Engine/Transmission (1998.5 - 2002) Fuel Psi good then dwindles to 0 - long read

[Joe Mc]

Truck in sig.

In-line pre-screen filter, Walbro GSL-392 pump (powered from stock relay to provided with kit relay to pump), regulator (dumps to tank fill neck), delivery line w/psi sender to spin on Fleetguard filter all on frame w/big line kit, tank has draw straw. System has been in place for "years" (at least 5) with regulator set to deliver 22# (via number of washers stacked inside regulator to beef up or lessen spring psi) regardless of edge box setting and or go pedal position I have never seen below 20# even when "ringing the snot out of it.



This Thursday 1/24/13 the temps were about 23F. I had to take a trip about 50 miles away, hauling nothing other than my old arse. Fired up normally, let it run a little (a few cycles of the rpm creeping up and down) then off to grab a coffee. Let it run while inside and was still on high idle when I came out, hit the brakes once - off of low idle and away I go. So, I'm about 20 miles into the trip on the highway cruise set about 65-70 mph and I notice as I the road inclines the fuel psi starts to dwindle down slowly to 0 = WTF friggin great! Truck running fine though. As I aproach top of the hill and the load reduces the fuel psi creeps back to norm 22#. So, I give a bit more go pedal and observe same thing. Figure maybe water in fuel, freezing in the line or regulator (holding it open) or in pump causing it to run then not run? Who the "F" knows I'm now 30 miles from home and 20 from destination. So I keep an eye on psi and throttle accordingly to keep at least around 10# and reach my destination. On the way home that afternoon all was normal, temps up above freezing, I could lay into the go pedal and rock solid psi as usual. So I think must have been a little water in fuel freezing, or whatever, and now it's cleared up? I filled up the Saturday before 1/19/13 at the station I always go to which has fair amount of diesel traffic and I always use either Power Serve or Diesel Mate additive about 4oz/fill up. Don't forget this dwindle of psi has never happened before regardless of outside temps or go pedal/edge situations.



So, Friday 1/25/13, I had to take another trip into the city of "Brotherly Love" (Philadelphia - yeah right) anyway truck started as normal and I payed special attention to psi. All seemed normal until the truck started to go into high idle then the psi started to dwindle down again if I hit the brake to stop high idle psi crept right back to normal. It was even colder out on Friday than Thursday. So I head on to coffee up and such, come out truck on high idle psi a tiny bit lower than norm, tip the break pedal high idle off and psi back to normal, off I go. I get about 1/4 mile down the road and notice psi @ 0, WTF! Come to a stop and it creeps back up real slow? Head down the road and it's lower than norm but holding about 10-15#. Pull off into store on roadside and let it run a bit, shut completely down, turn on key, jog key to run pump 40-45 seconds and it's wizzing away making good psi, truck fires right up and off I go. As I go the psi is pretty much all over the place between 0 and 22#. I hit the highway and as I aproach 45-50 mph there's 0 psi I'm like WTF! and then the truck starts bucking and bouncing like a wild bronco. So, I'm heading home now right? Right! As I hobble down the road at about 40mph with very little go pedal the psi is remaining rock solid at "0". If I even tip in on the go pedal a little bit it's off to the rodeo so I hobble on home grab the wifey mobile (bummer) and head to my appointment.



So I figure a bit of water in fuel and what to do now. Figure I'll remove the regulator and check for ice the next day (Saturday). Of course it snowed Friday so that was out. But, I did start the truck up and here's what came of that. I turned on the key wait to start out then turned off key, key back on then jog. Wizzz goes the pump, psi to 22 and I wait for the pump to stop running then start truck. fires up fine and goes into high idle (pretty cold out again) psi seems fine. After running for about 5 minutes I kick out the high idle and let it settle in at normal idle. I increase the rpms (no load sitting in P in my driveway) and watch the psi dwindle down = Great! WTF Again. So I increase rpm to about 2500 and let off psi comes back to normal. Now I notice a "Check Engine" light - oh boy this just keeps getting beter I think. Read codes and just a "can't remember the number" it said it was a manufacturer code for parameter hi or low something like that? Friggin figures I forget so I cleared the code and the truck still runs fine but the psi still acts up.



Today Sunday 1/27/13 decide to take psi reg off and apart, it's friggin cold out there. All is clean no signs of ice or dirt or anything out of order with regulator, put it back together and reinstall. Figure I'll take the pump off and get inside garage where it's a bit warmer and investigate. Of course it's a gear rotor pump so you can't blow thru it so I turned the inlet facing down and let it drip into a clean tupperware storage container. Not much comes out as usual. The pump is pretty cold to hold onto so I figure a blow dryer to warm it up a bit, and then it dawns on me (no not that I'm dealing with fuel and the possibility of a boom) if there's ice in it heating the pump may reveal - prove or dissprove - if there's ice in it.



So, at present the pump is in the container out in the garage and I'm warming my fingers typing away here for someone to hopefully trudge thru this thesis and tell me something like

"Yo! Knuckle head, stop taking sh_t apart and go out and pick up some "Bla, bla, bla" fuel additive and that'll get whatever moisture is in your system run thru the truck so all will be well in your little world again".



It's OK to hope isn't it? Oh well fingers are warm now time to get back out to the garage and my little cylinder of fuel pumping prowess, or not...



More to come, hopefully from me good news? Or at least when I return someone replies Yo! Knuckle head...

 

[JLandry]

I'm not well versed in cold weather operations, but this smells to me like possible wax buildup on on the fuel filter or simply bad fuel.



I'd start by replacing the fuel filter and adding a bottle of Diesel 911 to the tank. If that clears up the problem, then be preprared to replace the fuel filter if symptoms return.



Good luck and please keep us posted,



John L.

 

[BarryG]

Joe:
Not sure what you are using for a regulator. However on my old RASP pump the bypass I was using one from Kinsler that has the spring and the piston. After talking with Kinsler they hand lap their pistons to the bores so that they seal better. Well after 120k of that piston moving, fuel and whatever other garbage running through it took its toll upon close inspection. Wasn't bad but it didn't seal like it used too. So I swapped in a different one that I had now this one had a rubber oring around the end of the conical piston. It didn't last nearly as long as the previous one before I noticed fuel psi problems maybe 40k. When I took it apart the oring was definitely not in great shape. Might be worth a look could also be the spring is getting weak. Or as JLandry pointed out perhaps a wax buildup in the filter.

 

[Joe Mc]

Guys thanks for replies.

Barry the regulator you mention (the 1st one you had) sounds like the one I have = no O-rings.



Here's what I did yesterday since there was a little heat wave = 29* then up to 35 later in the day.

Removed the regulator, used a clear catch pan and no water anywhere. I took the regulator apart and no signs of water or stickiness, spring in good shape. Figured while I had a heat wave I might as well pull the Walbro and take a look, no water. I was able to let the pump stand up in a clear catch container and actually able to get the fuel to come out of it, nothing but fuel. So, then I figured I might as well remove the fuel filter and check it, even thou there was less than 2k miles on it, "But" since it is in the upright position and fuel comes in and goes out thru the top if there was water anywhere it would be there. Of course, no water there either? So now I'm really wondering WTF happened? I connected a volt meter to the pump leads before I reinstalled and it hit 12. 1volts upon key jog and stayed steady for 20 +/- seconds. I connected everything up and fired up the truck.



Let it run for a good 10 minutes or so, must have been having a heat wave as the heater was actually starting to make some heat. So, off I go. The psi was good until I laid into it a little and then it started to dwindle, but unlike the other day when the bronco was bucking as I was "trying" to get home, it would come right back when I eased off the go pedal. Later on that night, it was a bit warmer than it was earlier in the day, so I decide to "go for a test ride". Friggin psi was rock solid and truck ran great!? I even put the edge on 5/5 and blasted it, rock solid!?



I'm not a firm believer in taking stuff apart and "wow, I don't know what happened but it's fixed now... " so today, temps about 32 ish. I had to go out for a bit and decided to take the truck. It ran fine, until I hit the go pedal a hard, it pulls hard until it starts fueling pretty hard (about 2,200rpms) then the psi starts to dive. If I ease off the go pedal it comes right back? If I'm easing into the go pedal until I'm powered up the psi remains solid? This is with or with edge off, on 1/1 or 5/5.



So, I decide to check some running conditions: highway 60 mph, floor it to 80, psi starts to dwindle when the rpms hit about 2,400, if I ease off a little the psi comes right back - same thing regardless of edge on/off/1/1 or 5/5. Highway 60 mph, ease into go pedal and letter go psi rock solid - I backed off around 90 mph. From a 20 mph floor it in 3rd gear, down shifts to 2nd takes off and not until it starts fueling hard (at 2,200) the psi remains solid.



So, at this point I'm thinking (duh) something somewhere in the fueling system is wacky. Now here's a thought, isn't there a screw on relief on the VP that internally opens and dumps excessive feed to the IJ fuel back to the tank? I seem to recall when I replaced the VP there was a new one in the box that I had to install and there were specific instructions that if the old VP core was to be returned without the old relief (or whatever it is) there would be a $50 fee. Of course I used the new relief and returned the old one on the core VP. So, I'm wondering if something's going on with that? Your thoughts?



I'm also not a big fan of "throwing parts" at something until the problem goes away, so I'm still wondering what the actual culprit could be. Once again, this VP (Stock SO-VP Bosch Cert Rebuild by Thoroughbred) has been on the truck since 3/09 and the fueling (GSL-392) has been there quite a bit longer.



Thanks for reading.



More to come...

 

[DavidC]

Do you have another relay ?. It is a long shot but the relay contacts arc when energized or de-energized and could be pitted enough to cause problems that a meter will not show as a meter places no load on the system. No spare relay ?, connect the wires to the pump together and bypass the relay for test.

Dave

 

[JLandry]

You still haven't replaced the fuel filter... right? It still might be as the restriction at higher flow rates.



If you had a pressure reading before the filter you'd know for sure.



John L.

 

[cerberusiam]

Sounds to me like the gauge is going south. Had a crappy glow shift do the same exact thing when it was warm.

 

[DavidC]

Sounds to me like the gauge is going south. Had a crappy glow shift do the same exact thing when it was warm.

But that would not account for the bucking Joe said was going on. He did state a CEL light. Maybe more than one thing happening or they are related.

Dave

 

[gtwitch]

I chased a similar problem over a year ago and that lasted over 7 or 8 months as an intermittent problem of the fuel pressure going away both in cold and warm weather, but mostly in cold weather, so with spring last year, put new filters and checked the pump (holley Blue on frame) all to no good,!! problem still there so replaced the electric fuel pressure gauge sending unit and problem vanished!!! BAD Pressure sending unit!!!



gtwitch in wyoming

 

[Joe Mc]

Thanks for replies. Not gauge as when I had the worst experience on highway (Friday) when it was really cold and 0 psi remember the old bucking bronco and hobble home routine.



cerberusiam-checked relays contact points look good on the relays and receptacles - I had previously given them a coat of dielectric grease when repalced last spring (why replace just because they were old), still have them as spares. But I did think about them as a possibilty so I swapped around and same thing so put newer ones back in.



JLandy-you picked up on it - no I still didn't change the filter, drained and inspected fuel for water = none present reinstalled. But, it's very possible there's a restriction in the filter - even though it's only 3 mos and only 2k miles old. Hummmm, last Monday I did run fuel so low that it started and stalled in my driveway, it's about a 5 degree slant to the street, roll into street where it's more level than the driveway, crank a few times and off I go to the fuel station. If there was minor water in the fuel and then that got traped in the filter membrane and didn't come out when inspected (absorbs into membrane) then the moisture still remains in the membrain. So, when "not so cold" it (moisture) isn't frozen but milky and clings to membrane creating minor restricition, then when it's really cold it freezes. Ah Ha! Makes sense! I'll try a new filter (duh) sometimes it's those "way to simple" things that just get by the thought processes... Thanks Brother!



So, what's a filter cost = nothing when there's a spare or two in the garage. I'll give it a go and see what happens.



I wanted to take it out today as the temps were between 45 - 50 but was to busy working. Maybe tomorrow, of course after a fresh filter install... . More to come. Hopefully all good.



But wait, I just realized something, the psi sending unit is installed "post" tee by 10 - 15" from where the regulator dumps back to tank fill (as suggested with system install instructions) and "pre" the line that runs to the filter adapter... . so, the psi sender is located between the pump and the filter - if the fuel filter was restricted wouldn't the psi remain solid? Argh!!!! :{We'll see what happens with the filter change.

 

[ChrisOlson]

Thanks for replies. Not gauge as when I had the worst experience on highway (Friday) when it was really cold and 0 psi remember the old bucking bronco and hobble home routine.

cerberusiam-checked relays contact points look good on the relays and receptacles - I had previously given them a coat of dielectric grease when repalced last spring (why replace just because they were old), still have them as spares. But I did think about them as a possibilty so I swapped around and same thing so put newer ones back in.

JLandy-you picked up on it - no I still didn't change the filter, drained and inspected fuel for water = none present reinstalled. But, it's very possible there's a restriction in the filter - even though it's only 3 mos and only 2k miles old. Hummmm, last Monday I did run fuel so low that it started and stalled in my driveway, it's about a 5 degree slant to the street, roll into street where it's more level than the driveway, crank a few times and off I go to the fuel station. If there was minor water in the fuel and then that got traped in the filter membrane and didn't come out when inspected (absorbs into membrane) then the moisture still remains in the membrain. So, when "not so cold" it (moisture) isn't frozen but milky and clings to membrane creating minor restricition, then when it's really cold it freezes. Ah Ha! Makes sense! I'll try a new filter (duh) sometimes it's those "way to simple" things that just get by the thought processes... Thanks Brother!

So, what's a filter cost = nothing when there's a spare or two in the garage. I'll give it a go and see what happens.

I wanted to take it out today as the temps were between 45 - 50 but was to busy working. Maybe tomorrow, of course after a fresh filter install... . More to come. Hopefully all good.

But wait, I just realized something, the psi sending unit is installed "post" tee by 10 - 15" from where the regulator dumps back to tank fill (as suggested with system install instructions) and "pre" the line that runs to the filter adapter... . so, the psi sender is located between the pump and the filter - if the fuel filter was restricted wouldn't the psi remain solid? Argh!!!! :{We'll see what happens with the filter change.

Hello Joe
Sorry to hear of your troubles. Here is a thought I am not trying to Flame you or cause troubles However. Quoting you

So I am only offering up a thought and I am not sure this will resolve your problem. My view is in bold, Italics and underlinend

good luck

You Said
"checked relays contact points look good on the relays and receptacles - I had previously given them a coat of dielectric grease when repalced last spring"

FRom WIKI
Dielectric grease

Dielectric grease is electrically insulating and does not break down when high voltage is applied. It is often applied to electrical connectors, particularly those containing rubber gaskets, as a means of lubricating and sealing rubber portions of the connector without arcing.

A common use of dielectric grease is in high-voltage connections associated with gasoline engine spark plugs. The grease is applied to the rubber boot of the plug wire. This helps the rubber boot slide onto the ceramic insulator of the plug. The grease also acts to seal the rubber boot, while at the same time preventing the rubber from becoming stuck to the ceramic. Generally spark plugs are located in areas of high temperature, and the grease is formulated to withstand the temperature range expected. It can be applied to the actual contact as well, because the contact pressure is sufficient to penetrate the grease. Doing so on such high pressure contact surfaces has the advantage of sealing the contact area against corrosion.

Another common use of dielectric grease is on the rubber mating surfaces or gaskets of multi-pin electrical connectors used in automotive and marine engines. The grease again acts as a lubricant and a sealant on the nonconductive mating surfaces of the connector. It is not recommended to be applied to the actual electrical conductive contacts of the connector because it could interfere with the electrical signals passing through the connector in cases where the contact pressure is very low. Products designed as electronic connector lubricants, on the other hand, should be applied to such connector contacts and can dramatically extend their useful life. Polyphenyl Ether, rather than silicone grease, is the active ingredient in some such connector lubricants.

Silicone grease should not be applied to (or next to) any switch contact that might experience arcing, as silicone can convert to silicon-carbide under arcing conditions, and accumulation of the silicon-carbide can cause the contacts to prematurely fail.

 

[cerberusiam]

Not gauge as when I had the worst experience on highway (Friday) when it was really cold and 0 psi remember the old bucking bronco and hobble home routine.

That does not preclude the gauge or sending unit from being bad, Doesn't neccessarily mean its good either. It is a VP-44 and we all know how finicky that system is. You could easily have a bad sending unit on the gauge and a filter with problems or even a IP issue, per your description.

Hope you find the problem, it suscks when you can't trust the truck in the cold.

 

[Gary - K7GLD]

I have nearly the exact same setup as you, cold weather temps and untreated fuel can cause problems for sure, and I think the BEST option is this one:

"Yo! Knuckle head, stop taking sh_t apart and go out and pick up some "Bla, bla, bla" fuel additive and that'll get whatever moisture is in your system run thru the truck so all will be well in your little world again".

:-laf

 

[Joe Mc]

Chris - thanks wow I didn't know that? Learn something every day. Have to find some shmutz that's for contact surfaces.



Gary - Thanks man I really needed that laugh!



No update just swamped with work. Working at home can make for extreemly long days... . Just finishing up now and it's almost 11:30 PM.

 

[hcole]

Joe, this is a long shot, but do you think that the inside of one of your rubber fuel lines is seperating? I've had this happen once on my brake lines and wouldn't fully release pressure on the calipers. What if you have a liner that is just hanging inside the rubber line and occasionally blocks the flow? I can't say whether to look on the suction or pressure side of fuel pump. Just a guess.

 

[Joe Mc]

hcole - MAN! I would have never thought of that? I've had that happen on brake hoses but never would have thought about that on the fuel system. ARGH! That will be a royal straight flush of a PIA to diagnose "oh dear, oh my" (Lost in Space - Dr. what was his name?)



Anyway, So the other day it wa sa balmy 40 degrees figured I go for a spin to see what was or wasn't happening. Didn't change the filter yet. I went for 180 mile round trip she ran like a dream = no fluctuation at all???? Don't get me wrong I'm happy about that but WTF happened last week?



Well, today presently it's 20* out with anticipated high of 29 and a low of 25 - ??? If it's presently 20 and the low is supposed to be 25 who the heck is entering that info? Accuweather on my smart phone, for stupid people that's how I ended up with it. So I'm going to venture out and see what is or ain't going on. More to come... ...

 

[DavidC]

Maybe fuel heater not working ?. Everything gets thicker when cold.

Dave

 

[Joe Mc]

Aftermarket system everything low and back on the frame = stock fuel filter and heater "long" gone 8+years.



So anyway temps today never higher than 28, ran like a champ!? I'm happy but not yet satisfied stil trying to figure out the whole bucking bronco deal with no fuel psi last week? More to come???

 

[jeepit]

I have nearly the exact same setup as you, cold weather temps and untreated fuel can cause problems for sure, and I think the BEST option is this one:



:-laf

Wow! Gary how ya doing?

Haven't seen you here for along time! Hope all is well!

 

[Joe Mc]

So today temps were 22, made the 160 mile trip and then after a 2 hour cool down, a short trip of 33 miles. Running like a top PSI Rock solid... . I'm not going to reply anymore unless someone else does with an idea or if there are new developments.