pappyscrapster

Hey guys I have a fuel related issue, I did try and search this and other diesel sites for imput, I think I'm closer to figuring it out.
To date I’ve had my warning light come on 6 times, in 5 week’s, this light is just a low pressure sender to tell me that my fuel pressure is at or below 5 or 6 psi, I do know that when the money flows better I have a gage in mind, but until then I know fuel pressure is at the very least not constant, so would like to start there.
I’ve noticed that it tends to happen more after I’ve come to a full stop at a traffic light perhaps 2 maybe 4 minuets, ( I drive like there is a egg under the pedal) I get going, the bright red l.e.d. light comes on, even at the slightest pedal pressure, so I pull over right quick, turn it off, ponder stuff, start it up light stays off.
Tank is usually ½ or full. L/P and I/P was replaced before I got this truck, I would guess at or around 75k
I’m good about maintenance, etc . this happened 2 times before, but only when I was pulling a light load, also I have posted here before about when I have changed my fuel filter, I have noticed a small amount of a black colored, tiny suspended particulate residing in the left over fuel that I’ve drained from the old filter, “https://www.dieseltruckresource.com/...1#post1971691” doesn’t look like rust, just a very fine almost power like crap.
I did look into a nice link (found hear) about 5 well-documented issues that can be looked into, but before I go and get greasy, drop tanks I wanted to pass it by the likes of this crew,
I’ve noticed only one thing that my be an indicator of a clogged screen?? and that is when I open the gas cap I hear air either rushing in or out, not sure which it is, you would think it would be easy to call that, but as yet no luck. Any one care to enlighten me as to things I can do to pin this thing down?

jentas

If you've only got a warning light, how do you know the fuel psi isn't dropping down to almost nothing? What kind of lift pump is on there now, a stock carter on the side of the block?
If the warning light is coming on, chances are you're lift pump is dying or already dead. The newer ones will allow the vp to suck through even when the lift pump is shot.
If it was my truck, I wouldn't even drive it until confirming that the lift pump is still working. You could rig up a real basic temporary psi tester with a cheap water pressure gauge, or you can get everything you need to install a decent mechanical gauge for about $40.

pappyscrapster

Hi jentas and thanks, when the light is off, and remains off, your pressure is above 7 psi. I think the current pump is a factory one.
I carry a replacement rail mounted pump w/ me at all times.
What type of gauge are you talking about for that price?
Thanks

jentas

No problem, I remember it was a real headache dealing with those stock lift pumps.

So, if you wanted to put in a decent gauge on the cheap, you could get a liquid filled fp gauge from Jegs for less than $20. Then, you can get the fittings, fuel line, and a needle valve from Vulcan performance.

I found the email from when I ordered my stuff from Vulcan. Although the connection for tapping into the fuel system will be different (I tapped in right at the inlet to the vp44 with a tapped 90 degree jic fitting), I can give you a list of the fittings I needed to make all the connections from the tapped fitting to the gauge if you're interested.

I went through the same thing with dying lift pumps, carrying a spare, worrying about them dying...etc, before I went ahead and upgraded to a decent fuel supply system. If your lift pump is on its way out, I'd really consider selling the spare on ebay and upgrading to an Airdog or Fass. Those cheap Carter type replacement pumps are not worth much, might last 2 years or might last 2 months.

leeboy

Mine is doing the same......( except i have a westach electronic, and a manual gauge) When mine drops to 4 psi, i pull over and re-start, and back to 16 psi....I have a FASS stock replacement on order. $265 US....

jentas

Where is that warning light tapped in?

Could it be an air leak in the system, dirty filter? But those are probably among the issues you said you were already reading about.

I'd assume the worst though if its one of the stock replacement style lift pumps.
Less than 6 psi is really bad, especially if you're pretty much stock and not pulling a load.

pappyscrapster

Thanks guys ,,I'm taking all this is, am leaving town for a few days will re-plug in when I return

dkenny

what happens if you leave the gas cap loose. I don't think there should be any pressure/vacuum in the tank. if its a vacuum you lift pump is working harder than it should.

you might want to pour some biocide in the tank just in case you an algae problem. but then be ready to change the fuel filter. maybe a couple of time


-dkenny

sheriffav8r

A simple gauge from Northern Tool is about $6 (http://www.northerntool.com/webapp/w...4153_200324153). I mounted one under my cab on the driver's side frame rail. I have a Quadzilla commander inside the cab and use the exterior one as a check. The $6 one is pre-fuel filter and the Quadzilla is right before the IP so I can see when I need to change my fuel filter by the pressure drop. I think it's pretty cheap insurance....

Clunk

The lift pump and the fuel fitting between the lift pump and fuel tank are troublesome. I didn't like my fuel pressure with the original pump so I bought a new Carter 4601HP from Summit, installed it on the frame rail just in front of the fuel tank and haven't had any delivery problems since.

One problem that keeps showing up is the '98.5-'99 stock/Carter pumps don't seem to last long...in fact they fail way too quick and often. Because the ECM powers the lift pump, I blame the ECM.
One way around it is a relay that the ECM lift pump power signals then power it from the battery or aux. circuit then the lift pump gets a full, steady 12 volts.

pappyscrapster

sheriffav8r,, Some good input thank you,
and dkenny I have just today loosened/opened the gas cap "just to see" what gives... so Ill have to report that in the near future, thanks for that.
Clunk, Ill have to give that some more brain attention I'm just getting savy about these things, I do know I can still make a mess, so I will wait until I'm forced to "get in to it, and find myself more "bank" to make it all happen, I'm sure you know what that's about.. Thanks I'm still working on a diagnosis so until then.

pappyscrapster

Hey guys, just a short update, after my last attempt at figuring out why my low pressure fuel light was coming on, I decided to look into my fuel filter, and as I witnessed for the past 3 changes, I have again found that ever so tiny blackish/grey crap, in the outer portions of the filter, in fact I'm figuring that because that crap was partly obstructing the incoming fuel I can only (for now) conclude that it was my filter. after I changed it, I have not had the light come on, at all, even while pulling, so that may have been the problem.
Now lets say that stuff I'm finding is the problem, what could it be, where is it coming from, and who has a fairly reasonable method of back flushing the fuel system? This is that stuff I'm finding in the filter. any solid input?

picture of residue from filter
https://www.dieseltruckresource.com/...d.php?t=194512

Clunk

Congrats...that junk didn't get into your injector pump and ruin it

I'm seeing just a little of that stuff in mine too...must be some crap from the fueling stations....and I pump slow to try to give the filters at the truck stop a chance to catch that crap.

pappyscrapster

Any idea what it could be, also where do you get your fuel?

sheriffav8r

I sometimes see some small junk in the bottom of the fuel bowl. I personally think it is residue from having a fuel tank, lines, fuel filter assembly, and connectors that are 8 years and 190,000 miles old. As long as you remove the detritus from the bowl and change your filter regularly you should be okay; the filter assembly is doing its job. Just my opinion, though....