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Discussion Starter · #1 ·
I'm trying to diagnose a possible fuel system problem with my 99 Dodge Ram Sport. The truck starts easily, idles properly, and the check engine light is off. When I put the truck in gear and try to accelerate the engine bogs down and tops out at 25-30 mph. I replaced the distributor cap/rotor, plugs, and wires, checked the air filter/housing and hoses, and put in a fresh tank of fuel and some Lucas fuel system cleaner. The fuel pump sounds like it's running and I haven't noticed any fuel leaking... next step recommendations? Thanks!
 

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Check fuel pressure, under load. With gage you might need to have an extend ed hose, 45 lbs is the mark after that would be a vacuum leak.
 

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Discussion Starter · #3 ·
Sounds like it's time to buy the gauge and pull out the Haynes manual... Thanks for the reply!
 

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The dodge bible is a good thing to have.
 

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it's the fuel pump. if their was a vacuum leak you would have a very POOR rough idle. if the fuel pump is no good then you can have a perfect idle provided pressure is min of 35 psi, however once the engine has a high demand for fuel the pump won't be able to meet the demand and the computer stuck in it's loop won't know what to do and the engine will die and sputter backfire and it sucks (especially when you are 150 miles from home with no money in the middle of georgia).... errr


anyway's just buy a new pump, pumps die in all cars. worst part is pumps dies more often when they're not in use.
 

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your forgeting that they also like to do it right after you have just filled the tank to the top. micanics get kind of pissie when you tell them that bit of good news.
 

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your forgeting that they also like to do it right after you have just filled the tank to the top. micanics get kind of pissie when you tell them that bit of good news.
Well I guess I have been lucky, it died almost empty. But I'm my own mechanic so it doesn't bother me, I just pump it to another vehicle if I have to. Besides the hell with the mechanic.

Oh by the way, it's queen family truck' ster. metallic pea
 

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Discussion Starter · #8 ·
it's the fuel pump. if their was a vacuum leak you would have a very POOR rough idle. if the fuel pump is no good then you can have a perfect idle provided pressure is min of 35 psi, however once the engine has a high demand for fuel the pump won't be able to meet the demand and the computer stuck in it's loop won't know what to do and the engine will die and sputter backfire and it sucks (especially when you are 150 miles from home with no money in the middle of georgia).... errr


anyway's just buy a new pump, pumps die in all cars. worst part is pumps dies more often when they're not in use.
I kind of thought the fuel pump was going bad because my truck was stalling every so often leaving me stranded for 5-10 minutes at a time and then starting like there was never any problem... sounds like it finally gave out... I've had the gas tank off before to replace a rear brake line so i might as well replace the fuel pump myself. I think the tank is about 1/2 full but that's a good idea to siphon it to my other truck. Thanks for the info!
 

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Are you sure it's not the exhaust being restricted? clogged cat will cause that as well. Just a thought. Most fuel pumps just go they don't half way go they just flat out fail.
 

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Are you sure it's not the exhaust being restricted? clogged cat will cause that as well. Just a thought. Most fuel pumps just go they don't half way go they just flat out fail.
I just replaced my fuel pump about 2 hours ago and my previous pump made it 16 years (carter brand fyi). The pump still pumped the engine would turn over and everything however once in a while the engine would stutter but then everything back to normal. Then one day I was driving and all of a sudden the van stuttered doing 80 on cruise on highway, then all of a sudden I hear a big bang (backfire) and I would hit the pedal and it wouldn't accelerate the engine wouldn't even rev I also threw a code for the O2 sensor being to lean (lack of fuel). Had 17 gallons of gas in the tank. Well anyway's it had finally died at a gas station and I had it towed home then the next day I started up the van and it ran perfectly no problems made it 100 miles then when I went to 80 it would die and before when you would drive their would be no acceleration like it was dragging. Well I had said it must be the transmission, so I rebuilt the transmission and found 2 physically damaged parts OD Hub and 3-4 Acuum Spring. I replaced all my bushings, seals, rebuilt valve body the works and put alto reds and alto kollene steels etc... Anyways After I rebuilt it put new torque converter and everything I install it and started up the van and well it started and I drove it a little and after about 6 miles it shuttered and then when I was on my street (thank god) I decided to just do a stall test and well I did and the engine died, backfired shudder and the works, I went home connected my fuel pressure gauge and read 35PSI at idle which is about normal in actuality the pressure at idle should really be in the 40's. It would shudder even in park so that ruled out the transmission. Well I replaced my fuel pump today and not only does my gas gauge work (thank you LORD) but my engine doesn't shudder, stutter, backfire, it runs BEAUTIFULLY and most of all the engine has acceleration and the lagging dragging feel is completely gone. I do recommend you replace the pump because when I removed my gas tank and pump their was RUST because the pump has metal parts and the filler tube rusts also. The filters on the pump were black and it was just toast. But now everything works smooth and perfect it idles much better and when I hit the gas it MOVES and I mean moves. Surely a bad O2 sensor can cause running and idle issues just as much as anything else.

But trust me fuel pumps don't just die flat out cause obviously from my story my pump still worked, it just didn't work enough. Besides fuel pressure the pump also has to be able to deliver the correct volume of fuel. Typically the pump wares out but the regulator clogs as well as filters. If you do decide to replace your pump I can tell you of a place that sell great pumps for low price, I bought my pump for 129.98 shipped and it has a lifetime warranty they even pay all shipping if the pump fails. The pump is also made in the USA.

One your trucks if it's newer then 1995 you will probably has two O2 sensors one before and after the CAT, mine only has one before the CAT. Anyway's if the CAT was no good then it's possible you would throw a code for the O2 sensor but you need to have a sensor after the CAT. Older vehicles with a O2 sensor before the CAT can run without a CAT because of the sensor location, surely you will put holes in the ozone but atleast you can drive. Any questions just ask.
 

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Discussion Starter · #11 ·
So I bought a fuel pressure gauge yesterday but haven't had a chance to use it yet because of the holiday... I talked to a mechanic at a repair shop and a tech at Advance Auto who both said aside from the fuel pump it could be a clogged catalytic convertor... how would I know/test to find out if that is the problem? The check engine light is OFF and the truck starts easily and idles perfect... ramvan2500, what's the name of the place that sells fuel pumps? Advance Auto wants $250-$300 for a new one. Too many good football games on today to be wrenching in the garage but I should know more tomorrow. I have to be back on the road by Tuesday afternoon... Happy New Year! and thanks for all the helpful posts...
 

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So I bought a fuel pressure gauge yesterday but haven't had a chance to use it yet because of the holiday... I talked to a mechanic at a repair shop and a tech at Advance Auto who both said aside from the fuel pump it could be a clogged catalytic convertor... how would I know/test to find out if that is the problem? The check engine light is OFF and the truck starts easily and idles perfect... ramvan2500, what's the name of the place that sells fuel pumps? Advance Auto wants $250-$300 for a new one. Too many good football games on today to be wrenching in the garage but I should know more tomorrow. I have to be back on the road by Tuesday afternoon... Happy New Year! and thanks for all the helpful posts...
www.highflowfuel.com I was able to get my pump for 129.98 shipped the same brand is sold at advanced for 185 bucks. The fuel pressure at idle should be 43PSI lowest should be 40. Many say 35 PSI but the engine will idle fine at 35PSI however the pressure should really be 43. My old pump read 35PSI and the truck idled perfectly, the new pump reads 43 PSI and idles perfect and also runs perfect too!

I doubt it's the CAT because you're not throwing any codes for one and well frankly I have a 16 year old vehicle and the fuel pump died and the CAT is still perfectly fine no issues at all. And I had similar issues as you running problems. Even if the pump doesn't fix the issue you have to say to your self that you won't have to worry about the pump dieing on you out in the middle of no man's land. It really sucks when the fuel pump dies, you can crawl with a bad CAT but not with a bad pump. But I strongly feel that the pump is no good, generally the filters in the pump clog and the pump also wears out of course. When you hook the gauge up it should hook up to a test port that is on the fuel rail. Screw the gauge on then put the key in ignition and turn to the ON position the pressure should be between 35 and 45 PSI. Then turn the vehicle on, the pressure should be at 43 if it's a healthy pump, if the pump is worn it will be at 35 or lower. Again at 35 PSI the vehicle can still idle but will have running problems especially under load.
 

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Discussion Starter · #13 ·
I'm definitely following you. You're van is a few years older than my truck but we both live in FL (less rust issues) and it doesn't make sense to me that the CAT would become completely clogged overnight... I'll check the fuel pressure tomorrow and go from there. I think I'll pull the fuel tank tomorrow and inspect everything regardless. If nothing else, I can clean the tank, filters (or replace), and fuel line. Just to cover everything, have you ever had a problem with the fuel injectors not pulsing correctly causing similar symptoms? or water in the fuel?
 

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I'm definitely following you. You're van is a few years older than my truck but we both live in FL (less rust issues) and it doesn't make sense to me that the CAT would become completely clogged overnight... I'll check the fuel pressure tomorrow and go from there. I think I'll pull the fuel tank tomorrow and inspect everything regardless. If nothing else, I can clean the tank, filters (or replace), and fuel line. Just to cover everything, have you ever had a problem with the fuel injectors not pulsing correctly causing similar symptoms? or water in the fuel?
Well I live in FL now for the past 5 years but my van spent about 10 years in NJ and well goes without saying.
As far as the fuel injectors go, no I haven't had an issue with the operating of the fuel injectors, I am a perfectionist the second I hear some kind of noise I drive home and have the van jacked up and I'm under it lol...

Generally if you have a fuel injector that is cycling properly then it would be because of generally 3 things, bad ECM (not likely), bad wire (possible with rodents), or a bad fuel injector (possible but again not likely). Check the resistance of a suspected injector, the resistance should be 14-15K ohms give or take. Do the ohm test quickly to avoid damage to the injector's solenoid coil. I generally use fuel injector or fuel injector + intake valve cleaner every 3000 Miles.

As for the fuel tank, you are likely to find some rust particles in the fuel tank and sometimes find the gas to be brown rust colour. Replacement of the fuel lines isn't needed, their are 3 filters on the pump and well that's plenty filter action. Just do a fuel pressure test and if it's low replace the whole pump, better off to replace the pump then try and salvage the old one. That web site that sells those pumps gives you a lifetime warranty, they will even pay shipping both ways.

As far as moisture in the tank it's going to happen. My van at one point sat for 4 years and I put a little gas it and it worked. If you have a moisture issue use of fuel injector cleaner generally eliminates any moisture in the fuel system.

Another thing to check in advance is the mounting bolts and nuts, sometimes they seiz and will need replacement. In my case I had to replace them (about 25 bucks) You will probably want to replace the filler neck tube grommet on the gas tank as well. The rubber dries out and cracks and can leak if reused. Grommet is only about 12 bucks cheap insurance for half tank of gas to go leaking.

I can tell you the best way to clean the tank from experience. Empty the tank as best as you can, then wash the outside of the tank with a garden hose and a rag. Then remove the pump, grommets, and the roll over valves if equipped. Then rinse the inside of the tank with water and empty and rise and then use your rag to clean the inside of the tank of any rust debris and then just rinse and since the tanks are black you can just put some shop towels in the tank then put that tank in the sun for 20 minutes and it will be bone dry. I for safety just wiped the inside of the tank dry with shop towels. I then put it all together used PTFE die electric lube on the rubber and grommets to help get them in then just put the tank back on the van put bottle of fuel injector cleaner and 5 gallons of fresh gas in and started it up. It only took about 3 hours, removing it was somewhat of a pain because of the frozen bolts but after that it was a piece of cake. Be sure to use locktite 242 (Blue) on the mounting hardware. Just need to tighten the straps snug.
 

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Discussion Starter · #16 ·
So I checked the fuel pressure this morning and with the key in the ON position the gauge read 40 lbs and when I started the truck the gauge pegged at 47 lbs and stayed there... Now I'm not sure if I should pull the fuel tank and inspect everything or not???
 

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So I checked the fuel pressure this morning and with the key in the ON position the gauge read 40 lbs and when I started the truck the gauge pegged at 47 lbs and stayed there... Now I'm not sure if I should pull the fuel tank and inspect everything or not???
Wow, off as hell. Everything you were describing is of that a fuel problem. The weird thing is that if it's a CAT or a o2 sensor you would typically throw a code. You know I want you to try something, because these O2 sensors are heated O2 sensors meaning they won't get proper readings until they're heated to 600 degrees which is why they are made with heating elements. I want you to idle the truck until it reaches temperature then try and increase idle speed and see if it bogs. It is possible you have a faulty cat or bad O2 sensor. Thing is if you have a post O2 sensor and it was the CAT you would almost certainly throw a code.

After you idle the truck to temp. Let the engine cool down all the way so go have a beer. Then hop in the truck and drive it around your street and keep your eye on the tamp gauge, what we're looking for is if the engine begins to have trouble as soon as it reaches temp. Once it reaches temp it is in closed loop and it's getting the measurements from the O2 sensor for fuel mixtures and for proper emissions. The purpose of the post o2 is for emissions while the pre cat o2 is for fuel mixture.
 

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Discussion Starter · #18 ·
I was convinced it was a fuel system problem too... I took a look at the exhaust and there's an o2 sensor before and after the CAT. I idled the truck and it did seem to bog more as it reached temp and especially when I increased idle speed. About an hour later I drove it to a repair shop (for a diagnosis) and the truck bogged increasingly worse as it approached temp. I just got a call back and it's a clogged CAT verified by a back pressure test. Any tips for replacing a CAT?
 

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I was convinced it was a fuel system problem too... I took a look at the exhaust and there's an o2 sensor before and after the CAT. I idled the truck and it did seem to bog more as it reached temp and especially when I increased idle speed. About an hour later I drove it to a repair shop (for a diagnosis) and the truck bogged increasingly worse as it approached temp. I just got a call back and it's a clogged CAT verified by a back pressure test. Any tips for replacing a CAT?
I have no tips for replacement of the cat because I haven't needed to replace one yet. Only thing I can say is if you have a plain steel exhaust get a plain steel Cat, don't get stainless because of dissimilar metals. I must say I am at awe about the CAT, like said usually a code would pop up some where.
 

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Discussion Starter · #20 ·
Actually, leading up to this most recent problem the truck would run great until it got up to and stayed at temp for about 45 min. Then it would stall for about 5-10 min. and when it re-started the check engine light would be on for a day or two and clear... I suppose those were the telltale signs of the CAT getting more and more clogged... I was lucky it would always eventually start but the problem kept getting worse. I think I'll cut out the old CAT and clamp in a new one for now until I can have the entire exhaust replaced...
 
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