Hi folks,


I have a 84 blazer with the 6.2 liter. It is an old military M1009, and unlike alot of others, I have had fantastic luck with mine, and drive it everyday on both short and long trips. Anyhow, here is my problem. When the engine is cold, it starts right up. If I go to the store, stop it come right out and start it, it starts right up. But if I go to the same store and it sits for about 2 hours or so, and go to start it, it takes quite a few cranks to start, and when it does, it really has a bite to it and a little smoke comes out. Tonight, it took a long time to start and even without the engine starting, some smoke was slowly swirling out the tailpipes. Finally, as usual, it eventually started. Why in the world is this happening? The engine is not cold, as the glow plug lights do not come on, and the engine is not hot, but rather warm.


Mike

The DB-2 is know to have hard start problems warm, when the head and rotor in the pump gets warn out.

Mike,


I'd start doing some TS on the glow system before delving into the IP, which may indeed have a problem, but start with the glow system, if it isn't working it will make any IP wear problems worse to contend with,


Put some data on your sig line so you don't have to keep reposting your trucks config with each post and with a quick glance we know what equipment you have, make it easier for us to help you to troubleshoot your problem,

Thank you for the replies. I have relied so much on this Blazer because of it's history of reliability, that I have remained an idiot when it comes to diesel engines. That being said, why would my glow plugs work great when it is cold, and the truck start right up when it is cold or hot, but not when it is warm? Why the mysterious wierdness when it has just been sitting around for a couple of hours cooling down? I apoligize if this is a repeat of other posts. I looked at some others and I noticed they all mentioned the pump as a culprit. I am curious to know why the hard starting when it is warm only. And, I will add the data you mentioned Turbine Doc....Thanks again.

When worn the warm pump has trouble building the necessary pressure to start the engine at cranking speed. Check all the easy stuff first ie glows, battery connections, filters.

Wait To Start indicator should illuminate at start even with engine hot, but with shorter duration.


Check temperature sending unit in coolant crossover - passenger-side, in vicinity of heater hose tap - has two wire connector.


If not there, '84 system may be in heads, at at top rear on each side.


Also, glow relay timing circuitry may be detriorating when warm.


There are a few websites for the military vesions, with complete shop manuals, including wiring diagrams, posted - might give those a check for military-specific troubleshooting procedures and hints.


Check your glow system first - no Wait To Start indicates electrical trouble. Edited by: gmctd

Okay--will try all these things. I have been around this Blazer since 1996 and the wait to start lights have never illuminated even for a half a second when the engine was warm/hot; only when it was on the cold side. Thanks for all your input; I appreciate it.





Mike

The hot hard-start scenario, mentioned by QM, is resulted from excess clearances between rotor and distributor head, with insufficient pressure to 'pop' injectors.


Can also be caused by slow cranking speed - low batterys, bad cable connections, worn starter bushings - even when inj pump is not worn.


Check Glow first including WTS ndicator lamp bulb, then electrical including starter, then inj pump.


And don't forget to check out the mil cucv forums.Edited by: gmctd

The problem is your injection pump is worn since the pistons aren't developing the pressure when the pump is warm. When your engine is warm then the glow plugs do not come on. And a bad battery or connections would cause hard cold starting. A rebuilt pump doesn't cost that much.

6.2 hard start hot problems due to worn head and rotor are quite rare.

Cougar, Pumps don't have 'pistons' they have plungers, also, he did mention truck start well when cold.

I do agree with you that rebuilding the pump would be a good idea, better to do it when the truck is still working than when it completely fails, thats when it can get expensive.

Another quick thing to check is the supply pump, or just replace it, they can give similair problems.

A worn injection pump can start a 6.2L diesel when it is cold, but fail when it is warm. That is because when it is hot the clearance is excessive around the piston and sufficient pressure will not build up for proper operation, i.e. the fuel pressure will not open the injector valve or it doesn't atomize properly to have ignition. An emergency step is to use the glow plugs to help the starting by short circuiting the glow plug relay while someone else cranks the engine. This is from my experience as well as others.

You can get a rebuilt injection pump for the same price regardless of when you trade it in to a shop, or at least it is that way in the U.S. where I have exchanged pumps.

Most problems can be solved by making sure it cranks at full speed (batteries, cables, starter, etc.), glo-plugs come on and fuel is available. You have fuel available by the smoke upon cranking. Is it cranking up to normal starter speed? If so, bypass the glo-plug system and see if it starts.

My pickup is so old and tired, it won't start warm without glo-plugs. (loss of compression heat from ring wear) The engine just doesn't make enough heat of compression to start it. By adding glo-plug heat, the engine fires right up! The engine also idles a little rough from the afore-mentioned low compression.

The injection pump problems can accent these other problems, but usually, a worn IP will show other problems as well.

Like the other guys say, check all the basics before getting into the IP.

Its not uncommon at all for the head/rotor to wear to a point where startability is diminished and the truck run perfectly normal once its started. Without a doubt though, glowplugs, batteries, starter, supply pump, etc. all need to be checked out first. There's a lot of other things that can go wrong inside the IP that can cause startability concerns other than head/rotor wear, 6.2s rarely had this happen to them anyway. I always reccommend pump to be rebuilt whenever either its history or performance are in question. Its really not that expensive, most shops have exchange units available and can get your truck back to you same day. Its also cheaper to have yours rebuilt when its getting a little weak rather than when it fails.

I agree about rebuilding the IP before it fails. The failure rate is proportional to the mileage distance traveled from home! The engine seems to knock louder when you get farther from home also. The farther you get from familiar surroundings, the greater the failure rate of everything I own!!

If you would like to entend the life of your injector pump, buy a cheap elctric fuel pump and install it back by the tank. Run a wire to any hot ignition lead.

This will ensure that you have an ample fuel supply at your IP.

I have seen hundreds of IPs needlessly rebuilt, or replaced.

I have seen hundreds of IPs needlessly rebuilt, or replaced.
Thats an interesting comment you just made, because I personally have rebuilt hundreds of IPs, and I can't think of one of them I would classify as a 'needless' rebuilds. There's a lot of components and subassemlies in an IP, certainly going through one, replacing gaskets, cleaning serviceable parts and replacing worn ones, reassembling, testing and recalibrating can't be deemed 'needless' just because nothing major is wrong.

Texas Diesel Guy, I think some confusion about rebuilding an IP comes from the improvements made over the years to the design of the pump. Since the advent of the EID, sleeved advance piston, etc., the early failure rates have dropped significantly. (We used to have to repair the pumps at low mileage intervals because of the pellathane governor weight retaining ring failure). The pump would let you know (gradually, with lots of early warning signs if you were lucky) when it was time for service and the problems we experience from normal higher mileage wear today were fixed without the owner even knowing it was occuring. Today's pumps are just designed too darn good! I don't get to repair near as many as I did in '78 - '80!

Thats an interesting comment you just made, because I personally have rebuilt hundreds of IPs, and I can't think of one of them I would classify as a 'needless' rebuilds. There's a lot of components and subassemlies in an IP, certainly going through one, replacing gaskets, cleaning serviceable parts and replacing worn ones, reassembling, testing and recalibrating can't be deemed 'needless' just because nothing major is wrong.
I should clarify that the problem is not really with needless rebuilds it's with mechanics that more familiar with gassers. Most mechanics will at any sign of trouble with a diesel choose to replace the IP. Where as us experienced diesel guys will exhaust all other possibilities before replacing the most expensive assembly on the truck.

You are probably right most of the pumps you see are worn, and will benefit from the rebuild, but by adding a simple fuel pump could extend it's life in the truck dramatically.

I agree with you there completely, electric lift pump improves longevity, startability and performance. I also agree with you that there are a lot of garages out there that take on some of these diesel jobs that should really leave them alone. With any complaint, smoke, hard start, low power all can be caused by a variety of problems within the system and misdiagnosing the problem can be costly.