New 2 Door Owner, ABS, No start, Oh my.

[Oelyles]

Greetings to all. My wife is the owner of a '98 2 door Tahoe. Trying to sort things out on the vehicle. It ran fine, needing some TLC here and there. I deleted ABS for starters. Couldn't get a good pedal and shop confirmed ABS unit was bad. Here's the situation. After the delete I can't get the truck to start. No starting issues prior to this except for a parasitic drain I hadn't figured out before. As long as there was good battery power it started fine.

My question is this. Are there some wiring issues I may have caused removing the ABS module. I just unplugged everything from the ABS module when I removed it. Now it just cranks as if it isn't getting fuel. Gonna check relay today but wanted to post question to come back for ideas.

Also, fuel guage is now showing on full and I know it's not. Read correctly prior to this.

Thanks in advance.

 

[exp500]

Take a look at the wiring diagram in the Factory service manual. You disconnected a few things you need!
Also likely ABS wasn't bad, just needed a ABS brake bleed.

 

[Oelyles]

Shop tried to perform ABS bleed. That's who told me the unit was bad. So basically I should leave the module connected for wiring purposes? Been looking at wiring diagrams but haven't found one specifically for ABS module wiring.

 

[YukonGTmaster]

The brake pedals on our trucks are notoriously “soft” with lots of travel.

 

[OR VietVet]

If you know it started before the module removal, then like @exp500 said, put it back and see if starts after reinserting the wiring. Then if you really want the module gone, you need to get a wiring diagram for that and see what is related to the no start and try to wire around it, if you must. IMO, I would take to another shop for diagnostics if restarts. If still no start after reinstall module, start the basics. Does it have spark, fuel pressure and cranks over the way it should.

 

[exp500]

Post the pages you are using so we can walk along on your journey. Most show the Pin #,connectors and color codes. Sometimes to follow all the way there can be 6 or more pages.
We are here to help.

 

[east302]

Shop tried to perform ABS bleed. That's who told me the unit was bad. So basically I should leave the module connected for wiring purposes? Been looking at wiring diagrams but haven't found one specifically for ABS module wiring.

It’ll be referred to as the EBCM (electronic brake control module). Here’s one for a 98. The only thing that may mean something is its connection to the EVO/Passlock module.

The above is from alldatadiy which copied it straight from the GM manual. You can download PDFs of the 98 manual volumes here:

88-98 Service Manuals

Over the years I have collected a bunch of GM service literature. Links to PDF Scans of service and STG manuals and a links to the Parts manuals. You'll need the FREE Adobe Acrobat reader to open these files. Get it directly from Adobe here {http://get.adobe.com/reader/} If you're not...

www.gmt400.com

 

[Eman85]

I doubt your ABS was a cause of low brakes. These OBS trucks had notoriously low pedals and the only fix I've found is use a NBS MC. You'd be amazed at the differece.

 

[JackFox]

As a technician, here is what I would do:

pull fuel pump relay out. Diagram is on the side of the relay. Jump the female connectors that the relay goes into, than connect 12V to the load (the pump in this case) you should see a spark as you connect and disconnect it. That is called a capacitive spark. Let's you know current is moving. You'll get it disconnecting as well. It's because air continues to conduct the electricity until the gap is too big. SPARK! You should hear the pump as well. I do this and if I hear the pump, I start it. If it starts, the I have nailed down the AREA the fault is in. The fuel pum circuit! Last time I dealt with this was weeks ago. Finished rebuilding a trans. No start after installing. No spark, no pump noise. resistance from relay load side (pin 87) to ground is out of limits (open circuit or more than 10 MEGAohms resistance). Tested for voltage with relay out and pin in place to connect 30 to 87. Had voltage all the way to about 3 inches of the rear connector. Took off the wiring corrugation protector tube, had some tape. Inside tape, bulging wire. Inside bulge, GREEN! Replaced 6 inch section of wire, and put silicone over the 5 differect wire spots I stabbed. Which is what obviously led to that wire getting corrosion in it. Also.... IT HAD NOTHING TO DO WITH THE TRANNY JOB LOL!!!! Hate that crap. Brother never had a fuel pump problem. Even when it was barely running off a single strand. But I work on it and BOOM! no start.

 

[Oelyles]

I doubt your ABS was a cause of low brakes. These OBS trucks had notoriously low pedals and the only fix I've found is use a NBS MC. You'd be amazed at the differece.

In my research I came across this and put the NBS master in. Same result. Only after deleting ABS I got a good pedal. But now no start. So that's the only thing that could be causing it. Only removed module for room to work running new brake lines. Gonna reinstall and see what happens. Broke one pin removing a connector. Hope its not needed. Gonna try and jump the relay as well. Wiring diagrams make my brain bleed so my work is cut out for me.

Thanks for the replies and ideas.

 

[exp500]

Brake hardlines bypassing ABS sounds like a reasonable solution to keep the EBCM plugged in till you can replace missing ABS. Although problem could well be EBCM to start with. A visit to Upullit might be time/money well spent as well as having unmodified brakes.

 

[Oelyles]

Got it started today. Thing is, I put in a new fuel pump relay to rule that out. Fired right up. So I believe that was the culprit because I disconnected the wiring for the ABS module again to make sure that wasn't it and it starts fine without the wiring connected to the module. I wonder if that relay could cause a parasitic drain if bad and on its way out because I was dealing with that issue as well?

 

[exp500]

Oil pressure switch always hot. Powers thru relay so check or replace oil pressure sender switch if parasitic drain.

 

[Oelyles]

Will check that. Thanks