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73-87 Chevy _ GMC Trucks => 73-87 Chevy & GMC Trucks => Topic started by: 1979C20 on July 17, 2012, 01:44:51 am
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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.
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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
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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i know the relay to the right is the fuel pump relay.switch them and see what happens
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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.
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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.
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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?
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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 (http://www.aldlcable.com/sc/details.asp?item=aldlobd1u)
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Man thats pricey. I wonder if I can make one.
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you can, but the you need to figure out the USB interface, never went that far.... http://winaldl.joby.se/aldlcable.htm
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Well I did some research, you have to go from the aldl to an rs232 circuit and then into usb. The usb cable for a nokia ca-45 is an rs232 circuit to usb, so I ordered one of those cables from ebay and will make my cable for about 10 bucks. Ill let you guys know when I get it all put together and get some data. Ill probably be using the datalogging software TunerproRT, as ive heard its a good program for it from my research.
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I use WinALDL, it was free.
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Ooooooo. My favirite "F" word. Ill try that out.
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Link if you need it: http://winaldl.joby.se/
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Oooookay....... Im just going to roll with it. I just gave my buddy the first hundred and he gave me the keys. Said I could take it to my house to work on it. he charged the battery up and I had my roomate take me to it. It started up fine and idled rough. Still had the check engine light. I drove it 1\2 mile and it started running great, but seemed like it wasnt shifting. i stopped at my work and tested the alternator and battery. Battery was good but needed charging. The voltage regulator failed in the alt. When I started the truck up the check engine light was off. It drove like a dream. I got home and pulled the alternator off. Took it to my work and bench tested it. It passed with flying colors. So, I got a new serpentine belt, some locktite fof my sloppy tilt wheel, and an alternator pigtail just in case. The old belt was very loose, cracked, and glossy. So, im thinking it was slipping on the alternator. After I got it all put back together, i started it and disconnected the battery. And it stayed running. So I drove it about 10 miles and so far so good. Im just going to take it as it is and not ask questions. The only thing I can assume, low voltage.
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Well, having some more problems with it. The check engine light came back on. But it will randomly turn back off. When the check engine light is on, it runs rich, idles rough, and has little power. When the light is off it idles smooth, seems like the A/F is correct, and has awesome power. But, the check engine light was off, i started it and idled. I popped the hood and watched the injectors. it randomly sprayed a ton of fuel and killed the engine after running for like 45 seconds. Then the check engine light came back on and flickered like mad. When the light is flickering, the IAC is making a slight, fast ticking noise. and I can feel the tick. The relays on the firewall also click on and off with the check engine light. While the truck is running, I can unplug the brand new TPS and IAC with no change in idle. Any ideas.
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ECM?
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Thats what I'm starting to think, but when I unplug the MAP sensor connector the truck dies out. I did find one burnt wire from the O2 sensor, which I repaired. But, When the check engine light is flickering, I can tap the ECM with my flashlight and the light will go solid. So, it seems like the ECM the culprit. Is it as easy as, unplug the 2 main harnesses, unbolt the bolt to the strap and pull the ECM out? Then swap the prom and reverse process for the new one? I unplugged the main harnesses and felt the prongs on the ECM, none of them are sticking out. I'll probably go into work a bit early tomorrow and pull an ECM off the shelf and slap it in there to see if it works. If it does, then I'll buy it and be happy. If not, then I don't know whats next.
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Have you tried running an extra ground to the ecm just to see if that solves it? Just a long shot guess. Installing an ecm and then putting it back on the shelf sounds like a no-no!
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I already asked my manager. He said "you break it, you buy it". Where would I run the extra ground? To the case of the ECM or into the harness? Where is the original ground, for that fact?
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Well, I have determined the ECM to be in fact - bad. When using the GM approved "tap" test, the ECM failed the test. I started it up, no check engine light and running awesome. Tapped the bottom of the ECM and the truck stumbled and died. Loose/ bad circuitry has been the culprit. So, ill probably be getting a new ECM tomorrow. With a life time warranty, hopefully.
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Alright, got the new ECM in and all is well. Runs awesome now!
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Good deal. Now, let's see some pics of this beast!
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I'll probably borrow my gf's phone tomorrow. My nice phone broke so I'm using an old blueberry until I get paid so I can do an insurance claim on the phone. I'll hopefully take pics tomorrow if its not dark when I get home from work. I'll start a new post in the members rides section. Hopefully if anyone else has similar problems as me they can find this post and perform the "tap" test.
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An 89 should have a np241 transfer case if i'm not mistaken .
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You're correct. I wasnt sure if it was the Original trans or not. But I crawled under and checked it out. It is the np241