Engine Stalling

[oldschool]

My engine stalls @ idle increasingly. It also did it on the highway when I backed off the throttle to switch interchanges several times already. It's been dangerous putting it to neutral @ 50 mph or whatever road speed I find myself to restart the engine. If I start it up cold and leave it idle, it will stall within 10 to 15 minutes. If I catch it floundering I've given throttle and saved it from stalling. When this condition occurred I've seen my fuel pressure steady @ 30psi before during and after. I have an Air Dog pump with a big draw tube with that kit. I also confirmed that the shut down solenoid holds steady. I changed out the fuel filters. In recent months the engine has been hard to start and getting worse. I've been writing that off as factory injectors @ 135,000 miles. I cant see how that it would be idling strong and stall on injectors. The stock automatic transmission finally hit an impasse as the lockup converter chatters and slips. I can't accelerate hard or tow anything in lockup. I can't see that failure stall the engine in park or neutral, but it's an issue. At this point I'm thinking it might be the injector pump. I'm really stumped. I could use help with this. Thank you

[MnTom]

The first thing I would check is the fuel shut off solenoid. It sounds a lot like it is not lifting the shut down lever quite far enough. Check the boot on the bottom of the solenoid for deterioration and see if the linkage is corroded. You may also try starting the truck and see if you can lift the linkage any by hand.

[oldschool]

Thanks MnTom, like I said above, it held steady. I had my hand on it one time when it stalled and nothing moved. I recently replaced it with a bigger solenoid from Larry's along with the relay. If I'm quick I can hit the throttle and keep it running. I could always recheck to double check. I'm scratching my head with this.

[YabbaDoo]

This may not be it, but thought it was worth mentioning...Sounds like a similar issue I had with my 94 a couple years back when the Crank position sensor crapped out on me ... Is your truck throwing any codes?

[oldschool]

I dont know if there are codes. Can I pull them with a regular reader? I thought the crank sensor only gave me a signal for the tach. I thought the only way electrically to shut this motor was through the shut down solenoid via mechanical linkage. Maybe when It goes to stall I could also monitor what the tach does. Thanks YabbaDoo.

[YabbaDoo]

Your welcome... Hope it helps... My first thought was the FSS but since you said it was good my second thought was what happened with my 94 a couple years back... I use an OBD2 reader for my 97...

[oldschool]

Nice. I'll try pulling codes tomorrow.

[MnTom]

The CPS on a 12v is what tells the PCM the truck is running. That will energize the alternator, gauges, tach, and A/C too. Now you got me thinking.... What is your idle speed? To low would cause it to stall at an idle too, more so cold, but still cause a stall.

[oldschool]

The truck has no codes. The idle is steady and normal. I started it cold @ temp of about 50 degrees and it held a strong idle. I only recall the stall condition after warmed up sporadically. I didn't wait for a stall condition yet to monitor the tach.

[MnTom]

So what RPM does the engine idle at? It is supposed to be 750RPM warm in gear and the A/C on. That would put it 850+ in park.

[oldschool]

Yea, I"ve got about 850 in park. It stalls out in park too. I could recheck the throttle stop. A few years back I raised it to get the proper rpm. I'm the original owner and only did it once because I noticed wear on the stop causing low rpms. It's definately worth eye balling. It would be good to rule out something moving around or maybe a problem with the stop. That's a good lead. Thanks.

[oldschool]

I got out there and ran the engine for about 20-30 minutes and no stall. I shook the linkage around and pushed the stop lever laterally just in case it can go off the stop. I moved the throttle back and forth and multiple times pushed in the return direction trying to stall it. No dice. It did'nt even stall today. I'll keep trying and re-post if I find something. Thanks for the help

[MnTom]

If it stalls out in park then it is not an idle speed problem. I have seen mine idle at less than 500 RPM in park (makes it real tough to get going like that). When it stalls, tell me what it sounds like. Does it quit like you shut the key off, just gradually die out, or does it seem like something is trying to load it up and make it quit?

[oldschool]

It doesn't shut off quick like with a key. It takes 5-10 seconds. Sounds like its missing and choked off. As far as loading up I thought It was possible the lockup convertor (that is no good) was doing this but it seems that it would need to be in gear for that failure to stall. It's been increasingly very hard to start even in warm weather. I have to give 1/4 throttle to help. On warm or cold re-starts I have the same thing. I'm thinking the injector pump may be ready to change.

[MnTom]

Are you sure you don't have an air leak somewhere? Like maybe the return line on the back of the engine or even something around the heater? The rubber lines are known to leak air and not fuel. I have a hard time believing that your IP is bad. P7100 pumps usually last forever so if yours is wore out at 135k miles then it would really surprise me.

[Mopar1973Man]

I've got the same though a air leak possibly. Oldschool says he's got a AirDog on his truck. I wonder if its a quick connect fitting possibly throwing a bit of air in the system. Fuel pressure gauge?

[oldschool]

That is correct, I have an Air dog and removed the stock filter and fuel heater. It's all Air dog now. Air leaks are possible. I was just looking into that with research. Good call. The other possible on the same note may be the tank vent. Fuel pressure gauge is above 30 psi steady. What's the best way to check for air leak? I hope you're right about the IP. This truck is in need of a transmission and some other mods. It's going to cost. I've got to give the truck credit, this truck never let me down and I've hauled so much weight and so powerful with low fuel consumption. Now I'm just using it on the farm until I figure it out plus time and $. My "replacement vehicle" a 1990 suburban 2500 4X4 w/ a 6.2 diesel is such a dissapointment in comparison. It's offensive to even say comparison with the Dodge.

[Mopar1973Man]

Simple method would be to pressurize the fuel tank and look for wet spots or wet joints. Do the tank pressure test right after running the truck to ensure the fuel lines are all filled with fuel. Then hope the 1-2 PSI of fuel tank pressure is capable of pushing fuel out the air leak. Sometimes it works and other times it don't.

[oldschool]

Ok that sounds good. I'm a bit confused, the Air Dog pump is mounted on the frame just ahead of the tank. I'm pushing fuel to the engine. If the suction from the tank is in question doesn't the Air Dog remove air from the suction line from tank and return the air back to the tank?

[MnTom]

Have you found anything yet?