Calling Tom Lawrence

From : steve lusardi

Q: tom i finally figured out the high speed miss on the cummins. it was water in the filter jar. this little exercise has taught me a few humbling lessons. first my schedule to dump fuel from the filter needs to be shorter than every 6 refuelings. i understand this is dependent on the environment but there was no water in the bowl alert which should have occurred. i borrowed a drb3 and ran all the tests in order to familarise myself with them and a few tests created strange results. if you would could you please verify or interpret these readings. fuel water sensor voltage = 5.2 v water in the bowl. no error boost pressure at idle 750 rpm = 100kpa 0 psi on gauge boost pressure ignition on engine stopped = 99 kpa 0 psi on gauge boost pressure wot max speed 3200 rpm 30 lbs on guage = 260 kpa max egt 1100 f thanks in advance steve .

Replies:

From : tom lawrence

i finally figured out the high speed miss on the cummins. it was water in the filter jar. really hmmm... would have thought that would have it running like crap all the time - not just at high rpms. first my schedule to dump fuel from the filter needs to be shorter than every 6 refuelings. i understand this is dependent on the environment but there was no water in the bowl alert which should have occurred. ive found the stock wif sensor to be practically worthless... mine goes off from time to time and there is zero water in there. i have another water separator as part of my fass system and thats always clear too. fuel water sensor voltage = 5.2 v water in the bowl. no error boost pressure at idle 750 rpm = 100kpa 0 psi on gauge boost pressure ignition on engine stopped = 99 kpa 0 psi on gauge boost pressure wot max speed 3200 rpm 30 lbs on guage = 260 kpa max egt 1100 f the boost numbers are good... maybe a little low on the max number. if i remember you have a 600 engine which should peak around 35psi or so stock. however if you did this test on a dyno especially an inertial dyno the boost might not build as much... as for the wif sensor readings you should be measuring resistance across the sensor. with fuel in the bowl the resistance should be off the chart ie. very high. with water in there it should drop to around 30000 ohms or so. id be more concerned about where the water is coming from. in my three years of owning my truck ive never had water in the bowl i drain it every filter change and look closely... after the third fuel filter change i purposely added some water to see what it would look like... definately never looked like that. .

From : greg surratt

on fri 07 apr 2006 003829 gmt tom lawrence tnloaswpraemnmcien5g@earthlink.net wrote i finally figured out the high speed miss on the cummins. it was water in the filter jar. really hmmm... would have thought that would have it running like crap all the time - not just at high rpms. i had the same experience. i was on a road trip and bought fuel about 600 miles from home. about an hour later the engine started missing at high rpm. accelerating became almost painful. the further i went the lower the rpm where the miss occurred until when i got home i had the miss at cruising rpm for 65. truck ran great at 55 though. there was no water in fuel sensor indication at the time. changed the fuel filter and it was like i had bought a new truck. im just glad i didnt have the trailer with me on that trip. greg .