Getting an 89 gmc suburban from a buddy. Need some help

[1979C20]

So my buddy picked up this suburban a few months back for 12. He had to have the trans rebuilt and it cost him 800. He told me a couple days ago that he was thinking about selling it to pick a part. They offered him 650. I told him id buy it before he did that. Its got a 4 or 6 inch lift with 35s. Tbi 350, th400 and I think an no203. Corp 14bolt rear and a d44 or 12 bolt front. Its having some issues though. He said it has a check engine light (OBD1) but he said that when he tried to read the code it said connect plug. Ao it seems to have a break somewhere between the ecm and the pkug. He said it pretty much just dumps fuel into the engine and eventually bogs out. He replaced the tps, map, and 02 sensors already. Im going to make payments on it and pick it up for 1300. Any ideas on reading the code? He said he couldnt use the junper technique either.

[Captkaos]

I would use the jumper code regardless and check it.  If it is throwing codes this should work.

No 12bolt front, didn't exist, and 89 burb is going to have a 10 bolt unless someone swapped it

[1979C20]

Forgot to mention, its a 2500. And I meant 10 bolt or dana 44. Its a big 8 lug beast. It seams as though the obd1 plug isnt connected to the ecm, so using the jumper technique on tghe plug ended with no results.

[jsetrum]

Should be a np208 transfer case. Could be either a 10.5 14 bolt full floater or a 9.5 14 bolt semi-floater. Someone didnt convert that thing to a carbeurated engine did they? Might explain the communication issue between the ECM and obd1 port. Sounds like a pretty sweet deal but I hope your buddy wasn't going to dump it to the wrecker for 650 and then upped the price because you wanted the whole thing.

[DnStClr]

I don't know if it's true, but I read on thirdgen.org that a bad cig lighter can cause the ecm to stop communicating to the ALDL.
The first code seen should be 12. it flashes 3 times. It indicates that there is a communication from the ecm to the ALDL. Actually, I think it's confirmation that the ecm is sending 5 volts to one of the terminals at the ALDL and the ground is good..
From what you're posting, assuming you've checked the elect. plugs for tightness, it looks like the ecm is bad.

[1979C20]

No, he said he wanted to junk it but pick a part offered him 650. He would have pulled the transmission out of it and sold it seperately. He was going to take 1000 but wasnt aure if he really wabted to get rid of it, so I upped it to 1300 to seal the deal. Im pretty sure its a full float, havent looked at it yet. And its the stock tbi motor. Can I jump the wires directly at the ecm to find the code? A couple of guys at work recommended  the fuel pressure regulator.

[Captkaos]

Pretty much nothing after 1976 had the D44 front the factory.  10bolt fronts was used on everything after that  up to 3/4T.

I just ripped out all of the TBI wiring on my R10, the Cigarette lighter has nothing to do with the ALDL output..  I would trace the wires back up to the ECM, and see if they pulled it loose.

[1979C20]

Alright, made a little progress. Jump started it and test drove it. Light acceleration is fine. But qhen you "kick" the throttle, the engine cuts out for a second and then revs up. It does that an any rpm, but only when you quickly press the trottle. I watches the injectors spray, they have a nice cone ahaped mist, and when you press the throttle quickly the spray gets stronger. The fuel never cuts out. I checked the number one spark plug and its rich. i cannot get a code from it though. When I jumpped terminal a and b, the top right I the SES light stays solid. But we were sitting there for a bit with the key on and all of the sudden from the area where the ecm is it started making a typewriter sound and the check engine light flashed with it. Then, I tapped the bottom of tge ecm and tge check engine light started flashing. So im thinking the ecm may be bad. Its only 60 bucks my price though.

[1979C20]

Okay, I made some more progress. There is someyhing that is badly drawing on the battery, so I had to junp atart it again. I had the jumper cables hooked to my truck for 30 minutes beforr it would start. But, while the battery was charging, I was able to get engine codes. i followed the wires back to the ecm and jumped them there. Here are the codes I got.

12 system normal
13 o2 sensor
14 coolant temp sensor
32 egr valve.

But, then the check.engine light started flickering and turned off. Then the next time I got a bunch of codes, and they would only flash 1 time, instead of 3 for each. And then I found where the "typewriter" noise was coming from. There are 2 relays on the firewall at like 11 o clock looking at the distributor. The left one clicked like crazy. And the check.engine.light flashes with the clicks.

[jt1200r]

i know the relay to the right is the fuel pump relay.switch them and see what happens

[1979C20]

O guess the relay on the left is the blend door relay and it clicks all the time. Im going to have my buddy warranty out the o2 sensor and im going to buy a new coil, spark plugs, and a new ecm and see if that works.

[dahoyle]

Do not buy a bunch of parts to "see if it works"

Troubleshoot the system as it sits,  and if something points to a fault,  then replace the part.

The first thing you need to do is get the electrical issue you are describing,  SORTED OUT.  If there is really a problem with the charging system,  then you are obviously going to have issues with a system that relies entirely on electricity to work correctly.

Get the engine running(jump it if needed),  let it charge for a while,  and then check voltages in  the cab.  If you have 13-14 volts on your fuses,  then it has enough voltage that you can effectively rule it out as a source of the problem.  That doesn't mean there isn't a problem,  but it should mean that it is working well enough that it shouldn't effect the TBI functions.

Identify what relay is buzzing.  Check it out.  If there is a weak voltage to the relay coil,  then it will buzz like that.  If it is the fuel pump relay,  then obviously,  you are not getting enough fuel to the injectors.

It is foolish to throw a bunch of money at parts,  when you already have a strong indication of where your problem lies.  The ECM is probably fine.  The EGR is easily tested,  but it is controlled by a solenoid which is very similar in operation to,  you guessed it, a relay.


I see nothing in any of your descriptions which would point to any particular problem except an electrical one.    Fix that first,  or you will be pitching money down the toilet.

As for swapping parts.....Go to a salvage yard and get a bunch of sensors,  if you feel the need to shotgun everything.  heck I keep spares in my console.  On the other hand,  you can test almost all of them with nothing more complicated than a digital voltmeter. 

If you really want to learn the nuts and bolts of the TBI system,  then buy an ALDL\USB cable,  and do some data logging.  It will tell you exactly what each sensor is doing. 

[1979C20]

Well, im not going to be throwing much money at it. It NEEDs plugs. It could use a new coil because i dont know how old the current one is. The egr is only 25 bucks and the ecm is 60. All of thebother parts I listed are going to be warrantied. As they have all been replaced within the last year. The ALDL-USB sounds like a neat idea. How would I go about viewing the information through that cable? Some form of software I presume?

[DnStClr]

If you get the ALDL/USB cable, make sure it's the 12 pin cable and not 16 pin.
http://www.aldlcable.com/sc/details.asp?item=aldlobd1u

[1979C20]

Man thats pricey. I wonder if I can make one.