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95 ram 2500, All stock with AFE air filter
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Discussion Starter · #1 ·
Morning everyone. I wanted to get some advice on a miss I’m having. I recently purchased a 95 2500. It was an old farm truck. The PO didn’t do a great job at maintaining it so I’ve been going through it. I’ve been chasing down a miss and I think I’ve narrowed it down.

First, there is almost no blow by, cracking the injectors all make the truck miss more. Fuel pressure is 40 at idle. I am leaning towards p pump, fuel heater leak or bad vent valve on gas tank.

Now for the part I’m questioning,
The truck doesn’t have a miss until the coolant temp gets above 150ish degrees. As the temp goes up it gets progressively worse until it completely misses at idle. A little smoke and haze until it is completely warms up. But if I open the fuel heater bowl, close it and start the truck back up the miss goes away and slowly comes back. Also the soft fuels lines look like they’re are almost being sucked in and collapsing due to a vacuum. My thought is that the lift pump is pulling a vacuum on the lines and killing off the fuel flow. Is this even possible? Could it be my pressure valve on the tank is stuck? I’ve tried to check everything before I take up another post but I need a professionals opinion on this one.
 

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95 ram 2500, All stock with AFE air filter
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Discussion Starter · #3 ·
Try pouring cold water over the p pump when it heats up and starts missing.
Oh yes sorry, so I poured a whole bunch of standyne in it and drove for an hour hopping it was some build up in the system. When I got home I sprayed the pump with the hose for a couple minutes and nothing changed.
 

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My 94 did the same thing. Low fuel pressure gave me a missfire when hot. Considering the age of these trucks i suggest going through the fuel system. Replacing all the lines and filters is not a bad idea.

A temporary fuel pressure gauge under the hood will help, but a permanent one in the cab is better.
I like this one


My truck ended up having a bad OFV, and a weak lift pump.
 

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Could it be my pressure valve on the tank is stuck?
The rollover valve doesn't open until there is a bit of vacuum in the tank.

PIESSURE RELlEF/ROLLOVER VALVE
These vehicles are equipped with a combination
pressure relief and rollover valve. This dual function
valve will relieve fuel tank pressure and also prevent
fuel flow through the fuel tank vent hoses in the
event of an accidental vehicle rollover.
Tank pressure is relieved through a calibrated orifice,
in the valve, to the canister.

Easy to check, just remove the fuel cap. A slight rush of air is normal. If the problem stops then it is clogged.
 

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95 ram 2500, All stock with AFE air filter
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Discussion Starter · #6 ·
My 94 did the same thing. Low fuel pressure gave me a missfire when hot. Considering the age of these trucks i suggest going through the fuel system. Replacing all the lines and filters is not a bad idea.

A temporary fuel pressure gauge under the hood will help, but a permanent one in the cab is better.
I like this one


My truck ended up having a bad OFV, and a weak lift pump.
Copy that. Im leaning towards that as well. I have a temp one but I went ahead and ordered some glow shift gauges to get a permanent one in the cab. I have gone through and replaced the small feed line behind the motor to the fuel heater hardline. I also ordered a fuel heater delete. I think it’s letting air in the system.
 

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95 ram 2500, All stock with AFE air filter
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Discussion Starter · #8 ·
The rollover valve doesn't open until there is a bit of vacuum in the tank.

PIESSURE RELlEF/ROLLOVER VALVE
These vehicles are equipped with a combination
pressure relief and rollover valve. This dual function
valve will relieve fuel tank pressure and also prevent
fuel flow through the fuel tank vent hoses in the
event of an accidental vehicle rollover.
Tank pressure is relieved through a calibrated orifice,
in the valve, to the canister.

Easy to check, just remove the fuel cap. A slight rush of air is normal. If the problem stops then it is clogged.
That makes sense. I pulled the valve out this morning and it seems to be working just fine. No blockage.
 

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I also ordered a fuel heater delete..
Kit? Just unscrew the prefilter basket, remove the heater (takes an allen wrench) and screw the prefilter basket into the hole the heater retainer was in. Done. Caution, when removing the basket there will be about a half cup of fuel coming out. Keep you face and eyes clear.
 
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That makes sense. I pulled the valve out this morning and it seems to be working just fine. No blockage.
You dropped the tank and removed the canister?
 

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95 ram 2500, All stock with AFE air filter
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Discussion Starter · #11 ·
Kit? Just unscrew the prefilter basket, remove the heater (takes an allen wrench) and screw the prefilter basket into the hole the heater retainer was in. Done. Caution, when removing the basket there will be about a half cup of fuel coming out. Keep you face and eyes clear.
Ohhhh I didn’t not think of that. Looks like I’m going back outside for a bit. Thank you.
 

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95 ram 2500, All stock with AFE air filter
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Discussion Starter · #13 ·
Ohhhh I didn’t not think of that. Looks like I’m going back outside for a bit. Thank you.
Removed the heater and it ran great for a while then started to miss. The gasket for the bowl looks pretty ate up and dry though.
 

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I had the same issue a few weeks ago. miss would start once the truck had about 10-15 mins of run time. narrowed it down to #1 cylinder. Everyone on the forum said it was the injection pump, but I had low fuel pressure(15 when starting, less than 10lbs once warmed up). replaced the lift pump and all the hoses and removed the fuel heater and the miss went away. If lines are caving in, I'd personally replace them first and see if it helps. Also I pulled the delivery valves(turned engine over by hand) while I was waiting on the pump to be shipped and I didnt see where the barrel had been hot, but I also swapped #1 and #2 delivery valves, even though I didnt see any visible issues. Also checked the valve adjustments, just to make sure nothing had happend there.
 

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95 ram 2500, All stock with AFE air filter
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Discussion Starter · #15 ·
I had the same issue a few weeks ago. miss would start once the truck had about 10-15 mins of run time. narrowed it down to #1 cylinder. Everyone on the forum said it was the injection pump, but I had low fuel pressure(15 when starting, less than 10lbs once warmed up). replaced the lift pump and all the hoses and removed the fuel heater and the miss went away. If lines are caving in, I'd personally replace them first and see if it helps. Also I pulled the delivery valves(turned engine over by hand) while I was waiting on the pump to be shipped and I didnt see where the barrel had been hot, but I also swapped #1 and #2 delivery valves, even though I didnt see any visible issues. Also checked the valve adjustments, just to make sure nothing had happend there.
Okay. I think it is something dealing with the lift pump/pre heater. I’m waiting on parts to just delete it.
 

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It's a PIA and a bad idea to eliminate the prefilter. That screen is the last line of defense for your lift pump. Instead, I recommend you buy a new strainer kit. It will come with a new gasket.

 
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Discussion Starter · #17 ·
It's a PIA and a bad idea to eliminate the prefilter. That screen is the last line of defense for your lift pump. Instead, I recommend you buy a new strainer kit. It will come with a new gasket.

Okay. I’m not to fond of waiting until October 2021 to get a screen and oring...
 

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Crap.... I just ran out of those.....
 

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Okay. I’m not to fond of waiting until October 2021 to get a screen and oring...
News flash. Lots of venders sell the kit. The link gives you the Cummins part number.
 

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95 ram 2500, All stock with AFE air filter
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Discussion Starter · #20 ·
Finally got around to the delete kit. When I pulled the lift pump off I decided to run some air through it. Only 10-15 psi but, the weep hole on the side Of it is letting air out when I pressurize from the feed side and P7100 side. Is this normal?
 
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