spark only sometimes on an Hei - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Electrical
User Name
Password
lost password?   |   register now

Reply
 
LinkBack Thread Tools
  #1 (permalink)  
Old 09-10-2010, 09:55 PM
Registered User
 
Last photo:
Join Date: Feb 2008
Location: Formerly Calgary, Ab, Canada, now in France
Posts: 279
Wiki Edits: 0

Thanks: 1
Thanked 5 Times in 5 Posts
spark only sometimes on an Hei

I have just installed an OEM TBI fuel injection on the 250ci inline 6 in my '57 Chevy Suburban. I have modified the distributor to be run by the ECM.
I have gas at the throttle body but not much sparks.
I have pulled 3 spark plugs (1 at a time) to check for spark, cranking the engine, and:
1 spark plug has spark often, normally, it seems;
another spark plug had spark some times, like 4/5 sparks then none for a few seconds then again a few...
yet another spark plug had only one spark over the 10-20 seconds I was cranking the engine!
With my limited electrical knowledge, this does not make sense at all!
Plugs, plug wires, cap, rotor are new; coil is not new but worked a few months ago, module is junkyard used
Can anyone help?
Thanks!

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 09-11-2010, 03:29 AM
cobalt327's Avatar
WFO
 
Last wiki edit: Intake manifold
Last journal entry: 1980 Malibu Wagon
Last photo:
Join Date: Mar 2009
Location: Atlanta
Age: 60
Posts: 5,037
Wiki Edits: 1616

Thanks: 128
Thanked 598 Times in 547 Posts
For one thing, the HEI coil needs to receive full battery voltage. You cannot power it by using the resistor wire/ballast resistor that was used on the car originally, you need to run a wire to the HEI that does not have added resistance.
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 09-11-2010, 01:37 PM
Registered User
 
Last photo:
Join Date: Feb 2008
Location: Formerly Calgary, Ab, Canada, now in France
Posts: 279
Wiki Edits: 0

Thanks: 1
Thanked 5 Times in 5 Posts
Quote:
Originally Posted by cobalt327
For one thing, the HEI coil needs to receive full battery voltage. You cannot power it by using the resistor wire/ballast resistor that was used on the car originally, you need to run a wire to the HEI that does not have added resistance.
The truck had the HEI before the EFI mod and worked fine, electricity comes directly from the ignition switch.
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 09-11-2010, 03:26 PM
LATECH's Avatar
Hotrodders.com Moderator
 

Last journal entry: Motor - vator
Last photo:
Join Date: Jul 2010
Location: Northeast Pennsylvania
Posts: 5,436
Wiki Edits: 0

Thanks: 230
Thanked 295 Times in 274 Posts
What or how did you modify the distributor and what distributor did you use?
Also which efi system?, from what , ? And what is the ecm number and what is the prom number?
Also you should put a test light on the positive side of coil to check while cranking. Maybe you are losing power while it is cranking.That old school ignition switch might not be too good or capable of handling the power that is required by the hei.

Last edited by latech; 09-11-2010 at 03:39 PM.
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 09-11-2010, 04:13 PM
vicrod's Avatar
life is a ride
 

Last journal entry: 2014
Last photo:
Join Date: Nov 2005
Location: Telford, PA
Age: 72
Posts: 1,361
Wiki Edits: 0

Thanks: 0
Thanked 63 Times in 59 Posts
What year Chevy is the TBI from?
What mods were done the distributor?
Have you installed all the sensors and controllers that the ECM needs to operate?

Coolant sensor.
WOT switch.
Closed throttle switch.
Vehicle speed sensor.
Barometric pressure sensor.
Manifold absolute pressure sensor.
Idle speed control switch.
Distributor reference pulses.
Throttle position sensor.
Oxygen sensor.
ETC

vicrod
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 09-11-2010, 04:45 PM
Registered User
 
Last photo:
Join Date: Feb 2008
Location: Formerly Calgary, Ab, Canada, now in France
Posts: 279
Wiki Edits: 0

Thanks: 1
Thanked 5 Times in 5 Posts
http://www.ifsja.org/forums/vb/showthread.php?t=69362
These are the main instructions I have used to modify the distributor; I did this without taking the distributor out, it was very easy.

http://www.binderplanet.com/forums/s...ad.php?t=47254
This is a site where I have found a lot of info, too.

The harness and ECM, as well as all sensors, come from an '88 Chevy half-ton. All the sensors are conected except the 02 sensor, because my exhaust is not done yet. I have read that the engine should run without the 02 sensors.
The distributor is a '78 Camaro, the engine is a '75 Camaro; it all worked fine before the mods. The ECM number ends in 747, I think, a very common one.
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 09-11-2010, 06:47 PM
randolphi's Avatar
Registered User
 
Join Date: Aug 2010
Location: South Central Texas
Posts: 46
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Ok or not ok---plugwires-maybe

I have run in to this problem, more than once, new wires, with the ends not installed (do it your self), and also pre-assembled but economy brands, that often disapointed me. The best test for the coil for me, after I make sure the connections are good, including (plugs back in).
I take the end of THE COIL LEAD TO distributer out of the distributer, but not all the way off of It-- just prop it up near the distributer center- about a quarter inch, and then watch and listen for spark, while cranking-- should sound continuous without any pauses, and be bright, and loud, also (BE PREPAIRED iF THE ENGINE STARTS.) YOU KNOW parking brakes, in neutral, no fumes from gasses, no tools near fanbelts, and OH yeah dont have someone hold the wire while you crank.
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 09-11-2010, 07:01 PM
Registered User
 
Last photo:
Join Date: Feb 2008
Location: Formerly Calgary, Ab, Canada, now in France
Posts: 279
Wiki Edits: 0

Thanks: 1
Thanked 5 Times in 5 Posts
Quote:
Originally Posted by randolphi
I take the end of THE COIL LEAD TO distributer out of the distributer, but not all the way off of It-- just prop it up near the distributer center- about a quarter inch, and then watch and listen for spark, while cranking-- should sound continuous without any pauses, and be bright, and loud, also (BE PREPAIRED iF THE ENGINE STARTS.) YOU KNOW parking brakes, in neutral, no fumes from gasses, no tools near fanbelts, and OH yeah dont have someone hold the wire while you crank.
My HEI distributor is a coil-in-cap...
Reply With Quote Quick reply to this message
  #9 (permalink)  
Old 09-11-2010, 09:57 PM
vicrod's Avatar
life is a ride
 

Last journal entry: 2014
Last photo:
Join Date: Nov 2005
Location: Telford, PA
Age: 72
Posts: 1,361
Wiki Edits: 0

Thanks: 0
Thanked 63 Times in 59 Posts
GM made a change in 1980 where the distributor was redesigned and known as an Electronic Spark Timing (EST) distributor which is part of the C4 or CCC systems.
The older distributor is likely not compatible with the 1988 TBI you have.

vicrod
Reply With Quote Quick reply to this message
  #10 (permalink)  
Old 09-11-2010, 10:34 PM
LATECH's Avatar
Hotrodders.com Moderator
 

Last journal entry: Motor - vator
Last photo:
Join Date: Jul 2010
Location: Northeast Pennsylvania
Posts: 5,436
Wiki Edits: 0

Thanks: 230
Thanked 295 Times in 274 Posts
I looked at the info you posted and if you did it like the instructions the only thing that comes to mind would be maybe you have the pickup coil hooked up backwards polarity.It doesnt say what color the positive or negative should be. The "P" wire and the "N" wire may be reversed but you should check polarity with a dvom. it will read the value generated and also the polarity will be displayed. does your harness have the little tan with black wire with connector for timing setting?adjust? if so maybe unplug it and check spark integrity then. I just dealt with an 88 pickup equipt with the 1227747 ecm and tbi and the timing was all over the place due to a POS ecm.
The pcm doesnt come into play untill it sees an engine rpm of about 400 rpm as the module has a bypass circuit for starting but it could be wacking the spark and timing if it is signaling the module to switch or sending mixed signals as the ecm sends a 5 volt signal to the module to switch it.unplugging the timing connector and rechecking will at least eliminate that as a possible culprit. I would check the polarity of the pickup first.

Last edited by latech; 09-11-2010 at 10:56 PM.
Reply With Quote Quick reply to this message
  #11 (permalink)  
Old 09-11-2010, 10:36 PM
LATECH's Avatar
Hotrodders.com Moderator
 

Last journal entry: Motor - vator
Last photo:
Join Date: Jul 2010
Location: Northeast Pennsylvania
Posts: 5,436
Wiki Edits: 0

Thanks: 230
Thanked 295 Times in 274 Posts
I would also have started with a newer model year distributor like an 83 or 84 with est.( as vicrod suggested). There were 2 designs and the one would have the external coil and you would not have had to alter the harness for the coil and the distributor.but i guess you run what ya got. good luck
Reply With Quote Quick reply to this message
  #12 (permalink)  
Old 09-12-2010, 05:55 PM
Registered User
 
Last photo:
Join Date: Feb 2008
Location: Formerly Calgary, Ab, Canada, now in France
Posts: 279
Wiki Edits: 0

Thanks: 1
Thanked 5 Times in 5 Posts
Quote:
Originally Posted by latech
I would also have started with a newer model year distributor like an 83 or 84 with est.( as vicrod suggested). There were 2 designs and the one would have the external coil and you would not have had to alter the harness for the coil and the distributor.but i guess you run what ya got. good luck
I know about these different designs distributors, but with a 250ci inline6, the choice is limited! This is also why I have modified my distributor, to make it compatible to the EFI system, locking the weights and adding an electronic module, for instance. Yes, I run what I got and it would be easier if I were rich!
Reply With Quote Quick reply to this message
  #13 (permalink)  
Old 09-28-2010, 07:08 PM
Registered User
 
Last photo:
Join Date: Feb 2008
Location: Formerly Calgary, Ab, Canada, now in France
Posts: 279
Wiki Edits: 0

Thanks: 1
Thanked 5 Times in 5 Posts
OK, so I appreciate all the help from you guys, but I am still stuck. I have gone over the distributor wiring to make sure it is good; tried to unplug the timing connector; checked the polarity of the pick up coil (and even switched the wires to make sure), but still nothing! I have tried 2 ECMs, 2 ignition modules.
I have heard that the ignition and the injectors are "connected" and that one will not work if the other does not: I always had gas at the throttle body (wet butterflies, gas smell), so... Although last night, there was no sign of gas...
The O2 sensor is not connected because the exhaust line is not built yet, but nowhere have I heard or read that it was needed.
I guess I need to go over the whole harness, how do I do that? Is it just a matter of checking continuity for each single wire? Is it possible to check that the connectors to the ECM are good?
Any other ideas?
Thanks!
Reply With Quote Quick reply to this message
  #14 (permalink)  
Old 09-28-2010, 07:36 PM
LATECH's Avatar
Hotrodders.com Moderator
 

Last journal entry: Motor - vator
Last photo:
Join Date: Jul 2010
Location: Northeast Pennsylvania
Posts: 5,436
Wiki Edits: 0

Thanks: 230
Thanked 295 Times in 274 Posts
did you use the ignition module from the 88 pickup truck when you converted the distributor from the camaro?
Reply With Quote Quick reply to this message
  #15 (permalink)  
Old 09-28-2010, 08:40 PM
Registered User
 
Last photo:
Join Date: Feb 2008
Location: Formerly Calgary, Ab, Canada, now in France
Posts: 279
Wiki Edits: 0

Thanks: 1
Thanked 5 Times in 5 Posts
Quote:
Originally Posted by latech
did you use the ignition module from the 88 pickup truck when you converted the distributor from the camaro?
Yes, harness, ECM, module, connectors, throttle body all come from the same donor truck, '88 Chevy truck.
Reply With Quote Quick reply to this message

Recent Electrical posts with photos

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Chevy HEI - Weak Spark daveturnbull Electrical 5 07-25-2011 10:58 AM
318 ignition spark mystery(help!) androopa Electrical 8 10-31-2008 12:07 AM
350 TBI spark problem driving med crazy!! Erst Engine 12 04-26-2007 11:18 AM
HEI: No Spark Goobzilla Electrical 17 04-17-2003 01:27 AM
Do I Need Little HEI Box for New HEI Dist? Mr.56Chevy Electrical 0 12-23-2002 03:38 PM


All times are GMT -6. The time now is 02:04 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.