Hi
I have a 91.5 250 Auto with 260,000 miles, I bought it 10 years ago with 180,000 miles the injection pump had just been replaced. It is bone stock and never gives any trouble till last week.
While doing some alternator testing on my truck I found that it missed at WOT and made lots of white smoke with the engine cold (40 F weather running 5 minutes grid heaters done cycling) it was better when warm but not right. I removed the injectors and cleaned them with Carb cleaner and a brass brush.I borrowed a tester to check pressure and spray pattern
I tested my six and three others that were from a 120,000 mile truck. Four of mine had an even spray pattern that popped at 2500 PSI one popped at 2000PSI and one only sprayed from 4 of the 6 holes, of the extra 3 one was good one popped at 3000 PSI and one sprayed from 4 holes so I swapped a couple parts and got 6 that popped at 2500 PSI and all holes sprayed, some were a finer mist than others some were more like a garden hose but thats all I had.
I put them all back in and now it makes just a little white smoke and hits on all 6, I know it is not quite right but don't think it will cause any damage.
Now I want to understand the proper way to test injectors and how to open up plugged holes and the pressure they should pop at just to see if I could get the spray patterns better.
The funny part is that I have a new set of Bosch PW injectors that I bought a few years ago that I intended to install but cannot find them in all my stuff.
I look foreward to finding the right way to service injectors.
Thanks Hyperpack

 

The stock pressure for ours is 3550psi. So even though it is better than it was, it could still be better.

You will need to diassemble them to get the tips cleaned out. Then you will need shims to bump up the pop pressure. Then you may still need new tips, as they can leak with age and light use. If you need one new tip, you need 6. You also need to keep your needle valves with their respective tips, as they are a matched pair. Local shop here uses a solvent; others use a sonic bath to clean the tips.

Daniel

 

Thanks dpucket
Now that I know the right pressure I can play with the 3 extra I have, I bet 1000 pound higher popoff will make a big difference.
If I get the pressure right and the pattern is still bad is there anything I can do to improve it? The needles looked good on mine didn't seem to be stepped, I did keep the needles and tips as matched pairs.
What wears out, The holes, The needles?
What is the proper way to pump the tester, Slowly or quickly on the handle?
Thank you Hyperpack

 

Quick on the handle.

 

I've seen the guys at the pump shop do both. first go quick, then hold it about 50psi below pop to see how well stuff seats, and if it dribles or not. If it dribbles, you need a new tip (no tthe only indication, I'm sure).

You can clean the tips and get the holes clean with the right solvent. Sorry cant be any more help than that. Sometimes, they squirt out even though they are popping at the right pressure and have been cleaned. New tip time.

DP