1991 Buick Century LOSS OF FUEL DELIVERY - DIES IN FLIGHT

Tiny
FORDDADDY
  • MEMBER
  • 1991 BUICK CENTURY
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 10,500 MILES
We have an intermittent engine failure, after warm-up. Car might run 15-20 minutes, then quit. When in the non-running state, we have pulled a plug wire and cranked to confirm spark, which was good and strong- jumped wide gap. We then purchased a fuel filter, which helped performance, but did not ultimately solve problem. We attached a fuel pressure guage to the fuel rail and observed a consistent 40 lbs with key on/engine off, and 35-42 with engine running. We left guage in place and ran until fail. At this time, fuel pressure was still evident on guage. We allowed the pressure to bleed down, somewhat, then turned the key on and it popped back up to 40, but would not start. After a longer rest/cooling (30 min or so) car starts up like nothing ever happened. What is the best way to determind the source of the fuel interruption (if that is the issue), or what else can I do to check this further. I could possibly rent a code reader if that would help.
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Thursday, July 23rd, 2009 AT 9:36 AM

22 Replies

Tiny
JDL
  • EXPERT
Hello, do you have an injector pulse, with the engine cranking? If the computer doesn't see an rpm signal, no injector pulse.

Your obd 1, so you should be able to check codes, yourself.


http://www.2carpros.com/forum/automotive_pictures/170934_aldl_20.jpg



To check codes use a jumper between the A & B terminals of the datalink connector, turn the key on, no crank, then the cel starts flashing, you count the flashes to get the codes.
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Thursday, July 23rd, 2009 AT 10:19 AM
Tiny
FORDDADDY
  • MEMBER
JDL - Thanks for quick reply. After getting codes, what is a good resource for reading the code I get?

Also, please explain a couple of your terms.

What is odb1?

I assume cel is check engine lite.

Where would I find the datalink connector.

I assume that I would have to read this code while car is in fail mode, or will it store past issues for replay?

Thanks!
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Thursday, July 23rd, 2009 AT 10:32 AM
Tiny
JDL
  • EXPERT
OBD is onboard diagnostics. With the driver door open, in a kneeling position, the datalink connector should be visible along the lower edge of dash. If you find any codes, you can post them here, somebody will tell you what they mean. You should be able to find codes at the autozone site. Register your vehicle, click on vehicle repair info, should be under emissions link.

You need to see if the computer is grounding the injector/s?
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Thursday, July 23rd, 2009 AT 11:27 AM
Tiny
FORDDADDY
  • MEMBER
So, per last question, does this need to be done in fail mode, or does it store failure codes from last several restarts?

Also, if no rpm signal, what would be next step?

Lastly, how many questions does $20 get me? :O)

Thanks.
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Thursday, July 23rd, 2009 AT 11:33 AM
Tiny
JDL
  • EXPERT
I'm not sure what you mean by fail mode? With diagnostics, I hook-up a scanner that shows live engine data. I can look at data, key on engine off, and cranking. I also check codes, just out of habit. It is possible there are some old codes.

With the injectors, you can unplug an injector, use a noid lite on the connector, crank the engine, see if the lite pulses, if it does, there is voltage and ground. It is possible to use an led testlite on the injector plug terminals.

If there is spark at the plugs, there is an rpm signal, but, if the computer doesn't see it, no injector pulse. There is probably a purple wire with white tracer, going from the ignition module to the computer, carries the rpm signal, no signal, no injector pulse. I have heard of faulty ignition modules causing this problem. I can't be positive from here.

You can ask as many questions as you want, there is no limit. You may reach the limit of my capabilities?
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Thursday, July 23rd, 2009 AT 12:31 PM
Tiny
FORDDADDY
  • MEMBER
By fail mode, I meant car won't run at that moment. I assume that would be when I read the codes, while the malfunction is present. Do you agree?

I assume the injector voltage is 12v or less, can a volt meter be used, or is the pulse so short to not register?

As for the purple/white wire, is the ignition module under the 3 coils on the engine, and the computer is inside maybe?

We will try not to make this your second career, but thanks for the knowledge.
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Thursday, July 23rd, 2009 AT 1:20 PM
Tiny
JDL
  • EXPERT


http://www.2carpros.com/forum/automotive_pictures/170934_buick_century_3.jpg



I'm not sure that is readable, I tried to do something different, my computer skills aren't very good.
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Thursday, July 23rd, 2009 AT 2:09 PM
Tiny
FORDDADDY
  • MEMBER
Barely, but I got it. A good way to answer, but very small text.

Is a noid lite easily procured?
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Thursday, July 23rd, 2009 AT 2:18 PM
Tiny
JDL
  • EXPERT
Yeah, I need to practice on that text stuff. The autoparts stores should have noid lites. If you have a regular test lite, that may work on the injector terminals, see if the lite pulses, engine cranking.
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Thursday, July 23rd, 2009 AT 2:35 PM
Tiny
FORDDADDY
  • MEMBER
Will get on this after work and see if we can get a pulse. What time zone are u?

Thanks.
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Thursday, July 23rd, 2009 AT 2:41 PM
Tiny
JDL
  • EXPERT
I'm central time zone, right now, it is 3:20 in the afternoon, here. I usually get on here about 9:oo, shut down about 3;00, my eyes get tired. If nobody else talks to you, I'll be back tomorrow, not sure what time, I've several errands to run. Usually with a donation, the moderators will talk to you, no you don't need to donate anymore.
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Thursday, July 23rd, 2009 AT 3:29 PM
Tiny
FORDDADDY
  • MEMBER
JDL, we did a code read, and saw 12 3 times, followed by a long wait (30-45 sec) and then it repeated. sat thru 3 repeats, but never got anything other than 12.

I understand that this means "system functional" but no errors.

Do I now drive till it fails and read again?

Thanks.

p.s. found this site for the codes.

http://www.2carpros.com/trouble_codes/obd2
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Friday, July 24th, 2009 AT 12:43 PM
Tiny
JDL
  • EXPERT
Hello, I misunderstood your question about the codes. You can check codes at any time, you don't have to wait for the vehicle to fail. If the check engine lite comes on going down the road, even if the vehicle still runs fine, there should be a code. If the lite doesn't come on, there probably aren't any codes, or just the code 12, which is normal. I always check for codes, just from habit.

Did you ever get a chance to check injector pulse. Use a digital multimeter between the two terminals for the injector plug engine cranking, or testlite. There are several ways to check for a pulse.
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Saturday, July 25th, 2009 AT 9:54 AM
Tiny
FORDDADDY
  • MEMBER
Still getting there on the pulse check, juggling my schedule with the kid's. Will try to go after that today.

We finally got to check for codes while the car was in a un-startable mode (fail mode), and still nothing but a 12, but the check engine lite has never come on during operation, per your latest comments

Thanks, and I'll let you know about the pulse check when I get it done.
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Saturday, July 25th, 2009 AT 1:49 PM
Tiny
FORDDADDY
  • MEMBER
Jdl, finally got back to the problem and have found the injector pulse is being interrupted when the car won't run. So, next would be to work back upsteam and find why. Your earlier message spoke of the purple/white wire from module to computer. Do I probe this with a 12v lite like I did the injector wire, or could this harm anything?

Thanks,
Forddaddy
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Friday, August 21st, 2009 AT 9:57 PM
Tiny
JDL
  • EXPERT
If you have a digital multimeter that has a tach--duty cycle or a dwell setting, any of thses settings should react to a dc pulse. I've never used a testlite on that circuit? You can take the connector loose for the purple/white wire, use a noid lite on the injector plug, turn the key on, you don't have to crank, with the testlite connected to positive battery post, tickle the terminal for the purple wire with white tracer, if the noid lite pulses, everything from the purple wire to injector plug is ok. If no pulse on the purple wire with white tracer, I suspect the ignition module.
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Saturday, August 22nd, 2009 AT 8:40 AM
Tiny
FORDDADDY
  • MEMBER
Well, maybe I didn't understand your instructions completely, but I explain my latest observations. We first tried the 12v test lite in the purple/white tr wire, and it would kill the engine when ever I grounded the lite with the probe touching the purple wire. I then tried a digital voltmeter (just set to DC voltage) on the wire and saw no voltage with key on, but after starting, got a steady 3.7vdc. WE then drove the car till it failed again and tested voltage on the purple wire at that point, but stil saw 3.7v during cranking, even though it wouldn't fire.

So, did I prove anything?

Or do I need to try to do what your last post said with the noid lite?
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Monday, August 24th, 2009 AT 2:10 AM
Tiny
JDL
  • EXPERT
It looks to me like you do have an rpm signal. My next test would be with the noid lite, while the problem is ongoing.
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Monday, August 24th, 2009 AT 7:15 AM
Tiny
FORDDADDY
  • MEMBER
I need a little further clarification about the noid lite test. I understand that the noid lite will be in the injector plug to show pulse, but your comment about using the test lite to "tickle the purple wire with the test lite connected to the battery" means that I'm putting a full 12v into a wire that usually carries about 3.7v. I checked with a voltmeter to find what voltage would come thru the test lite and it did not really drop any voltage, showing 12.3v after the lite. Is putting this voltage on the purple wire what you intended?

Thanks.
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Monday, August 24th, 2009 AT 2:26 PM
Tiny
JDL
  • EXPERT
Hi, I'm not sure how you did the testing? A digital volt meter will read the difference between point A and point B. If point A is 12.3 volts and point B is zero, the meter will read 12.3. All I can say, is I have done this before without any problems.
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Monday, August 24th, 2009 AT 2:47 PM

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