TBI Issues... Please help! - Pirate4x4.Com : 4x4 and Off-Road Forum
 
Pirate4x4.Com : 4x4 and Off-Road Forum  

Go Back   Pirate4x4.Com : 4x4 and Off-Road Forum > Brand Specific Tech > Chevy
Notices

Reply
 
Share Thread Tools Display Modes
Old 06-30-2009, 08:42 PM   #1 (permalink)
Registered User
 
Join Date: Jan 2002
Member # 9216
Location: Kimberly, Wisconsin
Posts: 1,830
Send a message via AIM to Mr McGee Send a message via Yahoo to Mr McGee
TBI Issues... Please help!

Here's what I know:

No spark, no injector pulse. Good fuel pressure. Fuel pump runs for 2 seconds after turning key. Fuel pump does NOT run while engine is cranking. I don't have a test light for the injectors, but I can't feel/hear them clicking...plus ZERO fuel comes out even after system is pressurized (not even a dribble) so i know they're not being pulsed. Oil pressure gauge shows pressure while cranking. Ignition module tested ok. Good battery voltage. Service engine light works=computer is getting power. No codes (but does have the wherewithal to show all clear #12 when aldl jumped).
Can't think of any more info at the moment...
My suspicion leads to computer (don't know if box goes bad or just the chip), but I wanted to see what some other opinions were before I threw a new brain at it.
I could really use this truck in running condition, so I would really appreciate any advice!
Thanks,
Max
__________________
Nick Hietpas...1985-2003
Rest In Peace
Mr McGee is offline   Reply With Quote
Old 06-30-2009, 10:36 PM   #2 (permalink)
Registered User
 
just4cuz's Avatar
 
Join Date: Aug 2007
Member # 98655
Location: Alta Loma, Ca.
Posts: 1,945
It is something simpler than the computer. I think in the distributor, but I don't have my book here with me.
just4cuz is offline   Reply With Quote
Sponsored Links
Old 07-01-2009, 07:22 AM   #3 (permalink)
Zeus of the Sluice
 
Binder's Avatar
 
Join Date: Sep 2000
Member # 1684
Location: Everett Wa USA
Posts: 2,787
Off hand I'm thinking a couple things. The module could be bad even though it tested OK or you lost the engine crank signal to the computer. The latter would be a broken wire possibly one going to the starter....More than likely the ignition module.
__________________
S.N.O.R.T.
Binder is offline   Reply With Quote
Old 07-01-2009, 07:53 AM   #4 (permalink)
Registered User
 
Join Date: Sep 2002
Member # 13786
Location: moved 7 miles to colfax, ca.
Posts: 4,330
change the module, it controls both the injectore pulse and the spark. AND use a factory part.
KWTMECH is offline   Reply With Quote
Old 07-01-2009, 07:56 AM   #5 (permalink)
Registered User
 
Join Date: May 2009
Member # 135799
Location: NC
Posts: 15
this might sound dumb but i had a 92 chevy come in monday with no injector pulses and such. EFI fuse (bottom left corner i think) in the under dash block was blown somehow. it feeds the ECU power.
84whteyody is offline   Reply With Quote
Old 07-01-2009, 08:40 AM   #6 (permalink)
Zeus of the Sluice
 
Binder's Avatar
 
Join Date: Sep 2000
Member # 1684
Location: Everett Wa USA
Posts: 2,787
Quote:
Originally Posted by 84whteyody View Post
this might sound dumb but i had a 92 chevy come in monday with no injector pulses and such. EFI fuse (bottom left corner i think) in the under dash block was blown somehow. it feeds the ECU power.
True but this would not allow for a code 12 or SES light.
__________________
S.N.O.R.T.
Binder is offline   Reply With Quote
Old 07-01-2009, 09:56 AM   #7 (permalink)
Registered User
 
just4cuz's Avatar
 
Join Date: Aug 2007
Member # 98655
Location: Alta Loma, Ca.
Posts: 1,945
KWTMECH, thats what I was thinking of. Could not recall which part of dist.
Thanks for refreshing my memory. The distributor module. Make sure it is plugged in good, that the wires are undamaged and if and when you replace it it seems to me the heat insulating grease needs to be put underneath it to prevent heat damage to the module. Anybody ever used a dab of RTV instead of the grease? Seems to me the RTV may have better insulating properties than the grease.
just4cuz is offline   Reply With Quote
Old 07-01-2009, 01:15 PM   #8 (permalink)
Registered User
 
Join Date: Sep 2005
Member # 52872
Location: Where it's too damn cold.
Posts: 310
Quote:
Originally Posted by just4cuz View Post
and if and when you replace it it seems to me the heat insulating grease needs to be put underneath it to prevent heat damage to the module. Anybody ever used a dab of RTV instead of the grease? Seems to me the RTV may have better insulating properties than the grease.
The grease that comes with the module is a "heat sink" it helps to pull heat away and out of the module into the dizzy housing. Its not a insulator to keep heat away from module, and it is very important to use.
__________________
[COLOR="gray"]Horsepower is like a Condom.....I would rather have it and not need it than to need it and not have it

[/COLOR]
grasshopper77 is offline   Reply With Quote
Old 07-02-2009, 12:43 AM   #9 (permalink)
Registered User
 
Join Date: Jan 2002
Member # 9216
Location: Kimberly, Wisconsin
Posts: 1,830
Send a message via AIM to Mr McGee Send a message via Yahoo to Mr McGee
got it running...
I figured with all the strange symptoms that trying a different computer couldn't hurt. Sure enough, a trip to the junkyard and $40 later, problem solved! The beast fired right up!
I tore the computer apart and found that the wiring on the ecm was seperating from the pcb board. It looked rippled and I could tell it wasn't normal. I got a new 7747 ecm and swapped chips.
I'm glad it was this easy before I started throwing parts at it!
Also, I appreciate all the advice given...All the pointers were great.
Thanks,
Max
__________________
Nick Hietpas...1985-2003
Rest In Peace
Mr McGee is offline   Reply With Quote
Old 07-02-2009, 09:44 AM   #10 (permalink)
Registered User
 
just4cuz's Avatar
 
Join Date: Aug 2007
Member # 98655
Location: Alta Loma, Ca.
Posts: 1,945
Quote:
Originally Posted by grasshopper77 View Post
The grease that comes with the module is a "heat sink" it helps to pull heat away and out of the module into the dizzy housing. Its not a insulator to keep heat away from module, and it is very important to use.
So insulator or heat sink, either way whats the verdict on the RTV idea? That the grease will take the heat away and the RTV will keep it in, or absorb it. Let me know what you think.
just4cuz is offline   Reply With Quote
Old 07-02-2009, 11:47 AM   #11 (permalink)
Registered User
 
Join Date: Jan 2002
Member # 9216
Location: Kimberly, Wisconsin
Posts: 1,830
Send a message via AIM to Mr McGee Send a message via Yahoo to Mr McGee
Bad news again...
Like I said above...swapped computer and truck ran great.
Today, went to start it and same problem as i originally had. All the same symptoms. Now I'm wondering if my computer was even bad to begin with. I tried one injector at a time to see if they were shorted and no luck. Could a bad fuel pump relay cause these problems? I still have a hard time believing the module is bad, but i may try a new one anyways. I'm definately stumped here!
Again, any advice is appreciated!
Thanks,
Max

edit: What are the chances that the pickup in the dizzy (small coil that plugs into ICM) could be bad? Seems unlikely but...
__________________
Nick Hietpas...1985-2003
Rest In Peace

Last edited by Mr McGee; 07-02-2009 at 11:51 AM.
Mr McGee is offline   Reply With Quote
Old 07-02-2009, 11:57 AM   #12 (permalink)
jtr
Rock God
 
jtr's Avatar
 
Join Date: Jan 2005
Member # 41068
Location: Northern, NV
Posts: 1,136
We were just through something like this with a TBI454. It turn out to be the connection from the dizzy to the computer, if the computer does not see the tach signal it will never turn on the fuel.

In our case we cleaned out the connector that attaches to the dizzy with a torch tip cleaner (make sure it has enough tension to make a good contact too) and it has been working since. Parts store can also check you ign module for you.
__________________
1990 Ranger 393w, C6, 60/14, full hydro, 4 link rear, H1s
1997 F350 Powerstroke dually, 4wd conversion
1965 Chevy 4x4 frame, step side, daily driver, TBI 350, TH350, 205, D44, D60
jtr is offline   Reply With Quote
Old 07-02-2009, 12:07 PM   #13 (permalink)
Registered User
 
just4cuz's Avatar
 
Join Date: Aug 2007
Member # 98655
Location: Alta Loma, Ca.
Posts: 1,945
You said you got the fuel pump to run for a few seconds before starting. So it is not the relay. A bad relay will not prevent the engine from running. Once the ecm sees an oil pressure signal it will deliver fuel. I have 2 that work that way now. Engine spins a couple times before the fuel feeds, then starts. I've just been to busy to fix them.
just4cuz is offline   Reply With Quote
Old 07-02-2009, 01:57 PM   #14 (permalink)
Registered User
 
Join Date: Jan 2002
Member # 9216
Location: Kimberly, Wisconsin
Posts: 1,830
Send a message via AIM to Mr McGee Send a message via Yahoo to Mr McGee
Quote:
Originally Posted by jtr View Post
Parts store can also check you ign module for you.
Module supposedly checked out ok. I'm suspicious of the actual pickup though...

Quote:
Originally Posted by just4cuz View Post
You said you got the fuel pump to run for a few seconds before starting. So it is not the relay. A bad relay will not prevent the engine from running. Once the ecm sees an oil pressure signal it will deliver fuel. I have 2 that work that way now. Engine spins a couple times before the fuel feeds, then starts. I've just been to busy to fix them.
Does the ecm deliver spark no matter what? I am assuming the op sensor is ok because the gauge on my dash even works.

Also, just checked the injectors and they both show the same resistance...so they must not be shorted.
__________________
Nick Hietpas...1985-2003
Rest In Peace
Mr McGee is offline   Reply With Quote
Old 07-02-2009, 02:13 PM   #15 (permalink)
Zeus of the Sluice
 
Binder's Avatar
 
Join Date: Sep 2000
Member # 1684
Location: Everett Wa USA
Posts: 2,787
If you want to eliminate the oil pressure switch as the problem just jumper the two wires together at the switch. If you want to eliminate the fuel pump relay just hot wire the fuel pump or better yet put a jumper on the relay. Should be pins 30 and 87 on the relay. To verify a crank signal to the ECM supply 12 volts to pin C9 of the ECM. Should be a purple and white wire.
__________________
S.N.O.R.T.
Binder is offline   Reply With Quote
Old 07-02-2009, 02:22 PM   #16 (permalink)
Zeus of the Sluice
 
Binder's Avatar
 
Join Date: Sep 2000
Member # 1684
Location: Everett Wa USA
Posts: 2,787
Quote:
Originally Posted by Mr McGee View Post
I'm suspicious of the actual pickup though....
You can test the pickup with a multi meter. This is from the Binder Planet FAQ....
Quote:
Pick-up coil continuity is tested by connecting the ohmmeter (on low range) between the white and green leads. Normal resistance is between 500 and 1500 ohms........ Replace the pick-up coil if the reading is outside the specified limits.
Quote:
Originally Posted by Mr McGee View Post
Does the ecm deliver spark no matter what?
No it does not.
__________________
S.N.O.R.T.
Binder is offline   Reply With Quote
Old 07-08-2009, 01:39 AM   #17 (permalink)
Registered User
 
Join Date: Jan 2002
Member # 9216
Location: Kimberly, Wisconsin
Posts: 1,830
Send a message via AIM to Mr McGee Send a message via Yahoo to Mr McGee
update:

verified that the ecm has crank signal on c9...works
measured resistance on pickup...8xx (ok)

Could my prom be bad? Should i just throw an ignition module at it anyways? I'm runnin out of things to test/replace! Again, thanks for any help!
-Max
__________________
Nick Hietpas...1985-2003
Rest In Peace
Mr McGee is offline   Reply With Quote
Old 07-08-2009, 11:09 AM   #18 (permalink)
Registered User
 
Join Date: May 2008
Member # 114732
Location: Lakeview Or.
Posts: 65
The pick up coil/hall effect switch in the dizzy. I've seen where the plastic coating on the wire breaks down and shorts intermittently causeing the same issue you describe.
Flyinwillies is offline   Reply With Quote
Old 07-08-2009, 01:06 PM   #19 (permalink)
Zeus of the Sluice
 
Binder's Avatar
 
Join Date: Sep 2000
Member # 1684
Location: Everett Wa USA
Posts: 2,787
Quote:
Originally Posted by Binder View Post
The module could be bad even though it tested OK ....More than likely the ignition module.
I would swap it out and if that's not the problem just keep the old one for a spare.
__________________
S.N.O.R.T.
Binder is offline   Reply With Quote
Old 07-08-2009, 05:41 PM   #20 (permalink)
Registered User
 
Join Date: Jan 2002
Member # 9216
Location: Kimberly, Wisconsin
Posts: 1,830
Send a message via AIM to Mr McGee Send a message via Yahoo to Mr McGee
Quote:
Originally Posted by Flyinwillies View Post
The pick up coil/hall effect switch in the dizzy. I've seen where the plastic coating on the wire breaks down and shorts intermittently causeing the same issue you describe.
how do i go about removing the actual coil? remove dizzy and pull the gear?

I will replace the ignition module and the coil and report back...

Thanks
__________________
Nick Hietpas...1985-2003
Rest In Peace
Mr McGee is offline   Reply With Quote
Old 10-05-2009, 04:37 PM   #21 (permalink)
Registered User
 
Join Date: Jan 2002
Member # 9216
Location: Kimberly, Wisconsin
Posts: 1,830
Send a message via AIM to Mr McGee Send a message via Yahoo to Mr McGee
Fixed!!!

Quote:
Originally Posted by Mr McGee View Post
how do i go about removing the actual coil? remove dizzy and pull the gear?

I will replace the ignition module and the coil and report back...

Thanks
well, i've been working out of town a ton so I wasn't able to give this project the full attention it deserved...

Anyways, I replaced the pickup coil, re-installed and nothing. Shit. So, I figured I'd replace the ignition module that tested GOOD. Bingo! Fired right up! Went and tried it a few days later and it fired up again! I was avoiding replacing it due to the cost, but I should know better that even if something tests good, not to trust it completely.

THANKS!!!
__________________
Nick Hietpas...1985-2003
Rest In Peace
Mr McGee is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not 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



All times are GMT -7. The time now is 07:50 PM.


Powered by vBulletin® Version 3.8.6
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Search Engine Optimization by vBSEO 3.6.0 ©2011, Crawlability, Inc.