1996 Yukon HELP before I burn it~!

[treepete]

holy crap... so they put it on YOU to figure out what you wanna do>?

Christ.

 

[TahoeGoBoom]

you mean they havent replaced the pump yet?????
sounds like you need to get that truck outta there. Hopefully they'll give you a hefty bit of compensation. good luck.

 

[shawnkfl]

i'll tell you what i think your problem is. i've done this before (welding on a vehicle). if you weld, and don't disconnect the ecm/pcm, it's fried. the circuits in them are very minute and welding current will fry them. sure, sometimes you can get away with it, but a mig or arc welder will most likely fry them. i would bet, if you replace the ecm with another one, it will fire right up. they're like $30.00 at a scrap yard. i'd do that before throwing a few grand in it.

better yet, if the mechanic is competent, have them hook up a reader and see if it even reads the prom. that will tell you even if no codes are showing (which they won't)

 

[96ProCompTahoe]

we welded on several vehicles with MIG's back in auto body class and never fried a computer. you unhook the ground wire on the battery. if its only getting 14PSI of fuel pressure, that is most likely your problem.

i take it the starter tries to crank it over and it won't fire?

 

[shawnkfl]

unhooking the ground wire from the battery is good when you work on anything electrical. but when welding, you hook a ground back up and ground the whole vehicle. there is then welding current through the whole thing while welding. sometimes, you'll get away with it, but it only takes once to fry an ecm, and you won't do it again.

 

[95TwinTT]

i'll tell you what i think your problem is. i've done this before (welding on a vehicle). if you weld, and don't disconnect the ecm/pcm, it's fried. the circuits in them are very minute and welding current will fry them. sure, sometimes you can get away with it, but a mig or arc welder will most likely fry them. i would bet, if you replace the ecm with another one, it will fire right up. they're like $30.00 at a scrap yard. i'd do that before throwing a few grand in it.

better yet, if the mechanic is competent, have them hook up a reader and see if it even reads the prom. that will tell you even if no codes are showing (which they won't)

What he said!

The ECM's in vehicles today are not protected by just disconecting the ground cable from the battery. In many cases, the individual sensors have their own ground. Plus the computers have gone to swiching grounds on active circuits to save running a lot of current through the ECM. In other words, the ECM can be fried through the pos cable of the battery.

The new "switching power supply" welders have the ability to send RF cursing through all the circuits of the car. It only takes a few milliamps to blow a 5 volt chip if the current is coming from the wrong direction.

The safe bet is to unhook the ECM itself B-4 welding.

The fuel pump cannot function without the proper commands from the ECM and it will not give the correct commands if any of the sensor circuits are messed up that advise said ECM.

If nothing else, they should have a "test" ECM in the shop they can connect to your truck and find out in a few minutes if that is the problem.

There are a lot of mechanics working at garages these days that are still not up to speed on electronics. It's too bad because it cost the customer a lot because of their lack of knowledge.

Any dealer with the normal compliment of tools should have diagnosed this problem within minutes.

It's hard to totally understand what the dealer is capable of from here, but it does not sound like they have gone about this repair in a logical manner.

I understand the frustration, but I also think yelling a them will not help. It's like talking louder to someone who does not understand english.

 

[41racing]

Your truck needs 3 things to run, fuel spark, and compression and you need them at the right time. If it's missing one of them it's definitely not going to run. I doubt compression is your issue. What is the fuel pressure after they replaced the fuel pump? If it's not at least 55psi it's never gonna start. If you have the correct pressure the fuel pump is fine. Next have them check for spark, it's very simple to do and any dealer should be able to do it. If they can't they shouldn't be in business. I personally think you will find that you have no spark, although it is possible that your injectors might not be firing. Why don't you have them check all the fuses. I think you might have fried something with the welding. On a side note at our shop we have done welding on a lot of vehicles and never removed a computer, and never fried one. You just need to have a very clean spot very close to what you're welding for your ground cable. Keep up up to date on what's going on.

 

[41racing]

What he said!


There are a lot of mechanics working at garages these days that are still not up to speed on electronics. It's too bad because it cost the customer a lot because of their lack of knowledge.

It's sad, but true. Luckily for the rest of us that are up to date these idiots won't be in business for very much longer. When I go to classes for the new stuff I almost always here some old timer say "We didn't need these stupid computers in the old days", and "All this electronic stuff is garbage, just give me a carburetor." I just shake my head and say "yeah, but in the old days your car was completely wore out before 100,000 miles, and when it's -30 degrees outside you couldn't push a button from your couch and start your car."

 

[tracey-canada]

Hi guys,

really, I appreciate all the help!!!

These are the questions I'm going to ask them today:

Check the Fuse, is the fuse good?
Is there any burnt or bad connectors @ the tank connector?
check the ECM/PCM - do you have a test ECM in the shop you can hook up to test with?

any other suggestion?

 

[treepete]

after all of this mess I sincerely hope they can get you back on the road.

This may be noobish electrical question, but why would they put in a diode to protect the ECM from reverse current?

 

[tracey-canada]

Resolved Finally!!!

Hi Guys,
Well - first, thanks for ALL your help - I owe each of you a great big hug!

My truck is fixed!!!

the service manager called this morning. the truck is starting, idling fine getting the right PSI for fuel.

Apparently, GM changed out the part # for the fuel module last year. At the same time, they changed the wiring plug and upgraded the harness for this part. The directions however were never updated. So when the dealer recieved the part, they followed the directions - which were wrong.
They did the same steps on the 2nd pump.

Last night, they called some GM hotline and determined that 2 wires needed to be switched out (one in one hole, one into the other) and VOILA my truck started!!!

They aren't charging me either since it was originally all under warranty as i had the pump changed out @ the dealer last year (Jan 18th so this crapped out just under the warranty window!!)

I think he's a bit ticked still however at me being right that it's the pump.....when I asked what i owed he said
I'm not going to charge you, I just want your truck out of my shop.:shy: oh well, I'll be sure to take it to the Chevy dealer in town now if need be vs. the GM dealer itself.


Thank you! Thank you! thank you for all your advice & help - i will be SURE to come here first for all my issues!!!

Tracey

 

[tracey-canada]

you are not going to believe this.

i just picked up my truck.

NOW when i press on my brake pedal, my fuel guage is all wonky and goes up and down into overfull! WTF?!

What does that mean?!!!

I AM NOT TAKING it back to them.

 

[95TwinTT]

you are not going to believe this.

i just picked up my truck.

NOW when i press on my brake pedal, my fuel guage is all wonky and goes up and down into overfull! WTF?!

What does that mean?!!!

I AM NOT TAKING it back to them.

Do the turn signals in either direction cause the fuel guage to move when the brakes are not on?

 

[95TwinTT]

This may be noobish electrical question, but why would they put in a diode to protect the ECM from reverse current?

The short answer is, diode's have a forward voltage loss. The greater the ampacity of the diode, the greater the loss.

 

[treepete]

Thanks Del. I meant to say "wouldnt" in my question, but you answered it anyway

OMG. I would SOOO CALL THE OTHER DEALERSHIP. explain the situation.
it sounds like that place is just full of hacks or something.

My needle wiggles really fast, but it doesnt jump around. whatever they did... you should take it somewhere else.
Im just speechless when I hear about customer service issues like this.