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Cummins 350 cylinders 1-4 not developing power
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By JVR - Monday, December 16, 2019 10:58 AM
I have a Cummins 350 in my '86 Freightliner COE. It goes under 1K miles per year and has for 20 years now and with next to no problems.
Recently it was very hard to start, felt like it had a miss and seemed to improve with a short drive, but not to perfect level. We found water in the fuel and changed the filter, drained the bottom of the fuel tanks and made new fuel inlet hose and tank cross over hoses all to no real improvement.
Then I used a temp gun on the exhaust manifold and found that only the rear two cylinders were developing power. And there is a lot of loud rattling. It starts easily, no smoking issues. I checked the filter in the fuel pump & found it quite clogged. I ordered a new filter but I started it with no filter in the pump to test and didn't find any improvement.
How can I test the fuel pump itself? And what does anyone suggest I do next?
Merry Christmas,
Jim in Arizona
By 444xtmike - Monday, December 16, 2019 3:17 PM
If the screen in the fuel pump was clogged there is a good possibility the injector inlet screens are plugged. If it fuels from the rear, the injectors towards the front would be the first to plug.
By JVR - Tuesday, December 17, 2019 11:19 AM
In the Cummins 855 if some injectors became stuck is there any trick way to try to unstick them short of removing them?
By Two-Books - Tuesday, December 17, 2019 12:25 PM
My past experience from years ago that this problem if the result of water in the fuel the likely only remedy will be to pull the injectors and have them serviced. If the injectors are in fact stuck they and possibly others will have scoring damage to both the barrel and plunger. One other outcome due to water contamination can also damage the gear pump and or the throttle shaft in the pump itself...good-luck.
By Newto - Tuesday, December 17, 2019 10:32 PM
Pretty sure you can discount the fuel pump (because they are pretty much bullet proof with water and goo issues & won't give you a misfire ) but.......depending on how much foreign matter you found in the filters & how much water ingress you had your problem is in the injectors.

Either blocked fuel inlet screens on the injectors with crap (most likely) or maybe even a cracked injector cup (due to water) and possibly (because of lack of tell-tale smoke) a combination of both!

Either way.......all injectors out!.............sorry!!............

If you have blocked screens you can easily remove and clean them, re-oring the injector and refit.......AFTER looking at the cups for signs of a crack......(pretty obvious usually)...and check for free plunger travel by pulling out the injector plunger, removing the spring then refitting the plunger till it bottoms out in the cup.....should slide up and down easily.

watch out for fuel spraying out of the cup when you replace the done inside a bucket to catch the fuel and protect eyes!!!!!!!