ride_a_hd

I just replaced my overflow valve with the new one from Precision Diesel Injection and Turbo Inc. (Marty Tompkins) and now I'm getting whitish/blue smoke and ROUGH running 1500-2000 RPM (can't get past that rpm).

During installation I had a bit of fuel leak so I figured it would be a hard start and it was. I cracked the overflow valve and primed the lift pump until fuel came out the overflow valve. Fired up after some coaxing, ran a bit rough, but then smoothed right out. I didn't adjust/move/mess with anything else during installation.

Running down the road, I couldn't get above 1500 rpm in 1st (not granny) without the smoke/rough running. I could get between 1500-2000 in 2d and 3d before it started smoking again. (Couldn't really get up to speed to go to 4th.) The roughness doesn't go away if I stay in that RPM band once it starts. The truck just starts bogging down until I let off the throttle.

I tried draining the fuel/water separator getting only fuel. It idles fine. Not sure what changed... It got dark so I couldn't try putting in the old (original) overflow valve and see if it was just the valve, though the new one looked fine upon initial inspection.

Any ideas?
Dave

dieselhawg

I would try reinstalling the old valve and trying it.You may have recieved a bad valve,weak spring or stuck check ball.Also try blocking off the return line for a test.I recently installed one of Marty's valves on my truck and it worked fine,but once in a while a new part may be defective.Just my 02.

Hemi Cat

I agree. The quickest way to check the new overflow vlv is put the old one back in if it was good to begin with. If it runs good, then the problem is obvious. If the problem continues, check for fuel/air leaks. If still in doubt, put a pressure guage on it to check fuel pressure. That should tell you where to go next.

ride_a_hd

Okay, pulled the new valve. Looks fine. Can easily move the ball/spring pressing in with a toothpick, so it's free. The stock/old valve is just a bored out bolt with four holes. There's nothing else inside it. No ball/spring. Is this right?

Could it be that there's not enough fuel pressure to work the new valve? I don't have a pressure gauge to do any measurement testing, either...

I know the fuel shutdown solenoid was replaced and can restrict fuel supply. How do I check it and/or adjust it? What are the specs for it?

Thanks!
Dave

ride_a_hd

Found how to check/adjust the shutdown solenoid:

http://dodgeram.org/tech/dsl/trouble..._solenoid.html

dieselhawg

ride-a -hd, i've only seen valves with a ball and spring.Someone must have problems with it and removed the in sides,are you sure you are installing it in the proper location at the pump back side at the return line?If the fuel shut off solenoid is pulling up all the way with the key in start position,i would think its working ok.If the overflow valve is returning too much fuel to the tank it will retard the pump timing making it run sluggish.Hopefully some of the senior members will chime in and give you some more idea's.

ride_a_hd

Thanks dieselhawg, I kinda thought a hollow bolt was wrong... Yes, it's installed in the correct location. Did a bit of research online before I started. I'm headed out now to check the adjustment of the shutoff solenoid, as it appears easy to do. Every bit helps. Thanks!
Dave

ride_a_hd

Reinstalled the old valve and runs like a champ! Smoke black as coal accelerating down the county road!! Almost not worth putting the new one on and finding the problem!

Checked the shutoff solenoid and it's right on adjustment. Probably low fuel pressure but will have to wait to check that one...
Dave

Rhino

94's and some 95's had the "hollow bolt" overflow valve. It seems that you got your problem solved.

I'm just curious as to why you replaced the valve in the first place. Did you suspect a low fuel pressure issue?

infidel

No doubt the new valve was bad. Give Marty a call and he'll send you a new one.
The OF valve on the 12 valve is one part that for sure wears out. If you don't have the means to check the pressure replace every 75k.

ride_a_hd

Rhino, heard they wear out and should be replaced every 75k or so (as infidel said) so I was doing some preventive maint. If it's supposed to be hollow, though, don't see how that would wear out... I'm just wondering if low fuel pressure is preventing the new valve from working properly...

Rhino

I agree they certainly do age and wear, but I was just wondering if you were having any problems.

dodgeman01

My 94 had the ball and spring in it. I got a new one and shimmed it up a little to raise my fuel pressure even more.
DM01

CarlJensen

The valves do go bad because they DO have a check ball and spring in them. If you have the kind that comes apart(two halves unscrew with wrenches), measure the spring for .5 inches length. Be carefull to not lose the ball or small washer inside, useless without them. The spring can be lengthened for more pressure.

ride_a_hd

Okay... I guess my issue is that my stock valve has no ball/spring but runs very well. I am getting about 16 mpg right now, so wonder if the new valve would improve that. Unfortunately, when I install the new one, I have the problems listed in my original post. I probably need to call Marty whom I got it from and see what he says...