Engine/Transmission (1998.5 - 2002) Lift pump fuel supply woes

[DavidC]

This is something to check if you have low pressure on the pump side of the filter. I have a gauge post filter that showed 9 psi at idle and could zero the needle on long steep grades even after installing a new lift pump. Put a mechanical gauge on the pre-filter side which read 10 psi idle. Picked up 5 foot of 5/16 fuel line at Checker auto and ran the line from the lift pump to a 5 gallon jug. Started the engine and 14 psi on the gauge. I then proceeded to fire up the air compressor and blow 125 psi back to the tank thru the existing fuel line (after removing the fuel cap). Reinstalled the line to the pump and reprimed the system. Started the engine and wa-la 14 psi on everything. Apparently the filter in the tank had gotten plugged up with something (probably not good) and cut the supply to the pump pretty good. Back in my hot rod days we use to make it a point to remove the sending units and throw those in tank filters in the trash and I guess that may be what happens to this one. So for all you guys that are going thru lift pumps you may have another problem and it may not be the pump.



Dave

 

[USMCBay]

This is certainly interesting... Is it easier to lift the bed or drop the tank?



I wouldn't mind removing the intank filter and placing a screw-on setup and NAPA filter before the LP as one of the members here did...



This sounds like it worked for you - will be interesting to see how it increases the life of the LP...

 

[lsenus]

Every race car I ever built had either a sump system or in-tank/cell pick up with an inline filter outside the tank prior to the pump. With diesel being as dirty as it is and the possibility of bio growth, it would make sense to have the filtration external for ease of cleaning.

 

[DavidC]

This is certainly interesting... Is it easier to lift the bed or drop the tank?

. .

In my case it will be drop the tank. I have a 40 gallon aux. tank/tool box and a 5th wheel hitch. I have 3/8 of a tank right now so I will drive it a while and keep an eye on things. The pressure (no pun intended) will be on if the problem does not arise again by the time I run low on fuel. Do I drop the tank or fill it up. I am leaning towards tank and internal filter removal. I am not sure about an external filter as the lift pump would have to suck the fuel thru it also. I would think all filters should be on the pressure side, but I was wrong once before, I think.



Dave

 

[USMCBay]

Here is a photo of the FREE FLOWING Filter installed Pre Pump...



#ad




It seems to be a great option vs. the in-tank filter. This would be a lightining quick change that could be done with little expense... Heck I think I'll do it.



Heres something that may back this theory... Okay - July 4th I moved the LP South and hooked it up wrong at first - filled the line with diesel going back to LP and Tank - I bumped the Starter over a dozen times and got nothing (Pump was now facing opposite of engine mount location so it was pumping the priming diesel back into the tank) I figured this out and then swapped the fuel line into correct sides of LP... Started right up then! Had a stiff 15psi - Now three days later (7-07-2006) it is at 13psi... Hmmm Maybe because I was backwashing my in-tank filter while priming the fuel hose while hooked up wrong... SO... this may have cleared my in-tank for a day or so and now it is clogging again...



Certainly Worth a thought.



Someone with a "Down South" LP may want to reverse your fuel hose and bump the starter a few times and see if your PSI's go up... if so you may have backwashed and cleaned the In-Tank Filter... Hmmmm



What do you guys say?

 

[DavidC]

I just got off the phone with Racor and the tech recommende the 690R series filter for the suction side. I explained to him that the Carter pump has to try to suck from the tank approx. 10 to 15 feet away and I was concerned about causing a restriction to the pump with the filter.

http://www.parker.com/EAD/displayCa...&menu_divid=109&catid=2557&catdesc=600 SERIES



Dave

 

[DavidC]

Drove about 1/2 mile and noticed pressure dropping again. Hooked up the mechanical gauge again, 10 psi from the tank. Blew the line again 14 psi. Drove 1/2 mile 10 psi. Drove around using up fuel and dropped tank with 1/4 tank. The intake filter is one piece at the bottom of the sump. It appears it is a woven type screen with a bottom and top piece. The suction line goes thru the first layer and snaps into the second which allows maybe a 5/16 screen at the suction. The second screen appears to be for the return line back to the tank and sump assembly. Either way the whole screen assembly was so waxed up I do not know how anything got thru it. Tried some brake cleaner on it and it did not even touch it . Needless to say it is not going back in. What a pain in the a** for something like this.



Dave

 

[NoSeeUm]

Overflow valve OK?



Jim

 

[DavidC]

To tell you the truth I thought of the overflow but dismissed the idea as everytime I would blow the line back to the tank I would have good pressure for a while. The junk on the tank filter looked like someone had coated it with vaseline. Right now I did a 10 mile drive and things appear to be ok with no in tank filter. I am looking into an inline strainer right now to keep things from getting to the lift pump. I think I have found what I am looking for here.



http://www.enginegearonline.com/instforoildi.html



Dave

 

[USMCBay]

Drove about 1/2 mile and noticed pressure dropping again. Hooked up the mechanical gauge again, 10 psi from the tank. Blew the line again 14 psi. Drove 1/2 mile 10 psi. Drove around using up fuel and dropped tank with 1/4 tank. The intake filter is one piece at the bottom of the sump. It appears it is a woven type screen with a bottom and top piece. The suction line goes thru the first layer and snaps into the second which allows maybe a 5/16 screen at the suction. The second screen appears to be for the return line back to the tank and sump assembly. Either way the whole screen assembly was so waxed up I do not know how anything got thru it. Tried some brake cleaner on it and it did not even touch it . Needless to say it is not going back in. What a pain in the a** for something like this.



Dave

Ah Ha - Possibly another - if not "THE" culprit of the LP Sudden Death Syndrome...



I will be gutting my Dead LP and looking for signs of slime or "diesel algea".



Dave - Let us know what the FP is reading now that you are removing the intank filter...



... maybe a pre LP free flowing in-line filter could help open up the flow of fuel and cut down the restrictions... and Thanks Dave for the link - I haven't found a price as good as this! $22. 60 is an affordable option.



http://www.enginegearonline.com/instforoildi.html



I will be dropping my tank soon and the intank filter will be MIA...



Anyone know the GPH requirements?

 

[DavidC]

Okay, Here is the skinny from Fleetguard. They recommend the FF5079 147 micron. They do not recommend a filter on the suction side of the lift pump (meaning a lower micron rating). They also recommend using a dispersnt fuel additive CC2588 once in a while that will clear build up the tanks, lines etc. I told them the strainer when scraped with the finger nail was just like scraping your finger in a vaseline jar. They do not have any idea what this stuff is. I have ordered the serviceable unit from Enginegear as it is 3 inches wide and I can clean it. The FF5079 is a can and not serviceable. So far after removing the in tank mesh I am holding at 14 psi at idle where I was hanging around 9 before.



Dave

 

[USMCBay]

Hmmmm - this is a new angle on the LP issue...



I will be following suit with you and pulling my tank screen this weekend.



Thanks for the research Dave!

 

[Bob4x4]

Hmmmm - this is a new angle on the LP issue...



I will be following suit with you and pulling my tank screen this weekend.



Thanks for the research Dave!

Its not really new the tsb that explains the lift pump test procedures includes testing the restriction to the pump... ... ... ...



Bob

 

[AWeik]

i know this is a little off topic but i didnt want to start another thread about LP's. what does the FP gauge do when the lift pump is dieing or does it just go. my gauge is acting funny. maybe the iso needs to be bled?

 

[klaybus]

Very interesting indeed! I'm on LP #6.



Clay

 

[DavidC]

i know this is a little off topic but i didnt want to start another thread about LP's. what does the FP gauge do when the lift pump is dieing or does it just go. my gauge is acting funny. maybe the iso needs to be bled?

Best way to test is to install a mechanical gauge on the lift pump side of the filter if your in cab gauge is after the filter. If both gauges are close and low try blowing 125 psi back to the tank (with tank fill cap removed). Then rebleed the system and check pressure again. Mine would instantly jump up and with in a mile fall back off after the vaseline type substance would start plugging the strainer back up. Of course you have a strainer in the Carter pump also which could be another problem. Another way to check as I did was fill a 5 gallon jug with diesel and run 5 foot of 5/16 fuel line from the jug to the pump, eliminating the tank and lines on the vehicle. If the pressure increases significantly you probably have strainer issues.



Dave



Dave

 

[DavidC]

Fleetguard recommended using this once in a while to clean the fuel system as they say it is a dispersant. Fleetguard # CC2588. May help.

http://www.hoeslidiesel.com/specials.htm

Scroll down to the additive.



Dave

 

[Alphacowboy]

hey Shawn, thats my setup that you pictured off DTO so far, its still working well. I have had problems with fluctuating fuel pressure for a couple weeks, but I can tell its the pump cavitating, but it only does it at idle, under throttle its fine... go figure. My sending unit died about the same time I got this fuel pressure issue, so I am thinking that the gauge not working and messed up FP might be from the newer Bio mixed fuels that have implemented in MN in the past few months. Probably broke loose a bunch of junk in my tank and is clogging the filter screen in the tank... now that I think about it, when the pressure fluctuates, thats exactly what the pump sounds like, like a vacuum when you plug the hose... hmmmmm. Hopefully I am going to pull the tank and replace the sending unit tomorrow, I will post up what I find.

 

[DavidC]

Installed the enginegear strainer today 7/15/06. Idle pressure is still hanging at 13-14 instead of 8-9 with the intank strainer. The screen is a nice setup as it is clear plastic and you can see the fuel and any trapped bugs. This so far is better than the in tank strainer that you can not see or clean with out major work. I did see something black hanging in the bottom of the strainer although being 3" wide I will let it sit in there. Now thinking about a Rasp or Mitusa.



Dave

 

[DMannon]

I just ordered the Glacier 392 system... DavidC, what's your impressions of the strainer you bought?