1987 Bonneville has me stumped

Reply

  #1  
Old 04-14-08, 10:31 PM
Member
Thread Starter
Join Date: Apr 2008
Posts: 9
Question 1987 Bonneville has me stumped

I was headed out to work one morning last week and my Bonnie lost power. Since then, using process of elimination, I have managed to replace parts on this car without any improvements in its performance..iow..it is still not startiing.

I am overlooking the obvious, obviously.

I replaced the ignition cylinder lock, for it was broken and in need of replacement. I also replaced the three ignition coils, and the crankshaft sensor. The coils tested bad on the primary side and tested good on the secondary side. The crankshaft sensor was old, oily and cracked, so I simply replaced it and didn't test it. I tested the ignition module and it passed. I cleaned and gapped the spark plugs. Changed the fuel filter. With the ignition switch in the run position I tested the fuel pump pressure at the fuel tank and at the filter discharge also, both indicated at 60+psig. At the fuel rail I get a pressure reading of 36psig, which is slightly under the 41 to 47 psig optimum, but within the 34 to 39 psig operating range. The vacuum controlled fuel pressure regulator shows no signs of diaphram rupture/failure. Ignition and fuel pump relays and fuses are all good. Air Mass Flow Sensor has been cleaned with approved CRC electrical cleaner, but not tested since testing requires that the engine be running at an idle.

And of course, I forgot to read the Engine Trouble Code, prior to disconnecting the battery to perform work on this car..lol..up to that point I would occasionally recieve a trouble code for the oxygen sensor

So, this car will start, but stops after a couple of seconds and will not restart. In tryiing to nurse it home, (I ended up calling AAA), I found that I could disconnect, remove, remount and reconnect the ignition coil for cylinder #1 and the car would start and stay running for a mile, or two, before shutting down again.

What I would like to know, for starters is..
1. Has anybody had similar problems with this same GM product configuraton?
2.At the fuel pump discharge, what psig and volume (gpm) measurements should I get?
3. Is there a way to test the AMF Sensor off the vehicle?

It's late and I am not thinking straight, so if any clarifications are needed, please ask.

Thank you, Guy
 
Sponsored Links
  #2  
Old 04-15-08, 05:27 AM
carguyinva's Avatar
Member
Join Date: Nov 2003
Location: Shenandoah Valley
Posts: 1,147
fuel pressure spec is 34-43 PSI static (key on engine not running) 29-34 at idle. there is no spec for volume but a very good rule of thumb is a pint in 30 seconds

you cannot test the MAF sensor off the vehicle. at idle (i know that doesn't last too long sometimes) try tapping gently (no hammers) on the MAF sensor, if the engine stumbles or quits...replace it. you can also unplug it and put the system into default, if it quits stalling then (it won't run great, but it will stay running) replace it. you can also tap test the ECM this way and the same goes...if the engine stalls or starts running all weird, it's a safe bet that something has failed on a board inside the controller.

the crank sensor that you replace...it goes right behind the balancer, correct? that sensor should be adjusted for clearance...if the vanes on the back of the balance touch it, it'll break and you'll be buying another one.

if this doesn't help, try driving it with a fuel pressure gauge attached (make absolutely sure you have NO leaks) to see if you lose pressure when it quits. likewise you can take a spark tester and a noid light with you...when it quits and won't start, put the spark tester on a plug wire (spark plug end) and crank it, do you have spark? thet same goes for the noid light, disconnect an injector connector and stick the light in it. crank the engine when it won't start and see if the light blinks, does it?

the trick here is to determine whther you have a fuel or ignition problem first, then we can go from there.
 
  #3  
Old 04-15-08, 06:48 AM
Member
Thread Starter
Join Date: Apr 2008
Posts: 9
Thanks carguyinva.
I knew my psi numbers were off, I get conflicting numbers and a typo from my reference sources. Since the vehicle runs but a couple of seconds before shutting down I will first try to determine if I have a viable spark.

As for fuel, when I by-pass the fuel pump relay,(chock/hold the relay contact points shut), I get a continuous static flow from the fuel rail test port, but the engine will not start and run continuously upon cranking.

I took care to position the crankshaft sensor when I installed it, but I will inspect it to reaffirm its position.

I have yet to attempt to start this engine since cleaning the MAF Sensor, but I do remember I did disconnect it to see if the engine would run in default mode, but by then the battery was pretty well drained and nothing in the ignition/emmissions/fuel systems wanted to function properly, so I've had the battery on trickle-charge overnight and after breakfast I shall start anew beginning with one final psig test of the fuel system before progressing further.

Thanks again, Guy
 
  #4  
Old 04-21-08, 07:11 PM
Member
Thread Starter
Join Date: Apr 2008
Posts: 9
What the..? My whole reply dissappeared when I hit spell-check.So, here goes again...lol

I have no spark, have fuel, have power to injectors, have good MAF, have Good ECM, (Stress-tested it three times-in-a-row on the parts house test machine) forgot to tap on it though.... Cleaned and re-gapped sparl plugs, tested alternator at parts house, dissassembled alternator for inspection anyway..brushes are worn and in need of replacement soon. Cleaned all engine and chassis ground connections and retightened, cleaned and retightened fuse-block connections. Charged to battery to full charge of 14.5 amps and started the car which idled for about 20 minutes before it went dead again. Wouldn't restart until I put a full charge on the battery again and then it only ran for a few minutes. I didn't even think to check the alternator output during those 20 minutes.

At full charge it wouldn't start today until I changed-out the spark control module (SCM) with an old used one I had lying around. The engine cranked and ran for just a few moments and then not again after that.

Once I fiigure-out which wire is which and for what, I plan to run static checks on the SCM and the Engine Control Computer harnesses and look for voltage drops of greater than 1-volt.

Again, thanks for all of your insight and input.

Guy
 

Last edited by the_tow_guy; 04-22-08 at 04:46 AM. Reason: Not necessary to quote entire previous post.
  #5  
Old 04-21-08, 07:22 PM
Banned. Rule And/Or Policy Violation
Join Date: May 2007
Location: Wisconsin
Posts: 8,629
And to think that back in the 70's this old lady with a caddy in Sarasota got rid of it because it would not start. I was curious as to how long all this stuff took you, on your old car. How many miles she got on her.
 
  #6  
Old 04-21-08, 07:42 PM
ukrkoz's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Jan 2008
Posts: 222
1. get - or maybe it's already in it - your car into a pitch black area. or wait till night. pop hood open, and try starting. you should see sparks leaking down off bad plug wire onto the engine. PLAASSSMMMAA
2. i have just read that you can spray slightly soapy water on wires and they'll start sparking on the bad one.
ain't gonna start if there's no spark, right? it just sounds like something's draining your electricity, and very fast, so it shuts itself down. no juice - no spark/no fuel pump. no nothing.

you must have some real good memories related to this vehicle. i'd have donated it to charity/write off on taxes. you are VERY patient person. the way it goes with gas prices lately, you can get a truck with less than 100K miles on it for peanuts.

good luck!!
 
  #7  
Old 04-21-08, 09:23 PM
Member
Thread Starter
Join Date: Apr 2008
Posts: 9
Originally Posted by ecman51` View Post
And to think that back in the 70's this old lady with a caddy in Sarasota got rid of it because it would not start. I was curious as to how long all this stuff took you, on your old car. How many miles she got on her.
Not quite sure what you're asking here, but I've put 2-sets of timing gear/chain and one rebuilt tansmission in this 2nd-owner car and right now the odometer is reading just past 250,000 miles. It gets 2 oz. of Marvel Mystery [email protected] of gasoline and 1 qt of MMO between oil [email protected],000 miles. I've been taking my time on the Bonnie, no hurry much, just want to understand why it's doing what it is doing..It's a great little work car..weathers construction sites and following behind highway traveling rock-haulers pretty well.

I'm curious..Back in the 70's did you buy the Caddy from that little old lady?
 
  #8  
Old 04-21-08, 09:41 PM
Member
Thread Starter
Join Date: Apr 2008
Posts: 9
Don't know about the soap thingy, but I have tried it in the pitch black of night and no spark. That's how I checked it for my spark test, in the blackness of night. And yes, low voltage no nothing becayse the sensors default everything into "no-run" to protect the computer from losing energy. That's why I checked the charging system (alternator) and still suspect the charging system is the culprit. Just turning it over during initial cranking drains 234 amps off the battery in no time, that's why this car has a 120 amp alternator, to cover cold cranking power-up of everythinh, sensord, fuel pump, injectors, computer and emmission control. That alternator needs real-time amps for
staring this car.

And patient? Me? haha. I like the 33 mpg I get out of this car when I keep new timing chains & gears on it, They will be happy memories now that gasoline is at $4.++ per gallon. , since most of my work, on average, is at 51 miles 1-way.
 

Last edited by the_tow_guy; 04-22-08 at 04:47 AM. Reason: Not necessary to quote entire previous post; please use the "Reply" button instead.
  #9  
Old 04-22-08, 03:19 PM
Banned. Rule And/Or Policy Violation
Join Date: May 2007
Location: Wisconsin
Posts: 8,629
Originally Posted by GuyMike View Post
I'm curious..Back in the 70's did you buy the Caddy from that little old lady?
No. I heard about it at the garage I helped out at sometimes on weekends, for sport, when I was off-duty from hi-rise construction. I was too late. All the car needed was a new battery.
 
  #10  
Old 04-22-08, 03:36 PM
Banned. Rule And/Or Policy Violation
Join Date: May 2007
Location: Wisconsin
Posts: 8,629
Originally Posted by GuyMike View Post
I was headed out to work one morning last week and my Bonnie lost power. Since then, using process of elimination, I have managed to replace parts on this car without any improvements in its performance..iow..it is still not startiing.

So, this car will start, but stops after a couple of seconds and will not restart. In tryiing to nurse it home, (I ended up calling AAA), I found that I could disconnect, remove, remount and reconnect the ignition coil for cylinder #1 and the car would start and stay running for a mile, or two, before shutting down again.
Per your last 4 lines I am quoting you on: Huh. How in the world could disconnecting, then reconnecting a coil wire help? Unless it breaks the flow from say the computer, and then it resets. But - if the key is off at the time, how would the computer know you disconnected and reconnected the wire? Have you ruled out a coincidence, that it would have started by itself after that same down-time frame?

You are handling, as a common denominator, the wire. So could that wire be bad? I can't recall now if you said you changed that out.
 
  #11  
Old 04-22-08, 06:47 PM
Member
Thread Starter
Join Date: Apr 2008
Posts: 9
Originally Posted by ecman51` View Post
Per your last 4 lines I am quoting you on: Huh. How in the world could disconnecting, then reconnecting a coil wire help? Unless it breaks the flow from say the computer, and then it resets. But - if the key is off at the time, how would the computer know you disconnected and reconnected the wire? Have you ruled out a coincidence, that it would have started by itself after that same down-time frame?

You are handling, as a common denominator, the wire. So could that wire be bad? I can't recall now if you said you changed that out.
I'm pretty sure it was coincidence now, but at the time I was perplexed by it..I think the amount of time it took to change-out the coil and reconnect the wires caused the computer to "sense" a different amperage, a false reading, from the coil and therefore determined that the engine should start ? I don't know. I'm past that point of diagnosis now anyway and will be concentrating on finding the real cause of no spark. If anybody has an accurate, concise source for the ignition wiring harnesses, short of buying from AllData, let me know. If I have to purchase it, though, I will.
 
  #12  
Old 05-08-08, 08:59 AM
crazycory22's Avatar
Member
Join Date: Jul 2005
Location: USA
Posts: 375
It almost sounds as if an Injector could be bad. Had one go bad on a car that I was working on when I worked at a local garage, and it caused those exact same symptoms. I would check each injector. It can eventually short the injector drive out completely in the ECM then you'd have to replace the ECM. Just my .02
 
Reply

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 Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes
'