Engine loading up

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alfman

Junior Member
Joined
Jan 12, 2014
Posts
1
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Ram Year
1993
Engine
Cummins 5.9
1998 Ram 2500 4x4 with 5.9 engine and automatic. Runs OK but it acts like it is loading up when idling or driving. Has a lot of carbon in the exhaust. Only code is the fuel pump relay which has a wire hooked up to the ground prong on the relay (the way I got it). Is the fuel pump relay grounded through the ECU? I also have a shifting problem where it feels like it is holding gear too long before shifting. Any suggestions?
Thanks
 

jamesfarris

Junior Member
Joined
Aug 15, 2017
Posts
10
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Ram Year
1995
Engine
5.9
do you still have cats on it? it sounds like you cat converters are full. does it have a strong exhaust flow? if you still have cats, drop your exhaust before the cats and see if it still feels like it loading up.
 

Yeret

The Village Drunk
Joined
Oct 2, 2014
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938
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Location
Under the hood fixing/breaking something.
Ram Year
1999
Engine
5.9 Magnum
There are two hots and two grounds in the fuel pump circuit. One hot energizes the coil inside the relay, which closes the switch for the other hot, and grounds through the ECU (the ECU opens/closes this ground as appropriate). The other hot passes through aforementioned switch which is closed when the coil next to it is energized. This hot energizes the fuel pump and grounds there (I'm guessing to the frame somewhere).

Now, there aren't supposed to be any wires sticking out of any of the relays. If I were to wager a guess, I'd say a fault developed in the ECU ground which will prevent the relay from closing and therefore prevent the fuel pump from running. Someone figured that they could "fix" the circuit by creating a new ground and jammed that wire in there. The problem is doing this will result in the fuel pump circuit always being hot, which is absolutely not supposed to happen (will certainly result in premature failure of the fuel pump not to mention the constant pressure on inactive fuel injectors definitely won't do them any favors). The reason why I think the fault is in this ground and not the fuel pump ground is because of your CEL referencing the relay. When the ECU closes the ground for the relay, it is expecting to receive power from it. Because it is not receiving power, it perceives the ground as being open and is setting the code. If the fuel pump ground were the issue and the relay was switching properly, the ECU would receive power from the relay and not think anything is wrong, despite the fact that the engine won't run.

I've always said it, computers are smart but they're not that smart.

I would personally pull the relay and the wire and swap in a different one from somewhere in the box. If you have a spare, use that. Otherwise, use one for the A/C or the headlights or anything that won't prevent the engine from running. If the engine starts and runs just fine afterwards, you've found your problem and, if you don't have a spare relay, will need to buy a new one.

In regards to your shifting problem, I'll say a thing or two but my knowledge involving trannies isn't great. To me, it sounds like you have a pressure issue within the tranny. Try checking the fluid level/color. The tranny needs to be warm (go for a drive) and in neutral before you pull the dipstick. If you're under the full mark, add some fluid (ATF+4 ONLY!) until you're full. If it's anything other than pink/dark red, the fluid is excessively dirty and should be changed ASAP. Be warned, if the fluid is any shade of brown, then it's burnt, meaning damage to the internals and changing it now may result in the transmission not functioning at all due to contaminates now thickening the fluid and allowing pressure to be generated that way (an engine with excessive bearing wear may still develop oil pressure in the same way). If your fluid level/condition are fine, you're looking at something else. I'll let others who know more about transmissions chime in here.
 
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jlbayes

Senior Member
Joined
Aug 3, 2017
Posts
191
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Ram Year
2001 & 1997
Engine
5.9l cummins
Yes the fuel pump is pcm controlled, C3 pin 19. No fault codes? Ever watched the o2 sensors with a scan tool for proper switching?
 
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