Blazer not running fuel issue?
 

So I bought an 85 K5 last month. When gas tank got to a half tank it started running rough. I filled up ran like a champ... well got to half tank and again running like crapola. So I replaced filter in carb. There are no in line filters. I am back to a full tank. So dropping the tank would be a PITA. It will not stay running without pedaling. If I drive it will bog and die. It's hit or miss.... If I stomp on it..... it will stutter the pickup quick then bog down and stutter again.... I think it may be a gas issue. I put a bottle of heet in tank for moisture no help..... Is there some type of filter in the tank? What would you suggest?

diffinitly sounds like a fuel delivery problem! Does it do this hot or cold or if you run it from full to half non stop does it do this? Is it popping like its lean or is it act like its loading up and dying? Just trying to give you a better diagnosis!!

When it's cold I have to pedal it for a min or so to keep it running. Once it warms up it will idle low... as soon as I go to drive it will try to die unless I start the pedal tapping :).... I recently bought so I was throwing tank fill up out there. Since last fill up it's still acting up. Not too sure about running lean.... If I push pedal in steady it will die. Like it's either loading up or running dry. I'm no mechanic, I know it's hard to understand my explanations.

Your fuel pump should be mounted to the engine on the front passenger corner. You could be experiencing a weak pump. The lower the fuel level in the tank, the harder the pump has to work to get that fuel out. Or, you may be experiencing a problem with the pickup tube inside the tank. If the pickup tube had a hole in it, it would cause the pump to suck air whenever the fuel level drops below the hole.

The pump is easy enough to change out and at a typical price of $15-$20, it won't be hard on the wallet either. This would be the first step I would take.

Here is an image I took from the engine out of my Chevelle for someone else quite a while ago. It shows the pump, how it's mounted, and the pump push rod retaining bolt location (where applicable).
http://i11.photobucket.com/albums/a1...el_pump_01.jpg

Thanks, Do you know the bolt size of the top of your head? I will change this weekend and update...

Which bolt? The one in the front? If so, just take one of the two bolts that hold the pump on and use that. They are long enough to get in there and retain the pump push rod. Hand tight is good enough. It just has to hold it well enough that gravity doesn't let it drop down into the lower cavity.

IIRC, you'll need a 9/16" wrench. Having a liner wrench helps get the fuel line off the pressure side of the pump (what runs up to the carb).

LOL I did not mean "of your head" OFF.
Great thanks for the update.

:icon_shrug:


Hand tight does not work :icon_shrug: So I turned the long bolt with wrench two turns and the rod was still loose. No connection, so I backed the bolt out and it was really tight. I hate to force it. Would you suggest keep going until it touches?

Thanks again

Bare with me...Got the new pump today. It has two input lines. The old one only had one. BUT.... There was another smaller tube just hanging by the frame. Return line I suppose... The word "in" is in between the smaller input line and the output line to the carb. The big input line (same size as old fuel pump) beside it. I put the small return line on the smaller input 1/4 (which said IN) and the bigger input line with the bigger hose (the hose i removed from the old pump). Truck runs the same.... should I try swapping those hoses first?

Sounds like you have it installed correctly, but it's worth a try at switching the lines. Did the new pump come with anything stating the function of each port?

of course not

Another possibility is that the float inside the carb is malfunctioning.

My first old vehicle. I'm clueless, but slowing learning. What do you think about sticking a pressure guage in fuel line before carb?... Hopefully to find out whether it's before carb or the carb.

You could test the pressure. You are looking for somewhere between 6 & 8 psi.

I do not have a tester.... I figured cheaper to buy just a gauge lol...

A gauge will work. That's all that is used to test fuel pressure. :icon_wink:

update

replaced metal fuel line with rubber line and inline fuel gauge. Is it normal for a fuel gauge to bounce super fast? (0-4 just back and forth) It's bouncing to around 4 lbs.

I swapped line on pump..... there were correct because it ran out of gas lol.

Before putting back on pump I pump air with the compressor to line and blew back into the tank. Runs a lot better but still hesitating. Fuel up to around 8 lbs still bounces steady.

Problems obviously in the tank.. what do you think? Currently I have about $100 in the tank I hate to drain it :icon_shrug:

It is normal for it to bounce with a diaphragm style pump which is what you have. Each revolution of the cam causes the pump push rod to push on the diaphragm arm which pumps fuel.

0-4psi sounds a bit low, but 8psi is good.

Have you considered tearing down the carb and rebuilding it?

Just drove about 5 miles... It's driving fine... BUT idle it's rough and wants to die. When I returned home 3 psi again.

I have never done it before. I suppose I could bring in house and tear apart.

If it drives ok and only the idle is crappy, that sounds like a carb issue.

Is it the factory carb, Rochester Quadrajet?

You know, I just bought it last month. I have never owned anything carbed. lol, I just need to do some reasearch once it's out. I have no idea what kind of carb it is. It's black as **** from gunk :)

You can try adjusting it first.

If its a Q-jet, the idle screws will be in the front of the carb located in the base plate. They are recessed into the base plate and are at a slight angle to the carb centerline. The typical initial setting I have always used is to unscrew each one of the idle screws 1.5 turns out after bottoming the needle valve. When you are turning it in, count the number of turns and write it down for each screw then set them at 1.5 turns.

You can also set idle speed using the adjustment screw near the primary throttle shaft on the driver side of the carb (where the throttle cable attaches).

How about that aligator clip. I thought I got a deal on this thing but man I have spent a lot of money on it so far :( I see the throttle screw and that's it. Help me out



http://i241.photobucket.com/albums/f...7/IMG_0038.jpg



http://i241.photobucket.com/albums/f...7/IMG_0039.jpg
http://i241.photobucket.com/albums/f...7/IMG_0040.jpg


http://i241.photobucket.com/albums/f...7/IMG_0041.jpg

http://i241.photobucket.com/albums/f...7/IMG_0042.jpghttp://i241.photobucket.com/albums/f...7/IMG_0043.jpg

Yep, that's a Q-jet.

I marked the locations of the idle adjustment screws in the attachment below:

I found the one on the left. It was out 2 turns. I put at 1.5 for now. The only screw on the right is the idle screw. It was not even touching the lever that goes to the pedal. I turned the idle up a little i would say by ear it's idling too high. Idles fine as soon as i put into gear it dies unless i give it gas. :icon_doh:

But hey since idle turned up I'm reading 8 lbs. Maybe I'm a retard I just cannot find the 2nd screw you are referring to.

ok watched some youtube. I have the safety emissions caps still over screws :).... I was adjusting the high speed screw in my earlier post.

Yeah, there may be caps over the idle screws. I would remove the carb and give it a good cleaning. Remove the caps and set the idle screws.

While it's off, check the primary throttle shaft for play which can cause a vacuum leak leading to poor idle quality. If there is play in the primary throttle shaft, you may want to consider getting a rebuilt carb. There are quite a few on eBay.

Not sure what's going on but... it's running like a champ. Suppose turning idle up a bit... the screw was not even touching the throttle lever before adjustment. I have driven about 10 miles last two days. Starts right up. I still have to pedal it for a sec to keep it running. Just going to drive over next couple of days and see what happens.

i am having a similar problem. but my blazer doesnt want to start. I was low on gas and dry on oil because of my oil leak. I turned it off for about 45 mins and tried to start it. it turns over but doesnt want to start. i put oil in it, and filled it up to half a tank. still nothing. i also tried jumping it with my boyfriends car. i just dont want to put tons of money into this vehicle...if its not worth it. help!!

And what are you driving, ajeremiah? If it is a fullsize with a carb, run through the checks listed in this thread and let us know what you find. If it isn't a fullsize and/or it doesn't have a carb, then you really should start a new thread in the applicable tech section.