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89 GMC truck problems

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stevetx

10-09-2004 09:24:54

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My 89 Gmc truck won' start. The other morning I was going to work and when I stopped at a red light it just died. I rolled it to the curb. I finally towed it home that afternnon since I wasn't far from my house. I don't have any fire at the plugs and no gas pumping into the throttle body. I can't hear the fuel pump running ether when I turn the switch over. I thaught it was the computer so I ordered a new one from Napa. They switched out the chips in the computer and I brought it home and plgged ti up but it still won't start. Checked the mudule under the rotor and it checked O.K.. Any suggestions as to what else I need to check or replace? Thanks for your help.

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GEORGIA BEEF FARMER

10-14-2004 16:43:43

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Re: 89 GMC truck problems in reply to stevetx, 10-09-2004 09:24:54

IM SORRY BUT EVREY ONRE WHO OWNS A gm product has a problem buy a ford ha ha ha

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Charles (in GA)

10-09-2004 15:38:00

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In the future, don't forget the fuel pump shut off in reply to stevetx, 10-09-2004 09:24:54

I see you fixed it, but don't forget, most (possibly all I hope) modern fuel injection vehicles have a impact safety switch, designed to shut off the fuel pump in an impact. Sometimes a auto gets bumped in a parking lot, or hits a large pothole, or for whatever reason, the little steel ball drops off the magnets in the switch and the contact breaks and the pump quits.

It ain't gonna start till you reset the switch. Read the owners manual to find out where it is. Most Ford autos have it in the trunk, my Ranger its above the passengers feet.

Hope this might help someone in the future.

Charles

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J C-IL

10-25-2004 01:29:31

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Re: In the future, don't forget the fuel pump shut in reply to Charles (in GA), 10-09-2004 15:38:00

This truck used an oil pressure sending unit by the distributer to turn off the fuel pump. BTDT ;)

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Bob

10-09-2004 17:49:57

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Re: In the future, don't forget the fuel pump shut in reply to Charles (in GA), 10-09-2004 15:38:00

GM vehicles of this age, fortunately, don't have the shutoff like the Dorf's.

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Kendall

10-09-2004 10:51:20

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Re: 89 GMC truck problems in reply to stevetx, 10-09-2004 09:24:54

Go to the link below and about half way down the page there is a link to troubleshooting. There you will find how to jumper 2 pins on the diag connector, turn ingition to "on" position and read the error codes displayed by the number of blinks from the "check engine" light. My '88 suburban came up with "lean" error code. Turned out to be the fuel pump. Couldnt pump enough pressure to get past an idle. Hopefully, you'll just have a malfuncting sensor somewhere. The computer doesn't sense fuel pressure so you will have to figure out how to test it. The fuel filter is under the truck, right side about half way back. Might be a good place to test pressure since it's screwed in inline. May as well replace it while its out. Auto Zone will give you a free "trouble code reader key" Looks like a key and the end has 2 prongs that fit right into the diag connector. A wire will work but the slots are flat and thin so use a small wire. The first code should be 12 ( one flash, pause, two flashes. (repeat 3 times). This says the ECU is working. Next comes any stored codes, each repeated 3 times, then goes back to code 12 to let you know thats all. Once you figure out any codes, you're on the way to fixing your problem. By the way, a cool way to check the injectors is to hook your timing light to the center terminal on the distributor and aim it at the intake. You should see really nice cones of fuel spraying out. Weak or malshapened cones indicate injector problem (or in my case, feeble fule pressure). This will most likely generate a code 44, lean exhaust.

GM Throttle body web page

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Allan in NE

10-09-2004 13:26:14

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Re: 89 GMC truck problems in reply to Kendall, 10-09-2004 10:51:20

Hi Kendall,

Excuse me for saying so and I sure don't wanna sound out of line here nor do I want to contradict your statements, but your boy and his little web page are somewhat full of prunes.

Code 12 is not an indication that the ECM has �entered the diagnostic mode", nor does it in any way mean that all is well within that ECM itself, the prom, or any of the connecting circuitry.

A thrown code 12 merely indicates that the ECM is seeing the lack of a primary ignition signal (as compared to the 5 volt reference signal) at the distributor module, as one would most certainly expect to see with the key on and the engine not running.

Also, I notice he does not give any reference to hard codes vs soft codes in any way whatsoever.

No mention of Quad-driver function, reference signal voltages nor sine wave management, all of which leads me to suspect that this is nothing more than a young feller with a flat-bed scanner, an old Camero service manual and a lot of extra time on his hands.

Just an observation,

Allan

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Kendall

10-11-2004 18:24:41

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Re: 89 GMC truck problems in reply to Allan in NE, 10-09-2004 13:26:14

Allen, all I can say for sure is that these early electronic ignitions were much more basic than they are today. not nearly as many possible codes as on a new motor. I had a multitude of problems on my daughters '88 subruban and in each case, entering the diag mode, code 12 was the first code repeated 3 times, followed by stored codes (each repeated 3 times), and finishing up with code 12. As I hammered out each problem, I cleared the stored codes, and dove in again. Again, code 12, followed by stored codes, finishing up with code 12. After dang nearly every sensor was replaced( she burned up the motor, dang her hide!) and new fuel pump, all error codes went away, just code 12, meaning the computer is working, even if just not receiving a timing signal. I did a lot of internet searching before starting this project and all the web sites I came across said code 12 would be first, followed by stored codes, finishing up with code 12. I think the point here is that if you dont see code 12, you got a problem bigger then just a sensor.
Whew, that was a lot of typing. Anyway, the '88 'burb is cranking up and running fine now with a new motor and a shopping cart of new sensors.

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stevetx

10-09-2004 12:16:10

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Re: 89 GMC truck problems in reply to Kendall, 10-09-2004 10:51:20

Thanks Kendall. That is very useful infro. I'am going to print all of it out for the next time.

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Kendall

10-09-2004 11:00:23

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Re: 89 GMC truck problems in reply to Kendall, 10-09-2004 10:51:20

By the way, to clear error codes, remove the fuse labeled ECMB for 15 seconds.

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stevetx

10-09-2004 09:56:44

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Re: 89 GMC truck problems in reply to stevetx, 10-09-2004 09:24:54

I did check the rotor and it does turn and the fuel pump is working. Could it be the coil?

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Kendall

10-09-2004 10:56:55

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Re: 89 GMC truck problems in reply to stevetx, 10-09-2004 09:56:44

Did you check fule pump pressure, or just hear the pump running? See my other post. In my case, it was running, but no pressure. coil, - that would be a good thing to check.

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Ron in Nebr

10-09-2004 10:48:42

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Re: 89 GMC truck problems in reply to stevetx, 10-09-2004 09:56:44

Had this same problem on an 87 with TBI. Turned out to be the pickup coil in the distributor(down where points used to be on the old style dist.) The pickup coil sends a signal to tell the injectors when to pulse. Betcha that's the same problem you have. :)

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stevetx

10-09-2004 09:40:15

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Re: 89 GMC truck problems in reply to stevetx, 10-09-2004 09:24:54

I forgot to mention that I do have power to my radio, lights, and starter, etc.. It cranks over fine except that my battery is getting drained from all the cranking.

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Bob

10-09-2004 09:39:55

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Re: 89 GMC truck problems in reply to stevetx, 10-09-2004 09:24:54

First off, the fuel pump should run for about 3 seconds each time the key is cycled from the "OFF" to the "RUN" position. Have you listened carefully for this? Have you checked any and all fuses labelled "ECM" or "fuel pump"?

If it does not run, a bad fuel pump sounds likely, but you say you have no spark, either, so that sounds like a bad electrical connection, blown fusible link, or a bad ground affecting the ECM. (Broken ground wire?)

If the fuel pump DOES it's 3-second run when the key is turned on, but does not restart upon cranking the engine with the starter, and there is no spark, suspect the pickup coil, or the module in the distributor.

Verify that the distributor is actually turning when the engine is cranking, as a failed timing chain, or failed distributor drive pin will cause the distributor not to turn, and the computer won't realize you're cranking it, and there will be no spark, or fuel pump, and the injectors won't be pulsed.

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stevetx

10-09-2004 10:48:18

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Re: 89 GMC truck problems in reply to Bob, 10-09-2004 09:39:55

Thanks Bob. It was the module in the distributor. In all it cost me $130.00 to fix it but it could have been alot worse so I'am not complaining. Your information was very useful. Thanks again, Steve W

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Bob

10-09-2004 11:10:50

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Re: 89 GMC truck problems in reply to stevetx, 10-09-2004 10:48:18

I'm glad to hear you got it going! Often, when I encounter this, I replace the pickup coil along with the module. They fail, also, with age. The downside is, you've got to pull the distributor, and remove the drive gear, and pull the shaft!

A word of caution, if the module was "blown", be sure there is no missfire caused by a bad spark plug wire, as a bad plug wire can "kill" the module. Also, be sure the mounting surface for the module is clean, and use the heat-transfer grease provided with the new module.

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stevetx

10-09-2004 12:25:45

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Re: 89 GMC truck problems in reply to Bob, 10-09-2004 11:10:50

The module did come with a small tube of grease so I did like you said. The plug wires are only a few months old but I'am going to check them to make sure their still good. Thanks again for all the help.

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Kendall

10-09-2004 11:05:11

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Re: 89 GMC truck problems in reply to stevetx, 10-09-2004 10:48:18

Sounds like you found your problem a lot faster than I found mine! I hope all this info helps someone else some day.

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Ron in Nebr

10-09-2004 10:51:27

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Re: 89 GMC truck problems in reply to stevetx, 10-09-2004 10:48:18

Oops- I was typing my reply about the pickup coil when you were typing yours about the module. Come to think about it, when it happened to mine I replaced both the module and the pickup coil at the same time. Glad you got her fixed anyway!

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stevetx

10-09-2004 12:20:55

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Re: 89 GMC truck problems in reply to Ron in Nebr, 10-09-2004 10:51:27

Thanks Ron for the help. I'am going go ahead and replace the pickup coil too, but at least I got it running to today. Like I told my wife, it's cheaper to replace a few old parts now then break down somewhere down the road. Thanks again

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stevetx

10-09-2004 09:42:42

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Re: 89 GMC truck problems in reply to Bob, 10-09-2004 09:39:55

Thanks very much Bob. I'am going outside to check the timming chain. Thanks for the help

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