2002 Dodge Ram

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 it's 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 didn't really fix the issue completely, it just didn't 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 couldn't 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 didn't 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 didn't 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 didn't 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 wasn't 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 I've had. Does that seem to make sense to everyone else? It doesn't 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 can't find much about it on the web, doesn't 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
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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, it's a fueling issue (you need fuel to make boost - it takes heat to spool the turbo). Due to the extreme intermittent nature, I'd 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).
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I haven't had the gauges in long enough to see what happens at highway speeds when I lose power.

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?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Right around there.... it's stuck into the top of the intake manifold, towards the rear of the engine. It's a three-wire connector.

It's 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).
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
SNIPPED

Thanks, I'll check it out, but if it's intermittent, who knows what I'll find....
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.