I have a problem with my 6.2 and hope that some of you have some ideas. When the truck sits for a while, over night or while i'm at work it seems the injector pump looses it's prime. If I crank on it for a minute it will start, it used to start right away. I changed the lift pump and fuel filter, and it was ok for two days then it went back to loosing it's prime again. My theory is the lift pump is going on it, but would like some ideas from somebody who knows a little more about them than me. I'm hoping maybe it's something simple because I don't want to stick alot of money in this truck. Any ideas would be great.

 

Probably getting air in the system. Do you have any drips anywhere?

 

I don't know which engine you have, (1/2 ton or 3/4 ton truck) but there should be a water temp sensor in the upper water jacket on the passenger side of the engine toward the firewall. Its used to determine if you glow plugs should come on or not. When these get old they loose there sensitivity causing inaccurate information to the Glow Plug controller.

I had a 6.2 in a 2500 suburban some years ago. I have whats left of the chasis manuel. Most problems with starting with these engines are glow plug related. The only way around it is to install a toggle switch under the dash that you control by bye passing the system. You would turn the system on no longer than 8 seconds. Longer times will tend to swell the glow plug and keep you from removing it.

First thing I would do is check the glow plugs and make sure they are all working. Use a 12v test light. Clip the alligator click on the positive battery terminal and touch the glow plug on the metal piece on the glow plug. If the light turns on, the glow plug is OK, if it does not its bad. If you have 3 or more bad, it will not start some times. Get a book on the 6.2 at Auto Zone and look at the Glow Plug electrical circuit.

Another problem is cranking speed. Batterys terminals have to be clean and the common double cable screw on, 5/16 head terminal screw must be tight. Check the inside of the two. Any white stuff, clean them out. I've seen on my own truck that I would tighten this up to much and actually put a hole in the battery causing acid to migrate into the connection.

Fuel pump. I had to install a electric pump after 150k. The mechanical pump would not put out more than 3psi. I think the lobe that drove the pump must have been worn bad.

You might be able to find info on the intranet on the Glow Plug circuit. I may be able to copy the Glow Plug info from the chasis manual and e-mail it to you if you wish. Just PM and give me you address. Can't do it until Tuesday. Will be out of town.

One other thing. Go to the front of the engine and find the Injection pump. You'll see a 1/4 rubber line coming off the top of the pump. Thats the fuel return line. Pull the hose, remove the check valve the hose was attached to.
Hold the check valve up to a bright light and look into it. If you see black specs or large specs around the glass spring loaded valve, the pump is sheding some parts and stopping up the return line. If this valve gets stopped up it will shut down the engine. Just squeeze the hose with the engine running and it will shut down. If this check valve is beggining to plug up, you should change it or just drill the glass eye out so it can free flow. It will run forever like that. I have seen many 6.2 on the road with the hood up and would stop and change the valve for them with a spare I kept in the truck. I got their's and they drove away without a tow job. Symtoms are a real soft feeling pedal, It feels like there is no fuel, but really the return system is failing.

Hope some of this helps. Like I said I don't know what your driving.

Dave

 

I had a 1982 6.2 GM that had some hard starting when I bought it cheap because they had to start it with starting fluid.
I led them on that it would cost a lot to fix.
When I got it home I replaced the fuse for the glow plug controller, replaced the 2 batteries and it worked fine.
Without glow plugs unless it is already warm you will just run the batteries down.
I had air getting to the fuel somewhere so I installed a section of cleat tubing on the fuel inlet to the injection pump and then checked for bubbles.
If the fuel is aerated at all you will have hard starting and once it is running you will have a loss in performance.
I found my lines were sucking air at the selector valve and at the connection to the tanks.
It also had an air leak when the tank would get almost empty and I found the sock on the end of the fuel pipe was cracked. The sock is for the water separator in the tank.

Other than a few injection pumps and 3 blown 700R4 transmissions that truck was great. I had it until it got totaled and bought my Dodge.

On the earlier thermal glow plug controllers if the engine is ever low on coolant where the controller is not immersed and the wait to start is iniated it will be destroyed almost immediately

Never start it with Ether, use WD-40 it works great and is a lubricant for the cylinders. A shot into the intake horn and it will fire up without glow plugs.
(In warm-ish climates)

Back then when they started taking the sulphur from the diesel fuel the throttle on the Stanadyne pumps would stick, the only thing that would fix the problem was to use Stanadyne fuel additive to increase the lubricity then it would work again.
Jim

 

Thanks for the info, i'll check the fuel lines maybe they are sucking air. I checked the glow plugs they are all good, batteries are good, the starter is new. The truck has always started good in warmer weather, I got in it one day to start it and it ran for a couple seconds and quit then I had to prime it to get it going again. Anyway it's in a 3/4 ton 4WD truck if that matters anymore ideas would be great. Thanks

 

That's not entirely true. The glow plugs could be severely eroded and still pass that test. The best way to really check them is to remove all the glow plugs, compare with a new one to check the amount of erosion, and then using jumper wires and a good battery, momentarily hook the positive to the connector tab and the negative to the glow plug housing. If they smoke in a couple of seconds, they should be fine. WARNING! DO NOT leave them connected for more than 5 seconds as this much amperage will damage the glow plug! A properly functioning glow plug system is crucial to easy starting for the old 6.2 and 6.5 GM diesels. There is a reason that most dealers stock a set of glow plugs just like they do spark plugs for a gas engine. My early years as a dealership technician fell when 6.2s and 6.5s were common and still under warranty.

Good Luck and keep us posted.

 

If you have to replace the glow plugs at any point, buy the Delco 11Gs, these are the best around. They last a long time, and you can keep the juice going to these for a long time and they will not burn out.

If the engine is cold, it will not start if the glow plugs are bad. So chances are that either your glow plugs are marginal, or a couple are bad, or you could have a faulty glow plug controller. Also, if your rubber fuel lines are over two years old, I would look into replacing these. If they start dry-rotting, and air gets in to the system, this can cause a loss of prime as well.

 

Good advice, i'll pull all the glow plugs and check them and replace the rubber fuel lines. I know this hasn't been done since I owned the truck. Thanks for the help.