I would check it for codes. Most likely a bad MAP. If not that, I would suspect VP next.

But lots of things can cause this issue. Those just seem to be the big ones.

Dave

 

Kinda sounds like what Big Ed is saying, I had a similar problem on my 95, getting 12MPG no matter that I did. Turned out the fuel line going from the filter housing to the pump had cracked and was spraying fuel all over the place. Of course, as soon as I shut the motor down it would stop, and it never left a puddle anywhere (more than normal, the timing case gasket leaked, so catching one leak over another was kinda tough). I popped the hood one day when the engine was running and got sprayed in the face with diesel.... Replaced the line and it was good as new. I never really lost any noticeable power, so I didn't expect a fuel leak, but sure enough!

 

There seems to be lots of good suggestions here but it would seem a few thoughts are missing.

1st, you have a slush box transmission that has likely seen better days and is in need of a TC and VB - let alone a service, I'm sure.

2nd, check for leaks at your fuel filter canister - the washers that house the drain **** wear out and will let air in and fuel out. Same goes for the test port at the VP44 injection pump. Even with a HY35 turbo that boost seems a little on the low side and I would think even bone stock that you should hit 20 or so. Perhaps a boost leak which is yet again another common problem the older the truck gets. You see the OEM boots aren't great and they tend to dry out, crack and split. This would cause low boost and low power as well as less than stellar fuel economy. Granted under most cases this condition would also present black smoke as well.

3rd, as indicated filtration makes a huge deal to these trucks. Never run anything on the fuel system that isn't approved by cummins. In fact best bet is to stick with Fleetguard filters but that's just me. Never use FRAM oil or fuel filters - ever.

4th, your fuel pressure is VERY low. Remember this is a VP44 powered truck and not a CP3 pump. Idle for good pressures you need to be above 13 and WOT you need to be above 11. Dodge will tell you something different but they never really solved that problem so I don't agree with what they will tell you. My guess is that you are loosing or have lost your lift pump and that this is dramatically effecting the injection pump. There may not be any codes at this stage but it is very likely that you will be replacing both here very soon. Get your truck scanned for codes at AutoZONE or some place with a real (decent) scanner. If you know someone with a smarty box this will do it too. You will want to replace that VP44 pump with a rebuilt from one of the sponsors here and you will also want to install a FASS or equal lift pump (with filters is my suggestion) to keep that pressure up and the fuel system from clogging on crappy fuel with the extra filters.

That truck with an auto and 3.55 gears should see HWY mileage of around 22 empty and city of around 17 or so. You are way too low and something is wrong.

Another secret about the older diesels like ours a drop in fuel economy from day to day and you know something is not working as it should and you don't even need a computer to tell you that...

If you have any other questions don't hesitate....

Cheers

 

thanks wyatt, had already checked every thing mentioned.

so installed new airtex e 7153 lift pump ( i know its not a fass but its localy avalible and cheap. )
now idle press 20psi cold engine but rises to 25psi when engine is at normal op temp
wot press 13 psi

now the big ? starts great runs good (seems a little better with new lift pump)
BUT with engine warm i had 2 hard starts then a no start. let engine cool 3 hrs and it started great (just touched the key and running)
i have read and heard about high press causing hard starts but what is too high?

 

Have you followed this advice?

 

Tom,

The problem then in all likelihood is the injection pump!
Sorry.

 

thanks ,yes i have checked. no codes

 

How?

Did you use a scanner?

Its rare but an injector pump can die without throwing a code. Have you noticed any white smoke?

 

thanks again and yes i checked. no codes

---AutoMerged DoublePost---

auto zone scanner, no white smoke

 

Evil,

It is rare but it isn't impossible. The VP44 pump can die without throwing a code. That said, your lack of power is coming from somewhere and my gut is pointing to the pump.

---AutoMerged DoublePost---

I'm still leaning on the VP because your boost pressure is low - when boost is low it means low fuel supply or an air leak somewhere.