Mopar friends, I need your assistance.

jos51700

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Today has been a **** day.

This automotive problem has been ongoing, so I am going to use it to distract from my other issues of the day.

The vehicle: 1994 ram 3.9 v6, 5 speed. A billion miles. Bone stock except for a gutted cat.

This truck runs GREAT until it gets thoroughly warm. Then when you shut it off and go to restart, it's flooded. When driving it doesn't really act up that I've noticed, but park it and let it heat soak, and it's flooded. You have to hold the throttle WOT, and then it'll clear out but if you don't get moving...... glug glug

All 6 plugs come out BLACK and it'll stink my whole yard with fuel vapor. Doesn't smoke until it floods, and then it smoked black. Idle is great until it's Noah Time.

New plugs didn't fix it, cap and rotor are new, tried another coil, the previous owner replaced all manner of sensor with factory ones. He even replaced fuel pump (I got 40 psi when it's flooded, didn't try when it would run).

I can't even figure out any codes. No CEL.

The clean idle and lack of smoke tell me that the plenum gasket is probably ok. There's no downstream o2, since it's obd1.

Any advice on a magnum efi that floods when hot?
 

318willrun

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Has to be an electronic because all 8 cylinders are getting overloaded with gas. Almost acts like the throttle position sensor is in WOT causing the injectors to go fat ????
 

leechris81

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Just one thought immediately pops into my head but may not be relevant to your application. What about a leaking fuel pressure regulator? Some of the GM stuff had them located under the intake and when they leak they flood the engine.
 

Mike69cuda

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I had a similar thing happen on a non Mopar. It was a temp sender. There were two temp sensors on the engine. I didn’t know that. I replaced one. It was the one that was for the temp gauge. I thought that I had eliminated the temp sender as a possible cause. Took a dealer to figure it out.
 

jos51700

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Has to be an electronic because all 8 cylinders are getting overloaded with gas. Almost acts like the throttle position sensor is in WOT causing the injectors to go fat ????
Maybe tps? I think previous owner replaced that
Just one thought immediately pops into my head but may not be relevant to your application. What about a leaking fuel pressure regulator? Some of the GM stuff had them located under the intake and when they leak they flood the engine.
Dunno. I thought regulator was in tank

Bad temp sensor? Sensing cool air then trying to compensate?
I would think that would present drive ability problems?
I would suspect leaking injectors. Have they ever been replaced?
Is it throwing any codes?

Leaking injectors. Common on “million mile” stuff.

Would it make it run equally rich on all 6? That's plausible but it seems unlikely to hit 6 in a row
 

jos51700

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I had a similar thing happen on a non Mopar. It was a temp sender. There were two temp sensors on the engine. I didn’t know that. I replaced one. It was the one that was for the temp gauge. I thought that I had eliminated the temp sender as a possible cause. Took a dealer to figure it out.
Will look. Never occurred to me that there might be two
 

TT5.9mag

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The temp sensor “should” throw a code. As well as the tps. You said no codes which points me to fuel system. So fuel pressure regulator (maybe), injectors most likely. Could also possibly be map related but I think that’ll trigger a code as well.
 

RustyRatRod

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The temp sensor can cause this and it's something that's cheap enough to throw at it.
 

YY1

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TPS sensor is a known issue.

If it's never been replaced- replace it.

They are cheap and easy to replace.
 

toolmanmike

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Do you have a good scan tool? If not, haul it off to a shop that does that kind of work. You will throw parts at that thing until your charge card is maxxed out and you still won't find the problem.
 

missing linc

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Had a similar problem with a different make, IAT sensor was bad, not sure if that one has or not, but might be worth checking out.
 

rumblefish360

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Sounds like the injectors are not fully closing and/or the 02 sensors are shot thinking it’s lean.
 

YY1

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Sorry, I meant IAC motor- on the back top of the throttle body.

Causes the same symptoms as flooded- need to hold gas to floor to start and then feather to keep running.

Still a known issue and cheap and easy.
 

6pak

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I flushed my dirty *** cooling system and put in a 180* thermostat. Mistake. These are looking for 195 or they are in open loop mode- like the choke is on.
Even had black smoke out the exhaust. -
No code. - had to monitor w tool while running to figure it out.
 

'68cuda416

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I would put a fuel pressure gauge on it and see how long or if the pressure stays up, after shut-down.
Wouldn't tell him anything just off of that without being intimately familiar with that particular year, make, model, engine, etc. because not all pumps will hold pressure after shut and that is their designed nature but others do.
 

Ironracer

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I flushed my dirty *** cooling system and put in a 180* thermostat. Mistake. These are looking for 195 or they are in open loop mode- like the choke is on.
Even had black smoke out the exhaust. -
No code. - had to monitor w tool while running to figure it out.
I put a 195 in the 02 Ram 5.9 I had.. Napa Perscribed. Went back to a 180. Just to hot for mid south Fla. Didn't notice any adverse affects, just the temp a Lil lower!
 

'68cuda416

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You need to have the ability to look at scan data and preferably something that can graph........there are plenty of cheap scan tools that can accomplish this.......forget about downstream O2 sensor and concentrate on the upstream and when it acts up running rich it should be reading .7 ish to around a volt which in that case it would be doing it's job of reading the exhaust stream, but if it's low voltage and by that I mean .1 maybe .2 volts then it could be a sensor that is stuck lean and the computer is compensating for what it is seeing from the O2 sensor. O2 sensors can be quickly and easily checked for normal operation by inducing a rich or lean condition into the system.....if you have one that reads rich and you don't know if it's rich from something else or the sensor is stuck all you have to do is induce a vacuum leak and the sensor should respond immediately with a low voltage reading. Conversely if you have one that is reading .1 to .3 ish range and not changing from that state you can give the vehicle a hard snap throttle and you will see a quick reaction to lean and then a shift to rich......this way you can tell if the sensor can react to something induced.....you could also introduce propane into the system to richen it up and see if the sensor immediately reads it. Start there......if all that checks out then I would look at MAP sensor data.
 

'68cuda416

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TPS sensor is a known issue.

If it's never been replaced- replace it.

They are cheap and easy to replace.
TPS failure would be more of a hard to stay idling, hunting at idle, possibly a shift issue also , and or stalling at a stop but very doubtful would cause his complaint.
 
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'68cuda416

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I had a similar thing happen on a non Mopar. It was a temp sender. There were two temp sensors on the engine. I didn’t know that. I replaced one. It was the one that was for the temp gauge. I thought that I had eliminated the temp sender as a possible cause. Took a dealer to figure it out.
I guarantee you could unplug the temp sensor and it would default to -40 degrees in most cases and it will not simulate his running issues.
 

'68cuda416

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Today has been a **** day.

This automotive problem has been ongoing, so I am going to use it to distract from my other issues of the day.

The vehicle: 1994 ram 3.9 v6, 5 speed. A billion miles. Bone stock except for a gutted cat.

This truck runs GREAT until it gets thoroughly warm. Then when you shut it off and go to restart, it's flooded. When driving it doesn't really act up that I've noticed, but park it and let it heat soak, and it's flooded. You have to hold the throttle WOT, and then it'll clear out but if you don't get moving...... glug glug

All 6 plugs come out BLACK and it'll stink my whole yard with fuel vapor. Doesn't smoke until it floods, and then it smoked black. Idle is great until it's Noah Time.

New plugs didn't fix it, cap and rotor are new, tried another coil, the previous owner replaced all manner of sensor with factory ones. He even replaced fuel pump (I got 40 psi when it's flooded, didn't try when it would run).

I can't even figure out any codes. No CEL.

The clean idle and lack of smoke tell me that the plenum gasket is probably ok. There's no downstream o2, since it's obd1.

Any advice on a magnum efi that floods when hot?
Why would you care about a downstream O2 ? Will almost never cause a running problem.....that is not why they are placed where they are in the exhaust....they are for cat monitoring and testing primarily with 10-15% fuel control at best.
 
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