Engine/Transmission (1994 - 1998) Start smooth, stumble at 10 seconds, smooth??

[salty]

Hey smart folk. . My 95 12V with 430k miles has always run terrific. I replaced LP recently and overflow valve for good measure. Very recently I'm having a smooth immediate start but after about 10 seconds a stumble for about 10 seconds where I need to give throttle or I'll stall. Then smooth as silk again.



Obviously checked for all connections and lines and found no air leaks. Changed water seperator unit, and am now thinking pre-heater.



To add a teist I have run veg oil for about the last 130k with zero issues, but what this means is that the LP is now pulling rather than pushing. The diesel comes from the tank to the pre-heater, then diesel filter, solenoid, LP, IP.



Again all runs super, just annoying start up.

 

[BrentAnderson]

Updates?

I'm currently having the same problem... I'm researching it now on this site, but if anyone has any suggestions please feel free to point me in the right direction.



I'm thinking that I need to check the solenoid. It seems as if it starts right up, then stalls out after 10 sec or so. Then I crank it for about 10-15 sec, it starts Rough. . blows alot of white smoke (I'm guessing unburnt fuel) almost like its flooded... but can that really be true? After about 10-15 sec of coughing and rough idle, it seems to smooth out and away I go. By the way... its a 97 ram 2500 Manual with around 256000 miles. Just replaced the Lift Pump, OFV, and yes I checked for air leaks... .

 

[hsmith]

Don't leave out the prefilter screen. WVO can really plug it up.

 

[fest3er]

Y'all haven't checked thoroughly enough for air leaks. A diesel requires three things to operate: air, fuel and compression. Since it is highly improbable that the engine is suffering a momentary lapse of air or a momentary loss of compression, that leaves a disruption in fuel supply.

You have air entering the fuel system somewhere. Were I to hazard a guess, I'd say in the return line, allowing a bit of air to get into the p-pump. , causing the one-time stumble. The leak may be smaller than a pin hole. It may only leak under vacuum and never under pressure. But it's enough to allow air into the system and cause the stumble.

 

[GaryOwen]

Might want to check connections to air intake heater also. May not be getting full voltage/current. Worked for me with similar symptoms.

 

[KBurgoyne]

make sure the line that screws into the top of the lift pump is in securely. the one for the pefilter too. the prefilter has a rubber grommit that keeps air out, but the lift pump doesnt.

 

[BrentAnderson]

thanks for the info so far... I did also forget to mention, I removed the pre-heater... . so that eliminates the problems that are typically caused by the 1/2 elbow leaking and craked heater bowl... .



I'll re-check my hoses... . make sure they are all tight... I'll post an update.



Just to make sure this doesnt sound at all like a solenoid problem though correct?

 

[GAmes]

Just to make sure this doesnt sound at all like a solenoid problem though correct?

If the solenoid is malfunctioning there wouldn't be an intermittant problem. Once it pulls up it won't fall until you turn off the key. Easy to check. Go to the start position, then leave the ignition on whether the engine is running or not. Push up on the lever, it should be to the top. If it is only partially up remove it and clean it up. If it is not up the engine won't start.

 

[fest3er]

... Just to make sure this doesnt sound at all like a solenoid problem though correct?

Correct. When my truck did the same thing, that was one of the things I checked. It went through full travel every time. Futzing with it while the engine was running made no difference.



Eventually, it got so bad that it could only be a fuel line. Turned out the steel return line (generally above the LP by the F/W) had rotted through enough to allow a steady stream of fuel to stream out against the firewall and undercarriage--enough to eliminate rear tire traction on wet highway, even with reduced power. Replaced that and it got better for a while. Then it got *real* bad, to where it would barely run. The supply line had rotted through, too.



So it's not just hoses that fail. The hard lines can rust through, too (given a salt and battery effect). If you let it go long enough, the leak will become apparent. (Come to think of it, mine became apparent right about this time of year, too. )

 

[JKosten]

Could you rack arm be hanging up on the stop plate?

 

[BrentAnderson]

fuel level

so... I havent had a chance to really dig into this yet... but I did fill up the other day... . the past few days, I havent had a problem? So I guess I have a problem with my fuel pickup... . time to research that a bit... .



any suggestions on replacements if that is infact my problem?