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Discussion Starter #1
Hi there, I recently purchased a 96 dodge 3/4 ton with 110k on it. It seems a little doggy when driving normal at higher rpms. Last weekend I pulled an empty trailer and I could barely pull it 60! I had to hold it to the floor the whole time and it wouldn't rev up and wouldn't gain anything. I'm thinking its a loss of fuel at high rpms but I'm no expert. Also, shouldn't the transmission kick down when going 50-60 so i can gain some rpms? The guy I bought it from said that someone told him it needed a lift pump, do you agree? Also, he had the tps sensor replaced, could this need adjusting? Any ideas on this would be greatly appreciated since I have never worked on these before and I know it shoul dbe a pulling beast. The mileage also is poor at around 12 mpg. Thanks!
 

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You should first get some gauges, specifically a boost gauge and an egt gauge. It's just about impossible to troubleshoot the symptoms you're having without info from those two gauges. Right now, possibilities (in no particular order) would be wastegate stuck open, afc housing misadjusted, plugged fuel filter, plugged prefilter screen, weak lift pump, slipped timing...you get the idea.

I hate to not have a helpful answer for you, but we really do need the readings from those two gauges first to be able to really tell you anything.
 

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If it starts and runs ok then your symptoms sound like an AFC failure. Is your truck a CA model with an EGR valve? If it has an EGR valve then the AFC fittings can get plugged up with soot. It's easy to test. Remove the AFC, cover the hole with something to keep oil from splashing out, and go for a test drive. If the AFC is the problem it will smoke a lot and have a lot of power. If the AFC is not getting boost then the foot does not move out of the way so you have very limited throttle.

In order to help you with problems you need to fill in your signature so we know what you have.

As v8440 says, gauges are a real help in diagnosing problems.
 

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Discussion Starter #4
Where would I purchase these gauges and what exactly are they? Where woudl I install them, would they be permanent? The truck does not really smoke too much and I doubt its a california truck. Thanks guys
 

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Our trucks start defueling at around 2200 RPM... And if u have a stock auto like i do you would prob be in o.d. and lock-up at 60MPH right around 2000-2100 RPM... Mine does the same thing invest in a 4k GSK kit... but if u plan on winding it past 3000 RPM often install a set of the 60 l.b. heavy duty valve exhaust springs

But before doing any mods GET SOME GAUGES!!!

Also check that fuel filter and pre-filter screen... hey when ur down there u can pull the O.E.M. fuel heater which will prob cause u issues down the road
 

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The catalytic converter may be plugged and need removal.
 

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Discussion Starter #7
I order a new straight pipe kit that will eliminate the cat completely so that should help that if its an issue. Is there an O2 sensor on these diesels that I have to worry about? Snafu722, I do have a stock auto tranny and in overdrive mine is more like 1800 rpm going down the road at 65 or so in OD. I see they sell 3k governor spring kits, I'm guessing this would be good, I won't need to rev anything over 3k. I will probably change the fuel filter, where is the pre filter screen? Do i just remove the fuel heater completely? Thank you very much for the info. For gauges you mean permanent ones that go on the pillar in the cab? What get Boost psi and fuel pressure? Thanks again. All of this info is very helpful.

Blake
 

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Discussion Starter #9
Guys, I drove it into my barn tonight so I could look at it a minute, its -10 degrees out so I got cold looking at it outside. Once I got it in I noticed there is a spring down on the side of the injector pump that hooks to some linkage that is rusted off. What does this do and would this affect anything for me? Thanks again guys
 

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there is a spring down on the side of the injector pump that hooks to some linkage that is rusted off
It's the throttle return spring. There's supposed to be two of them. On some engines they are side by side, on others one inside the other.
Broken or missing springs make it hard to keep the throttle steady, truck will be jerky especially with a load.



 

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Discussion Starter #12
Hey thanks for the diagram, yes that was the spring. i replaced it tonight. I also put the straight pipe exhaust on it and drove it, didn't make much difference so I don't think the cat was plugged. I ordered an Overflow valve to try, if that does do it I'm going to order the gauges. ALso, how would I check to see if the wastegate valve was stuck open? Also, when driving it, shoulnd't the transmission kick down at 50mph when I step on it? It just doesn't pull at all. Also, what modifications could I do without wrecking the stock tranny, could I do the 3k gov spring kit or adjust the afc? THanks for all of your help.
 

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first thing you do is read, at the top of the forum pages you'll see stickys...read everything you can. by doing that you'll have the knowledge that you need to understand what the replies mean therfore you won't have to ask them to explain their answers. good luck to you, let us know how it goes.

rande
 

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Have you tested the AFC to see if it is working?
 

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Discussion Starter #15
Ok guys I got a fuel pressure gauge put in tonight. Here is what we got. At idle when its cold I have 11 psi. I took it out for a drive and it runs up to about 22-23 psi at probably 1800rpm. When I lay it to the floor and put a heavy load on the engine. It pulls from 22 to about 19psi and hold there all the way through. WHen I got back it was warm and then at idle I had around 17-18 psi. ANything ring a bell here? I thought it sounded kind of low and was confused why I would have better pressure when it was warm. Let me know what your thinking. Thanks again!
 

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Ok guys I got a fuel pressure gauge put in tonight. Here is what we got. At idle when its cold I have 11 psi. I took it out for a drive and it runs up to about 22-23 psi at probably 1800rpm. When I lay it to the floor and put a heavy load on the engine. It pulls from 22 to about 19psi and hold there all the way through. WHen I got back it was warm and then at idle I had around 17-18 psi. ANything ring a bell here? I thought it sounded kind of low and was confused why I would have better pressure when it was warm. Let me know what your thinking. Thanks again!
Your pressures are barely within spec and will probably get worse.
Buy a new OF valve here to have on hand> Overflow
 

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Discussion Starter #18
I replaced the overflow valve before I put the gauge in last week. I did notice when I took the banjo bolt out on the inlet line on the pump. That when I reinstalled it, I had to pump up the lift pump a lot and when I pulled my hand out, it was full of fuel, like the lift pump primer was leaking fuel. Would this cause me a loss of pressure you think?
 

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Would this cause me a loss of pressure you think?
No but it could cause an air leak that causes hard starting after overnight parking.
Sometimes OF valves are bad out of the box.
To test pinch the rubber return line that passes behind the fuel filter with pliers, engine idling.
Gauge should shoot up to at least 60 psi, if it does the OF valve is defective.
If it doesn't hit 60 then the lift pump is bad.
If you bought the OF valve from the link above he will give you a new one no questions asked.
 

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illflem;3813798 To test pinch the rubber return line that passes behind the fuel filter with pliers said:
This seems confusing to me. If the gauge DOES hit 60 = bad OFV. If it DOES NOT hit 60 = bad LP. Sounds like dammed if you do, dammed if you don't. What should the gauge read if both the OFV and the LP are good?
 
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