Replacing fuel pump and injectors

I have a 1991 suburban with a 6.2liter "J" engine stock that has begun to start hard. All the glow plugs are new and the glow plug controller is new. I have 186000 on the original pump and injectors that i assume ( from what i am reading) that should be replaced based on what I am experiencing.
Because I want to do upgrading as I can afford it my plan was to replace the injectors with 6.5 liter high flow injectors (bosch) and aremanufactured injector pump and adress exhaust and air as I go. Is there any trouble at this point of going with this type of injector or am I missing the boat and should i stay with standard injectors?

As long as you have a coordinated goal in mind, an incremental approach to performance improvement is fine. On thing I would recommend is that you add and exhaust gas temperature (EGT) gauge before you get too far along in the modifications.

If you replace the pump with a 6.5L pump at the same time you add the 6.5L injectors, you will be in fine shape. You may have to turn DOWN the fuel until your intake and exhaust mods are in place.

Have you reviewed my article on performance improvements in the naturally aspirated engines?

Go to
http://www.thedieselpage.com/reviews/avanteng.htm
to assist in your understanding and planning process. Let us know how it goes, and Welcome! to TheDieselPage.com.

Dr. Lee :cool:

Tom,

When you mentioned the truck was hard starting, you didn't mentioned anything about the timing. With the 186K miles you have on the engine, are you still using the stock timing chain. These stretch over a period of time and will affect the timing. This can be partially compensated for by periodically adjusting the pump timing but eventually the crank and cam are so far out of time that there are noticible power losses. A very small adjustment of the pump can make a difference on how well the truck starts.

TimK

Quote:

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Originally posted by TimK:
Tom,

When you mentioned the truck was hard starting, you didn't mentioned anything about the timing. With the 186K miles you have on the engine, are you still using the stock timing chain. These stretch over a period of time and will affect the timing. This can be partially compensated for by periodically adjusting the pump timing but eventually the crank and cam are so far out of time that there are noticible power losses. A very small adjustment of the pump can make a difference on how well the truck starts.

TimK

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I can attest to that after removing my timing chain after 175,000+ miles and finding it had over 1" of stretch - I found a ton more torque low down after replacing it with timing gears :D .

The timing chain has never been checked and the injector pump has never been adjusted. Under heavy accelerating I don't even see any black smoke. The truck does idles very smooth and accelerates smoothly but I do notice that I can't maintain speed up hills even with no load unless I hit it going 75mph.The truck was very well maintained with the oil being changed every 3000 mile and the fuel filter changed every 15000 and was used for only light loads. Presently I have repaced the radiator and pump, rebuilt the transmission and the tranfer case recieved all new seals and the torque converter was replaced. My mileage is 16 to 17.5 mpg. To be clearer about the starting issue I will describe it. All summer long the truck starts when used at the end of the glow plug cycle with out touching the pedal just turn the key and it's running.If it's left for several days it will start hard and appear to be flooded and needs to be cleared out. and naturally it's worse as it gets cold but it does always manage to start. I will start by checking the timing chain play, I saw the process review of "how to" in another posting

Tom,

What you describe as "flooding" probably appears as white smoke out of the tail pipes while cranking. This is unburnt fuel from not having enough heat in the cylinders to ignite the fuel. This can be caused by the cylinder compression being too low, or the glow plugs not providing enough heat or the fuel not being injected at the proper time in the combustion cycle to ignite the fuel. A stretched time chain would cause the injection pump to inject the fuel too late. A worn pump can also have a similiar effect as it does not bring the pressure at the injector up soon enough to open the injectors at the proper time. Overall I think the 6.2L is very forgiving when it comes to worn parts but if you have a lot of wear (i.e. low compression, timing, injectors, pump and week glow plugs) these all add up to hard starting.

TimK

My truck acted the same way you described above...hard to start after a few days, cold weather difficulties, white smoke....changed my pump and injectors and it now cranks in only 1 sec. Couple nights down in the 30's lately...last year would have had to crank and crank...or even plug it in...now, it just starts like a new one. 180,000 miles.