Engine/Transmission (1998.5 - 2002) Erratic Fuel Pressure

[ILIANBG]

If it was me I would remove that filter before the pump and install just a mesh inline small filter. It looks like it's too much for the pump to pull from the tank. Diesel is really good in Germany. I had almost the same problem when I installed my Airdog. My screen inside the tank canister was clogged up. I could not clean it so I removed it. Then installed the drawstraw from Vulcan Perf. . I never run the truck with qarter tank, seldom even with half tank (just a habit). I have never had an issue since then- about 70000 miles on my current set up. Original VP-44 (knock on wood)
Ilian

 

[KrisKringle]

Um, the pressure/bucket test was done w/o filter.

If it was me I would remove that filter before the pump and install just a mesh inline small filter. It looks like it's too much for the pump to pull from the tank. Diesel is really good in Germany. I had almost the same problem when I installed my Airdog. My screen inside the tank canister was clogged up. I could not clean it so I removed it. Then installed the drawstraw from Vulcan Perf. . I never run the truck with qarter tank, seldom even with half tank (just a habit). I have never had an issue since then- about 70000 miles on my current set up. Original VP-44 (knock on wood)

Ilian

Thanks for the info. I will do the rest of the write-up in a bit. However, I did the test directly from the source to the pump, i. e. , without any filter in the loop... my truck has over 150K, and the PO changed the VP. (He did not even know why a pressure gauge was important. )... More in a minute... Jonathan

 

[KrisKringle]

Update...really a mess, and getting urgent.

Ok. So it has been more than a few minutes. I promise I will write the whole thing out later with pictures.



The A and O (That would be the Alpha and Omega) of the situation is this. In the last couple of days I have noticed that the pressure was getting worse... at WOT, I could almost get to 0 today! OK, so maybe the filter is at fault. I removed the filter, and bridged the line. Bumped the starter, and had 12 PSI... OK. Did it again to make sure all of the air was out... =0 PSI. Loosened the PR valve... a few bubbles, but still no pressure. WTF??? Took the line from the pressure gauge, and ran it into a Coke bottle. NO FLOW: Put 80 PSI of air into the filler neck of the tank... a dribble. Jeepers. Put the old lift pump in, same deal. Finally there was pressure (and diesel everywhere)... ran the truck. at 'fast idle'... 2 PSI. Truck off, only 9 PSI...



Put the FASS back in. Until I pressurised the tank, there was nothing. Then I had 14 PSI... (and another flood of Diesel). Since it was after midnight, I did not think it was a good Idea to run the truck up to 'fast idle' again.



OK, before anyone says that there is an air leak in the feed: I put over 80 PSI into the tank, and there was no indication of leaks... (before the draw straw, yep... the cap on the evap vent was split. (Remember: The whole story of the Draw Straw is not written up yet... )



SO: Tomorrow I will see what happens. I predict that I will still have 10 PSI at Idle, and that the pressure will drop to almost 0 at WOT...



Any ideas? I am ready to replace the entire line from tank to pump... but I doubt that the problem is in this area...



Results later... . Jonathan



Oh, BTW; I can now change a lift pump in about 15 minutes...

 

[cerberusiam]

Replace all the lines from tank to filter. You could easily have a flap of rubber INSIDE the lines that is closing off the flow at random times. Only sure way to know is line replacement.



FYI, that type of failure is a #@$%! to find and WILL drive you nuts.

 

[KrisKringle]

Replace all the lines from tank to filter. You could easily have a flap of rubber INSIDE the lines that is closing off the flow at random times. Only sure way to know is line replacement.



FYI, that type of failure is a #@$%! to find and WILL drive you nuts.

Thanks for the suggestion. I do not see any rubber lines between the tank and pump. Only steel, and the factory hard plastic. I took a good look at the lines, and see no kinks, or leaks. I think I am going to try putting the fuel sender on the Schraeder Valve at the factory filter inlet, and see what I have for pressure there. The only rubber lines are between the pump and the filter, and between the filter and the injection pump. I am also going to put a clear plastic line between the filter and VP, and check for air bubbles.



However, the suggestion that a line is getting sucked closed somewhere would really fit with the symptoms...

 

[KrisKringle]

More information...

... It could be the lines from the tank; BUT when I did the Bucket test, I connected the supply directly to the pump, and ran the truck. (Pump was connected to the battery, so no voltage change. ) At 'Fast Idle' the pressure dropped, just like it does when connected to the filter or tank. At idle now, there is 12 PSI. it drops to 5 PSI under normal driving (shifting at 1800 RPM. At WOT, it has dropped as low as 1 PSI... I am going to change the rubber hoses between the FASS and the VP-44-the one between the filter and VP does not look so sporty...



Another thing, is that before this started happening, at WOT, the opposite would occur. The pressure would jump to 15-20 PSI, back to 10 PSI and then settle down... this was with both the Carter, and then the FASS. Since the pressure drop issue, this has not occurred#@$%!.

 

[ILIANBG]

Try replacing the lines from the fuel filter to the VP-44. If that does not fix it with the drawstraw installed, then I have to question the fuel pump. I suppose you have the FASS installed in the OEM location by the fuel filter, and not by the tank.
Your set up is a bit different than mine. My AD is next to the tank and I have 1/2" lines running from the tank to the VP-44. I did it all in the same time I installed the AD. But since then not one issue with pressure. Yes, I never run the tank low.
So, try the lines first. maybe you have some restriction there.
I hope you find a fix very soon and hopefully you do not need to buy anything else, which I imagine could be more time consuming in Germany. I know how frustrating is when you spend all that money and you can't get it to work as it should.
Ilian

 

[KrisKringle]

Still hoping for some infos...

Try replacing the lines from the fuel filter to the VP-44. If that does not fix it with the drawstraw installed, then I have to question the fuel pump. I suppose you have the FASS installed in the OEM location by the fuel filter, and not by the tank.

Your set up is a bit different than mine. My AD is next to the tank and I have 1/2" lines running from the tank to the VP-44. I did it all in the same time I installed the AD. But since then not one issue with pressure. Yes, I never run the tank low.

So, try the lines first. maybe you have some restriction there.

I hope you find a fix very soon and hopefully you do not need to buy anything else, which I imagine could be more time consuming in Germany. I know how frustrating is when you spend all that money and you can't get it to work as it should.

Ilian

Thanks for the support. BTW; parts are not impossible to get, just expensive. I managed to get the fuel sender here through the dealer... cost 135$ though... Injectors are available too... as well as filters. When the parts guy looks them up, they come up as Caterpillar parts :-laf



Anyway, as to your comment about the pump. When I did the bucket test, I did not feel like having a 3 foot line full of diesel, so I pulled it out of the canister, and waited for the pump to draw enough fuel out of it so I could remove it without making a mess. It was a bit strange that it took almost 30 seconds empty the line... really makes me wonder about the FASS. I expected it to suck the thing dry in a few seconds...



Still leaning towards the Pressure Relieve valve as the problem. I replaced the line between the VP-44 and the filter. No difference. I plan on putting a clear line between the LP and filter, so I can check for air... but I doubt there is any. More later, and thanks again for the help... Jonathan.

 

[KrisKringle]

Ordered Check valve.

Well... I replaced the lines between the filter and VP-44. No difference. Since I do not have a rubber tip on the air gun, and given the other posts, I just ordered a check valve using the Bosch number; 1467445003. It cost less than 20€, and will be here tomorrow Hopefully it will fix the problems I have been having with pressure... if not... then the story goes on.

 

[KrisKringle]

Check Valve in...Survey says....?

Well... Check valve is installed. In addition, I checked for the screen mentioned in the post Is hindsight 20/20? Guess what? No screens. I even pulled both bolts off the pump, and at the filter to see if I had swithced them up during the midnight Lift pump test, swap, test and swap.



With everything back together again, I bumped the starter to run the Lift Pump. I do not think I ever saw 15 PSI before, so I was pretty excited.



Then I started the engine, and? Little or no difference.



Here is what I have done so far:

1. Bucket test
   
2. Installed draw straw
   
3. Replaced all rubber lines from pump to VP
   
4. Replaced Overflow valve.
   

The conclusion? I think the FASS DDRP is junk. #@$%! Hopefully they will honour the warranty. It is only two months old after all...

 

[DonFitzwater]

I'm going to install a FASS but not the ddrp. I'll be installing the dual filter HD unit. Thank you for keeping after your problem and keeping us all posted. TDR is a great resource for all of us!

 

[KrisKringle]

Update...jeeper creepers. still no progress.

Weeellll Campers,



I just installed a new 3/8" line from the new Draw-Straw to the DDRP. The last couple of days, as the fuel pressure relatively often approached, and ended up at '0'#@$%!, I figured perhaps the quick connects were leaking, or perhaps as suggested, the hard plastic had a crack somewhere.



I have not driven the truck, but the pressure drops to 5 PSI at fast idle (From 12 PSI), so I am not too optimistic.



On a brighter note, I ordered a Carter pump from Rock Auto on THursday, and it arrived today! (In Germany) Can you believe it? Oo.



Next step is to swap the DDRP for the Carter, and see what happens... I will keep you posted.



Running out of options at this point. I am beginning to think that I should get a VP-44, and stick it on the shelf... JIC...

 

[DonFitzwater]

Well Kris, what have you discovered?

 

[ILIANBG]

Hi Kris, what did you find out? Is the Carter on? I bet you are really quick in swapping those pump now You will figure out what's wrong, you are at the end of the tunnel.
Ilian

 

[KrisKringle]

Sorry...no results yet...Filter? I cannot believe it.

Hi Kris, what did you find out? Is the Carter on? I bet you are really quick in swapping those pump now You will figure out what's wrong, you are at the end of the tunnel.

Ilian

Sorry It has taken so long to reply. Real quick. No change from the pressure, except at idle, I see maybe one PSI more... sometimes.



The only things I have not done is change the filter and the pump. The Carter is sitting in the box.



My Father would be dissapointed to hear that I never did 'the most simple thing first;' that is to change the filter. However, with only 2. 500 miles, I cannot believe the filter could be blocked. The diesel here in Germany is not the rat-pee that sometimes occurs in the US... since there are so many diesel autos here, it is a primary fuel, and is of high quality.



I will post results tomorrow. I only will have time to change the filter, but I really think the DDRP is kaputt. Before I go anywhere tomorrow, I will change the filter. If that has no effect, I will quick change the pump.



You are right, I can change a pump in under 20 minutes... Jonathan. (Kris Kringle is my user name... long story).



Oh, BTW, I had over 1. 8 kilo tons (2640pounds) on the rack (not in the bed) the other day... I won't do that again... but no damage, no ticket, no problem... really had an eye on the fuel pressure though.

 

[KrisKringle]

Normally, listen to your Father...however, this time I was right. Still no solution.

Weeellll... for those following the story so far...



Finally followed my Father's advice, and changed the filter. (Easy stuff first, remember?) Turns out my logic was correct however, and after a couple thousand kilometres, it was still clean... However, there appeared to be 'metal filings in the filter housing... Anyway, I changed the filter. NO DIFFERENCE! #ad




So, in with the new Carter pump... yep, changed it in 15 minutes. Inclusive looking for the dropped washers#@$%! for the banjo fittings.



Results? Pressure with jumper on pump: 9 PSI... . (FASS DDRP is 14 PSI) Running, idle 6 PSI... 'Fast idle: 1 PSI



So... my Brother, (Mr. Hemi here, I think) told me that a friend of his who is a Chrysler Mechanic, (Bill Whirley sp. ) said that the injectors were letting too much fuel pass by for 'cooling and lubrication. '



WTF is Joe Donnelly????? Maybe I need to post this in the 911 area...



Still at a loss for where the problem lies, but I know that in 15 minutes, I can install the FASS again so that I have at least 5 PSI when driving around, and now have two spare Carter pumps...



OK, for those of you late to the party, or (like me, hate going through back posts, here is a short recap:

1. Problem: Low pressure with normal driving. Pressure approaches '0' as the turbo pressure builds.
   
2. Dropped tank (yep, I still have not written up how I did it... I did a few things that are 'different' from the instructions. )
   
3. Changed all of the fuel lines from the pump to the VP
   
4. Oh, yeah, Installed a Draw-straw when I dropped the tank.
   
5. Installed a 3/8" line from the draw straw to the pump.
   
6. Installed an original Carter lift pump... .
   
7. End result... Install the FASS DDRP, and look for another reason for the low pressure.
   

So there you have it... a riddle like Archimedes knot... a sword will not solve this one however...

 

[cerberusiam]

Hmmm, I don't remeber you saying and too lazy to read all the posts again but, what do you have for a gauge? Electrical or mechanical? Have you verified pressure with at least 2 gauges?



"Injectors bypassing too much fuel and causing low fuel pressure at the IP inlet"



Well, injector lube and cooling is part of the injection event. That would mean that the pump is creating a huge injection event to draw the supply pressure that low. Would expect to voluminous clouds of black smoke at any time if thats the case.



Considering about 70-75% of the fuel supplied to the IP in idle range, 750-1500 rpms, is bypassed back to the tank, and, a diesel is load demand on fueling, and your seeing low supply pressure in a no load condition, pretty sure its safe to call BUNK on that idea.



It is beginning to sound like the IP has an internal problem routing fuel back to the tank. Wonder what the return rate is on VP-44 at idle? Not sure I ever heard a number for the VP.

 

[KrisKringle]

no smoke

I don't remember you saying and too lazy to read all the posts again What I meant is that I have (like most people) little time to go back through old posts to see what has transpired, so it is good to have a recap once and awhile...

Anyway, no smoke... or at least no clouds of black smoke. This whole situation started after I came back from the states after Easter. The truck sat for a week, and then started with the pressure problem...

To answer your question, I have an Electric gauge, with a snubber valve, connected at the inlet line for the VP... .

Considering about 70-75% of the fuel supplied to the IP in idle range, 750-1500 rpms, is bypassed back to the tank, and, a diesel is load demand on fueling, and your seeing low supply pressure in a no load condition, pretty sure its safe to call BUNK on that idea.

With the jumper wire installed, there is around 14 PSI with the DDRP, and 9 with the Carter. At Idle, there is 11-12 with the DDRP, and 7 PSI with the Carter.

... . and your seeing low supply pressure in a no load condition...

I do not know if I have explained this before, but... Here goes. At idle: 12 PSI. Going through the gears (shifting at 1500 rpm), the pressure drops to 5-7 PSI. When under load, such as going uphill or with a pile of wood in the bed, as the turbo pressure builds (5-10 PSI boost), the pressure can drop to 1-2 PSI. At WOT, the same... just above 0. If I back off the throttle (at least with the FASS), I can keep the pressure over 5 PSI...

Today I took the truck out, and as we live on a hill with almost 20% grade, I put the pedal to the floor, and (with the Carter), and the gauge stayed steady at 2 PSI... no smoke though. (And the neighbours were all awake when I was through)

 

[cerberusiam]

Depending on what gauge you have, the electrical sending unit types can have problems for no reason. Snubbers are also notorious for causing issues with fuel pressure.



Remove the snubber and see if there is any change. Test pressure in the same situations with a mechanical gauge and no snubber to verify pressures.



Without verification of pressures with a secondary gauge your still just guessing.



Hope you find something concrete soon. You have been at this for a bit.

 

[KrisKringle]

Snubbers' away....

Depending on what gauge you have, the electrical sending unit types can have problems for no reason. Snubbers are also notorious for causing issues with fuel pressure.



Remove the snubber and see if there is any change. Test pressure in the same situations with a mechanical gauge and no snubber to verify pressures.



Without verification of pressures with a secondary gauge your still just guessing.



Hope you find something concrete soon. You have been at this for a bit.

OK... DDRP back in. no change. As boost increases, Fuel pressure drops...



Snubber is away, and as I have about 50 cm. of rubber line, it is probably superfluous anyway.



Gauges are 'Glow-Shift. ', yep, I know they are not the best, but... probably all come out of the same factory in Taiwan anyway... I will have to wait until tomorrow to get to the shop and get my mechanical gauge set up... I do not have any here at the house.



Of course, now I noticed that the engine mount on the DS does not look to sporty. Probably the effects of the previous diesel leak from the drain valve, and the constant douching of Brake Cleaner it has been getting from all of the changes of fuel-lines, filters, and the last six lift-pump 'swaps. ' Cannot do it faster than 15 minutes though... not yet anyway.



It appears now that I have two 'spare' Carter pumps. Maybe a relay, and one on the frame as a 'pusher' to the FASS is the next step.



I will also try to find a sending unit. It should not be too hard...