As I've come to find out, OBD1 vehicles aren't the best at telling exactly what's wrong with them, I have no check engine light at all, I just filled up today for the first time since doing my full tuneup a couple weeks ago (don't put many miles per year on a vehicle) and will see what mpg this tank gives me versus the old worn out plugs/dist that was in before, but, ever since I've owned the truck there's been this gas or exhaust smell when it's running around it and even after I've parked it, stronger on the passenger side when I smelled it earlier. I thought it was the old dumped muffler under the bed, but I got two pipes running out the back now and the smell still remains, from reading around, possibly the pcv valve could cause this, or o2 sensor, or MAP sensor, is there any for sure way on an OBD1 vehicle to tell if they're good or not? I did look and the OBD1 only has a single pre cat o2 sensor which looks pretty old from the outside, I wonder how much trouble that old thing will be to get off....versus the pcv valve and map sensor being extremely easy to change out up top.

I know on the OBD2 2nd gen rams, the purge canister under the passenger side bed had a tendency to break its hoses after awhile and trigger a code, but, my old 01 3.9 ram had its hose back under there messed up the entire time I used to own it and I never had an exhaust smell or horrible mpg, just a CEL for the evap code. Its mpg wasn't the best in the world either but I attributed that to the poor little 3.9 pushing a (I believe) slightly lifted truck with big offroad package (99-01?) 17 inch dodge wheels plus big 17 inch tires.

I say all that, to get to my other point, I guess obd1 either didn't have all that evap environmental stuff tacked on, or somebody long ago removed the one on my truck, because there's no purge evap canisters under my passenger bed at all lol. Maybe bad egr valve? You'd figure I'd have a check engine light on for anything really serious.

it's not the end of the world, I'm grateful to have a reliable vehicle to get me from point A to B, but I would like the exhaust/gas smell to go away, I'll update later with how this tank yields, but I think a new o2 or map and pcv could improve mpg too. Really sucks not knowing the repair history of a used vehicle you buy

I drove it a little bit with a misfire before, but to a half tank or little less I only got like 193 miles.....it's long bed too so the 35 gallon tank, it's not exactly cheap filling it up all the way lol....I used to do better than that with the 3.9 2001 short bed with the 26 gallon tank with its big pumped up wheels/tires/lifted body...something on this 5.2 is ailing I suspect, but the dang old crude obd1 won't tell me....I just calculated it, about 11mpg(193/17.5 half tank, could be even worse but I was generous and calculated on half a tank) on this 5.2 with mixed city/highway driving, and about 15 on the 01 3.9(193/13)

 

My truck has a large charcoal canister under the driver's side of the cab (it's an early model '96 Ram 2500 that's a hybrid OBD1/OBD2). I just dropped my gas tank and noticed the steel lines going to and from the canister are rusted out, so I'm in the process of installing new steel lines. Might want to check this on your truck, however, I'm also wondering if your O2 sensor may causing some of this issue, too.

That '95 truck likely has an EGR valve on it (should be on the back of the intake with a pipe running to the passenger side exhaust manifold). Check it and the connections for the possible gas smell.

 

Thanks I'll look into that, the fuel lines rusting out around the gas tank are apparently a common failure point somebody else told me before....I suppose I'll start slowly replacing sensors like the o2, and map, and pcv for good measure, the o2 literally looks like it's been on so long it's rusted, so that'll be a joy getting off, lol. I figure it has to be one of those or the egr causing the fuel smell, I looked on the autozone site and there is some weird purge canister for some charcoal thing (maybe?) under the hood on my obd1, mine's a 95 1500 ram.

also a link to the egr, I always thought it was weird the obd1 rams had egr but yet obd2 didn't, my 01 ram even had its pcv on the drivers side while my 95 has it on the passenger, guess they swapped those around when the change to obd2 happened as well

egr: https://www.autozone.com/emission-co...lve/136000_0_0

I gotta be honest when I was climbing in the engine bay to do the dist. cap,etc on the tuneup I don't even remember seeing that egr back there but I should look again, maybe an old owner blocked it off...I heard on these obd1 rams the egr actually helped them get a little better mpg in theory than the later ones -shrug- I'm not sure though.

https://www.autozone.com/engine-mana...910164_0_12209

"Purge Valve Solenoid controls the flow of fuel fumes from the canister to the engine. When not replaced, vehicle may run rich causing excessive fuel consumption, failed emission test, and/or CEL illumination"

edit: well, just ordered a brand new ntk o2 sensor, wells map sensor, and pcv valve, pcv and map are same as autozone one iirc except the stuff was quite a bit cheaper on rockauto, supposed to arrive nov 30th, ordered an o2 deep socket too, I'll update once putting everything on.....many over the years have said just putting in a new map sensor alone brings good mpg and great power. If these don't fix it, it's gotta be the egr and/or that purge valve solenoid not working right, I'll have to read about how to block the egr off, that'll save 60 bucks alone lol.

 

Your evap canister should be on the drivers side, It changed over to the passenger side around 97-8 when they changed to the twin canister style. Fallow the vac line coming of the TB(lower left side) going to it. You may have leak somewhere causing both gas smell and poor mpg.

 

thx I'll check the drivers side in a bit after I eat and also try to see if I even have that whole EGR setup too, I don't remember seeing it when I did the tuneup. It's likely the hoses are either gone or rotted. I can live with the eh mpg, it's not the end of the world considering I don't put many miles per year on a vehicle, but the gas/exhaust smell is troubling....if some idiot were to toss out a cig in a parking lot near the truck I'm worried it might ignite the fumes

 

update: I looked under the drivers side and indeed find the big fat horizontal laying charcoal canister with a few hoses running from it, no visible tears although they look old and dirty

I never had a CEL code for the egr or purge solenoid, according to this chart I would, but, I'm thinking it's due to an old o2, map, or pcv, or the hose from the charcoal canister somewhere under the truck is rotted http://dodgeram.info/Engine-Gas/OBDI/pcm_fault_code.htm

I didn't get to look for the egr in the daylight, may look in a bit and see if I even have one back there, I swear I don't remember seeing or feeling one when doing the tuneup -shrug-

 

It should be right at the back of the keg.

If you O2 is original, it's well past time for a new one.

 

The o2 looks so old it honestly might be the original, new parts should be here this upcoming week, I'm thinking maybe that weird looking evap solenoid thing is alright, if it was bad it should technically throw a code 31, I figure the truck has to be running rich due to the old o2 and map and maybe even pcv or the hoses up under the truck somewhere are torn/rotted, they looked ok coming off the big fat canister itself. There were a few protrusions coming from the canister though that seemed to be capped/blocked off from the factory though, weird.

I'll take a pic in the sunlight tomorrow showing what I'm talking about, I couldn't find anything on google showing an old obd1 early 2nd gen ram charcoal canister, couldn't really see any on ebay either oddly or I'd post a pic of those and just circle what I'm talking about.

If the hose is rotted or broken, it would be somewhere under the truck, the driver side smell wasn't strong the other day when I filled up but was rather strong on the passenger side right where the bed starts

I'm actually excited to try out the new map sensor, many said that alone can give alot of power and good mpg, after so many years it apparently hardens inside and is no longer efficient even though it may not trip a code, I swear I bookmarked the forum link where lots had luck going with a new map but I guess I lost it...

 

If anybody could help that'd be great, map sensor came in and I started trying to take the old one off but it's at such a narrow space there under the old sensor on top of the keg by the throttle body..... I have that star shaped weird looking bit I need, but if anybody knows of a cheap tool or homemade contraption or ways you've done the map sensor on these trucks it'd be much appreciated. My socket is too big to reach down there, I have some combo socket tool I got sorta cheap awhile back but it's just such a cramped space under there there's no way to take the old map sensor out

 

Take the throttle body off the manifold, it really is the easier method.