2002 Dodge Ram
From : ed
Q: sorry in advance for the long post i thought a little history would help... 2002 2500 quadcab longbed/cummins turbo diesel/5spd manual/112000 miles. bought it used last may with 87000 miles on it. have a problem with the truck. when its cold it has no power and belches lots of white smoke. took it to the dealer last fall when it had 95000 miles on it. they replaced the lift pump for insufficient volume pressure was ok apparently. anyway that didnt really fix the issue completely it just didnt happen unless the outside temp was below 40f or so. so i just let the truck warm up for about 5 -10 minutes it usually works fine after that. never had the time to take it back to dealer while it was still under warranty about two weeks ago on a 400 mile trip empty no load the engine lost power at 70 mph 2100rpm i could keep it at about 55-60 1900rpm but couldnt accelerate. i pushed in the clutch and let it idle for a couple of seconds at 800rpm and then it would be ok again for awhile. this makes me suspect the lift pump is bad. on the way home a couple of days later the same stuff happened after about 2 hours or so and the coast method didnt always work so i turned the key to off and coasted for a few seconds started the engine up again ran ok for awhile. this happened usually up a grade but not always. the last hour or two of the trip it didnt happen anymore. i just finished installing some gauges pyro/boost/fuel press. started it up and drove away with the engine cold. no problems! so i thought about it a bit and figured that the schrader valve on the vp44 which i replaced with the fuel pressure gauge fitting maybe had been sucking air into the injector pump and that was the root of the problem...makes sense to me. fuel pressure was 15psi at idle and dropped to 12-13 while accelerating. boost was around 4 or 5 cruising and up to 10 - 12 while accelerating i didnt floor the throttle. pyro was 300-400 at the start and up to 750 - 800 accelerating dropped back to 500 - 600 cruising. then later that day i wanted to go up the road for something or another and had the same problem as before no power lots of white smoke. i noticed that there was 0 zero boost pressure fuel pressure was from 12 to 15 depending on my foot no change to the boost pressure. so i got to thinking that the turbo was flaky i shut the engine off coasted a bit turned the key on and popped the clutch to start the engine up again watched the boost gauge it jumped to 3 or so and pretty much stayed between there and zero depending on my foot. acceleration wasnt there but no noticeable white smoke. after a bit maybe two or three minutes of driving the truck suddenly jumped the boost pressure went up to about 8psi or so backed down to 5 and then seemed to work fine after that. floored the accelerator the boost went up to 20 psi the fuel pressure went down to 11 - 12 or so the pyro went up to around 1000 everything was fine again. gauges sure are neat! i wish dodge would put them on every truck they sell and train the new owners how to read them it would probably reduce alot of the service issues they get. bottomline i think the wastegate is not working properly and may be the root of the startup/cold operation problems ive had. does that seem to make sense to everyone else it doesnt seem to explain the highway speed power loss issue though...that may be another issue. how can i troubleshoot the turbo system is it an intermittent leak in the intercooler how do i check that out is it the wastegate how do i check that out i cant find much about it on the web doesnt seem to be many problems of that nature or it is not a user serviceable item... thanks in advance for your consideration and help.... eddie oklahoma .
Replies:
From : tom lawrence
where is the map sensor located on a cummins is it the connector on the drivers side behing the fuel filter near the plug where i put the boost pressure connector right around there.... its stuck into the top of the intake manifold towards the rear of the engine. its a three-wire connector. i can reseat the connector is the part checkable if i pull it and look at it or is it purely electrical that i need to check the waveform its essentially a potentiometer... a +5v reference voltage is supplied and as the boost pressure increases resistance drops so the signal voltage increases from near-zero voltage no boost to close to +5v max boost. .
From : tom lawrence
bottomline i think the wastegate is not working properly and may be the root of the startup/cold operation problems ive had. does that seem to make sense to everyone else it doesnt seem to explain the highway speed power loss issue though...that may be another issue. you left one important detail out... when driving and suddenly you lose boost - does the pyro go up indicating fuel without sufficient boost or does the pyro bottom out as well indicating a fueling problem if the temps go up briefly then yes - suspect a boost problem somewhere... either a leak stuck wastegate etc. if not its a fueling issue you need fuel to make boost - it takes heat to spool the turbo. due to the extreme intermittent nature id suspect a problem with a sensor rather than a failing vp44. my first guess would be the map sensor. the ecm will provide fuel based on among other things the amount of boost detected by the map sensor. timing is also controlled in part by the amount of manifold pressure. white smoke is incomplete combustion which is caused by either a too-cold air charge or by retarded timing once i had a timing box go flakey on me and the amount of smoke i was generating guaranteed no mosquitos for the next several years. .
From : ed
snipped its essentially a potentiometer... a +5v reference voltage is supplied and as the boost pressure increases resistance drops so the signal voltage increases from near-zero voltage no boost to close to +5v max boost. thanks ill check it out but if its intermittent who knows what ill find.... .
From : ed
bottomline i think the wastegate is not working properly and may be the root of the startup/cold operation problems ive had. does that seem to make sense to everyone else it doesnt seem to explain the highway speed power loss issue though...that may be another issue. you left one important detail out... when driving and suddenly you lose boost - does the pyro go up indicating fuel without sufficient boost or does the pyro bottom out as well indicating a fueling problem i havent had the gauges in long enough to see what happens at highway speeds when i lose power. if the temps go up briefly then yes - suspect a boost problem somewhere... either a leak stuck wastegate etc. if not its a fueling issue you need fuel to make boost - it takes heat to spool the turbo. due to the extreme intermittent nature id suspect a problem with a sensor rather than a failing vp44. my first guess would be the map sensor. the ecm will provide fuel based on among other things the amount of boost detected by the map sensor. timing is also controlled in part by the amount of manifold pressure. white smoke is incomplete combustion which is caused by either a too-cold air charge or by retarded timing once i had a timing box go flakey on me and the amount of smoke i was generating guaranteed no mosquitos for the next several years. where is the map sensor located on a cummins is it the connector on the drivers side behing the fuel filter near the plug where i put the boost pressure connector i can reseat the connector is the part checkable if i pull it and look at it or is it purely electrical that i need to check the waveform .