hello,
this is my first post to this forum, but i've researched a lot of information off this site. Thanks for all the information. I am having some reoccurring trouble though..
I just replaced the plenum pan gasket on my '95 ram 5.9. 110,000 mi. It had a definite pool of oil in the pan. My cat. converter had plugged up after a four hour trip. So, I thought the plenum leak might be the cause. I replaced the stock cat with a magnaflow hi flow system as well as a new flowmaster exhaust system. New plugs, dist. rotor/cap, 180 degree thermostat, new O2 sensor, new front camshaft seal. The truck ran so much better, it does not burn or leak any oil, better gas mileage. I just drove it to South Dakota and back from Seattle. It ran great all the way there (1200 Miles), but on the way back , the cat converter plugged up again. I checked down the TB, and it looks clean as it was when i put the new gasket in. i can't figure out what to check next. Burnt valves? I am thinking about dropping a new crate motor in, but i should figure out what is causing it to plug up the cat. converter. could there be any emissions parts that are faulty?
another question. could my new magnaflow cat. converter be totally plugged and junk now after 3000 miles?

 

welcome to DF..

what makes you think the cat is plugged? did you do a temp test on it? output hotter than input = a good cat... anything else and it's bad.

 

I have not done a temp test, how do you do that? This also happened at 40,000 miles. It was under warranty, and the dealer replaced it. The symptoms were the same then. It runs great for 100 miles of interstate 75mph, then it completely starts grunting and losing power, it will still idle, but nothing more. Then you let it cool down for 15 minutes, and off you go again for another 100 miles. It would typically act up while going up a hill, but not always. Before I fixed the plenum gasket, i had a frequent pinging and knocking problem under heavy acceleration. So far, that problem is gone. I'll try to do a compression test and temp test after the new year. thanks for the help.

 

forget the compression test, if your truck runs fine then fails, the compression is probably fine. you either have compression or you dont. your problem sounds likea possible fuel pump problem... when it fails it sounds like the pump volume is falling off.

 

I like the sounds of the that steve. I'll try to put a new pump in it this week as well as test the cat. Thanks for the advice and i'll post the outcome.

 

dont go thru the trouble of a pump unless you know it's bad... download the shop manual from the merry christmas thread referenced in the dodge info thread tacked to the top of the 2nd gen ram forum... IIRC it tells you how to test for volume output of the pump. the only thing is you have to have it fail to test it. one other thing you can do is to have a fuel pressure gauge handy and next time it fails, pop it on and see if it has the 49 psi needed to run your motor. if the motor starts ok, and pressure is holding, rev it up to about 2000 rpms and make sure the pressure holds. you can also have a 2nd person in the truck and have them pop it in gear with the e-brake on and their foot on the brakes and rev it up some to put it under load. you dont want to do that for long as the tranny fluid will start to heat up.

 

steve,
It looks like you were right again! I just got it fail while driving and checked the fuel pressure. It was running okay with 40 psi, but as soon as it started sputtering, i stopped and the gauge read 10 psi. shut it off, waited five minutes and the pressure went back up to 40psi. does that sound like a typical pump failure? when i bled the pressure off the gauge, it seemed to have a lot of air in the line... i just bought a Carter pump for $270, (ouch, but that is great news compared to what i thought the problem was) Anywho, i am sure this was the problem before i replaced the cat. oh well, i needed a new exhaust system anyway. should i expect any better performance from the new pump? the engine seems a little sluggish right now? would it help to replace the stock original injectors after 110K miles? Thanks so much for your help. i'm learning something in the process!

 

I wouldnt replace the injectors unles your upgrading... stock injectors are ok for stock motors... there are some better ones out there but for now you should just make your truck work right.

do one more thing before you swap the pump... swap the fuel pump relay with another relay... maybe the wiper relay... they should be the same p/n and are interchangeable... you can do this while you burn off the excess fuel.

have a look in the DIY forum... there is a fuel pump swap writeup there that should help with most of your swap. lemme know how it goes...

 

The only way I know of that a cat will get plugged is if you run leaded fuel.

I ain't never in my 20+ years of driving had one that did that, I've even ran diesel through and it didn't plug.

 

It does sound like the fuel pump assembly inside the gas tank is begining to fail.

When it does it begins dying suddenly 'out of the blue' with the fuel pressure falling from a healthy 40 psi to the stumbling 10 psi.

Turning the ignition switch to off for just a short time resets the pump, and it then goes back to 40 psi for awhile until it suddenly dies again.