Engine/Transmission (1994 - 1998) Fuel sytem before injection pump and Black Fuel out of fuel filter

[PGWIN]

Hi - i'm going through my fuel system to ensure no air leak integrity and have some questions I could use help with. Following Joe G write up.

Truck is 95' 101K miles, last fuel filter change 7 yrs and 17K miles ago. Driven sporadically as it is really a tow/vacation vehicle (Unfortunately).

What I've done so far:
1. Eliminated fuel preheater - it was clean and no apparent leaks.
2. Replaced pre-filter - it was clean - clean fuel, and very little sediment - looked like a few sand particles.
3. Replaced pre-filter to lift pump hose - it had internal hose spilt - visible if you squeezed it.
4. Pulled primer plunger from lift pump. mostly dry in the boot cover, but when plunging 1st time a teaspoon of fuel came out, perhaps it leaks past the plunger plastic ring seal).
5. Removed main fuel filter, 1st half cup of fuel came out separator tube clean. After moving the filter sideways etc to get it out of the truck the next half of fuel drained from sepator tube came out black - that was a surprise. Perhaps the movement of the filter dislodged black particles.

Key questions:
1. The lift pump primer plunger oring - is it meant to seal on the bore (when plunging) or only seal when it is static - in which the oring is compressed by the spring force holding the plunger outward?
2. Anyone know the original size of the oring (I've scoured the web to no avail). Mine is currently 14x1.6mm (it may have shrunk in cross section thickness though?).
3. Black fuel out of filter - normal considering 17k miles and/or 7yrs and obviously long durations between fuel fillups. I always start the truck every week or 2 at minimum, but not a lot of fuel going through the tank.



Thx,

Paul

 

[Missouri Mule]

Is the engine running good? Could be algae if engine running bad. Mite be just a chemical that is associated with diesel fuel.

Even though your not putting many miles on it you should change oil and fuel filter once a year.

 

[GrantP]

I can't answer your questions on the orings in the lift pump, if it were me I think I'd just buy a new pump and have the peace of mind. Granted you don't have a lot of miles on it, but it's been a lot of years which is probably why it's leaking. As for the fuel being black...I live in a very dry climate and have never had fuel turn black. If it's just the filter turning black that is completely normal. Might throw some algaecide in the tank and stock up on fuel filters...

 

[JR]

Agreed. Fuel filter should be annually but in all reality you could PROBABLY get away with every other year. Fuel breaks the filter media down which is why you see manufacturers recommend filter changes based on mileage OR time, which ever comes first.

As to what the black fuel is, it's a possibility you've got algae or asphaltine in your tank. Both are more likely if your fuel sits in your truck for long periods of time. A fuel conditioner would be valuable in that sense.

I would change the filter and pull it and check it again after running a tank of fuel through it.

 

[PGWIN]

Thx All for the replies. The black "particles" over night settled down to the bottom. So now it is translucent again, with a layer of black that settled to the bottom (thin layer). I think i'll add some biocide for good measure.

Guess i'll end up pulling the lift pump, as I pulled the fuel inlet fitting (piston barrel fitting) off, and the O'ring was very well shaped to the crushed position (21yrs), and a crispy edge. I replaced the o'ring but there is no way I can compress those springs in that awkward position with the pump installed. Kind of a catch 22, don't pull the fitting and always wonder if it leaks, pull it an suffer pulling the pump to be able to reassemble.

Ok i'll add one more part to replace - since I twisted the fuel outlet tube pulling the nut off of it (didn't realize the fitting nut below started to turn - ouch), so i'll be replacing that line as well. Well I guess one more mistake adds to the experience level!!!!!


Now i'll go find the tricks to getting the pump out - hopefully I can access it w/o taking half the truck apart. And get the studs for reassembly.

Thx,

Paul

 

[Grey Wolf]

Paul I would have to agree with the above posters. If you have black slimy fuel there is microbial growth present. This is about the best product I found for the "bugs"!

http://www.biobor.com/products/biobor-jf-fuel-additives/

 

[PGWIN]

OK - THE PLOT THICKENS!

Thx for all the imput - most valuable. I will also get the biobor treatment. I think the particles are not alge as it is only around the fuel filter, it separates, and the other fuel coming from the tank looks / feels new.

Augment initial information; the truck does still run good, wrt to starting in less than a second after starter engaged, never ever had an issue starting, never had an issue with it not running. I would say the power is less than what it came with stock brand new, but I didn't have it since new so I'm a poor metric, I would say the power has dropped off in the last few years, maybe 15% it would seem. still runs relatively smooth. My bigger "issue that has haunted me for the last 12 yrs, is why with the star wheel max forward would it not produce any haze of smoke with the plate in stock position and AFC housing in stock position.

Lift pump removed: When I got it on the bench, the piston easily slid out along with these "bits" that were behind the piston. These are the center plate diaphragm stop from the check valve in the fuel outlet fitting. It appears they had broken off of the check valve and then found there way down the fuel port from the cylinder (on the engine side of the piston).

Well this may explain the "no smoke" with star wheel all the way forward for the last 12 yrs, and perhaps why fuel tapers off to a max rpm of 2550 going down hill with my trailer. Let's hope his is the culprit!

Why did it fail? Only hypothesis I can come up with are:
1. The center casting was under a compressive load from the check valve being press fit into the fitting and eventually they broke from fatique.
2. Every time the valve closes the minute impact millions of time caused them to break (is there a pulse beyond the check valve return spring from the P7100?)

Has anyone seen the check valve fail like this before?
Is the check valve "normally" press fit in this fitting?

New pump: Current pump was made in England (says AC on it!). What is the best quality pump? Are there differences in origin of manufacture from Mopar, Cummins, Genos, LarryB's?

Thanks,

Paul

 

[GAmes]

The Cummins pumps from Genos are made in China, but I haven't had any problem with mine. It has close to 300k miles on it.

 

[PGWIN]

The Cummins pumps from Genos are made in China, but I haven't had any problem with mine. It has close to 300k miles on it.

Thanks GAmes

i did call Geno's and confirm it is a genuine cummins part same as I would get from cummins direct. So I'm good with that - as they have to have a level of Quality control.

Though mfg excursion rate from China is high in general - I've witnessed personally.

 

[PGWIN]

Ok so got the Cummins lift pump from Geno's, installed, found out the fuel inlet fitting on the pump is about 3/4" shorter than the original one.

The issue is - now the furl hose between pre-filter outlet and lift pump inlet (makes the 90) is kinked to the max and that will never work. If you can envision this - the pump barb needs to be out 1" to line up with the hose.

How is it that Cuminns figures this is a replacement part when it it not compatible with the remainder of the parts. Something is not adding up here.

Has anyone else encountered this. Looks like i could cut 3/4" off the hose i just bought, and it may work, but I don't really like that plan.

What have others done about this?

Thx,

Paul
Any thoughts on this.

 

[PGWIN]

Problem solved. Not necessarily ideal but I angled the inlet barb down about 40 deg. which allows it to make an extra bend.

Everything back to gether now.

It doesn't appear the previous lift pump (with broken non-functional check valve effected performance at all). Power is the same.

I think that closes this Chapter!

Thx.

pgwin