Multiple Issues

noelhoffman · September 4, 2008

I have a lot of issues, and I'll cover them one by one incase someone can help.

1. Brakes. I've seen multiple threads on this. Rear brakes have no fluid to them. Dropped at wheel cylinder no fluid; T on rear differential, no fluid; traced all the way to the bottom of the combination valve, no fluid from the bottom of the combination valve. I've read about a clip that can be used to bleed the combination valve to reset the rear part of the valve. Front brakes work fine, but the brake light is on, which I assume is due to the fault in the combination valve.

2. Starting issues. When cold it starts ok, acts somewhat like a dragging starter though or no cranking amps in battery. When you turn the key sometimes it seems like a really slow crank, and sometimes wont start. This issue becomes more common when the engine warms up, my guess is the solenoid or starter is getting warm and dragging. The battery was tested on an ARBST machine and cycled good even under load. Ideas?

3. Idle and power. The truck has a miss in it, and sometimes stalls out due to the miss, with the back brakes being inoperational, this is a very bad situation to get the truck stopped. Up hills it lacks power. The tailpipe blows black smoke drastically under a load such as a hill or hard acceleration. It burns about a quart of oil every 100miles. No sign of a class 3 leak(dripping or pooling oil in the garage). I can only assume it is burning the oil massively. Oil pressure seems to stay constant under load at around 60, off load around 45. Oil has been changed(black as night), air filter, and purolator oil filter. With the starter issues I think the miss could be due to fouled plugs from it not starting immediately and still applying fuel during crank cycle. I'm going to replace the plugs and see how they look, but can someone throw some more ideas out there to help me determine the issues I have. With it burning oil like it is, and loss of power, could I be losing compression in the cylinders from maybe a bad ring or something. There is no sign of damage to the head gasket. ?

This truck is my girlfriend's moms. She has a montana van that the transmission is going out on here; she is 62, a widow, and lives alone. The van is going to cost her probably a 1000, and she is on a very limited fixed income, and I need to figure out how to get this truck back in operational condition so she can rely on it through the winter while she gets the tranny on the van fixed. I work at an Advance Auto and I resource parts all over the web when I know which parts to replace, so if I can get some help diagnosing the problems, I can probably get this thing back in decent running condition. Thanks.

jgrh89 · September 10, 2008

I'm by no means an expert but, you can place large C-clamp

around the length of the comb. valve to hold the pins in -if the rearantilock brakes are still on truck bleed the large controll valve next to it too.You work at advance take the starter in and bench check it, if OK then look for bad battery connections or bad grounds from engine to firewall and frame(even though the battery grounds to engine this isn't enough) If blowing black smoke it's burning too rich, if blue smoke then it's oil, and white smoke indicates water. Try cleaning the drainback holes in the cyl head with a long stiff wire (they clogg alot and causes more oil to get past seals) do a compression check on all cyl. get a book from store for details. Check inside dist cap I've found a couple had really rusted internals and cracks causing poor running.

asilverblazer · September 10, 2008

Sounds rich to me too. More truck information?

noelhoffman · September 10, 2008

90 GMC Sierra 1500, 4.3L, 5spd. 87000 approx miles. I have a Haynes but I'll probably go out and buy a Chilton's for it, a lot better detail in them. I haven't unpacked my tools since moving 3 times this summer, but when I do, I'll have a compression test completed. I believe it is black smoke, but I will probably get someone other than my gf or her mom to follow me to give me a better determination. I have done common brake bleeding, but never anything specific with combination valve or ABS systems. I assume the rear valve is stuck closed, and don't have very detailed procedures to bleed the rear with any modification to the valve to get it to flow fluid to the rear. I know there are multiple comb valves on these vehicles, would i need to send you guys a pic of the valve for you to be able to give me a better explanation? The starter is coming off as soon as I can get the time to pull it, the terminals seem to be loose as well so I'm thinking that is contributing. Thanks for input, do I need to post a pic of the combination valve, or can someone provide a detailed description of how to bleed this system?

asilverblazer · September 10, 2008

Check engine light on?

Matts99z71 · September 11, 2008

1. I'd probably remove the rear line at the master cylinder to see if its possibly clogged there. Perhaps a bad master cylinder? Or combo valve?

2. Sounds like an worn out starter. My new (97 new to me) is kinda doing this too. When the starters are old, they sometimes get a "flat" spot on the windings of the armature of the starter motor. This makes them draw more power from the battery when they hit this spot. I've had this several times. Happened in my old 86 chevy, thought it was the battery, once I put a new battery in and it did the same thing I knew it was the starter. Even my boat will do this once in awhile. Especially if I happen to stop on that spot, it just clicks. I have to keep hitting the key.

3. Just a guess but perhaps the catalytic converter(s) are clogged. I had/have an 95 chevy G30 work van that had similiar symtoms. Ended up being a clogged cat. I cut it out, had a 20" piece of pipe cut with the ends flared, put it in and it was like I gained 50 horsepower. That one was easy because it was inline of a 3" pipe. Kinda harder with these trucks with sometimes multiple cats. I've always worried about how i'm gonna replace the cats on my trucks once they get clogged since they are pretty much part of the primaries. Dynatech makes a system that replaces almost the system that I have in mind.

noelhoffman · September 11, 2008

Check engine light is not on. Just the brake light. I checked the bottom brake line that comes out of the combination valve and their was not even a drip of fluid coming from it. I think the starter is dragging, so it will be the first thing I check out on that problem.