Engine/Transmission (1994 - 1998) Another Fuel Pressure Thread

[The patriot]

Have you thought of the screen in the tank pickup?

I was surprised how dirty mine was when I had the tank out.

There's actually two in the dodge factory tank.

 

[BSMcCauley]

Have you thought of the screen in the tank pickup?

I was surprised how dirty mine was when I had the tank out.

There's actually two in the dodge factory tank.

DITTO that! I had that problem with a '65 gasser car after a fillup of dirty fuel on the way home from college many years ago. I found the max point I could push the throttle and still make power and held it there until I found a place to pull off the highway and work on it. Dirty pick-up screen will only show up under sustained load because at idle and under testing, it will flow plenty to keep the engine happy.



BEST test indicator would be the fuel pressure to the injector pump while experiencing the problem (requires gage that can be read while belted down behind the wheel). Have you tried that yet?

 

[Mhannink]

i hate to say it but im betting its your lift pump. what makes these pumps so reliable is their simplicity. all the lp is is a pistion driven by the cam eccentric and 2 one way valves. the whole design is like that of a 2 stroke engine. everytime the piston retracts it draws fuel from the tank and every time it extends it pushes it to the engine. with the pressure being so low id say you have a valve failing. its sealing enough to build the pressure needed to maintain power at low speeds and or rpm. however when its loaded and with weight on going up a hill its a big load youre not getting enough fuel to the engine for it to maintain. i had one fail a long time ago, for a period of time before it finally failed completly fuel pressure would drop to 0 and even stay there. the engine would run with seemingly no problem. then pressure would jump back up and be just fine. finally what happened is the fuel pressure hit 0 stayed there and the engine started to die. i pulled over and that was it. got the truck towed home pulled the lp opened it up and found the inlet valve had failed. this caused the fuel to be pushed back to the tank instead of to the engine. starving the injection pump. my suggestion is pull the lp and remove the threaded ports and look at the valves if they look ok that might not be the problem but if it where me i would be replaceing the lp just incase. i know the one you have is brand new but failures happen right out of the box sometimes on any part and from any manufacture.

 

[JohnsonJim]

Alright... here we go. Been a couple of weeks since I have been able to get back to the truck. Been busy with the 3 F's. Football, Fence (around the property) and just F'N too tired!



Truck sat for 2 weeks... and fired right up after 2 revolutions... no air leaks there.



Fuel line(s) are now down to ONE. I am running straight to the left hand tank. NO switch valve and no crossover lines (remvoes the heat issue).



With a LOAD, 4th gear up a grade... about 2 min into the run... the same fuel starvation type issue as before... and the FP was at 17.



---



TODAY -



Went and picked up ANOTHER Cummins made in china lift pump... . and after running a dial indicator on the essentric lobe (all was good, . 250" lift) installed said new pump. Well what do you know... the SAME freaking 20 psi at idle. Pictures... almost forgot to add the pictures...



This is the low spot on the essentric... . it was a pain to get that indicator in there and set right... so 3-4 thou is where I got it at for my 'zero'



#ad




Was able to put a socket on the alternator nut and bar the engine over AND stretch and look at the indicator gauge. Here is the highest reading.



#ad




Ok... back to the blabbering... .



This time with the new pump on, I get the same damn 20 at idle but free revving the eingine... . the FP does go UP... got to 27.



This did NOT do it before with the 1st new cummins pump.



I have not taken the truck on the road to see what the FP does under a load...



I need to get a buddys OFV and swap out the Tork Tek one. I have a feeling that the adjustable OFV is bad, considering that it is 'supposed' to be pre set at like 35psi, and I have mine adjusted all the way in and get 22... . if I back it out... I get even less. Also intersting is that when I talked with Rob about that... no mention from him about a possible bad valve. Seems like a stand up guy so I doubt that I will have any problems returnig it if it is bad.



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Now another update on the injection pump issue. I called Columbus Diesel (kinda low key company... but big in the pulling truck world) and talked with them for a bit about the 'sticking plungers' and possible 'warped barrels". They confirmed as well that there was an issue with some of the 94-95 p-pumps on Dodges and also some p-pumps on dt466's (believe that is what he said) that had that issue. Told him what my goal was and he said to send the pump to them, 90 bux to diagnose and then go from there...

said usually there is no need for a complete overhaul... but if it did need it they could do that for 11-1200 and turn it up as well... plus install my gsk, set the timing, install furl plate etc. he siad most of the time is is a few hundred bucks. I like that a WHOLE lot better than just buying an off the shelf, supposedly tuned, pump... and ofcourse paying for a 'name'.



Wife seemed "OK" with this 'new pump' idea... . now to explain that I 'need' a new S300g turbo!



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Jim

 

[JohnsonJim]

i hate to say it but im betting its your lift pump. what makes these pumps so reliable is their simplicity. all the lp is is a pistion driven by the cam eccentric and 2 one way valves. the whole design is like that of a 2 stroke engine. everytime the piston retracts it draws fuel from the tank and every time it extends it pushes it to the engine. with the pressure being so low id say you have a valve failing. its sealing enough to build the pressure needed to maintain power at low speeds and or rpm. however when its loaded and with weight on going up a hill its a big load youre not getting enough fuel to the engine for it to maintain. i had one fail a long time ago, for a period of time before it finally failed completly fuel pressure would drop to 0 and even stay there. the engine would run with seemingly no problem. then pressure would jump back up and be just fine. finally what happened is the fuel pressure hit 0 stayed there and the engine started to die. i pulled over and that was it. got the truck towed home pulled the lp opened it up and found the inlet valve had failed. this caused the fuel to be pushed back to the tank instead of to the engine. starving the injection pump. my suggestion is pull the lp and remove the threaded ports and look at the valves if they look ok that might not be the problem but if it where me i would be replaceing the lp just incase. i know the one you have is brand new but failures happen right out of the box sometimes on any part and from any manufacture.

Good info! I posted above that I just got a 2nd new pump... I will take #1 apart and look at it.



I am still supect of the OFV... I should have more FP from this 'fancy adjustable one'.



Jim

 

[JohnsonJim]

Have you thought of the screen in the tank pickup?

I was surprised how dirty mine was when I had the tank out.

There's actually two in the dodge factory tank.

You missed post #10... here is what I wrote... . Here we go.



hose from filter to the gerry can. 20 psi.



changed out the OFV to the stock one... back to 14.



I can prime the lift pump button and it releases at 27psi.



Tork tech over flow valve should be factory set at 30-32.



when I rev the engine up... I may see 1-3 psi change.



stumped, other than bad LP... . that is NEW

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no screen, hose in 5 gallon can, same psi number.



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[JohnsonJim]

DITTO that! I had that problem with a '65 gasser car after a fillup of dirty fuel on the way home from college many years ago. I found the max point I could push the throttle and still make power and held it there until I found a place to pull off the highway and work on it. Dirty pick-up screen will only show up under sustained load because at idle and under testing, it will flow plenty to keep the engine happy.



BEST test indicator would be the fuel pressure to the injector pump while experiencing the problem (requires gage that can be read while belted down behind the wheel). Have you tried that yet?

Went back and looked at my posts, and in this thread I did not mention that I am aable to monitor FP going down the road. 20 or so running... get on it... goes to 12 and then back up... never higher. THAT was with the 1st LP.



Now with the 2nd newLP... Ihave not been able to drive it yet on the road... will do and check out the FP. Betting I have another 2 fold issue... HAD a bad pump, and have a bad adj overflow valve!



Jim

 

[Nyoest]

I bet it was all in the lift pump. A road test will tell the tale. And pat yourself on the back for diagnosing it before you just threw some parts at it!

 

[Missouri Mule]

Fuel pressure test: When return fuel line is pinched if pressure rises its a bad overflow valve if pressure does not rise or rises slowly its a bad lift pump.

(This is when you are not getting enough pressure. You are getting minimum fuel pressure that is allowed. 20 lbs at idle after fuel fuel filter. When you rev it pressure should rise. )

Could be something keeping the fuel getting to lift pump.

 

[JohnsonJim]

Fuel pressure test: When return fuel line is pinched if pressure rises its a bad overflow valve if pressure does not rise or rises slowly its a bad lift pump.

(This is when you are not getting enough pressure. You are getting minimum fuel pressure that is allowed. 20 lbs at idle after fuel fuel filter. When you rev it pressure should rise. )

Could be something keeping the fuel getting to lift pump.

Yep... already know that test.



1st new cummins lift pump... the squeeze did not get me more pressure and the truck did not build pressure either when revving. On to pump #2 from Cummins.



Pump #2 from cummins. 22 psi with the Tork Tek adjustable valve. Rev engine and 25-27... same on the road... could get 30 at times on the road. pinch return line... pressure spikes like it should.



Pull out the adjustable OFV... NEW stock OFV from Larry B. Idle pressure drops to 12 and 17psi if you wing the throttle.



I am off about 10psi. The adjustable tork tek should get me 30+ at idle...



Two new fuel filters, and whole system off (screen etc) and checked for leaks. None.



Truck can sit for a week and fire right up on two revolutions... so i dont think that air in the line is the issue. Have taken the metal line off from the filter to the IP and pressure tested... no leaks.



Need to find me a different tapped banjo bolt for the inlet side of the fuel filter. would love to check pressure BEFORE the filter...



I need to address the sticking plunger issue in the Injection pump... so it looks as if that the p7100 is coming off. A call to Columbus diesel and to PDR, and both say it is possible for the IP to be the cause of this low pressure issue...

 

[DRAG DIESEL]

Have we questioned the pressure gauge yet? LOL!

 

[JohnsonJim]

Have we questioned the pressure gauge yet? LOL!

Actually I have... before I got the 2nd pump... I set the regulator on the the shop air to 45 and then pressurized the line to the gauge. 45psi. I was thinking of getting another gauge... but then we are just throwing more money at stuff.



jim

 

[The patriot]

I'm not reading the entire thread, so sorry if it's been covered.



A friend of mine had a KW that would not make full horsepower.

Years later (and many $$$) he found that one of his fuel lines had a restriction that wouldnt give the engine fuel to make full power.

Just a thought.

 

[DRAG DIESEL]

I need to address the sticking plunger issue in the Injection pump... so it looks as if that the p7100 is coming off. A call to Columbus diesel and to PDR, and both say it is possible for the IP to be the cause of this low pressure issue...

I don't want to discredit what the pros say, but I would think knowing the design of the IP that once the overflow was blocked a sticking plunger would have little or nothing to do with lift pump pressure.

 

[JohnsonJim]

I don't want to discredit what the pros say, but I would think knowing the design of the IP that once the overflow was blocked a sticking plunger would have little or nothing to do with lift pump pressure.

I'm with ya on this too. This is a 2 part problem I have. low pressure and a bad IP. I guess what I meant to say and write is that the 'pump gurus' think that the low pressure could be caused BY the bad IP.



Pinch the line (return) and pressure goes up.



I really want to find a banjo bolt that will allow me to monitor FP before the filter.

 

[The patriot]

I dont know what a 95 fuel filter head looks like, but my 98 has the bosses cast into it just waiting to drill and thread 1/8" NPT and hook up a gauge. One for pre filter, one post filter.

In fact, that's what I did. :-laf

Look in my readers rig pics.

Even if it doesnt have the cast bosses, I'm sure with a little thought you can figure where to drill.

 

[DRAG DIESEL]

With the numbers you posted when the over flow was blocked, it should have been higher. I see almost 50psi at 3k out of mine with my modified over flow.

Just tap the stock banjo. I did mine years ago, and never have had any issues.

 

[JohnsonJim]

With the numbers you posted when the over flow was blocked, it should have been higher. I see almost 50psi at 3k out of mine with my modified over flow.



Just tap the stock banjo. I did mine years ago, and never have had any issues.

I am talking about theinlet not the outlet. Inlet has the banjo plus the injector return. The bolt is a bit different than the outlet bolt that is tapped... or in my case has a brass plug already. The snubber I have is for the IP inlet, 14mm and the filter head is 12mm.



IP is off and sent in for repair/rebuild. Injectors pulled and sent as well for pop testing. Parts will arrive at pump shop on monday 9/19.