Engine/Transmission (1994 - 1998) 95 CTD fuel pressure / lift pump?

[Kawi600]

Ive got a 95 ram 2500 that Ive been working on over the past few months trying to pin down a low power / fuel economy problem. I get about 10miles to the gallon so something is going on in there!

I installed a westach fuel pressure gauge and it shows 12psi at idle and anywhere from 12-20psi at 2k rpm depending on what it feels like doing. Iv e confirmed this with a fluid pressure tester. I should be seeing 20ish at idle and more importantly 25+ psi at 2krpm.

I have checked and cleaned the overflow valve. The spring was 1/2" in length. I had the heater screen cleaned and Ive cleaned the screen inside the tank. The only bad thing I can see externally is a little dry rot in the fuel return hose.

How hard is it to swap a lift pump? It doesnt look easy to get at.

Is this what Im looking for here?: http://www.citydiesel.net/supply-pump-dodge-12-valve-p-126.html?cPath=22_26_48

also how bad is it to replace the rubber fuel lines? Looks like there are some special fittings so Id need OEM lines? Or just lop off the crimps and use a clamp over the hose?

 

[Joe G.]

Swaping the lift pump is a last resort. They hardly ever fail. First thing to do is to replace the fuel hoses. If they are not bad now, they will be. You can get a kit with the proper hoses and clamps from http://www.fostertruck.com/dodge/default.htm . The fuel hose you can buy at most auto parts stores is NOT diesel rated in spite of what the clerks say.



Replacing the hoses or any other work in that area is a problem because of no room to work. Remove the two nuts that fasten the master cylinder to the booster and lean the master cylinder toward the fender. Remove the starter.



If fuel hoses does not do it them you most probably have an air leak somewhere. Any fitting is a suspect. The fuel heater may have over heated (probably burn the element so it doesn't work) that causes an air leak in the electrical connection believe it or not. The o-ring type of gaskets in the fuel heater/pre-filter assembly may be leaking air. The short curved hose between the pre-filter and the lift pump could be leaking air.



If it is still having a problem, take the lift pump off including the steel lines to and from it. Restrain the push rod so it doesn't blow out. Put about 20 PSI of air pressure in it and dunk the whole mess in a bucket of water. Bubbles will tell you where the air leak is.

 

[Kawi600]

Ok, I went by the local cummins dealer and picked up an overflow valve that the guy looked up and matched to the application. The opening at the bottom of the valve is much smaller than my old one, and the internals are much different. The old one had a little cup between the bearing and spring and the new one doesnt have that, but does have 3 different sized shims on top of the spring.

I get entirely different readings now. 28psi at idle of 750rpm and about 20psi at the lowest point at full boogie. Another oddball thing is I get no visible smoke with all these mods.

Anyone have any ideas? Im stumped!

 

[Joe G.]

You need to fill out your signature so we know what mods have been done to your truck. If the truck seems under powered and runs ok then you may have an AFC problem. One way to check that is to remove the AFC. Cover the hole up so that dirt stays out and oil stays in. Take it for a test ride. It should smoke a lot when you jump on it. If the AFC was restricting power you will notice quite a bit more power. Of course, that depends on whatever your other mods are.

 

[Kawi600]

Ok, it was under truck description I stuck it under my sig.

So take the whole AFC cover off? or just the back part with the vacuum diaphragm?

 

[Joe G.]

The cover holds the throttle stop. If it is not being pushed ahead because of an AFC problem then it will run fine, but be gutless because the governor follower will never get to the plate. So to do this test take the whole AFC off. The AFC is to control fueling until boost is high enough to burn the available fuel without smokeing up the place. So if you take it off there will be smoke during accelleration. If the AFC is the problem then you should notice quite a bit more power with your mods. Your stock injectors are the bottleneck to making a lot of power.

 

[Andy Redmond]

Here's a couple of other ideas too



Ck. the shut down solenoid to assure the shut down lever comes up fully and isn't defueling. If this cks out wire/ziptie it up to see if the power improves. If it does the hold coil could be getting weak and dropping the plunger enough to defuel (like a throttle stop). Before condemning the coil, adjust the plunger so its a bit shorter, if this solves your problem.



Have you ever ck'd to assure the governor lever isn't sliding under the nose of the "full forward" tst #6 per your sig?



The piers diesel site shows what to look for and how to correct this.



Full rack travel might equal the strap laying on the slope of the plate vs the end/top of the slope on the plate.



Joe has given good advice and you can ck. both of these items when you do the afc test, he suggested.



Also 18 degrees of time is quite a lot for your set up. I think you could improve drivability by dropping it back to the 15-16 deg. range.



To test whether you have low fuel pressure due to the ov. flow valve or the lift pump (other items) the following.



Have an assistant watch your fuel psi gauge at idle while you gently squeeze off /constrict 5/16" return line with soft jaw pliers, if the pressure build quickly and to proper levels (say maybe 30 psi), your lift pump sounds healthy and your ofv is causing your low psi issue. If no change the lift pump, filter restriction, line restriction etc. is likely the cause of the low psi concern.



Good luck

Andy