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Discussion Starter · #1 ·
my 84 GMC 1500 which had been driving perfectly quit on me today with little warning

I last drove it three days ago and noticed a little surging at high speeds but thought that I was just tired and inadvertently pushing the accelerator or simply just noticing things that were not there.

The last two or three times I drove it it seemed a little harder to start. But it has been cold so I just lit the glow plugs a little longer and it fired right up

To day while driving it it acted like it had run out of gas and I was able to coast into a parking lot where it started right back up

I drove it a little further and it started doing it again this time it stalled at a red light and after some trying I was able to get it to start again for a minute, but not enough to get it out of the roadway

After a few minutes it's started again and I was able to get it to a gas station before it quit.

It is acting all the world like it has no fuel.
It has two tanks one is full and one is pretty much empty
I was running it on the almost empty tank until I noticed and switched tanks
Shortly after that it started acting up, but I think that that may be a coincidence.

It is very low on oil but the engine is not seizing


That's the background her is my question
Anybody have any clue what is going on.

I would like to be able to keep this truck because it is an inheritance from my step father, but i am beginning to think that it is more than I can handle on a student budget.
I may have to sell it and just restore the 79 F100 that he gave me just before he died with the request that I restore it, that was really favorite truck anyway
 

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HWats the temps there, it very well could be geling the fuel!
 

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Discussion Starter · #3 ·
75s to 85s

I am using a Gumout additive that is suppoed to prevent gelling
Does that matter
 

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If you were running on the empty tank and it ran dry you sucked some air and need to bleed the system. Never run a diesel tank empty or you will have to bleed the system of air.
 

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Discussion Starter · #5 ·
I switched tanks before I ran out and before the problems started
The only way it actually ran out was if the tanks failed to switch or the secondary tank some reason did not allow fule to flow
 

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Next step is to check the fuel filter it may be clogged. I have plenty of knowledge with the 6.2 and 6.5 both in the Military HMMWV and CUCCV (Hummer and Chevy P/U 1984). After taking the filter off and you find particles it most likely is your problem. You will have to bleed the system after installing the new filter. You can accomplish this by pulling the pink wire from the injector pump this will keep the engine from trying to start, next loosen the top bleed valve which is located above the filter to the rear and have a friend turn over the engine until a steady stream of fuel is present and tighten the bleed valve. Now try to start your engine.
 

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Discussion Starter · #7 ·
I was wondering about bleeding after the switch out.

Would there be a delayed reaction if I had gotten some air in the lines prior to switching tanks.?
If that were the case would I have been able to get the truck started temporarily three times

I poked around today, but won't be able to actually dive in until next week

I found a component that fits in the rear of the engine about where a distributor would fit on some GM gas engines.

it has many vacuum lines attached to it

One is small and hard plastic, it was broken.
Some of the other vacuum lines leading to it are old and cracked.

from the component that the filter hooks up to there are two lines that go no where. One is a clear aquarium type tubing the other is about 3/8 and looks like fuel line and is attached with a hose clamp but the other end goes leads down into the fender well as if it were some type of drain line.

Also in the vacuum module under the air cleaner there looks to be a line missing. The module is dirty but there it is clean where a tube used to be. I can't find any tubes corresponding to this that or any empty tubing connection.

I know I need to buy the manual but that is not financially feasible at this time.
I have decided to get it running and park it at my mother rural property until I get out of school in six months
I'm really starting to get into this truck
 

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It is possible to start the vehicle a couple of times depending on the amount of air in the system before it just wont start anymore. The component with all the vacuum lines attached at the rear of you engine where it looks like a gas engine distributor would go I might not be able to help you on that. Military vehicles are exempt from many government emissions laws and don't have many of the lines you are seeing. But the part you are describing sounds like a tach sensor on a military vehicle it is yellow and should have two wires coming from it. As for the vacuum lines you described without knowing where they go I can only tell you that if they are broke or cracked replace them. The filter assembly should have an upper and lower bleeder which may have hoses attached and of course your inlet and outlet lines. The crank case depression regulator you described underneath the air cleaner on the right side of the engine (left side as you are looking at the engine from the front) has a hose underneath that goes directly to the manifold and on the side has a hose that should connect to your air cleaner.
 

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the vacuum pump is what you are looking at yep they just converted the distributor to a pump is the best way to say it. if you're leaking that much some vac controled items should be failing like defroster only? what is your temp outside? did you buy fuel where you usually do? was the gas tanker there dumping within the last hour before you pumped? if you have switched tanks then had a problem water in tank is my first thought, and filter plugging would kill start kill start
 

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Discussion Starter · #10 ·
Temp fluctuates from the 80s to the 50s but that day it was probably mid 70s.
I only get gas in one place and filled both tanks at the same time. No way of knowing when it was delivered.

The AC only works on AC if that's what you are saying.
The small plastic hose was broken in two in two places but I was able to reattach

Those two lines at the filter block would be the drain lines

I'll look for the hose to the air cleaner.

My step father always took very good care of his work trucks so I am assuming that he just didn't have the time to get to every problem on this one.
I do know that he had had it in the shop twice before he died.
once for burning out the glow plugs trying to start it.
Which tells me he was almost as ignorant of diesels as I am.

delawitt
Are you telling me that these are the same engines in Hummers
I thought that these engines did not get much respect
 

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Yep Military hummers started with 6.2 in the early 80's and by the early 90's 6.5 also the heavier models have 6.5 w/turbo. All are still in use and easy to work on. I don't think the military would spend the money for a DURAMAX when the 6.2 and 6.5 get the job done just fine. I will however say the turbo makes all the difference in the world to this engine.
 

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Discussion Starter · #12 ·
Sorry for the delay in response I had to reload from a virus. Beware of AntiVermin

I keep finding things in this truck that don't make sense.
It's going to be sometime around saturday before I can get to the repair work.

Today I found a fuel pump that looks like a typical crank driven gas engine pump but it has no lines running to it.
It has the fitting but nothing is connected or disconnected.

If I post photos of the engine would you be able to ID the things that are confusing me?
 

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Just my opinion, but I think that your injection pmp may be going (gone?) out. I would like to think that those old "roosa-master" pumps are kinda cheap by now. The instalation is easy, and I even watched a GM tech rebuild one once, i only took about an hour and it looked kinda easy!
 

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Today I found a fuel pump that looks like a typical crank driven gas engine pump but it has no lines running to it.
It has the fitting but nothing is connected or disconnected.
I did not see this post before my last response to you. After reading this, I kind of think that maybe someone bypassed the stock mechanical fuel pump and installed an electric one, if this is the case the electric one might be broken.

You might try tracing the fuel line backwards from the injection pump, (it is right in the middle of the engine) back towards the fuel tank. My money is on you finding an in line electric fuel pump somewhere in there, and I bet it is not working anymore.

Good luck!!
 

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Discussion Starter · #15 ·
I have been studying for a test that I probably wont pass and it's way cold so I haven't done any more looking

But looking it up and finding out that this is the standard pump I was thinking that there was an upgrade to electrical.

if the problem is the electric fuel pump
Is there an advantage staying with electric instead on returning to stock
 

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Discussion Starter · #16 · (Edited)
Ok electric pump is pumping
I blew the old filter out with an airgun, fuel that cam out was clean and clear.
Reinstalled filter and bled the system.still no go

Disconnected the the fuel line at the outlet from the filter and there was a strong steady flow of fuel

Any other suggestions

Do I need to bleed the lines at the injectors or is it just time to break down and buy the manual or an injector pump
 

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I would at first take a test light and make sure you are getting power to the injection pump solenoid. I think it is a bright orange wire. It should go on and off with the key.

If good, I would open the line that goes into the injection pump from the fuel tank, and briefly turn the key on. Your electric fuel pump should expell fuel from the open line.

If checks out I would loosen a couple of the "top" fuel lines at the injection pump and see if fuel is expelled when you roll the engine over. At this point be aware if air is escaping from the open lines, but be carefull this is high presure fuel, it can be dangerous especially if you put body parts directly over or directly in the path of the "squirting" high presure fuel, (it can be injected under your skin, big problem).

If you are getting air out of these lines I would tighten the lines at the pump, and loosen the lines at each injector, turn the motor over until all of the air is expelled. (the "surging" that you mentioned can be symptom air in the lines)
If fuel or air does not come out of these lines, I am prone to believe that your injection pump is broken.

I am checking some links now on rebuilt pumps, I will post back here in a few min.
 

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http://store.realdiesel.com/gmch6inpu.html

http://www.o-f-i.com/index.php?pid=14#REBUILT_EXCHANGE_INJECTON_PUMPS

Check out these links, there are many, many, links that end up on e-bay. With a little shopping I think you could do better.

Make sure you get the instalation kit, as this will have some wear parts for the pump drive. The second link has new pumps for your instalation, the rebuilt units are further down the page. Also, it looks like they have some pumps for "heavy duty" applications, this might give your truck a little more get go.
 

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Discussion Starter · #19 ·
I did some checking earlier and found the real diesel site.
I was hoping that they were decent

It's getting dark and I have to take a test tomorrow I'll have to check those things Wednesday

I did not mention that I removed the wire going to the pump and can hear a clicking that I assume is a solenoid

also did not mention that the electric pump never shuts off. I can hear it change tones when I bleed the filter or relieve the pressure at the lines but it keeps running.
Anyway I'm flooding it. Can you even do that with a diesel ?

I'm going to have to go the cheapest route right now
 

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I did some checking earlier and found the real diesel site.
I was hoping that they were decent

It's getting dark and I have to take a test tomorrow I'll have to check those things Wednesday

I did not mention that I removed the wire going to the pump and can hear a clicking that I assume is a solenoid

also did not mention that the electric pump never shuts off. I can hear it change tones when I bleed the filter or relieve the pressure at the lines but it keeps running.
Anyway I'm flooding it. Can you even do that with a diesel ?

I'm going to have to go the cheapest route right now
It is possible to "flood" a diesel but it is unlikely unless your glow plugs are not working right, and since they were aparantly working before they are probably good now.

As far as expense goes, I saw a used pump on e-bay yesterday with a bid of $75.00 with 13 min to go.

Good Luck!!
 
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