Is there a diesel mechanic in the house?

tod0987

tod0987

Say What?
Joined
Jan 9, 2017
Messages
2,043
Location
Eastern NC
Rating - 100%
8   0   0
I bought a military cucv with a 1984 6.2 Detroit diesel. It sat for a year after the owner lost interest and I bought it under the guise that it ran before parked and he showed me videos of it idling fine. The fuel had gone bad, (clear but dark orange) so I've siphoned it all off, replaced it with new with treatment, replaced the filter with a new spin on and I have good pressure from the fuel pump to the injector pump at 8psi. My issue is I'm not getting fuel out of the injector pump after cracking two lines to see it come out. I've also replaced the batteries, so I have a good crank. The fuel shutoff solenoid has also been replaced and works when powered. Fuel lines from the mechanical pump to the filter, to the injection pump have all been replaced and I'm working through all of the other rubber hoses to replace.

I was wondering if there is a diesel mechanic that would be willing to talk through before I swap out the injection pump (Stanadyne DB2) at a cost of $800?

Thanks
 
Last edited:
I'm no diesel mechanic but try this
To bleed air (or old fuel) out of the system on 1984 and later models:

These trucks were equipped with a combination fuel filter/water separator/fuel heater ("square" filter). If your truck is equipped with a "round" filter, see the procedure for early model trucks.

Hook an air compressor hose into the return line at the injection pump (IP). The line you want is the rubber one that goes into the front of the IP. Alternatively, you can stick the air hose into the filler neck, but that is not as effective. You can also modify a fuel cap with a valve stem off of a tubeless tire and use an air chuck to supply the air, which works good. Whatever way you choose, the next step is to open the air bleed valve. It is located on the top of the fuel filter mounting block. There is a hose fitting right next to it. Hook a hose onto that, and run the hose into a pop bottle (this will collect whatever fuel you bleed out). With the fuel cap on tight, turn on the air to about 4 psi. Give it some time to fill the fuel tank. Fuel will start to flow out of the bleed valve and into the pop bottle. When the pop bottle is about full, close the bleed valve. Then turn off the air. Disconnect the air line, wait for any remaining pressure to bleed out of the tank, and then reconnect the return line to the IP. If you used the modified fuel cap or the hose in the filler neck, you can ignore these last few steps.

Once you have bled the air out of the system to that point, you may need to crank for a while to get it to start. It is not necessary to loosen injector lines to bleed the system to the injectors on the 6.2. Simply crank until it starts. You will need to do this in several cranking sessions of about 15-25 seconds in length so that you do not burn out the starter.
 
Diablos said:
Air locked?
Click to expand...
I have been able to get fuel into the intake barb of the Injection pump at 6-8 psi according to the gauge on the filter. I've also primed/purged the air out of the filter so I do not think it is airlocked. I had cracked the lines on two thinking that could have been the case.
 
Schattenreiter said:
Try breaking all the lines loose then put an air blower in the fuel cap opening and pressurize the tank while cranking. Break the inlet line to the inj. pump loose first and make sure you have good fuel there.
Click to expand...
I'm pretty confident that I have good clean fuel at a good pressure going into the Injection pump. The gauge on the outgoing side of the filter shows 6-8 psi which is on the higher end of the manual specs.
 
If the air is out to the lift pump, then as @infasaid, crank to get the air out thats in the lines up to the injectors.

probably going to take a few cranking sessions 20-30 seconds max, allowing a few minutes in between for the starter to cool), and id have a charger hooked up.
 
Infamous1 said:
I'm no diesel mechanic but try this
To bleed air (or old fuel) out of the system on 1984 and later models:

These trucks were equipped with a combination fuel filter/water separator/fuel heater ("square" filter). If your truck is equipped with a "round" filter, see the procedure for early model trucks.

Hook an air compressor hose into the return line at the injection pump (IP). The line you want is the rubber one that goes into the front of the IP. Alternatively, you can stick the air hose into the filler neck, but that is not as effective. You can also modify a fuel cap with a valve stem off of a tubeless tire and use an air chuck to supply the air, which works good. Whatever way you choose, the next step is to open the air bleed valve. It is located on the top of the fuel filter mounting block. There is a hose fitting right next to it. Hook a hose onto that, and run the hose into a pop bottle (this will collect whatever fuel you bleed out). With the fuel cap on tight, turn on the air to about 4 psi. Give it some time to fill the fuel tank. Fuel will start to flow out of the bleed valve and into the pop bottle. When the pop bottle is about full, close the bleed valve. Then turn off the air. Disconnect the air line, wait for any remaining pressure to bleed out of the tank, and then reconnect the return line to the IP. If you used the modified fuel cap or the hose in the filler neck, you can ignore these last few steps.

Once you have bled the air out of the system to that point, you may need to crank for a while to get it to start. It is not necessary to loosen injector lines to bleed the system to the injectors on the 6.2. Simply crank until it starts. You will need to do this in several cranking sessions of about 15-25 seconds in length so that you do not burn out the starter.
Click to expand...
yes it did have the bread pan filter. I have removed it completely and installed a spin on filter housing (easier access to filters). The filter has a clear bowl at the bottom to see any water if it does make it in. It has 2 ports out, in one port I have a 0-15psi gauge and the other port goes into the intake barb of the injector pump. Given that the fuel was bad and varnished in places I cracked the line from the injector pump to 2 injectors just to see if any fuel was making it out while cranking to avoid excessive cranking and ware on the starter should the pump actually be bad.
 
Last edited:
Those 6.2 have forged pistons? if they do add marvel mystery or your other favorite lube to the fuel tank, then spray a small amount of ether in the intake and crank it over. If it trys to start have someone get behind the key crank it you spray ether in the intake, jsut a couple of short spurts to keep it running. do this a hand full of times then try to start it without ether if it does air is out of the system and pump is working if not well you got issues...
 
You've gotten some good advice on bleeding the system. Pick a method and do it. That 6.2 is notoriously hard to bleed. Many a good starter has been ruined trying to bleed them.
Also know that they plungers inside the injection pump on those get stuck easily. Especially when they have bad fuel in them for any length of time. Even if you take the pump apart to free them up, they'll never make enough pressure at cranking speed to pop the injectors off.

Please don't try starting fluid on that engine. It's an IDI motor at like 21:1 compression. You'll break something.
 
JoeR said:
You've gotten some good advice on bleeding the system. Pick a method and do it. That 6.2 is notoriously hard to bleed. Many a good starter has been ruined trying to bleed them.
Also know that they plungers inside the injection pump on those get stuck easily. Especially when they have bad fuel in them for any length of time. Even if you take the pump apart to free them up, they'll never make enough pressure at cranking speed to pop the injectors off.

Please don't try starting fluid on that engine. It's an IDI motor at like 21:1 compression. You'll break something.
Click to expand...
Thanks. Yes I was told to not use starting fluid/ether. ok yes I think I may be at that point with this injector pump given it did have bad fuel in it and sent to it for a bit.
 
Many years back I placed a diesel generator in service that had sat in a field for almost a decade. It was powered by a 400hp Big Cam Cummins.

An old diesel mechanic advised me to pre-fill new fuel filters with a 50-50 mix of diesel and marvel mystery oil, crack the lines at all of the injectors to allow the air to bleed out, and then crank the engine over until only fuel (and no air) was coming out of the cracked open lines. Then tighten up the nuts, and crank the unit over until the 50-50 mix of diesel and MM Oil was throughout the system. Then leave it sit for at least a day, and more days is better.

He told me that this method would help to unstick any stuck parts in the system. It worked like a charm, and I still use that generator to this day.

If I were you, I’d try something similar before spending the $ on a new injection pump. You have nothing to lose.
 
Scsmith42 said:
Many years back I placed a diesel generator in service that had sat in a field for almost a decade. It was powered by a 400hp Big Cam Cummins.

An old diesel mechanic advised me to pre-fill new fuel filters with a 50-50 mix of diesel and marvel mystery oil, crack the lines at all of the injectors to allow the air to bleed out, and then crank the engine over until only fuel (and no air) was coming out of the cracked open lines. Then tighten up the nuts, and crank the unit over until the 50-50 mix of diesel and MM Oil was throughout the system. Then leave it sit for at least a day, and more days is better.

He told me that this method would help to unstick any stuck parts in the system. It worked like a charm, and I still use that generator to this day.

If I were you, I’d try something similar before spending the $ on a new injection pump. You have nothing to lose.
Click to expand...
Thank you for the tips. I agree. MMO is some pretty good stuff.... Whatever it is. I'm going for broke but still hoping that a 50c fix is still possible lol I'm doing somewhat of that right now. The new fuel has a healthy dose of diesel kleen it in. There is an on/off solenoid at the top of the injector pump that is the fuel cut off to kill the engine. I've pulled the cover of this solenoid housing that is on the low pressure side and for the past 2 days poured a 50-50 mix of seafoam and diesel in and suctioned it out with a turkey baster until clear. I did have varnish initially. It's now currently full of seafoam for tonight and I've gone out every so often and bumped it over. My issue is I can't get anything out of the injection pump so I can't really pull a cleaning mix through right now.
 
Last edited:
Do you actually see fuel and not air at the line going into the pump. Don't trust just a reading on a gauge. My air compressor has a gauge on it.

Try taking the shutoff solenoid out and turning it over like that to see if you have fuel there. If you do make sure there is no air there.
 
Schattenreiter said:
Do you actually see fuel and not air at the line going into the pump. Don't trust just a reading on a gauge. My air compressor has a gauge on it.

Try taking the shutoff solenoid out and turning it over like that to see if you have fuel there. If you do make sure there is no air there.
Click to expand...
Thank you for the help. yes I have fuel coming in. I did that today. I opened the solenoid cavity on top of the injection pump and suctioned it out and then reinstalled the top and turned the truck over and it would fill up. Also, with the top off the on/off solenoid, I can pump the primer bulb on top of the filter housing (used to reprime after filter changes) to pressurize the line and fuel will slowly fill the solenoid cavity if I suction the cavity out (its full when I open it) or it just flows over. This afternoon I pressurized the line from the filter to the injection pump with the bulb and allowed it to fill the solenoid cavity and then suctioned it out with the turkey baster. I did this a few times over a couple of hours while working on replacing rubber lines elsewhere.
 
Last edited:
Thanks for the help yall.

A member here gave me a guy to contact that is familiar with these vehicles and it was determined that nothing else could be done for this injector pump and that replacement was necessary. They're like hen's teeth so I'm having to send it out to a specialty shop up in Milwaukee as the shops around here that rebuild pumps didn't want to mess with it.
 
Additional info for the curious. The pump mechanic called today with not so good news. He stated that its likely the owner before me tried to run a mix of cooking oils in it. This mix sitting for a year on the rotor that helps to compress the fuel actually ate into the metal due to its corrosivness and thus the rotor is shot making the pump as it is not rebuildable. I need to find another similar pump to take the rotor out of.
 
I'm kinda in a rush and didn't read all the above post but those pumps are bad for the roller sticking and not making high pressure. Do you have any HP fuel coming out injector lines. If not it's obviously not making HP. You can pull off a few lines and while spinning engine apply air pressure to to where the line was attached. This some times helps free up the rollers. I've had best luck using a 50/50 mix of acetone and atf and letting it sit over Nighy in the pump. And I'll heat and cool the pump several times using a electric heat gun. Heat it up till you can't hold your hand on it and let it cool.

I've dealt with these pumps alot on generators and they sit alot and the pumps get gummed up.
 
Diablos said:
could be an option for ya

www.dieselsite.com

6.5L 5521 HD Injection Pump

You'll find brand name diesel performance parts at Dieselsite. Get advice for your truck from the owners who are also certified AMSOIL distributors.
www.dieselsite.com
Click to expand...
Diablos, sorry to take so long to reply. Thank you for the comment. That is an electrical pump for a newer 6.5 vs the mechanical 6.2 which is driven off a gear from the crank.


#update 3/13

So they were able to rebuild it after replacing the head and rotor. I will give it to the shop they were very nice and called a few times and tried their best to save money offering options on what to do. If I had months to spend to find a cheap core I could have saved a few hundred but its still a crap shoot on a used pump as to whether or not those parts would be good for a rebuild. I've had pretty good conversations with 3 guys at this shop and this pump must have been a sight to see because it was well known throughout the shop even with the office staff lol. All I had to say was the military truck and they would chuckle... I think in pity. Honestly, while they probably were not the cheapest, actually getting customer service with recommendations and unpressured "What I would do" was very, very nice. I'm sure I'd still be talking to the one guy. The pump was rebuilt to a standard for sea-level running from the high-altitude pump it was and is now in the mail back home. They recommended, given what the saw in the pump that I clean out all the hard lines, inspect/test or replace the injectors, and drop the tank and wash it completely out to prevent any of the old junk fuel, while diluted from reinjuring the new pump. The one guy said you just paid me a bunch of money to do this I don't want to see you back. I laughed and thanked him for the comment.
 
Last edited:
You must log in or register to reply here.
Back
Top Bottom