Ok, here's the whole long story. The other day I replaced the fuel filter(85 blazer 6.2). I of course probvadly didnt do it right at first, but finally I opended the fuel valve and got the filter full of fuel. It still wouldnt start, so I poured a tad of diesel down the intake, and it fired right up.

Well Since then I've driven 1400 miles(this weekend alone) and the car runs great. STarting on the other hand sucks seriously. It will start if you give it enough cranks or time, but not until somethign under the hood is smoking.(starter I think). Also, the starter sounds like the battery is just dead, but really it shouldnt be. Those battery's are brand new. So when I have trouble I've been using wd-40 to save the starter.

Sometimes it starts up fine, no problems at all. There is no cold or warm tempature correlation. The other day it started fine in the moring, the last 2 mornings its been a pain. Even with wd-40 some of the cylinders didnt want to fire at first.

So, here's the few things that I think it might be, escpecially after searching the board.

1. Least likely, starter. I say least likley since it starts up fine most of the time, and spins very very fast. Sometimes it has a little more trouble. I've also noticed that when it does spin fast, the truck almost always starts. Not every time though.

2. Glow plugs. I pray its these, since I think these would be the easiest to replace. How's the best way to test these. Also, why would these go out as soon as I replace the fuel filter.

3. Injection Pump. Oh please lord no. I dont think I have the expertise to replace these on my own. Are they not really expensive too. Is there a way to test these? I probadly burnt it out when I replace the filter and was turning over the engine without fuel. What is the cost of replacement, or rebuilding these. help would be appreciated.

So thats what I can tell you. Thank you guys in advance for your advice. Like I've said, I've searched the board and I just want to confirm what I've found.

Guipo

I doubt that you hurt your injection pump. Get a 12v test light, connect the alligator clip to the + post on the battery, remove wire to glow plug, touch test light probe to glow plug spade. If light glows glow plug is at least opperational. If test light does nothing, glow plug is burned out. Repeat process 7 more times, remember wire has to be off of glow plug to be tested and you must touch only the spade(you are looking for a path to ground through the heating element) Let me know the results of this test.;) :grd:

well, the light lit up on all the glow plugs. hooked it to the positive of the battery, and unplugged each glow plug. touched the part that was sticking out of the glowplug. Lit up all of them.

So. I started it up after ward. After some fighting, the truck started. So it smoothed out after a minute, and wouldnt run right at first, like only a few cylinders were firing. but then it was running fine. So I killed it, started it again. It started perfect. Killed it, started again, started perfect. I thought maybe its a bubble in the fuel system. So i Released the pressure of the fuel system by the nozzle at the fuel filter. Started it again, smooth as a baby.

Now what do I do? Could it be a air leak since I replaced the filter?

Air in the fuel system will cause hard starting, rough running but.....! Most of the time, air in the system will cause the engine to start, run a few seconds and then, die, sometimes accompanied with the dreaded "rump, rump, rump" (surging) sound.

If the air leak is small enough, such as a filter housing bleed screw seal leak or an I.P. throttle shaft seal leak, the engine will purge the air and run just fine, until you shut if off and leave it sit. Sometimes as long as overnight. The cold seems to increase the condition. (the seals shrink when cold, expand when hot) When you start it up the next morning, it does what I decribed above.

Air is responsible for most of the "starts and dies" complaints on the 6.2, especially after the fuel system has been opened for service.

well, the it does not start and die. Once it starts up it runs like a champ. And sometimes, its only off for a hour or so and it dosent start.

I went ahead and loosened and tightened the bleed screw last night. This morning the truck was going to start, but it was still as if only a few cylinders were going to fire. I'll see how it starts for my wife later on. The truck used to start right up, no matter the tempature.

It has to correlate with the change of the fuel filter. It didnt start until I replaced it.

Guipo

I've had trouble with the bleed screw seals on the filter adaptor. I can usually lift them out with a dental pick and replace them. I've even had to "fabricate" them from a piece of vacuum hose (fuel resistant neoprene). The original seals were like a square cut O-ring style. They were a little over 1/8" long and the tapered vent screw made an angled impression in them that resembled a valve seat.

GM offered them in parts for a while. I haven't been able to get them lately. Maybe someone else knows where you could find some. If they leak, they usually make it start hard like you're describing. They don't leak fuel because of the low pressure, but they will let air into the system when the vehicle isn't running.

So I can check, the vent screw is the one on the top of the filter housing thingie right? Its like a plus on top. I'll see if I can get a new one, hopefully that is teh problem.

Get a clear piece of hose, 3/16 or 1/4 and replace the rubber hose from the injection pump to the fuel return line. Hose goes from top of injector pump to front of engine. After installation of clear hose and after waiting over night, start engine, look at fuel returning through clear hose. If there are lots of bubbles in the hose you have an air leak some where. Start with tightening all fuel line hose clamps and bleed valves.:grd:

The vent screw is the plastic with the cross on top, below it, in the bottom of the threaded hole is the seal. If you take it out, it usually comes out in pieces and/or unfit to reinstall. See if you can find one before you take it out. Follow D.Camilleri's thread on the clear plastic hose, look for air/bubbles in the hose.

hrmmm...sparks shooting out of the starter. Thats not related is it???

nope, sounds like you need a starter.
Pretty tough to 'fry' and injection pump anyway.

anyone else ever had sparks flying out of a starter. Also, the engine turns over kinda slow when I have my starting problems. Sould that be my whole problem?:confused:

Your starter is dragging, they all do it when they get old.

Your starter is sealed so you will not see any sparks flying out of it. Sparks can fly from a worn starter cable that is grounding out.

:help: I just want it fixed. Man. Anywho, it was a loose cable on the starter that was sparking, and as soon as I attached it again, it was fine. So I charged the battery all night after repressurising the fuel system.(I put a extra rubber tube in where the fuel filter air vent thingie is, so I dont think that is leaking. I still have to go get a clear tube to make doubly sure).

Anywho, I charge the batterys all night, and tried to start it this morning, and it was like the battery's were dead. The starter barely worked. I doubt the engine was even moving fast enough to start after a couple of seconds of cranking.

I am beyond frustrated. A few days ago it was starting fine, and now I'm back to it not even starting. I'm buying that clear tube tonight and will see if the fuel system is clear.

Guipo

Guipo, contact me off-board with AIM, or such (name mangus580 ) or email me at mmaynard at rochester dot rr dot com

I have all the military TM manuals on these, and I can try to help you out.

Test your voltage at the starter. Do you have 24v? if yes replace starter, if no repair wiring to get 24 volts to starter. A 24 volt starter will barely spin if it only has 12 volts to it. You should be able to test voltage at the starter solenoid terminal.:grd:

even if my trucks been converted to 12v?

Sorry, my mistake, if your truck is converted to 12v then check and make sure you have 12v at the starter. Better yet would be to see what the voltage drops to when you are cranking the engine. Check(take them apart and clean them) your grounds and battery connections, bad connections will eat up your voltage.

ok, so here's what happened now. My wife got it started, and drove it around. Ran perfect, started fairly easy. I went after it sat for a couple of hours, started right up. Drove it home, killed it, started it, killed it, started it, etc like 5 times. Wait 5 minutes, and its not starting again. The starter is going fast and strong too. Like normal. Its just not starting. Now what! uhghh!


**get this, just went to check thefuel pressure, and there is none. I unscrewed the fitting and there is no pressure at all. Why would I lose all the pressure in 5 minutes when it lasted 2 hours just fine?

***another update. Drained the air out of the filter, started right after that. could it be a bad filter?

OK, we have gone from a starter problem back to an air leak problem. To confirm the air leak, put a piece of clear hose in place of the rubber hose on top of the injection pump that goes to the fuel return line. Upon initial start up or no start look to see if there are air bubbles in the clear line. Air bubbles mean air leak. If you have an air leak, start by systematicly checking and tightening all fuel line hose clamps. A fuel line doesn't have to leak fuel to suck air. If this doesn't solve the problem, you can 1) pressurize the fuel tank, about 3 psi and check for leaks, 2) install a one way check valve in fuel line just before filter. Also inspect filter and make sure that there are no leaks. Note: any leak in the fuel supply line will allow fuel to siphon back to the fuel tank and leave an air pocket in the filter. When trying to start engine the air will be sucked into injection pump and no start will result. It can be cleared with lots of cranking.3) install electric fuel pump close to the fuel tank and use it with mechanical fuel pump. Use a 7 psi pump.;)

ok, I promise no more posting until I get those things done. Or at least some of them... ;)

Maybe your shutoff solenoid is sticking/binding, go to a fuel shop and buy a new topcover, or have them install one.

D. Cam, I think your on to something. But let me add some more now that I've worked on it this weekend.

I replaced the tubing, with clear tubing like you said. No air bubbles. Actually I saw one, but that was it. And it just kinda stuck there. The filter is losing pressure somehow. I thought maybe that I had a defective filter. It does the exact same thing. So of course, I bleed the filter until the air goes out, and it usually starts up pretty good as long as I dont lose the batterys.

If it's cold, And I get it started, and then turn it off, it'll start fine, even the next morning. It keeps pressure in the fuel lines. When it warms up and I turn it off, thats when It loses perssure, and All of a sudden, there's tons of air that I have to bleed out of the filter before it'll start again.

Another wierd thing. I kept getting tons and tons of air when I was bleeding the new filter. (after 10 minutes I gave up.) After I replaced the Fuel lines (I replaced a leaky one, and the fuel return one.) There was so much pressure coming out of the fuel filter that it filled the cup almost instantly and overflowed. Also there were no more bubbles. It was as if as soon as the bubble all came out, that the pressure went up 20 fold.

Oh, one question. How does one pressureize the fuel tank?

So there's a update. i'll continue replacing the fuel lines(the rubber ones), with the clear tubing I bought the other day, and making sure that all the injectors are tight.
Any other idea's would be appreciated. Or things I need to do.

The way that I pressurize a fuel tank is to drill a hole in your gas cap and insert a rubber tire valve stem, then add air, but be careful don't put in too much. It doesn't take much of an air leak to allow the fuel in the line to siphon back to the tank. Check all of your hose clamps, including the one on the injection pump under the intake manifold, it's a pia but it can be reached from the back side of the manifold from underneath. Good luck.

Or, take an air hose with a blower fitting on it, wrap a rag around it and push it in the filler neck. Just don't get too carried away, it is possible to rupture the tank.

Whoa, are you replacing the fuel hose with clear plastic hose and planning to leave it there permanently? I don't think that's a good ideal. Plastic won't withstand the heat in certain spots. I think Dcam meant to use it to test for air in the system and then remove it and reinstall/replace the good, reinforced fuel hose. Check it out before you leave plastic where it could melt and cause a fire. I've had that experience once. Not funny!

Like Fred482 said, clear hose is only for short duration testing purposes to find and eliminate air leaks. When it is fixed return to rubber fuel line.:eek:

Like Fred482 said, clear hose is only for short duration testing purposes to find and eliminate air leaks. When it is fixed return to rubber fuel line.:eek:
ok, thanks for the heads up. I've had good lick on motorcycles with that stuff, But i guess thats a different beast. I'll probadly leave the one on the pump that goes the the fuel return line on, until the problem is fixed. I have 3 or 4 of those little lines on the injectors leaking right now, and after those are fixed, I dont expect that to fix it, but I'm going to redo the lines going into the fuel filter housing. I will pressureize the fuel tank first of course, but thats the only other thing that could of been messed with when I replaced the fuel filter.

My wife drove it around town fine for 2 days, and then today it wouldnt work. doh.

ok, and for further clarification, the return fuel line is completley devoid of fuel right now. That would indicate a leak between the tank and the engine, or the fuel filter and the engine?

Any air leak between the fuel tank and filter will brake the vacuum hold on the fuel and let it return to the tank. If you want a quick fix that will help you find the problem, install an electric fuel pump on the frame rail in front of the fuel tank. Use a 7 psi pump, it should help you find your air leak and help with your starting. If there is an air leak in front of the pump it should show up as a fuel seep. A leak in one of your return lines will allow the fuel to drain from them, but should not have anything to do with the filter loosing it's prime.:grd:

I have a 84 cucv blazer 6.2. mine would not start unless the throttle was all the way to the floor and would not idle . the probleml started with low power. I changed the fuel model 80 fuel filter and it was not help. the probleml was a small check valve on the return line. it was located on the back of the engine. changed it and started and ran fine. I did not know this check valve was there. a shop mechanic located it.

ok guys, were is the check valve? For the life of me I cant find it.

After I shut the engine down, I can see the fluid disappear from the clear tube on top of the engine. So I'm assuming that there's a good chance that the check valve is bad. At least I hope.

Thanks again for everyone's help.

I am not sure about the military models. It seems to me that the check valve on the civilian models is in the top of the injection pump.:confused:

:thankyou2 (http://misc.php?do=getsmilies&wysiwyg=1&forumid=20#)
:banghead: (http://misc.php?do=getsmilies&wysiwyg=1&forumid=20#):banghead: (http://misc.php?do=getsmilies&wysiwyg=1&forumid=20#)

STARTER STARTER STARTER STARTER STARTER STARTER!!!

:banghead::banghead:

GAHHHH!

Seems that when I changed out the fuel filter, I released the magic blue smoke out of my starter. Hence, why it wouldnt start when warm, was sporratic, etc etc etc.

:banghead::banghead:

This is a formal apology for me being a idiot. Thank you all so much for your time, I appreciate your help, and I hope, beyond all hope that this thread will help someone else some day.

:banghead::banghead:

dumb dumb dumb

Glad you got it fixed! There is no such thing as a dumb question, unless you don't ask it!:p: :exactly: :cool2: :grd: :muahaha: