Checking for spark on SBC 350 TBI? - 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 04-04-2005, 11:59 AM
Neophyte's Avatar
I'm not superstitious
 

Last journal entry: Release catch for trunk lid pt.5
Last photo:
Join Date: May 2004
Location: Johannesburg, South Africa
Age: 45
Posts: 261
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Checking for spark on SBC 350 TBI?

I have a 91 TBI motor which I'm trying to start. It has an aftermarket computer. The injectors do give a pulse of fuel when switching on but it sounds like I'm getting no spark as there's no indication whatsoever that it wants to start.

How do I check if the coil is getting a signal from the dizzy and also if the coil is actually "firing"???

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 04-04-2005, 05:26 PM
docvette's Avatar
Hotrodders.com Moderator
 
Last wiki edit: Rebuild an alternator Last photo:
Join Date: Mar 2004
Location: Lafayette, california
Age: 62
Posts: 7,362
Wiki Edits: 12

Thanks: 0
Thanked 6 Times in 3 Posts
Spark

Doc here,

Easiest way is too put a timing light on any plug wire and crank it, If it strobes during crank, you have fire...(this way you don't get knocked on your butt holding a plug and wire off ground)

Have you tried Start fluid down the TBI Throat? If it fires for a brief period, then your Spark delivery system is good...Look at the fuel system.

Is this engine a "Transplant" into something else...Or did you just have to replace the computer?

Doc
__________________
Aftermarket Solutions
Electronic & Electrical
Innovations
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 04-04-2005, 10:16 PM
Neophyte's Avatar
I'm not superstitious
 

Last journal entry: Release catch for trunk lid pt.5
Last photo:
Join Date: May 2004
Location: Johannesburg, South Africa
Age: 45
Posts: 261
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Thanks Doc,

Was hoping you would reply.

Yes, this engine is a transplant into a 53 Chevy 210 4dr. Some V8 shops over here import "complete" motors with trannys from the U.S. which are unfortunately just "cut" from the donor vehicles. Mine was complete except for standard air-filter housing and ECU. Also the wiring harnesses aren't unplugged neatly from the vehicles but just cut.

Unfortunately I didn't have any starting fluid on hand but poured a few drops of fuel down it's throat. Just the same cranking tone. I did put a screw driver into the dizzy side of the coil lead and held it close to ground and didn't seem to get a spark. I will however try a strobe too which I think is a good idea. Never actually thought of checking for spark that way before.
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 04-05-2005, 11:25 AM
Neophyte's Avatar
I'm not superstitious
 

Last journal entry: Release catch for trunk lid pt.5
Last photo:
Join Date: May 2004
Location: Johannesburg, South Africa
Age: 45
Posts: 261
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Well, still have no spark. Doc, do you know by any chance how I can trigger the coil manualy or know of a good TBI resource to refer me to?
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 04-05-2005, 02:38 PM
docvette's Avatar
Hotrodders.com Moderator
 
Last wiki edit: Rebuild an alternator Last photo:
Join Date: Mar 2004
Location: Lafayette, california
Age: 62
Posts: 7,362
Wiki Edits: 12

Thanks: 0
Thanked 6 Times in 3 Posts
Spark

Doc here,

If your still not getting spark, Then First thing to do is pull the ECM from the distributer replace or have it tested at your local auto parts shop, and if you get a new one, have them TEST the new one as well, about 1 in 3 are bad out of the box!...Have them test it several times to be sure it won't fail under heat. This will kill spark.

Next If that won't Cure the problem, Does this Have A Crank position Sensor? If so, Check to be sure it is operating, and adjusted properly. This will kill spark also.

If all thats good, Test the Megnetic pickup and reluctor inside the distributor (electronic points) If it has failed, ( and I know you don't want to hear this..) you have to pull the distributor, disassemble it to get the "Ring" or pickup out...and the new one in...reassemble the distributor and re install it.

If all is good, and STILL no spark, Check the coil, I'm assuming were talking about a 350 SBC with HEI (since you never said what engine it was...) With an Ohm meter, set for auto range or Rx10k measure between the BATT terminal and the Rotor pickup inside the Cap, It should read between 6,000 ohms to 30,000 ohms, Next measure between the TACH terminal and the Rotor pickup, and it should read the same. Anything above or below those readings , replace the coil.

Check all your fuses, especially those marked ECM, Computer, CCR, INJ1, INJ2,(I assume you transplanted the fuse panel and harness as well)

Try those in the order easiest for you to test in, and tell us what you find.

Doc

Photos:Fuses good/ blown
HEI Exploded View
Fuse Panel
Attached Thumbnails
Click image for larger version

Name:	fuses.jpg
Views:	87
Size:	20.1 KB
ID:	4563   Click image for larger version

Name:	D1.jpg
Views:	98
Size:	22.0 KB
ID:	4564   Click image for larger version

Name:	F1.jpg
Views:	89
Size:	16.8 KB
ID:	4565  
__________________
Aftermarket Solutions
Electronic & Electrical
Innovations
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 04-05-2005, 10:35 PM
Neophyte's Avatar
I'm not superstitious
 

Last journal entry: Release catch for trunk lid pt.5
Last photo:
Join Date: May 2004
Location: Johannesburg, South Africa
Age: 45
Posts: 261
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Doc, the engine is a 91 SBC 350 TBI engine. Sorry, I didn't specify properly what engine I have. I only said it was a 91 TBI motor.

The coil is a smallish square coil sitting outside the distributor, just in front of it. There's also no crank sensor.

Unfortunately I wasn't lucky enough to get the harness and computer too. The importer reckons those don't come with when they import the motors from the states. I had to put an aftermarket programmable computer on. We did have some hassle with to start with as the signal from the distributor to the computer wasn't strong enough to trigger it so I didn't get any fuel as well. The guys then amplified that signal so now I've got fuel but still no spark. Can it therefore be assumed that the distributor module is bad causing it not to trigger the coil?

Fortunately there's an auto electrical shop close by that specialises in U.S. cars. I'll take the distributor there to have it tested.

Do you perhaps know how I can trigger this coil manually?
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 04-06-2005, 02:15 PM
docvette's Avatar
Hotrodders.com Moderator
 
Last wiki edit: Rebuild an alternator Last photo:
Join Date: Mar 2004
Location: Lafayette, california
Age: 62
Posts: 7,362
Wiki Edits: 12

Thanks: 0
Thanked 6 Times in 3 Posts
module

Doc here,

The module is ONE of the items that will kill spark. If you have a place that will test it do so...It will eliminate one link in the chain.

Find the wire that goes from the coil secondary to the mag pickup in the distributor, disconnect it and quickly ground it a few times , you should get high tension spark from the coil..If not, Check the mag pick~up & pole piece and/or replace the coil.

The lack of or weak Injector Reference pulse before is a clue, as it's signal is generated from the ECM to sync injectors to ignition..at the computer. you might want to look into why the signal there was attenuated.

Check the module first...It should be free, and easy to do. Don't forget lots of heat sink compound when re~installing it!

After that look at the Mag pick~up and pole piece..for operation, and "Air Gap" adjustment.

One of those should get you running.

Doc
__________________
Aftermarket Solutions
Electronic & Electrical
Innovations
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 04-06-2005, 02:47 PM
Neophyte's Avatar
I'm not superstitious
 

Last journal entry: Release catch for trunk lid pt.5
Last photo:
Join Date: May 2004
Location: Johannesburg, South Africa
Age: 45
Posts: 261
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Thanks Doc, I'll try to have the stuff tested tomorrow or Friday and let you know.
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
91 rs tbi 305 to 350 carbed tat2 Engine 2 05-15-2004 06:46 PM
305 tbi into an older 350? help... NOSBOSS Engine 2 03-23-2004 09:45 PM
TBI Questions on a 93' Chevy FS 350 IWANTMOREHP Engine 1 01-04-2004 01:42 PM
Very "lazy" '88 350 TBI help newsuburbanite Engine 9 12-01-2003 05:57 PM
rebuilt 350 TBI running rough warlok Engine 9 11-24-2003 07:02 PM


All times are GMT -6. The time now is 06:59 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.