I'v replaced a few parts on my 91 trooper. Its been setting for a while and I'm ready to get it back on the road. Me and my brother couldn't seem to get the timing right and decided to check the injectors to make sure they were firing properly. we took the fuel rail out and he held the injectors in while I turned it over and they all fired well except that they all fired at the same time and then paused only to fire together again and again. This explains why it was backfiring and couldn't get the timing right. We switched out the ECM and the distributor with ones from a working trooper and they still all fired/squirted at the same time. I would very much appreciate any helpful info on this mystery
thank you
Ben

They are firing correctly.
This type of injection system is known as a "batch fire" system.
All the injectors do fire at the same time, unlike a "sequential fire" system where each one fires individually.

All Isuzu engines up to '98 fire this way, if I'm not mistaken.
It wasn't until '98 and up until they went to the sequential fire systems.

If you are having problems setting the timing, you might
want to check that balancer. The outter ring with the timing marks on it are known to slip on the pulley and it will throw your timing marks all out of whack.

Thank you very much...I was wondering what the heck was going on, I still wonder how the engine can perform at all with them all going off at the same time but I have a feeling that what you are saying is correct...thanks again.
Ben
p.s. i will check the balancer next

93+ 2.6 is sequential, no?

I did some checking and I was mistaken, a little.

The 88 & 89 Turbo Impulse was 2.0l engine was sequential fire.
And all Isuzu engines '96 and up (Not '98, like I stated before) are sequential.
The '93+ 2.6 is sequential.

ah, always thought the later variant 2.6 w/oddball red injectors was seq, thanks for clarifying.

Nope. 93+ are SEFI. Different injectors, different dizzy and different ECU.

Michael

If you are having problems setting the timing, you might
want to check that balancer. The outter ring with the timing marks on it are known to slip on the pulley and it will throw your timing marks all out of whack. [/quote]

Yep thats how I blew my Headgasket last time around, We could not get the timing right and we kept advancing and one day it blew out, I still got home. The fuel injectors on my 2.6 fire at the same time also, we found this out after we had the engine apart and were messing around and hooked them up to see how fine the mist was and I had crap all over me, haha thats when I bought new ones, we thought they were messed up too. after research we found out different. BE SURE TO CHECK THAT HARMONIC BALANCER!.

About the quickest way to check the timing mark for certain is to pull the top timing belt cover. You can line up the timing mark on the cam pulley with the mark on the plate behind it, then the timing mark on the balancer should be at 0 degrees. If not, paint a white stripe on to be the new zero and paint a line across the gap where the rubber seperates the inner and outer parts so you can see if it continues to move on you.