Need Help With Diagnosis
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New User
Joined: Feb 2013
Posts: 18
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Need Help With Diagnosis
Ok, this problem started about three days ago. When I start my truck when it's cold, it fires right up like it always has. Then I back out of the carport and go up the driveway to the road. turn onto the road and proceed up the hill, maybe a 4% grade. Then the truck starts slowing down and missing like it's running out of fuel. I haven't noticed any smoke when it does this. I pull off the road and it dies. Key off and back on prime for a few seconds then try to restart. I always do a key off and back on before I try to restart, and wait for the Wait To Start light to go off. It finally restarts after about 10-12 seconds of cranking and runs real rough, usually dies again in after a few seconds, I have to give it full throttle to get it to restart every time. Most of the time it will idle but when I try to drive off it has no power for a few seconds then takes off fast then runs rough again and dies. I rev it up a few times and it will finally straighten out and run okay.
Here is the data I was able to gather.
IPR Absolute
Idle 466.7-489.9
holding RPM at 1750 890-910
Holding at 3300 1475 then ramps up to 3200 psi
have to keep increasing throttle to maintain rpm when the pressure starts to ramp up. then after it does this I can feel a miss at idle. also when returning to idle the rpm goes down to about 500 and roughens up a little then stabilizes around 750, still with a miss
cylinder contribution shows #4 and #8
Buzz Test
1 ok
2 ok
3 very slightly muted
4 a little more muted than 3
5 ok
6 ok
7 ok
9 ok
8 ok
Any help would be appreciated!!!!
Here is the data I was able to gather.
IPR Absolute
Idle 466.7-489.9
holding RPM at 1750 890-910
Holding at 3300 1475 then ramps up to 3200 psi
have to keep increasing throttle to maintain rpm when the pressure starts to ramp up. then after it does this I can feel a miss at idle. also when returning to idle the rpm goes down to about 500 and roughens up a little then stabilizes around 750, still with a miss
cylinder contribution shows #4 and #8
Buzz Test
1 ok
2 ok
3 very slightly muted
4 a little more muted than 3
5 ok
6 ok
7 ok
9 ok
8 ok
Any help would be appreciated!!!!
Senior User
Joined: May 2011
Posts: 454
Likes: 0
From: Portland, OR
I thought the same thing, fuel pressure is insufficient. If you don't have a pressure tester yet you can disconnect the inlet side of the frame mounted pump (just under the driver's seat under the truck) and blow some compressed air back into the tank, backflushing the pickup boot screen. If there's an in-tank restriction that should free it and only takes a couple minutes.
Take your fuel cap off to do this.
Take your fuel cap off to do this.
9 ECHO 1
Joined: Aug 2009
Posts: 12,467
Likes: 58
From: Missouri
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Elder User
Joined: Mar 2012
Posts: 534
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From: Quaker Hill
I had the same exact problem when I bought my first 7.3 diesel. Changed my fuel pump, checked my tank, etc. turned out my rotten oil pan was leaking faster than I thought. Oil level and quality are critical to these injectors and lack of either will give you low fuel pressure symptoms. I know from trial and error 
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Veteran/Sheepdog
Joined: Feb 2012
Posts: 6,047
Likes: 110
From: Western AR
These are the screens you are clearing when you blow compressed air back into the tank.
Don't use anything over 20 psi or so to blow air back into the tank.
Here is what a broken pickup foot assembly looks like inside your tank.
This will cause you to run out of fuel before you are actually empty, and it can cause air in the system.
IPR nut is something that is SOOOOOOO easy to check and rule out. Trey is right on that suggestion.
Don't use anything over 20 psi or so to blow air back into the tank.
Here is what a broken pickup foot assembly looks like inside your tank.
This will cause you to run out of fuel before you are actually empty, and it can cause air in the system.
IPR nut is something that is SOOOOOOO easy to check and rule out. Trey is right on that suggestion.
Thread Starter
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New User
Joined: Feb 2013
Posts: 18
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Should have mentioned also that once it's warm all is good except the miss after revving the engine. It has to have at least a 4 hour soak to act up. Also the ICP sensor does have oil in the connector but has been that way for awhile. The main problem started about 3 days ago.
Veteran/Sheepdog
Joined: Feb 2012
Posts: 6,047
Likes: 110
From: Western AR
Update/establish a signature that is attached to your posts. Put your truck's vital statistics in there so we can better answer your questions/offer help. Things like already having the hutch mod are not known unless you tell us in the original question or make a signature where it is offered as info.
Welcome to the site by the way!
Welcome to the site by the way!
Veteran/Sheepdog
Joined: Feb 2012
Posts: 6,047
Likes: 110
From: Western AR
I think you may need to rebuild/clean your IPR. The fact that it does it when cold and then goes away when warm point toward a possible oil temp/viscosity issue. The IPR does develop a build up inside the very small clearances inside it. This buildup needs to be removed periodically. Takes me about 10 minutes to get my IPR out and 10 to get it back in. Taking it apart and cleaning it takes about 30 mins. Although I did put the tiny needle in backwards the last time I did it
Definitely need to know what fuel pressure is as well, though. It's easier to check on the IPR than it is to come up with money for a gauge
Definitely need to know what fuel pressure is as well, though. It's easier to check on the IPR than it is to come up with money for a gauge