Poor performance / fuel filter

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afchap

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Joined
Dec 19, 2008
Posts
1,279
Location
...East TX, or on the road...
Apx 73k on my 2002 model Cummins ISC, 9 mo. since last service ...hit the road from AL to TX. Noted a couple of minor stumbles sometimes on acceleration from a stop. Seemed to take a bit longer to get to cruising speed, then I noticed cruise control could not hold highway speed even on the most gentle inclines. Cruising around 65, the speed would creep downward until it found a downhill run to get going again. At first I wondered if the turbo was not working well (no boost gauge, etc). Then I thought of the fuel filter. I realized I did not have a filter wrench with me, and stopped at a tiny "truck stop/cafe" off I20 East of Meridian MS. Mine has only one fuel filter, originally located high on the block on the pas side ...it was a two person difficult job to change in the original location, so I paid Cummins SW in Albuquerque $550 several years ago to relocate the filter to the rear. The "truck stop" had nothing more than fuel, and the filter was tight, so I went on to Meridian and got a filter wrench at Walmart while the DW got some supplies. It was very tight, but I got it off and put my spare filter on (in a very cold light rain), did the key on for 30 seconds to prime, off for 30, and a second time for good measure, then started the engine. Sounded good, got up to go close the hatch and it died. I went through the prime routine two more times before it finally stayed running. And when I got back on I20, it felt like I had a new engine!! Fuel starvation definitely causes power problems! Now I need to get another spare filter...
 
afchap said:
Apx 73k on my 2002 model Cummins ISC, 9 mo. since last service ...hit the road from AL to TX. Noted a couple of minor stumbles sometimes on acceleration from a stop. Seemed to take a bit longer to get to cruising speed, then I noticed cruise control could not hold highway speed even on the most gentle inclines. Cruising around 65, the speed would creep downward until it found a downhill run to get going again. At first I wondered if the turbo was not working well (no boost gauge, etc). Then I thought of the fuel filter. I realized I did not have a filter wrench with me, and stopped at a tiny "truck stop/cafe" off I20 East of Meridian MS. Mine has only one fuel filter, originally located high on the block on the pas side ...it was a two person difficult job to change in the original location, so I paid Cummins SW in Albuquerque $550 several years ago to relocate the filter to the rear. The "truck stop" had nothing more than fuel, and the filter was tight, so I went on to Meridian and got a filter wrench at Walmart while the DW got some supplies. It was very tight, but I got it off and put my spare filter on (in a very cold light rain), did the key on for 30 seconds to prime, off for 30, and a second time for good measure, then started the engine. Sounded good, got up to go close the hatch and it died. I went through the prime routine two more times before it finally stayed running. And when I got back on I20, it felt like I had a new engine!! Fuel starvation definitely causes power problems! Now I need to get another spare filter...
I had a simulier problem on my 5.9 Cummins.  That turned out to be a dying vacuum pump.  Replaced the pump and she was back to full power.  We also found a small leak in a vacuum line when the new pump was put in.  Made a heck of a whistle sound.
 
Mine takes several key cycles to prime the system fully. That's a ISL with the single filter configuration like yours.

Fuel filter and air filter are the #1 suspects with any such diesel performance problem. Replace them first before worrying about anything worse.
 

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