1987 Buick LeSabre Won't Start - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 09-24-2007, 11:23 PM   #1
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Default 1987 Buick LeSabre Won't Start

Hello. I'm Jerry and I'm a newbie here.

I am working on a 1987, 4-door, US-made, Front-Wheel Drive, Buick LeSabre Sedan, with a 3.8 Liter, Transversely Mounted, V-6 engine.
It has Sequential Fuel Injection and an Automatic Transaxle. The Odometer reading is 112617 miles.

I got the car from my cousin who has records of service on it from the time he bought it new. It has been well maintained.

While driving, it stalled at a red light. It was hard to restart, but started within thirty seconds. After driving about two miles, it stalled while I was braking for the next red light.
The second restart was much slower and it backfired a few times before restarting. I was able to drive it for about another mile when it stalled. I coasted to a stop. It would not restart, and hasn't since. It is in my driveway, now. There was a lot of backfiring, but the starter did turn the engine over. It did seem as though there wasn't any compression, after a few tries, because it seemed to crank over too fast, and the backfiring soon stopped. Now, it justs cranks over and over, but still will not start. After changing the fuel filter, I tried again. No luck.

Before disconnecting any battery cables or going any further, I plugged-in my SunPro code checker into the ALDL jack. It threw only a code 12 over and over and over.

So, I checked the spark by removing the wire from the spark plugs, one at a time, on the left bank---the side of the engine closest to the firewall---and grounding-out a 12-volt, simple, probe-type test light to the engine block. Using wooden clothespins to avoid shock, I placed the needle into the end of the spark plug boot and touched the metal contact while my neice cranked on the ignition switch. No fire.

I only checked only that one side of each coil. There are three coils plugged into the top of the ignition module. I figure that all three of the coils wouldn't go south at the same time, and that if one side was good, the other should be, as well. So I disconnected the negative battery cable and removed the coils and the ignition module. I took it to the auto parts store and had them check it. They checked it three times. They tapped it on the counter to simulate vibrations while they checked it. It checked-out fine. They can't check coils. I would like to know the resistance values for these coils, however, in case I ever need to check one. I understand that the crank position sensor could be faulty, as could the cam position sensor, and the ECM. I need instruction on how to test these, and the proper resistance values that I should obtain with a multimeter.

I understand that the rubber part of the harmonic balancer could have deteriorated and caused damage to the crankshaft sensor, by wobbling and beating it up. I think that the harmonic balancer can be pulled through the fender well, but I'm not sure. I need as much info as possible before a further undertaking of this repair. I would like to know how to test the crank sensor.

Haynes and Chiltons manuals do not even approach usefulness for my purposes.

If anyone can help, or has any ideas or comments, please post them. I have no reliable transportation.

Thank you for reading this.

Jerry.
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Old 09-25-2007, 12:42 AM   #2
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Okay, I'm not going to be much help, but thought I'd point out that a code 12 isn't really a code, it is the "handshake protocol" that is telling you it is OK. Getting nothing but 12 means you aren't throwing a code.
You would know if the harmonic balancer had let go. It makes a clanking knocking sound that is sometimes mistaken for rod bearing failure. It is hard to miss, unless you play your radio way too loud. If it had let go, it is possible for it to damage the crank sensor, but I drove mine like that for a couple of hundred miles. I don't think there is a test for the crank sensor, it either works or it doesn't. I'm sure someone will correct me if I'm wrong there.
First make sure the plugs are tight on all the appropriate sensors and that their wiring harnesses are in good condition. That is usually a lot easier than swapping sensors. I have been having rodent problems in my Bonneville, they like to chew the wiring.

I don't agree with your spark testing method. There is a lot more than 12 volts coming off the end of a spark plug wire. I suspect all you did there is blow the bulb out of your test light. Try this, pull a spark plug and connect it back on the wire. Hold it against the engine block to ground it and watch the spark plug while someone tries cranking the starter. See if you have spark then.

Can you hear the fuel pump cycle when you first turn the key on? They are pretty quiet, so you may need to try this at night if the car is in a busy noisy area. If you haven't been messing with it for a while, stick in the key and turn it to "ON" without engaging the starter motor. You should hear the fuel pump hum at the rear of the car for a couple of seconds as it primes the fuel rail. You may even need to be outside the car underneath it to hear it, Buicks are pretty quiet. Even if you hear the pump, it may not be producing enough pressure for the injectors to operate properly. You may need to check your fuel pressure. Obviously, if you don't hear the pump, you will need to address that issue accordingly. Check the fuse first.
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Old 09-25-2007, 01:55 AM   #3
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Quote:
Originally Posted by bastard
I don't agree with your spark testing method. There is a lot more than 12 volts coming off the end of a spark plug wire. I suspect all you did there is blow the bulb out of your test light. Try this, pull a spark plug and connect it back on the wire. Hold it against the engine block to ground it and watch the spark plug while someone tries cranking the starter. See if you have spark then.
Well, I figured the same thing, but the test light still works. I was reluctant to try it, but a buddy of mine does it that way and he said that it works, and I thought I'd have to do it alone, so I tried it.
Yeah, I always stuck a flathead screwdriver in the boot and held it close to the block, but it was a bright day.
Quote:
Originally Posted by bastard
Can you hear the fuel pump cycle when you first turn the key on?
Yeah, I can hear it power on for a moment each time
Quote:
Originally Posted by bastard
Even if you hear the pump, it may not be producing enough pressure for the injectors to operate properly. You may need to check your fuel pressure.
Thanks.
I'll try that.
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Old 09-25-2007, 03:44 AM   #4
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If the CPS went out it wouldn't have thrown a code (99% of the time at least).

Since you're only getting a code 12, that means that most of your sensors are properly functioning (with exceptions).

The stalling sounds an awful lot like a bad CPS, but defiantly check for fuel pressure first as that sounds like it could be a good possibility as well (and much easier to diagnose).

If you're hearing the pump prime when you turn the key over then that only means that its not dead and that you've not blown a fuse. But... it could be really weak. The quick and dirty way to test it would be to prime the pump (turn the key over but don't try to start it) and then depress the schrader valve (looks like an overgrown air filler nipple on the fuel rail). If you just get a dribble of fuel then definitely look into fuel pressure.

If you do end up needing to replace the CPS, its fairly easy to do once you get the harmonic balancer bolt off. You can access this from the passenger side wheel well, but to break it loose you'll need either a large impact gun or a really long breaker bar. 86 and 87 motors were particularly easy to do in comparison to later versions at least.

You might consider replacing the timing chain, gear, damper, etc. while you've got the balancer off if its not been done already (a bit of a paint to be taking the balancer on a off). Should be regular maintenance every 100k miles or so anyway.

Tutorial here: http://www.lesabret.com/phpBB/viewtopic.php?t=5516 (Vin C very close to your Vin B (or is it 3?), other than part numbers of course).

If you ever need LeSabre specific information feel free to drop over at LeSabreT , otherwise they're nearly identical to Bonnies and theres a wealth of info here.
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Old 09-25-2007, 02:58 PM   #5
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Default spark

Do check for spark first by grounding a spare plug against the block first as mentioned above. If you have spark, procede to the fuel test.
If no spark, suspect the coils, ICM or crank sensor.
Measure resistance across the two terminals of each coil within the pack. They all should be close to each other. If one coil is much higher resistance its bad.
My guess is a bad crank sensor or dirty ICM connector.
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Old 09-26-2007, 07:55 PM   #6
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Default Thanx

Excellent tutorial, Alibi!
I really appreciate that info!
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Old 09-26-2007, 07:57 PM   #7
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Default Re: spark

Quote:
Originally Posted by SSEBONNE4EVA
My guess is a bad crank sensor or dirty ICM connector.
Thanks, SSEBONNE4EVA.
How do I check the crank sensor?
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Old 09-26-2007, 08:05 PM   #8
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Default Rocker arms working.

I had my niece look into the oil filler hole while I bumped the engine over a few times.
She reports that the rocker arms are moving up and down.
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Old 09-27-2007, 12:10 AM   #9
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try replacing the pcm (computer) from one at a junk yard for about $25

to all my knowledge my opinion is that if you are not getting any codes and the car is still not starting
9 times out of 10 its a faulty computer (pcm) or a bad wire harness somewhere..( take them all off and clean them with electrical cleaner then put them back..( do them one by one so you no where they go.

try this and get back to me...
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Old 09-27-2007, 02:13 AM   #10
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Testing a crank sensor without a scope supposedly can't be done. I think I might have done it once with only a multimeter, but I'm not sure how relevant my test really was. Let me find that thread...

http://www.bonnevilleclub.com/forum/...ic.php?t=82626

Take it with a grain of salt - it'* unproven theory. That said, it did point me in the right direction.

I'd check the easy things first though. Try another spark test, just to be sure. A spare plug (as mentioned above) works good. Another quick clue to look for is wet plugs. If you've been cranking and cranking with no spark, you should be good and flooded by now. If not, I'd suspect a fuel issue.

If you have no spark, and your ICM really is good, then I would lean toward the crank sensor. I don't know how accurate their testing of an ICM is though. If you could easily find a spare to swap in, I would try that, just to confirm.

A cam sensor won't cause a stall, so rule that out.

As mentioned, I would highly recommend testing the fuel pressure. The way it'* acting, my gut feeling is a fuel pressure issue.

Keep us updated, eh?
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