Ok, here goes...

I'm on my way outside to either fix this truck or set it on fire. I've mentioned my various lighting problems in previous posts. Basically I have no taillights, brake lights, dash lights, or hazard lights. The fuses blow after about a minute. I've changed the headlight switch and it didn't help.

NOWWWWW it's running like crap. Won't start, when it does start it won't go. The more I put my foot into the gas the more it tries to cut off. Had to ride a mile home today spittin and sputterin and pattin the gas to keep it running. As soon as I pulled onto my street, it revved itself up to about 2k RPM, when I braked to stop in the driveway, it idled up to 3k and held it until I turned her off.

The CEL came on so I pulled the codes and checked them in my Haynes manual. I got:

Code 34: Vacuum sensor or MAP sensor. Code 34 will set when the signal voltage from the MAP sensor is too low. Instead the ECM will substitute a fixed MAP value and use the TPS to control fuel delivery. (This makes sense because the truck won't start and when it does it won't take any throttle input without trying to cut off)

Code 44: O2 Sensor Indicates Lean. Check the ECM wiring connections, particularly terminals 15 and 8. Check for vacuum leakage at the TBI base gasket. (I guess this one is a byproduct of the truck not getting fuel)

Code 54: Fuel pump. Low fuel pump voltage. Sets when the fuel pump voltage is less than 2 volts when reference pulses are being received. (This one confuses me a little bit. Is this because I was pumping the gas trying to keep it running so I could make it to the house? I'm gonna check the fuel pump relay just out of curiosity. The computer at work said to check it, so I will.)



Now, my biggest question is this: if you tie in these newest problems, along with my various lighting problems, do you think I could have a problem in the ECM itself?

I really don't have the money to start throwin parts at this bitch right now, so anything that needs to be done will have to wait till Friday, lol. I'm really lost on this one. I do think it's odd that ALL of this started happening all together. I know it all ties in together, but I'm not sure how. I'm not sure which is the faulty part. I'm thinking the MAP sensor.

Soooo...all that rambling and not a lot got said, lol. I'm just trying to put all the info out there in order to get better input. Thanks in advance for any help or advice you can offer up.



Ricky

 

Ok, so I went out there and took the breather off, sprayed it down with carb cleaner, made sure all the vacuum lines were hooked up. Took off the MAP sensor, sprayed it with electrical parts cleaner, checked the vacuum hose on it. Put everything back together, truck fired right up and idled like a champ. Talked on my cell phone for a minute, she never dropped off, just idled right where she always does.

Decided to try my luck and hopped in. Stepped on the gas, she bogged down and wouldn't go anywhere. Limped to the end of the street and had to turn around and come home under her own power. She runs better if I just let off the gas and let her creep. Any throttle input and she tries to knock off. The only major change is the idle, she idles 100x better now.

Question: On the 3 prong plug-in to the MAP sensor, the electrical connector that plugs in has 3 round green tube looking things. One of them is broken and the wires are exposed and just slide into the hole on the MAP sensor. They're making contact but does anyone think that's a problem?

Oh yeah, I should also mention that earlier this morning, the passenger window rolled itself down. Both switches are unplugged and that window has been messed up and hasn't rolled up or down in at least 3 months.

 

Ground?
The three main grounds I can think of at the moment. Black wire off the battery, make sure it has clean connections on the battery and the frame. Make sure the engine ground is also clean, this one will be the hardest. The engine ground is on the back of the cylindar head on the passengers side. Between the head and firewall. Make sure it is attached firmly at both ends. The third ground is a body ground in the cab. Look for it under the passengers feet on the firewall. In the same general location as the wiring harness and antenna cable.

Fualty recharge wire (which is where I think your problem lies)????
Is this on a '87?
I had similar problems on my '87 S10-Blazer. Ran like crap, took a whole stop light to get through the intersection, would hesitate big time any time you gave it gas, my battery voltage was low, even though my alternator was working fine, various electrical gremlins, lights, and blinkers that didn't want to work right, check engine light, etc.
I ended up fixing a combination of things.
To fix my non-recharging battery I ended up replaceing the wire from the alternator to the battery, turned out to have only a few strands of wire were still good, and practically fell apart in my hands once I had it off. Made my voltage meter read fine, however it didn't allow enough voltage/amps to recharge my battery properly, let alone provide enough juice for the rest of the truck.

I also ran a new battery cable to the starter, corrosion had eaten half of it away as well.

Plus I replaced the cab fuseable link. One night nothing in the cab worked, no dome lights, no head lights, no dash lights, nothing. See below for more info on why. Although we could get it too work by moving the cab wire on the starter, drove it home until I fixed it.

If this is for your '87 the electrical works like this. The battery provides all the juice to the truck until the engine is running, then the alternator provides all the juice plus trickle charge the battery. The battery power goes to the starter, then a wire attached to the same starter bolt goes to the cab of the truck (fuse box) and it has a fuseable link within 12" of the starter end. Your ignition key wire goes to the little bolt on your starter.
Once the truck is running the juice goes from your alternator to the battery via the wire between the two. Plus another wire with a fuseable link is attached to the same post on the alternator. This wire provides engine power once the engine is running. (Pretty sure, I didn't really trace it) Make sure both of these fuseable links are good. I rerouted the one by the starter so I could get to it easier in case of a trail repair. While your under the truck, make sure none of your wires are pinched, or close to heat sources. I also found pinched wires on the drivers side, oil pressure sending unit, oil switch, and front axle engagement sensor. Fixed the pinched wires, however since then my front driveshaft has ripped them off. I also rerouted all the passenger side sensor wires. Had to replace a portion of one, showed signs of being fried by my exhaust manifold.

Have your alternator and battery tested, make sure they are good. An alternator not putting out enough juice will give you the same problems. There just isn't enough juice to run everything and these trucks don't have any electrical management system. It all wants power, and if your system cannot provide enough juice, everything suffers. All sorts of things go wrong, lights don't want to work, the engine doesn't want to run right, the ECM doesn't know how to interpret the problems and kicks out all sorts of error codes.

 

The wire running from the battery to the back of the alternator has a bad connection I believe. There's a butt connector in the middle of it and sometimes I get no juice whatsoever and have to jiggle that wire until I hear a click, then it's fine.

I'm gonna start checking wires and fusible links like you suggested Hanr3, I really appreciate bro

 

Found a wire/hose/tube/something that's melted in the middle. One end runs into the bottom of the air pump, the other runs to a not yet determined area under the rubber weathershield thingy. Looks like it goes somewhere near the starter.

Also found a little round thing that looks like it has a Brillo pad inside of it with a hose in the bottom. Looks kinda like an EGR valve. I just found it laying on top of some front suspension pieces. I haven't determined what it is and have no idea where it came from.

Any thoughts?

 

And for the zillionth update of the day, that hose was just a vacuum hose and the lil round thing was a breather for the air pump.

The truck will start and idle like a champ. Take it down the road and it hesitates at first, then does fine until 3k RPM. When it hits 3k it dies down and I have to let off and let it shift. The more throttle you give it, the worse it tries to die. It doesn't have much gas in it so I'm gonna put some gas in it and see what happens. It only gets this bad when it gets below a 1/4 tank, I'm gonna change the fuel filter, and if need be, I'll drop the tank and change the fuel pump strainer. That'll be interesting since the back end sits about 3" off the ground now

 

First off, replace that wire from the alternator to the battery, it carries all your juice to recharge the battery, plus all the juice to run all your lights, dash, pcm, etc. I used a hunk of 12guage stranded electrical wire I had laying in the garage and two connectors. Half a wire here means only half the juice is getting to everything. Major cause of your issues.


Rubber weathershield thingy, is that your body to frame rubber thingy to keep water and mud out of the engine compartment. If memory serves me correct, it's about 1/8" in diameter and should be hollow. Vacuum line of some sort. I cut out the bad section and replaced it with a piece of rubber windshield washer hose. If it does run into the wireing harness by the starter, then its a electrical wire for the air pump. Just splice in a piece of good wire.

Yes, if it is what I am thinking it is. If so, it attaches to the back of your air pump. Good luck seeing where it connects. Easier to unbolt the air pump and hook it up. I'll verify all this in about 1/2" or so. My son gets home from work aorund 8:30pm my time and I'll take a quick look. I might not be able to post right away, I have to move a Piano yet tonight.

 

This could be a fuel pump. Dropping the gas tank is fun. Especially if it has never been out before. [:'(]

 

Well, last night, I borrowed my mom's car and went to the gas station. Filled up a 2 gallon gas can, came home, put it in the Blazer.

She fired right up, hopped in, took her down the road, didn't have a bit of trouble. Right when I got to work this morning she started hesitating again, so when I went on lunch, I filled her up and didn't have a lick of trouble.

She only starts actin up when she gets below a 1/4 tank, I'm thinking the fuel pump isn't pumping well enough to get that little bit on the bottom of the tank, either that or the fuel pump strainer is clogged. I have sucked the tank dry a couple times, so it's possible I killed the pump...

 

I think you nailed it with the strainer be partially plugged up. The fuel pump suck the gas off the bottom of the tank.

Has that tank every been out of the truck that you know of?
Might be time to refurbish it completely, or spend the money and buy a new one. If you want some tips, let me know.