Diagnosing the DB2 pump

[shadpeters]

So a while back I started a thread about an intermittent starting problem with 85 m1008. It would occasionally sit there and crank and crank and just would absolutely not fire up. Well, I figured out that I had a bad glow plug relay, so I replaced that and has been starting fine since... that is until yesterday. I went to go down the road and it started, ran rough for 5-10, and when I tried to give it a little throttle to even it out it just died. After that I cranked and cranked and it would not even fire.

The difference is that a few days ago I installed a tiny tac on my truck. I believe the way that those work is that they use a transducer to detect the high pressure pulses traveling through the fuel lines from the injection pump. I know that the new tac works, because I have had the truck running a few times, and it was working when the truck initially started up and then died. However when I sitting there cranking on it the tac just sat there zero.

This would seem to indicate to me that I don't have any fuel traveling through the the lines, otherwise It ought to show a couple hundred rpm when its turning over. Does that seem like sound logic? I have never had to work on the IP on one of these before, where should I start looking? I have an extra pump that came with the truck when I bought it, but I don't know for sure that its any good.

 

[cucvrus]

I doubt the truck is turning fast enough cranking it over with the starter that the tachometer would pick up any pulse. My opinion is do NOT waste your time putting a used injection pump on. Injection pumps are an expendable item on the 6.2 engine. I don't even put used starters on without putting them thru the rebuilder's shop. It saves a lot of rework that way. But if you want go ahead and give it a try. You can have the current pump rebuilt for about $300. + the gaskets. I would change the lift pump also while I was changing the injection pump. Also check the fuel flow from the tank to the pump. The fuel sock/strainer in the tank could be clogged. Worth a look see. Hope I did not scare you. But once you fix it right the first time it will last a long time. That has been my long time experience so far. Still going.

 

[royalflush55]

I would make sure the filter and fuel lines are staying fully primed and not sucking air somewhere. See if the check valve is working on top of the injection pump.

 

[m16ty]

You can have the current pump rebuilt for about $300. + the gaskets.

Where can you get a DB2 rebuilt for $300?

I can rebuild one myself for less than $300 (providing the head and rotor is usable) but most shops around here want $700+. If I could find somebody to rebuild them for $300 I'd do that instead of rebuilding myself.

 

[jpg]

Where can you get a DB2 rebuilt for $300?

I can rebuild one myself for less than $300 (providing the head and rotor is usable) but most shops around here want $700+. If I could find somebody to rebuild them for $300 I'd do that instead of rebuilding myself.

Diesel Care And Performance Inc, as recommended by cucvrus.
http://www.dcpcart.com/OScart/product_info.php/1982-fuel-injection-pump-62l-diesels-heavy-duty-p-122

 

[CUCVLOVER]

Diesel Care And Performance Inc
http://www.dcpcart.com/OScart/product_info.php/1982-fuel-injection-pump-62l-diesels-heavy-duty-p-122

They do great work. My truck runs great now that I had them rebuild my pump. It's only a 3-4 hour job to pull one. Just go easy and have fun.

 

[Jozseph]

Diesel Care And Performance Inc, as recommended by cucvrus.
http://www.dcpcart.com/OScart/product_info.php/1982-fuel-injection-pump-62l-diesels-heavy-duty-p-122

FWIW

Do a search for reviews of "Diesel Care & Performance", before you do business with them.

Reards

Joseph

 

[richingalveston]

I used badger diesel. I put my pump and injectors in a box with a $600 check. 7 days later I had a rebuilt pump (not the same one sent but does not matter) 8 new injectors (not rebuilt, brand new NOS). and the new return fuel line. I could not find a better deal when you include 8 new injectors and the fuel line.

very easy to work with. don't have mine back together but should in the next couple months. Work is busy.

 

[Skinny]

I would go through some preliminary stuff before swapping pumps out. Like it was said, check filters first. Check for flow to the IP while cranking. Do you hear the solenoid on the IP cover clicking when you apply 12v to it? Check the return line for blockage. Has the tank sock been inspected? All of these will make you dead in the water. Then spend the coin on a new IP.

If I was using this truck everyday and the IP is questionable, I personally would start at the tank and work my way up to the IP replacing everything. That way you are good for another 100k miles easy.

 

[richingalveston]

Pull the fuel line loose from the injection pump. The one that leaves your fuel filter. extend it into a bucket. Turn the truck over and if fuel is pumping out when you turn it over, everything is fine back to the tank, may not be perfect but will not keep the truck from starting.

IF you have fuel, you have a bad pump, if you do not have fuel, go to lift pump first.
Starting from the other end is definitely more thorough but check the parts that are most likely to fail first and you will get your problems solved faster.

one thing to do when checking the fuel pump, when you run the hose into a bucket, while you are cranking, you need to put your finger over the hose and make sure it pressures up and sprays. Your fuel pump can go bad but pump a lot of fuel when there is no restrictions but as soon as the line pressures the fuel stops pumping.

 

[sschaefer3]

FWIW

Do a search for reviews of "Diesel Care & Performance", before you do business with them.

Reards

Joseph

Also google Pensacola Fuel Injection. I got taken by them, thankfully I still had my original pump and had that rebuilt locally here in Phoenix.

 

[shadpeters]

We have a local shop with a good reputation that rebuilds pumps and injectors, if i end up needing one rebuilt I'll probably go that route.

 

[cucvrus]

Honestly I never had a set of nozzles rebuilt. I installed new ones after I put a new pump on and never noticed any difference in power performance or economy. So I don't change them anymore. Unless they leak. I have a friend that has a popper and he checks them for me.

 

[shadpeters]

So, I just went opened the bleeder valve on my filter houseing and I definately have fuel coming up (although the fuel coming out of the clear plastic house appeard to have bubble in it in the tube.. so maybe that is the problem?) Also, I cracked two injector lines just to make sure that I was not getting fuel up there and I am definately not.

I would go through some preliminary stuff before swapping pumps out. Like it was said, check filters first. Check for flow to the IP while cranking. Do you hear the solenoid on the IP cover clicking when you apply 12v to it? Check the return line for blockage. Has the tank sock been inspected? All of these will make you dead in the water. Then spend the coin on a new IP.

If I was using this truck everyday and the IP is questionable, I personally would start at the tank and work my way up to the IP replacing everything. That way you are good for another 100k miles easy.

What is the solenoid on the IP Cover, what does it do, and what does it mean if i don't hear it click? I assume its either one of the two green, or the red wire? do I just run a jumper to it from a 12v source?

I would make sure the filter and fuel lines are staying fully primed and not sucking air somewhere. See if the check valve is working on top of the injection pump.

what is the check valve? where is located? and how do I check it?

Pull the fuel line loose from the injection pump. The one that leaves your fuel filter. extend it into a bucket. Turn the truck over and if fuel is pumping out when you turn it over, everything is fine back to the tank, may not be perfect but will not keep the truck from starting.

IF you have fuel, you have a bad pump, if you do not have fuel, go to lift pump first.
Starting from the other end is definitely more thorough but check the parts that are most likely to fail first and you will get your problems solved faster.

one thing to do when checking the fuel pump, when you run the hose into a bucket, while you are cranking, you need to put your finger over the hose and make sure it pressures up and sprays. Your fuel pump can go bad but pump a lot of fuel when there is no restrictions but as soon as the line pressures the fuel stops pumping.

Will It work if I do the same thing with a plastic hose coming off of the bleeder valve on the filter housing or does it have to be the feed line to the ip?


Are there any external electrical components that would cause the ip to not function correctly?



I have another question, the Used IP that I have is a 4524 which is understand is a hmmwv pump, I assume that the pump that is on truck currently is original to the truck. were I to get one rebuilt, is one more desirable than the other?

 

[richingalveston]

best to check fuel at the connection on to the pump.
the pink or red wire on top of the pump is power to the solenoid that turns the fuel on and off right at the pump. that is how the truck starts and stops. It is the check valve mentioned but it is not really a check valve it is a solenoid controlled on of flow valve.

with the ignition on you should have 12v at that wire. when up connect and disconnect you should here a click, that is the valve opening and shutting.



Power to this wire is controlled by the ignition but there are fuses and fusable links

 

[royalflush55]

There is a check valve that screws into top of the injection pump. Make sure it is not restricted or stuck open. This is not the same as the electric solenoid.

 

[Jozseph]

PDF copy of "Stanadyne DB2 Operation and Instruction Manual"

At URL: http://www.steelsoldiers.com/showth...ne-DB2-Operation-and-Instruction-Manual-99009

 

[shadpeters]

SO, the truck has been parked for a while, I just haven't had a chance to work on it till now. I rented a fuel preasure gauge from O'reiley, and while I am getting fuel up do the filter, when I checked the psi it was not even enough to register on the gauge. now unless I used the gauge wrong in some way, this would seem to indicate to me that the lift pump is bad. would you agree?

 

[richingalveston]

yes, bad lift pump, they will move fluid when bad but not under pressure. That is why when testing by hand make sure the pump puts pressure and makes the fuel squirt when your finger is over it.

many people pull the line and turn it over and see fuel flowing and assume the pump is good when it is not able to push under pressure.

 

[Jozseph]

SO, the truck has been parked for a while, I just haven't had a chance to work on it till now. I rented a fuel preasure gauge from O'reiley, and while I am getting fuel up do the filter, when I checked the psi it was not even enough to register on the gauge. now unless I used the gauge wrong in some way, this would seem to indicate to me that the lift pump is bad. would you agree?

shadpeters, I posted this on another thread; attached are three pages from the GM Factory Manual for the 6.2

Covers Diagnosis Procedure for fuel pumps

View attachment GM 6.2 Diesel Engine pages 7-34-36.pdf

Attached is a PDF copy of the GM 6.2 Factory Service Manual

View attachment GM 6.2 Diesel Engine Manual.pdf

Regards

Joseph