Engine/Transmission (1998.5 - 2002) Erratic Fuel Pressure

[KrisKringle]

OK. I have searched all of the posts, but still cannot seem to find a difinitive answer. Recently I installed a FASS DDRP. At the same time I changed the Fuel Filter (Natuarally resulting in a leaking drain valve).



Since the installation of the FASS, the fuel pressure has never been as expected; maximum 12# at idle, 5-7' under WOT, but shooting to 15-20# under WOT. I contacted FASS, and they told me to do a pump volume test, as they suggest there is a blockage in the line /pickup in tank. Have not done this yet.



1. What should the pump volume be in the 20 second run time?



Also, more disconcerting is that the pressure now drops to zero for a few seconds (at idle /no load), then raises slowly to 12-14#. The light to fill up just came on BTW. ( I ran it low in anticipation of dropping the tank, checking the screen and installing a filter between the tank and pump.



2. is 25 micron to fine for a pre-pump filter? It is a canister type, similar to a normal PH 8A in size.



3. WHAT THE HECK IS GOING ON???



I pulled the connection from the pump and the connectors in the harnes as well as at the PDC and put a bit of Dielectric grease on them... no change.



Pump does not sound too happy... loud 'whirring' sound... perhaps because the tank is low, but still... and help would be greatly appreciated... . Jonathan

 

[JLandry]

Regarding the strange pump noise and intermittent no pressure, it simply sounds like the fuel level sender is inaccurate and the pump is sucking air. When you have the fuel tank module out, it would be wise to replace the sending unit.



You may also want to consider installing a draw straw or a tank sump to eliminate troubles altogether from the fuel tank module.



Best regards,



John L.

 

[KrisKringle]

Draw strw /sending unit.

Regarding the strange pump noise and intermittent no pressure, it simply sounds like the fuel level sender is inaccurate and the pump is sucking air. When you have the fuel tank module out, it would be wise to replace the sending unit.



You may also want to consider installing a draw straw or a tank sump to eliminate troubles altogether from the fuel tank module.



Best regards,



John L.

Thanks... could you give me a PN of the sending unit? Is it the same gas or diesel? Over here in Germany parts are a bit hard to come by, sometimes I can get them through the dealer, but need a PN... Thanks.

 

[JLandry]

Thanks... could you give me a PN of the sending unit? Is it the same gas or diesel?

Assuming a 35 gallon tank, then the current Dodge part number is: 04897669AB

The part number for a 26 gallon tank is: 05014461AA

It's the same for gasoline or diesel.

You can download a pdf copy of the Dodge parts manual HERE (for quad cab) or HERE (for regular cab).

Best regards,

John L.

 

[KrisKringle]

Thanks!

Assuming a 35 gallon tank, then the current Dodge part number is: 04897669AB



The part number for a 26 gallon tank is: 05014461AA



It's the same for gasoline or diesel.



You can download a pdf copy of the Dodge parts manual HERE (for quad cab) or HERE (for regular cab).



Best regards,



John L.

Thanks... should always have the parts manual with the repair manual...

Oo.

 

[KrisKringle]

Update...still not out of the woods.

Well... On the way to the shop, I thought I would put 20 or so litres in the tank, 'just in case. ' As I drove down the hill to the filling station, the pressure dropped to 0, and the truck stalled. I probably scared the spots from the cows when I dropped the clutch to bump start the truck. Luckily it fired back up, and I made it the the station. 20 litres later, I suddenly had pressure... hmnn.



Since I seldom drive the truck past a half-tank, it appears that when the 'low-fuel' light comes on, it means "Fill up RIGHT AWAY. " As a result, I immediately ordered a Draw-straw... Jeepers shipping is almost as much as the unit (38$)... I wonder if it gets through customs, and I have to pay Import duty on it as well...



At the shop, I had a whole list of stuff to do.

1. Install a pre-filter between the tank and the FASS
   
2. Relocate the Fuel Pressure Sending Unit
   
3. Check pump flow
   
4. Check for blockage in the Tank
   
   1. 
      

First I did a check for the flow from the pump:



In 25 seconds, it pumped only around 1. 5 litres. Then I blew air back through the line, to see if I could loosen anything up from the pick-up screen.



No Change... Hmmn. I really should have tried to check the pump by bypassing the tank; i. e. , directly from a container, but I did not have this option. (No Container, and not enough hose to run through the filler-neck)



I installed the filter I picked up at TSC in the States. (25 Micron Filter for log-splitters... Made in USA BTW).



#ad




I did not drop the tank, (the Draw-Straw is on the way), and I figured I would give the tank shock treatment of bactericide... man is this stuff expensive: Liqui Moly Anti-Bakterien... 30$ a quart!



In the end, I still had around 10# at idle (lost 1-2# as a result of the the additional restriction from the new filter), and 5# at WOT.



Curiously enough, when I hit the brakes, the pressure goes up to 11-12#... Hmmn. I really wish I tested the pump using another fuel container... more later.

 

[JLandry]

Jonathan,



That part about hitting the brakes and seeing the pressure is indeed strange behavior.



You could perform a vacuum test on the fuel line between the pump and the tank as outlined in the factory service manual, but this will likely just confirm what you already know... there's a restriction somewhere in the tank.



Sounds like you really need to drop the tank and investigate what's going on.



Good luck,



John L.

 

[DavidC]

When the in tank screen had a pasty coating on it my stock pump pressure was below 5. I did as you and blew air back in to the tank. Started the truck and 14lpsi. , drove about 1/4 mile and less than 5psi. Filled a jerry jug and installed a hose on the lift pump and a constant 14psi. When I dropped the tank and inspected the mesh screen the substance resembled Vaseline and I could not get it cleaned off. I finally cut the screen out and installed a Fleetgaurd inline strainer. I would do the alternate fuel source before dropping the tank as you did not see a change after blowing air back into the tank. Of course when I did it I had the compressor regulator set at 120psi.



Dave

 

[KrisKringle]

Thanks.

When the in tank screen had a pasty coating on it my stock pump pressure was below 5. I did as you and blew air back in to the tank. Started the truck and 14lpsi. , drove about 1/4 mile and less than 5psi. Filled a jerry jug and installed a hose on the lift pump and a constant 14psi. When I dropped the tank and inspected the mesh screen the substance resembled Vaseline and I could not get it cleaned off. I finally cut the screen out and installed a Fleetgaurd inline strainer. I would do the alternate fuel source before dropping the tank as you did not see a change after blowing air back into the tank. Of course when I did it I had the compressor regulator set at 120psi.



Dave

The draw straw is hanging at customs... I still have almost a full tank, so when I finally get the draw straw, I will drop the tank, and post the results. Thanks for the info... Jonathan

 

[cerberusiam]

When you pull the tank cannister you will likely see your problem. either the suction line has hole in it or there are pieces of plastic floating around in the bottom of the cannister plugging the pickup.



The stand alone draw straw is a whole set of problems of its own. They have always been and will always be problematic due to their size and position. If you want the pump to pull the fuel down to true empty mode the cannister with a new larger pickup and make sure all the return is routed like the OE system.



Dropping the tank to install a draw straw is the 2nd mistake. The tank will sit on the floor and compress somewhat. When you hang it and fill it all of a sudden the bottom if the pickup is not wher eit needs to be, hence the dreaded 1/8 issue and fluctuating pressures when you go on and off the brakes or throttle.



Aside from the tank slosh, putting the straw out of the cannister basket sucks all the crap floating on the bottom of the tank right thru the pump and into the filters. Some of it is gonna go thru the injection system, especially the water. You will also likely get cavitation issue with the straw at low fuel levels.



Overall, the cannister has a lot of benefits that will be felt downstream by retaining it.

 

[mwilson]

Well... On the way to the shop, I thought I would put 20 or so litres in the tank, 'just in case. ' As I drove down the hill to the filling station, the pressure dropped to 0, and the truck stalled. I probably scared the spots from the cows when I dropped the clutch to bump start the truck. Luckily it fired back up, and I made it the the station. 20 litres later, I suddenly had pressure... hmnn.



Since I seldom drive the truck past a half-tank, it appears that when the 'low-fuel' light comes on, it means "Fill up RIGHT AWAY. " As a result, I immediately ordered a Draw-straw... Jeepers shipping is almost as much as the unit (38$)... I wonder if it gets through customs, and I have to pay Import duty on it as well...



At the shop, I had a whole list of stuff to do.

1. Install a pre-filter between the tank and the FASS
   
2. Relocate the Fuel Pressure Sending Unit
   
3. Check pump flow
   
4. Check for blockage in the Tank
   
   1. 
      

First I did a check for the flow from the pump:



In 25 seconds, it pumped only around 1. 5 litres. Then I blew air back through the line, to see if I could loosen anything up from the pick-up screen.



No Change... Hmmn. I really should have tried to check the pump by bypassing the tank; i. e. , directly from a container, but I did not have this option. (No Container, and not enough hose to run through the filler-neck)



I installed the filter I picked up at TSC in the States. (25 Micron Filter for log-splitters... Made in USA BTW).



#ad




I did not drop the tank, (the Draw-Straw is on the way), and I figured I would give the tank shock treatment of bactericide... man is this stuff expensive: Liqui Moly Anti-Bakterien... 30$ a quart!



In the end, I still had around 10# at idle (lost 1-2# as a result of the the additional restriction from the new filter), and 5# at WOT.



Curiously enough, when I hit the brakes, the pressure goes up to 11-12#... Hmmn. I really wish I tested the pump using another fuel container... more later.

Not to be a pain, but that is a hydraulic filter. I don't know what Diesel will do to the media inside the can...

Just a thought.....



Mike.

 

[AH64ID]

Is that filter pre-pump?

While hydraulic filters will generally be okay with diesel, it's very hard to get a good rating for fuel on them because they are designed for a closed system.

Your pressures in the last post sound 100% normal for a DDRP, it's a direct replacement for stock and not much more fuel. I see 9 at idle, 5-6 WOT, 11-12 under heavy braking (braking moves fuel fwd to the sender).

At this point it's hard to say, sounds like a pickup restriction. The new filter pre-pump is probably helping mask it as there is more volume to put a suction to when the inlet is blocked. I see zero mods in your sig that would justify a draw-straw. I would stick with the stock pickup and find your problem.

 

[firefighter]

is the filter on the right fuel line it looks to me to be on the return line.

 

[KrisKringle]

Nope, on hte feed line.

is the filter on the right fuel line it looks to me to be on the return line.

The return line it the line up top. The line from the tank is the 3/8" line I tapped into... believe me, I checked. :-laf

 

[KrisKringle]

When you pull the tank cannister you will likely see your problem. either the suction line has hole in it or there are pieces of plastic floating around in the bottom of the cannister plugging the pickup.



The stand alone draw straw is a whole set of problems of its own. They have always been and will always be problematic due to their size and position. If you want the pump to pull the fuel down to true empty mode the cannister with a new larger pickup and make sure all the return is routed like the OE system.



Dropping the tank to install a draw straw is the 2nd mistake. The tank will sit on the floor and compress somewhat. When you hang it and fill it all of a sudden the bottom if the pickup is not wher eit needs to be, hence the dreaded 1/8 issue and fluctuating pressures when you go on and off the brakes or throttle.



Aside from the tank slosh, putting the straw out of the cannister basket sucks all the crap floating on the bottom of the tank right thru the pump and into the filters. Some of it is gonna go thru the injection system, especially the water. You will also likely get cavitation issue with the straw at low fuel levels.



Overall, the cannister has a lot of benefits that will be felt downstream by retaining it.

I will take a look. Thanks for your input. I was thinking of Pulling the bed to do the install of the draw straw. Also, the filter in the picture is before the pump... . Thanks. I will post an update when I get more info.

 

[KrisKringle]

Is that filter pre-pump?



While hydraulic filters will generally be okay with diesel, it's very hard to get a good rating for fuel on them because they are designed for a closed system.



Your pressures in the last post sound 100% normal for a DDRP, it's a direct replacement for stock and not much more fuel. I see 9 at idle, 5-6 WOT, 11-12 under heavy braking (braking moves fuel fwd to the sender).



At this point it's hard to say, sounds like a pickup restriction. The new filter pre-pump is probably helping mask it as there is more volume to put a suction to when the inlet is blocked. I see zero mods in your sig that would justify a draw-straw. I would stick with the stock pickup and find your problem.

Thanks, yep, no mods on the truck, and really none planned. I still have to install the Stage 1 injectors, and check valve clearance, but the truck has enough power to get the job done. Beside, it has the original 5-speed, and all 5 gears, and I would like to keep it that way. Parts are kind of hard to come by over here. :-laf

 

[KrisKringle]

Fuel sender.

Regarding the strange pump noise and intermittent no pressure, it simply sounds like the fuel level sender is inaccurate and the pump is sucking air. When you have the fuel tank module out, it would be wise to replace the sending unit.



You may also want to consider installing a draw straw or a tank sump to eliminate troubles altogether from the fuel tank module.



Best regards,



John L.

Thanks John. The fuel sender came today (Through a Dodge Dealer in Germany no less). The Draw straw is stuck in customs... hopefully I will still get it this week... Jonathan

 

[KrisKringle]

Not to be a pain, but that is a hydraulic filter. I don't know what Diesel will do to the media inside the can...

Just a thought.....



Mike.

It is a normal Paper element... thanks for noticing though.

 

[cerberusiam]

Also, the filter in the picture is before the pump... .

That can be problematic for the pump keeping its prime. The suction on these pumps is not that good and any restirction just causes more problems. A screen to keep the bug chunks out is about all that can be run without a high incident of issues.



Thats why retaining the factory cannister and keeping clean fuel in it is so important to rule out problems between the pump and the tank.

 

[KrisKringle]

Update: Not so 'FASS-inated.'

Weeeeelllllll... .



Here is the story so far:

1. Low pressure
   
2. Wrote an email to FASS
   
3. Received an answer (text to follow).
   
4. Eventually did the tests.
   

So the tests I did:

1. Bucket test; but a bit different.
   
2. Direct Jumper from battery to the pump.
   
3. Test for pressure with engine not running ( 14 PSI)
   
4. Test with the engine at idle : (12 PSI).
   
5. Test with the engine at 'Free Idle' (7 PSI).
   
6. All of the above were with the pump directly connected to a reserve canister, bypassing all filters.
   
7. Let the story commence... .
   

Ok, this could be long, or could be continued tomorrow.



First the email to FASS, since I knew I was coming to the States in April, I sent them and email regarding the problem the lack of pressure in the system, so they could send the 'correct' PSR spring. (My pressure gauge is connected at the Injection pump, BTW. )



Jonathan,



You should be getting 16-18psi @ idle. Sounds like you have a restriction in the tank. Was the factory pump doing the same thing?

There is no 'updated PR spring'. Your pump is built to make 16-18psi or it doesn't leave the factory. Try doing a bucket test. See:

Fass - Fuel Air Separation System





Thank you,



Brent Moreland

FASS Warranty/Technical Assistance

16240 State Hwy O, Suite B

Marthasville, MO 63357

636-433-2962

636-433-5913 Fax



I found it kind of strange that after reading a bunch of posts that said that there was an 'updated spring', that suddenly there was none...



OK, so it took a while, but since I was seeing pressures less than 5 PSI, I really was on edge. (Over here, an injection pump costs over 7. 000$ US) So, after reading all of the posts, I ordered a 'Draw Straw' as a precaution I think the pictures and installation will have to wait until tomorrow, as it is already 01. 45 here, and I have to get up early.



So, (now the day BEFORE yesterday), while I 'had the time' and access to a lift, I decided to drop the tank.



End result? No difference.



I am about to join the camp where the FASS DDRP is a POS. I can understand that the pump without the engine running only gives 14 PSI, as this is the relief-valve pressure at the DP-44. However, there is no excuse for the pressure to drop so much when the engine is running. More tomorrow... with the pictures I was able to take with my Handy. Strangely enough, they managed to turn out (almost) OK... I left the real camera at home. 'till tomorrow. JK



BTW; I took what pictures I could, and although the screen in the picture looks pretty strange, the tank was really clean... except for one 'toy surprise'... here is the picture:



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