good luck and let us know what you find...



Carl Harr : Driver NASCAR Pro Series #2
1978 Gadabout-Restoring
1978 Palm Beach
1976 Glenbrook
Prevost Featherlite H3-45
Re: No Spark, No Start [message #271163 is a reply to message #271155] Wed, 04 February 2015 02:59 Go to previous messageGo to next message
Ken Burton is currently offline  Ken Burton   United States
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
Senior Member
Well there is something strange to me here. You state you have a 403 and replaced all of the listed stuff. I do not know where there is a condenser on a 403 with HEI. That must be a radio noise condenser that I'm not familiar with.

If there is +12 at the correct connector on the HEI and the distributor is turning then it should make spark at the plugs.

So what haven't you done?

1. Replace the pick up coil in the bottom of the distributor.
This requires removing and disassembling the distributor.

2. Verified the ground connection.
The ground is accomplished by the mounting of the aluminum distributor to the steel engine block. Sometimes you get corrosion at the mounting connection, you loose the electrical connection through the mounting. I believe the mounting is really through the intake manifold. Temporarily add a jumper from frame of the distributor to the engine block as an alternate ground path. A simple jumper with some alligator clips will do. Dick Paterson, when he rebuilds distributors, adds a terminal on the under side of the distributor for this purpose.

3. Disconnect the tach connection if you have one. Sometimes a tach or tach wiring failure will cause the distributor not to work.

4. Verify the the new items you installed are good. Sometimes a bad coil will also take out the module. For this reason I carry a spare cap and coil already assembled along with a spare module. These have already been tested and all three of them get installed at the same time.

Those are my first guesses. I'm still wondering where you have the condenser installed.



Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
Re: No Spark, No Start [message #271167 is a reply to message #271155] Wed, 04 February 2015 06:22 Go to previous messageGo to next message
RF_Burns is currently offline  RF_Burns   Canada
Messages: 2277
Registered: June 2008
Location: S. Ontario, Canada
Karma: 3
Senior Member
In electronics there can be some "infant mortality"... if a component is going to fail from some manufacturing defect, it will usually fail in the first month... otherwise it will run for years.

You didn't say how many miles are on your new distributor parts, but I'd swap out the module first.. and its the easiest.

What plug gap are you running? About 0.40 is considered best... the 060 plus is hard on a module, too much electrical stress.

JWIWD


Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that
Re: No Spark, No Start [message #271177 is a reply to message #271155] Wed, 04 February 2015 08:43 Go to previous messageGo to next message
Gary Carlton is currently offline  Gary Carlton   United States
Messages: 59
Registered: February 2014
Karma: 0
Member
Guess I left out some pertinent information, sorry:

The rotor is turning.
The entire distributor is new from Pertronix and has zero miles (long and sad story).
Plug gap is 40.
It is not a condensor but the capacitor.

The most likely issue from all the suggestions is the grounding. I had just installed a new aluminum intake manifold and started it up. As I said it ran fine for a few minutes and has not restarted. I'll check that and try jumper to see what happens.

I very much appreciate the responses. Thank you.

gary


'78 Royale, "Road Grub" Bellingham, WA

[Updated on: Wed, 04 February 2015 08:52]

Report message to a moderator

Re: No Spark, No Start [message #271183 is a reply to message #271177] Wed, 04 February 2015 10:21 Go to previous messageGo to next message
GMC Cruse is currently offline  GMC Cruse   United States
Messages: 606
Registered: June 2009
Location: SE Michigan
Karma: 3
Senior Member
As KEN B. said, disconnect the Tach if you have one. I installed a Pertronix distributor in one of my Hot Rod's and couldn't get any spark. As a last resort I disconnected the Tach wire from the coil and it started right up.

Also, as Ken said, make sure you have at least 12v at the proper HEI connector. Another time I had a Hot Rod that cranked fine but wouldn't fire. Was getting a little less than 12v at the connector. After charging the battery, it fired right up.


Mike K. '75 PB Southeast Michigan
Re: No Spark, No Start [message #271184 is a reply to message #271177] Wed, 04 February 2015 10:22 Go to previous messageGo to next message
tphipps is currently offline  tphipps   United States
Messages: 3005
Registered: August 2004
Location: Spanish Fort, AL
Karma: 9
Senior Member
Capacitor, formerly called a condenser, an electrical device that can store energy. WikiPedia reference.
Same device, old name vs. new name.
Tom, MS II


2012 Phoenix Cruiser model 2552 KA4CSG
Re: No Spark, No Start [message #271185 is a reply to message #271155] Wed, 04 February 2015 10:28 Go to previous messageGo to next message
Chris Tyler is currently offline  Chris Tyler   United States
Messages: 458
Registered: September 2013
Location: Odessa FL
Karma: 7
Senior Member
You can test the pickup with an old school analog [gauge type] ohmmeter.
Disconnect the leads to it and hook it up to the pickup. Spin it over.
Be careful not to snag the leads. Don't ask me how I know that.
the meter will vary with a good pickup. A digital unit just gets confused
As someone pointed out, replacing it requres distributor removal

also: Make sure the carbon contact at the center of the cap is intact. Ive had that break and fall out of a brand new delco cap.
double check your tach and 12v coil terminals are in the right spot
Measure coil resistance


76 Glenbrook

[Updated on: Wed, 04 February 2015 10:30]

Report message to a moderator

Re: No Spark, No Start [message #271218 is a reply to message #271155] Wed, 04 February 2015 21:39 Go to previous message
Gary Carlton is currently offline  Gary Carlton   United States
Messages: 59
Registered: February 2014
Karma: 0
Member
Success is at hand and it is all due to the fine folks on this board. It was the tach lead. Unplug it and it runs like a top, plug it in and nothing. I got a new distibutor out of it and a good education so all is not bad. Thanks sincerely to all the people that offered suggestions.
gary


'78 Royale, "Road Grub" Bellingham, WA
Previous Topic: GMC in the news on BBC - with some familiar names?
Next Topic: [GMCnet] California smogged coaches
Goto Forum:
  


Current Time: Sat Nov 16 09:15:34 CST 2024

Total time taken to generate the page: 0.04796 seconds